€•!      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ-/translations/zh_CN/filesystems/sharedsubtree”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ-/translations/zh_TW/filesystems/sharedsubtree”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ-/translations/it_IT/filesystems/sharedsubtree”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ-/translations/ja_JP/filesystems/sharedsubtree”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ-/translations/ko_KR/filesystems/sharedsubtree”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒPortuguese (Brazilian)”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ-/translations/pt_BR/filesystems/sharedsubtree”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh–sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ-/translations/sp_SP/filesystems/sharedsubtree”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ SPDX-License-Identifier: GPL-2.0”h]”hŒ SPDX-License-Identifier: GPL-2.0”…””}”hh·sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1hµhhh²hh³ŒG/var/lib/git/docbuild/linux/Documentation/filesystems/sharedsubtree.rst”h´KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒShared Subtrees”h]”hŒShared Subtrees”…””}”(hhÏh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhhÊh²hh³hÇh´Kubh¶)”}”(hŒ|Contents:
1) Overview
2) Features
3) Setting mount states
4) Use-case
5) Detailed semantics
6) Quiz
7) FAQ
8) Implementation”h]”hŒ|Contents:
1) Overview
2) Features
3) Setting mount states
4) Use-case
5) Detailed semantics
6) Quiz
7) FAQ
8) Implementation”…””}”hhÝsbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1hµhhÊh²hh³hÇh´KubhÉ)”}”(hhh]”(hÎ)”}”(hŒ1) Overview”h]”hŒ1) Overview”…””}”(hhîh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhhëh²hh³hÇh´KubhŒ	paragraph”“”)”}”(hŒ!Consider the following situation:”h]”hŒ!Consider the following situation:”…””}”(hhþh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Khhëh²hubhý)”}”(hŒºA process wants to clone its own namespace, but still wants to access the CD
that got mounted recently.  Shared subtree semantics provide the necessary
mechanism to accomplish the above.”h]”hŒºA process wants to clone its own namespace, but still wants to access the CD
that got mounted recently.  Shared subtree semantics provide the necessary
mechanism to accomplish the above.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Khhëh²hubhý)”}”(hŒhIt provides the necessary building blocks for features like per-user-namespace
and versioned filesystem.”h]”hŒhIt provides the necessary building blocks for features like per-user-namespace
and versioned filesystem.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Khhëh²hubeh}”(h]”Œoverview”ah ]”h"]”Œ1) overview”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´KubhÉ)”}”(hhh]”(hÎ)”}”(hŒ2) Features”h]”hŒ2) Features”…””}”(hj3  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhj0  h²hh³hÇh´Kubhý)”}”(hŒXShared subtree provides four different flavors of mounts; struct vfsmount to be
precise:”h]”hŒXShared subtree provides four different flavors of mounts; struct vfsmount to be
precise:”…””}”(hjA  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K!hj0  h²hubhŒenumerated_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hXX  A **shared mount** can be replicated to as many mountpoints and all the
replicas continue to be exactly same.

Here is an example:

Let's say /mnt has a mount that is shared::

  # mount --make-shared /mnt

.. note::
   mount(8) command now supports the --make-shared flag,
   so the sample 'smount' program is no longer needed and has been
   removed.

::

  # mount --bind /mnt /tmp

The above command replicates the mount at /mnt to the mountpoint /tmp
and the contents of both the mounts remain identical.

::

  #ls /mnt
  a b c

  #ls /tmp
  a b c

Now let's say we mount a device at /tmp/a::

  # mount /dev/sd0  /tmp/a

  # ls /tmp/a
  t1 t2 t3

  # ls /mnt/a
  t1 t2 t3

Note that the mount has propagated to the mount at /mnt as well.

And the same is true even when /dev/sd0 is mounted on /mnt/a. The
contents will be visible under /tmp/a too.

”h]”(hý)”}”(hŒmA **shared mount** can be replicated to as many mountpoints and all the
replicas continue to be exactly same.”h]”(hŒA ”…””}”(hjZ  h²hh³Nh´NubhŒstrong”“”)”}”(hŒ**shared mount**”h]”hŒshared mount”…””}”(hjd  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hjZ  ubhŒ[ can be replicated to as many mountpoints and all the
replicas continue to be exactly same.”…””}”(hjZ  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K%hjV  ubhý)”}”(hŒHere is an example:”h]”hŒHere is an example:”…””}”(hj|  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K(hjV  ubhý)”}”(hŒ+Let's say /mnt has a mount that is shared::”h]”hŒ,Letâ€™s say /mnt has a mount that is shared:”…””}”(hjŠ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K*hjV  ubhŒliteral_block”“”)”}”(hŒ# mount --make-shared /mnt”h]”hŒ# mount --make-shared /mnt”…””}”hjš  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´K,hjV  ubhŒnote”“”)”}”(hŒ~mount(8) command now supports the --make-shared flag,
so the sample 'smount' program is no longer needed and has been
removed.”h]”hý)”}”(hŒ~mount(8) command now supports the --make-shared flag,
so the sample 'smount' program is no longer needed and has been
removed.”h]”hŒ‚mount(8) command now supports the --make-shared flag,
so the sample â€˜smountâ€™ program is no longer needed and has been
removed.”…””}”(hj®  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K/hjª  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j¨  hjV  ubj™  )”}”(hŒ# mount --bind /mnt /tmp”h]”hŒ# mount --bind /mnt /tmp”…””}”hjÂ  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´K5hjV  ubhý)”}”(hŒ{The above command replicates the mount at /mnt to the mountpoint /tmp
and the contents of both the mounts remain identical.”h]”hŒ{The above command replicates the mount at /mnt to the mountpoint /tmp
and the contents of both the mounts remain identical.”…””}”(hjÐ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K7hjV  ubj™  )”}”(hŒ#ls /mnt
a b c

#ls /tmp
a b c”h]”hŒ#ls /mnt
a b c

#ls /tmp
a b c”…””}”hjÞ  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´K<hjV  ubhý)”}”(hŒ+Now let's say we mount a device at /tmp/a::”h]”hŒ,Now letâ€™s say we mount a device at /tmp/a:”…””}”(hjì  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KBhjV  ubj™  )”}”(hŒD# mount /dev/sd0  /tmp/a

# ls /tmp/a
t1 t2 t3

# ls /mnt/a
t1 t2 t3”h]”hŒD# mount /dev/sd0  /tmp/a

# ls /tmp/a
t1 t2 t3

# ls /mnt/a
t1 t2 t3”…””}”hjú  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´KDhjV  ubhý)”}”(hŒ@Note that the mount has propagated to the mount at /mnt as well.”h]”hŒ@Note that the mount has propagated to the mount at /mnt as well.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KLhjV  ubhý)”}”(hŒlAnd the same is true even when /dev/sd0 is mounted on /mnt/a. The
contents will be visible under /tmp/a too.”h]”hŒlAnd the same is true even when /dev/sd0 is mounted on /mnt/a. The
contents will be visible under /tmp/a too.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KNhjV  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjQ  h²hh³hÇh´NubjU  )”}”(hXh  A **slave mount** is like a shared mount except that mount and umount events
only propagate towards it.

All slave mounts have a master mount which is a shared.

Here is an example:

Let's say /mnt has a mount which is shared::

  # mount --make-shared /mnt

Let's bind mount /mnt to /tmp::

  # mount --bind /mnt /tmp

the new mount at /tmp becomes a shared mount and it is a replica of
the mount at /mnt.

Now let's make the mount at /tmp; a slave of /mnt::

  # mount --make-slave /tmp

let's mount /dev/sd0 on /mnt/a::

  # mount /dev/sd0 /mnt/a

  # ls /mnt/a
  t1 t2 t3

  # ls /tmp/a
  t1 t2 t3

Note the mount event has propagated to the mount at /tmp

However let's see what happens if we mount something on the mount at
/tmp::

  # mount /dev/sd1 /tmp/b

  # ls /tmp/b
  s1 s2 s3

  # ls /mnt/b

Note how the mount event has not propagated to the mount at
/mnt

”h]”(hý)”}”(hŒgA **slave mount** is like a shared mount except that mount and umount events
only propagate towards it.”h]”(hŒA ”…””}”(hj.  h²hh³Nh´Nubjc  )”}”(hŒ**slave mount**”h]”hŒslave mount”…””}”(hj6  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj.  ubhŒV is like a shared mount except that mount and umount events
only propagate towards it.”…””}”(hj.  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KRhj*  ubhý)”}”(hŒ7All slave mounts have a master mount which is a shared.”h]”hŒ7All slave mounts have a master mount which is a shared.”…””}”(hjN  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KUhj*  ubhý)”}”(hŒHere is an example:”h]”hŒHere is an example:”…””}”(hj\  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KWhj*  ubhý)”}”(hŒ,Let's say /mnt has a mount which is shared::”h]”hŒ-Letâ€™s say /mnt has a mount which is shared:”…””}”(hjj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KYhj*  ubj™  )”}”(hŒ# mount --make-shared /mnt”h]”hŒ# mount --make-shared /mnt”…””}”hjx  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´K[hj*  ubhý)”}”(hŒLet's bind mount /mnt to /tmp::”h]”hŒ Letâ€™s bind mount /mnt to /tmp:”…””}”(hj†  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K]hj*  ubj™  )”}”(hŒ# mount --bind /mnt /tmp”h]”hŒ# mount --bind /mnt /tmp”…””}”hj”  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´K_hj*  ubhý)”}”(hŒVthe new mount at /tmp becomes a shared mount and it is a replica of
the mount at /mnt.”h]”hŒVthe new mount at /tmp becomes a shared mount and it is a replica of
the mount at /mnt.”…””}”(hj¢  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Kahj*  ubhý)”}”(hŒ3Now let's make the mount at /tmp; a slave of /mnt::”h]”hŒ4Now letâ€™s make the mount at /tmp; a slave of /mnt:”…””}”(hj°  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Kdhj*  ubj™  )”}”(hŒ# mount --make-slave /tmp”h]”hŒ# mount --make-slave /tmp”…””}”hj¾  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Kfhj*  ubhý)”}”(hŒ let's mount /dev/sd0 on /mnt/a::”h]”hŒ!letâ€™s mount /dev/sd0 on /mnt/a:”…””}”(hjÌ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Khhj*  ubj™  )”}”(hŒC# mount /dev/sd0 /mnt/a

# ls /mnt/a
t1 t2 t3

# ls /tmp/a
t1 t2 t3”h]”hŒC# mount /dev/sd0 /mnt/a

# ls /mnt/a
t1 t2 t3

# ls /tmp/a
t1 t2 t3”…””}”hjÚ  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Kjhj*  ubhý)”}”(hŒ8Note the mount event has propagated to the mount at /tmp”h]”hŒ8Note the mount event has propagated to the mount at /tmp”…””}”(hjè  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Krhj*  ubhý)”}”(hŒKHowever let's see what happens if we mount something on the mount at
/tmp::”h]”hŒLHowever letâ€™s see what happens if we mount something on the mount at
/tmp:”…””}”(hjö  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Kthj*  ubj™  )”}”(hŒ:# mount /dev/sd1 /tmp/b

# ls /tmp/b
s1 s2 s3

# ls /mnt/b”h]”hŒ:# mount /dev/sd1 /tmp/b

# ls /tmp/b
s1 s2 s3

# ls /mnt/b”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Kwhj*  ubhý)”}”(hŒ@Note how the mount event has not propagated to the mount at
/mnt”h]”hŒ@Note how the mount event has not propagated to the mount at
/mnt”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K~hj*  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjQ  h²hh³hÇh´NubjU  )”}”(hŒ}A **private mount** does not forward or receive propagation.

This is the mount we are familiar with. Its the default type.

”h]”(hý)”}”(hŒ<A **private mount** does not forward or receive propagation.”h]”(hŒA ”…””}”(hj*  h²hh³Nh´Nubjc  )”}”(hŒ**private mount**”h]”hŒprivate mount”…””}”(hj2  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj*  ubhŒ) does not forward or receive propagation.”…””}”(hj*  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K‚hj&  ubhý)”}”(hŒ=This is the mount we are familiar with. Its the default type.”h]”hŒ=This is the mount we are familiar with. Its the default type.”…””}”(hjJ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K„hj&  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjQ  h²hh³hÇh´NubjU  )”}”(hX“  An **unbindable mount** is, as the name suggests, an unbindable private
mount.

let's say we have a mount at /mnt and we make it unbindable::

  # mount --make-unbindable /mnt

Let's try to bind mount this mount somewhere else::

  # mount --bind /mnt /tmp mount: wrong fs type, bad option, bad
  superblock on /mnt, or too many mounted file systems

Binding a unbindable mount is a invalid operation.

”h]”(hý)”}”(hŒNAn **unbindable mount** is, as the name suggests, an unbindable private
mount.”h]”(hŒAn ”…””}”(hjb  h²hh³Nh´Nubjc  )”}”(hŒ**unbindable mount**”h]”hŒunbindable mount”…””}”(hjj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hjb  ubhŒ7 is, as the name suggests, an unbindable private
mount.”…””}”(hjb  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K‡hj^  ubhý)”}”(hŒ=let's say we have a mount at /mnt and we make it unbindable::”h]”hŒ>letâ€™s say we have a mount at /mnt and we make it unbindable:”…””}”(hj‚  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KŠhj^  ubj™  )”}”(hŒ# mount --make-unbindable /mnt”h]”hŒ# mount --make-unbindable /mnt”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´KŒhj^  ubhý)”}”(hŒ3Let's try to bind mount this mount somewhere else::”h]”hŒ4Letâ€™s try to bind mount this mount somewhere else:”…””}”(hjž  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KŽhj^  ubj™  )”}”(hŒs# mount --bind /mnt /tmp mount: wrong fs type, bad option, bad
superblock on /mnt, or too many mounted file systems”h]”hŒs# mount --bind /mnt /tmp mount: wrong fs type, bad option, bad
superblock on /mnt, or too many mounted file systems”…””}”hj¬  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Khj^  ubhý)”}”(hŒ2Binding a unbindable mount is a invalid operation.”h]”hŒ2Binding a unbindable mount is a invalid operation.”…””}”(hjº  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K“hj^  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjQ  h²hh³hÇh´Nubeh}”(h]”h ]”h"]”h$]”h&]”Œenumtype”Œ
loweralpha”Œprefix”hŒsuffix”Œ)”uh1jO  hj0  h²hh³hÇh´K%ubeh}”(h]”Œfeatures”ah ]”h"]”Œ2) features”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´KubhÉ)”}”(hhh]”(hÎ)”}”(hŒ3) Setting mount states”h]”hŒ3) Setting mount states”…””}”(hjä  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhjá  h²hh³hÇh´K—ubhý)”}”(hŒHThe mount command (util-linux package) can be used to set mount
states::”h]”hŒGThe mount command (util-linux package) can be used to set mount
states:”…””}”(hjò  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K™hjá  h²hubj™  )”}”(hŒmount --make-shared mountpoint
mount --make-slave mountpoint
mount --make-private mountpoint
mount --make-unbindable mountpoint”h]”hŒmount --make-shared mountpoint
mount --make-slave mountpoint
mount --make-private mountpoint
mount --make-unbindable mountpoint”…””}”hj   sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Kœhjá  h²hubeh}”(h]”Œsetting-mount-states”ah ]”h"]”Œ3) setting mount states”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´K—ubhÉ)”}”(hhh]”(hÎ)”}”(hŒ4) Use cases”h]”hŒ4) Use cases”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhj  h²hh³hÇh´K£ubjP  )”}”(hhh]”(jU  )”}”(hX  A process wants to clone its own namespace, but still wants to
access the CD that got mounted recently.

Solution:

The system administrator can make the mount at /cdrom shared::

  mount --bind /cdrom /cdrom
  mount --make-shared /cdrom

Now any process that clones off a new namespace will have a
mount at /cdrom which is a replica of the same mount in the
parent namespace.

So when a CD is inserted and mounted at /cdrom that mount gets
propagated to the other mount at /cdrom in all the other clone
namespaces.
”h]”(hý)”}”(hŒgA process wants to clone its own namespace, but still wants to
access the CD that got mounted recently.”h]”hŒgA process wants to clone its own namespace, but still wants to
access the CD that got mounted recently.”…””}”(hj.  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K¥hj*  ubhý)”}”(hŒ	Solution:”h]”hŒ	Solution:”…””}”(hj<  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K¨hj*  ubhý)”}”(hŒ>The system administrator can make the mount at /cdrom shared::”h]”hŒ=The system administrator can make the mount at /cdrom shared:”…””}”(hjJ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Kªhj*  ubj™  )”}”(hŒ5mount --bind /cdrom /cdrom
mount --make-shared /cdrom”h]”hŒ5mount --bind /cdrom /cdrom
mount --make-shared /cdrom”…””}”hjX  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´K¬hj*  ubhý)”}”(hŒ‰Now any process that clones off a new namespace will have a
mount at /cdrom which is a replica of the same mount in the
parent namespace.”h]”hŒ‰Now any process that clones off a new namespace will have a
mount at /cdrom which is a replica of the same mount in the
parent namespace.”…””}”(hjf  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K¯hj*  ubhý)”}”(hŒ‰So when a CD is inserted and mounted at /cdrom that mount gets
propagated to the other mount at /cdrom in all the other clone
namespaces.”h]”hŒ‰So when a CD is inserted and mounted at /cdrom that mount gets
propagated to the other mount at /cdrom in all the other clone
namespaces.”…””}”(hjt  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K³hj*  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj'  h²hh³hÇh´NubjU  )”}”(hXA  A process wants its mounts invisible to any other process, but
still be able to see the other system mounts.

Solution:

To begin with, the administrator can mark the entire mount tree
as shareable::

  mount --make-rshared /

A new process can clone off a new namespace. And mark some part
of its namespace as slave::

  mount --make-rslave /myprivatetree

Hence forth any mounts within the /myprivatetree done by the
process will not show up in any other namespace. However mounts
done in the parent namespace under /myprivatetree still shows
up in the process's namespace.

”h]”(hý)”}”(hŒlA process wants its mounts invisible to any other process, but
still be able to see the other system mounts.”h]”hŒlA process wants its mounts invisible to any other process, but
still be able to see the other system mounts.”…””}”(hjŒ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K·hjˆ  ubhý)”}”(hŒ	Solution:”h]”hŒ	Solution:”…””}”(hjš  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Kºhjˆ  ubhý)”}”(hŒNTo begin with, the administrator can mark the entire mount tree
as shareable::”h]”hŒMTo begin with, the administrator can mark the entire mount tree
as shareable:”…””}”(hj¨  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K¼hjˆ  ubj™  )”}”(hŒmount --make-rshared /”h]”hŒmount --make-rshared /”…””}”hj¶  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´K¿hjˆ  ubhý)”}”(hŒ[A new process can clone off a new namespace. And mark some part
of its namespace as slave::”h]”hŒZA new process can clone off a new namespace. And mark some part
of its namespace as slave:”…””}”(hjÄ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KÁhjˆ  ubj™  )”}”(hŒ"mount --make-rslave /myprivatetree”h]”hŒ"mount --make-rslave /myprivatetree”…””}”hjÒ  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´KÄhjˆ  ubhý)”}”(hŒÙHence forth any mounts within the /myprivatetree done by the
process will not show up in any other namespace. However mounts
done in the parent namespace under /myprivatetree still shows
up in the process's namespace.”h]”hŒÛHence forth any mounts within the /myprivatetree done by the
process will not show up in any other namespace. However mounts
done in the parent namespace under /myprivatetree still shows
up in the processâ€™s namespace.”…””}”(hjà  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KÆhjˆ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj'  h²hh³hÇh´Nubeh}”(h]”h ]”h"]”h$]”h&]”jÔ  Œ
upperalpha”jÖ  hj×  jØ  uh1jO  hj  h²hh³hÇh´K¥ubhý)”}”(hŒiApart from the above semantics this feature provides the
building blocks to solve the following problems:”h]”hŒiApart from the above semantics this feature provides the
building blocks to solve the following problems:”…””}”(hjû  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KÌhj  h²hubjP  )”}”(hhh]”(jU  )”}”(hXm  Per-user namespace

The above semantics allows a way to share mounts across
namespaces.  But namespaces are associated with processes. If
namespaces are made first class objects with user API to
associate/disassociate a namespace with userid, then each user
could have his/her own namespace and tailor it to his/her
requirements. This needs to be supported in PAM.
”h]”(hý)”}”(hŒPer-user namespace”h]”hŒPer-user namespace”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KÏhj  ubhý)”}”(hXX  The above semantics allows a way to share mounts across
namespaces.  But namespaces are associated with processes. If
namespaces are made first class objects with user API to
associate/disassociate a namespace with userid, then each user
could have his/her own namespace and tailor it to his/her
requirements. This needs to be supported in PAM.”h]”hXX  The above semantics allows a way to share mounts across
namespaces.  But namespaces are associated with processes. If
namespaces are made first class objects with user API to
associate/disassociate a namespace with userid, then each user
could have his/her own namespace and tailor it to his/her
requirements. This needs to be supported in PAM.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KÑhj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj	  h²hh³hÇh´NubjU  )”}”(hXð  Versioned files

If the entire mount tree is visible at multiple locations, then
an underlying versioning file system can return different
versions of the file depending on the path used to access that
file.

An example is::

   mount --make-shared /
   mount --rbind / /view/v1
   mount --rbind / /view/v2
   mount --rbind / /view/v3
   mount --rbind / /view/v4

and if /usr has a versioning filesystem mounted, then that
mount appears at /view/v1/usr, /view/v2/usr, /view/v3/usr and
/view/v4/usr too

A user can request v3 version of the file /usr/fs/namespace.c
by accessing /view/v3/usr/fs/namespace.c . The underlying
versioning filesystem can then decipher that v3 version of the
filesystem is being requested and return the corresponding
inode.
”h]”(hý)”}”(hŒVersioned files”h]”hŒVersioned files”…””}”(hj6  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KØhj2  ubhý)”}”(hŒ¾If the entire mount tree is visible at multiple locations, then
an underlying versioning file system can return different
versions of the file depending on the path used to access that
file.”h]”hŒ¾If the entire mount tree is visible at multiple locations, then
an underlying versioning file system can return different
versions of the file depending on the path used to access that
file.”…””}”(hjD  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KÚhj2  ubhý)”}”(hŒAn example is::”h]”hŒAn example is:”…””}”(hjR  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Kßhj2  ubj™  )”}”(hŒymount --make-shared /
mount --rbind / /view/v1
mount --rbind / /view/v2
mount --rbind / /view/v3
mount --rbind / /view/v4”h]”hŒymount --make-shared /
mount --rbind / /view/v1
mount --rbind / /view/v2
mount --rbind / /view/v3
mount --rbind / /view/v4”…””}”hj`  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Káhj2  ubhý)”}”(hŒ‰and if /usr has a versioning filesystem mounted, then that
mount appears at /view/v1/usr, /view/v2/usr, /view/v3/usr and
/view/v4/usr too”h]”hŒ‰and if /usr has a versioning filesystem mounted, then that
mount appears at /view/v1/usr, /view/v2/usr, /view/v3/usr and
/view/v4/usr too”…””}”(hjn  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Kçhj2  ubhý)”}”(hŒøA user can request v3 version of the file /usr/fs/namespace.c
by accessing /view/v3/usr/fs/namespace.c . The underlying
versioning filesystem can then decipher that v3 version of the
filesystem is being requested and return the corresponding
inode.”h]”hŒøA user can request v3 version of the file /usr/fs/namespace.c
by accessing /view/v3/usr/fs/namespace.c . The underlying
versioning filesystem can then decipher that v3 version of the
filesystem is being requested and return the corresponding
inode.”…””}”(hj|  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Këhj2  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj	  h²hh³hÇh´Nubeh}”(h]”h ]”h"]”h$]”h&]”jÔ  jú  jÖ  hj×  jØ  Œstart”Kuh1jO  hj  h²hh³hÇh´KÏubeh}”(h]”Œ	use-cases”ah ]”h"]”Œ4) use cases”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´K£ubhÉ)”}”(hhh]”(hÎ)”}”(hŒ5) Detailed semantics”h]”hŒ5) Detailed semantics”…””}”(hj¢  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhjŸ  h²hh³hÇh´Kòubhý)”}”(hŒuThe section below explains the detailed semantics of
bind, rbind, move, mount, umount and clone-namespace operations.”h]”hŒuThe section below explains the detailed semantics of
bind, rbind, move, mount, umount and clone-namespace operations.”…””}”(hj°  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KóhjŸ  h²hubj©  )”}”(hŒithe word 'vfsmount' and the noun 'mount' have been used
to mean the same thing, throughout this document.”h]”hý)”}”(hŒithe word 'vfsmount' and the noun 'mount' have been used
to mean the same thing, throughout this document.”h]”hŒqthe word â€˜vfsmountâ€™ and the noun â€˜mountâ€™ have been used
to mean the same thing, throughout this document.”…””}”(hjÂ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´K÷hj¾  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j¨  hjŸ  h²hh³hÇh´NubjP  )”}”(hhh]”(jU  )”}”(hXè  Mount states

A **propagation event** is defined as event generated on a vfsmount
that leads to mount or unmount actions in other vfsmounts.

A **peer group** is defined as a group of vfsmounts that propagate
events to each other.

A given mount can be in one of the following states:

(1) Shared mounts

    A **shared mount** is defined as a vfsmount that belongs to a
    peer group.

    For example::

      mount --make-shared /mnt
      mount --bind /mnt /tmp

    The mount at /mnt and that at /tmp are both shared and belong
    to the same peer group. Anything mounted or unmounted under
    /mnt or /tmp reflect in all the other mounts of its peer
    group.


(2) Slave mounts

    A **slave mount** is defined as a vfsmount that receives
    propagation events and does not forward propagation events.

    A slave mount as the name implies has a master mount from which
    mount/unmount events are received. Events do not propagate from
    the slave mount to the master.  Only a shared mount can be made
    a slave by executing the following command::

      mount --make-slave mount

    A shared mount that is made as a slave is no more shared unless
    modified to become shared.

(3) Shared and Slave

    A vfsmount can be both **shared** as well as **slave**.  This state
    indicates that the mount is a slave of some vfsmount, and
    has its own peer group too.  This vfsmount receives propagation
    events from its master vfsmount, and also forwards propagation
    events to its 'peer group' and to its slave vfsmounts.

    Strictly speaking, the vfsmount is shared having its own
    peer group, and this peer-group is a slave of some other
    peer group.

    Only a slave vfsmount can be made as 'shared and slave' by
    either executing the following command::

      mount --make-shared mount

    or by moving the slave vfsmount under a shared vfsmount.

(4) Private mount

    A **private mount** is defined as vfsmount that does not
    receive or forward any propagation events.

(5) Unbindable mount

    A **unbindable mount** is defined as vfsmount that does not
    receive or forward any propagation events and cannot
    be bind mounted.


    State diagram:

    The state diagram below explains the state transition of a mount,
    in response to various commands::

         -----------------------------------------------------------------------
         |             |make-shared |  make-slave  | make-private |make-unbindab|
         --------------|------------|--------------|--------------|-------------|
         |shared       |shared      |*slave/private|   private    | unbindable  |
         |             |            |              |              |             |
         |-------------|------------|--------------|--------------|-------------|
         |slave        |shared      | **slave      |    private   | unbindable  |
         |             |and slave   |              |              |             |
         |-------------|------------|--------------|--------------|-------------|
         |shared       |shared      | slave        |    private   | unbindable  |
         |and slave    |and slave   |              |              |             |
         |-------------|------------|--------------|--------------|-------------|
         |private      |shared      |  **private   |    private   | unbindable  |
         |-------------|------------|--------------|--------------|-------------|
         |unbindable   |shared      |**unbindable  |    private   | unbindable  |
         ------------------------------------------------------------------------

         * if the shared mount is the only mount in its peer group, making it
         slave, makes it private automatically. Note that there is no master to
         which it can be slaved to.

         ** slaving a non-shared mount has no effect on the mount.

    Apart from the commands listed below, the 'move' operation also changes
    the state of a mount depending on type of the destination mount. Its
    explained in section 5d.
”h]”(hý)”}”(hŒMount states”h]”hŒMount states”…””}”(hjÝ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KúhjÙ  ubhý)”}”(hŒ~A **propagation event** is defined as event generated on a vfsmount
that leads to mount or unmount actions in other vfsmounts.”h]”(hŒA ”…””}”(hjë  h²hh³Nh´Nubjc  )”}”(hŒ**propagation event**”h]”hŒpropagation event”…””}”(hjó  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hjë  ubhŒg is defined as event generated on a vfsmount
that leads to mount or unmount actions in other vfsmounts.”…””}”(hjë  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KühjÙ  ubhý)”}”(hŒXA **peer group** is defined as a group of vfsmounts that propagate
events to each other.”h]”(hŒA ”…””}”(hj  h²hh³Nh´Nubjc  )”}”(hŒ**peer group**”h]”hŒ
peer group”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj  ubhŒH is defined as a group of vfsmounts that propagate
events to each other.”…””}”(hj  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´KÿhjÙ  ubhý)”}”(hŒ4A given mount can be in one of the following states:”h]”hŒ4A given mount can be in one of the following states:”…””}”(hj+  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MhjÙ  ubjP  )”}”(hhh]”(jU  )”}”(hXY  Shared mounts

A **shared mount** is defined as a vfsmount that belongs to a
peer group.

For example::

  mount --make-shared /mnt
  mount --bind /mnt /tmp

The mount at /mnt and that at /tmp are both shared and belong
to the same peer group. Anything mounted or unmounted under
/mnt or /tmp reflect in all the other mounts of its peer
group.

”h]”(hý)”}”(hŒShared mounts”h]”hŒShared mounts”…””}”(hj@  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhj<  ubhý)”}”(hŒIA **shared mount** is defined as a vfsmount that belongs to a
peer group.”h]”(hŒA ”…””}”(hjN  h²hh³Nh´Nubjc  )”}”(hŒ**shared mount**”h]”hŒshared mount”…””}”(hjV  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hjN  ubhŒ7 is defined as a vfsmount that belongs to a
peer group.”…””}”(hjN  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhj<  ubhý)”}”(hŒFor example::”h]”hŒFor example:”…””}”(hjn  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M	hj<  ubj™  )”}”(hŒ/mount --make-shared /mnt
mount --bind /mnt /tmp”h]”hŒ/mount --make-shared /mnt
mount --bind /mnt /tmp”…””}”hj|  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Mhj<  ubhý)”}”(hŒ¹The mount at /mnt and that at /tmp are both shared and belong
to the same peer group. Anything mounted or unmounted under
/mnt or /tmp reflect in all the other mounts of its peer
group.”h]”hŒ¹The mount at /mnt and that at /tmp are both shared and belong
to the same peer group. Anything mounted or unmounted under
/mnt or /tmp reflect in all the other mounts of its peer
group.”…””}”(hjŠ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhj<  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj9  ubjU  )”}”(hXé  Slave mounts

A **slave mount** is defined as a vfsmount that receives
propagation events and does not forward propagation events.

A slave mount as the name implies has a master mount from which
mount/unmount events are received. Events do not propagate from
the slave mount to the master.  Only a shared mount can be made
a slave by executing the following command::

  mount --make-slave mount

A shared mount that is made as a slave is no more shared unless
modified to become shared.
”h]”(hý)”}”(hŒSlave mounts”h]”hŒSlave mounts”…””}”(hj¢  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhjž  ubhý)”}”(hŒtA **slave mount** is defined as a vfsmount that receives
propagation events and does not forward propagation events.”h]”(hŒA ”…””}”(hj°  h²hh³Nh´Nubjc  )”}”(hŒ**slave mount**”h]”hŒslave mount”…””}”(hj¸  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj°  ubhŒc is defined as a vfsmount that receives
propagation events and does not forward propagation events.”…””}”(hj°  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhjž  ubhý)”}”(hŒìA slave mount as the name implies has a master mount from which
mount/unmount events are received. Events do not propagate from
the slave mount to the master.  Only a shared mount can be made
a slave by executing the following command::”h]”hŒëA slave mount as the name implies has a master mount from which
mount/unmount events are received. Events do not propagate from
the slave mount to the master.  Only a shared mount can be made
a slave by executing the following command:”…””}”(hjÐ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhjž  ubj™  )”}”(hŒmount --make-slave mount”h]”hŒmount --make-slave mount”…””}”hjÞ  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Mhjž  ubhý)”}”(hŒZA shared mount that is made as a slave is no more shared unless
modified to become shared.”h]”hŒZA shared mount that is made as a slave is no more shared unless
modified to become shared.”…””}”(hjì  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M hjž  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj9  ubjU  )”}”(hX  Shared and Slave

A vfsmount can be both **shared** as well as **slave**.  This state
indicates that the mount is a slave of some vfsmount, and
has its own peer group too.  This vfsmount receives propagation
events from its master vfsmount, and also forwards propagation
events to its 'peer group' and to its slave vfsmounts.

Strictly speaking, the vfsmount is shared having its own
peer group, and this peer-group is a slave of some other
peer group.

Only a slave vfsmount can be made as 'shared and slave' by
either executing the following command::

  mount --make-shared mount

or by moving the slave vfsmount under a shared vfsmount.
”h]”(hý)”}”(hŒShared and Slave”h]”hŒShared and Slave”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M#hj   ubhý)”}”(hX3  A vfsmount can be both **shared** as well as **slave**.  This state
indicates that the mount is a slave of some vfsmount, and
has its own peer group too.  This vfsmount receives propagation
events from its master vfsmount, and also forwards propagation
events to its 'peer group' and to its slave vfsmounts.”h]”(hŒA vfsmount can be both ”…””}”(hj  h²hh³Nh´Nubjc  )”}”(hŒ
**shared**”h]”hŒshared”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj  ubhŒ as well as ”…””}”(hj  h²hh³Nh´Nubjc  )”}”(hŒ	**slave**”h]”hŒslave”…””}”(hj,  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj  ubhX  .  This state
indicates that the mount is a slave of some vfsmount, and
has its own peer group too.  This vfsmount receives propagation
events from its master vfsmount, and also forwards propagation
events to its â€˜peer groupâ€™ and to its slave vfsmounts.”…””}”(hj  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M%hj   ubhý)”}”(hŒ}Strictly speaking, the vfsmount is shared having its own
peer group, and this peer-group is a slave of some other
peer group.”h]”hŒ}Strictly speaking, the vfsmount is shared having its own
peer group, and this peer-group is a slave of some other
peer group.”…””}”(hjD  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M+hj   ubhý)”}”(hŒcOnly a slave vfsmount can be made as 'shared and slave' by
either executing the following command::”h]”hŒfOnly a slave vfsmount can be made as â€˜shared and slaveâ€™ by
either executing the following command:”…””}”(hjR  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M/hj   ubj™  )”}”(hŒmount --make-shared mount”h]”hŒmount --make-shared mount”…””}”hj`  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´M2hj   ubhý)”}”(hŒ8or by moving the slave vfsmount under a shared vfsmount.”h]”hŒ8or by moving the slave vfsmount under a shared vfsmount.”…””}”(hjn  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M4hj   ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj9  ubjU  )”}”(hŒsPrivate mount

A **private mount** is defined as vfsmount that does not
receive or forward any propagation events.
”h]”(hý)”}”(hŒPrivate mount”h]”hŒPrivate mount”…””}”(hj†  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M6hj‚  ubhý)”}”(hŒcA **private mount** is defined as vfsmount that does not
receive or forward any propagation events.”h]”(hŒA ”…””}”(hj”  h²hh³Nh´Nubjc  )”}”(hŒ**private mount**”h]”hŒprivate mount”…””}”(hjœ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj”  ubhŒP is defined as vfsmount that does not
receive or forward any propagation events.”…””}”(hj”  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M8hj‚  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj9  ubjU  )”}”(hXˆ  Unbindable mount

A **unbindable mount** is defined as vfsmount that does not
receive or forward any propagation events and cannot
be bind mounted.


State diagram:

The state diagram below explains the state transition of a mount,
in response to various commands::

     -----------------------------------------------------------------------
     |             |make-shared |  make-slave  | make-private |make-unbindab|
     --------------|------------|--------------|--------------|-------------|
     |shared       |shared      |*slave/private|   private    | unbindable  |
     |             |            |              |              |             |
     |-------------|------------|--------------|--------------|-------------|
     |slave        |shared      | **slave      |    private   | unbindable  |
     |             |and slave   |              |              |             |
     |-------------|------------|--------------|--------------|-------------|
     |shared       |shared      | slave        |    private   | unbindable  |
     |and slave    |and slave   |              |              |             |
     |-------------|------------|--------------|--------------|-------------|
     |private      |shared      |  **private   |    private   | unbindable  |
     |-------------|------------|--------------|--------------|-------------|
     |unbindable   |shared      |**unbindable  |    private   | unbindable  |
     ------------------------------------------------------------------------

     * if the shared mount is the only mount in its peer group, making it
     slave, makes it private automatically. Note that there is no master to
     which it can be slaved to.

     ** slaving a non-shared mount has no effect on the mount.

Apart from the commands listed below, the 'move' operation also changes
the state of a mount depending on type of the destination mount. Its
explained in section 5d.
”h]”(hý)”}”(hŒUnbindable mount”h]”hŒUnbindable mount”…””}”(hj¾  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M;hjº  ubhý)”}”(hŒA **unbindable mount** is defined as vfsmount that does not
receive or forward any propagation events and cannot
be bind mounted.”h]”(hŒA ”…””}”(hjÌ  h²hh³Nh´Nubjc  )”}”(hŒ**unbindable mount**”h]”hŒunbindable mount”…””}”(hjÔ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hjÌ  ubhŒk is defined as vfsmount that does not
receive or forward any propagation events and cannot
be bind mounted.”…””}”(hjÌ  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M=hjº  ubhý)”}”(hŒState diagram:”h]”hŒState diagram:”…””}”(hjì  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MBhjº  ubhý)”}”(hŒcThe state diagram below explains the state transition of a mount,
in response to various commands::”h]”hŒbThe state diagram below explains the state transition of a mount,
in response to various commands:”…””}”(hjú  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MDhjº  ubj™  )”}”(hXq  -----------------------------------------------------------------------
|             |make-shared |  make-slave  | make-private |make-unbindab|
--------------|------------|--------------|--------------|-------------|
|shared       |shared      |*slave/private|   private    | unbindable  |
|             |            |              |              |             |
|-------------|------------|--------------|--------------|-------------|
|slave        |shared      | **slave      |    private   | unbindable  |
|             |and slave   |              |              |             |
|-------------|------------|--------------|--------------|-------------|
|shared       |shared      | slave        |    private   | unbindable  |
|and slave    |and slave   |              |              |             |
|-------------|------------|--------------|--------------|-------------|
|private      |shared      |  **private   |    private   | unbindable  |
|-------------|------------|--------------|--------------|-------------|
|unbindable   |shared      |**unbindable  |    private   | unbindable  |
------------------------------------------------------------------------

* if the shared mount is the only mount in its peer group, making it
slave, makes it private automatically. Note that there is no master to
which it can be slaved to.

** slaving a non-shared mount has no effect on the mount.”h]”hXq  -----------------------------------------------------------------------
|             |make-shared |  make-slave  | make-private |make-unbindab|
--------------|------------|--------------|--------------|-------------|
|shared       |shared      |*slave/private|   private    | unbindable  |
|             |            |              |              |             |
|-------------|------------|--------------|--------------|-------------|
|slave        |shared      | **slave      |    private   | unbindable  |
|             |and slave   |              |              |             |
|-------------|------------|--------------|--------------|-------------|
|shared       |shared      | slave        |    private   | unbindable  |
|and slave    |and slave   |              |              |             |
|-------------|------------|--------------|--------------|-------------|
|private      |shared      |  **private   |    private   | unbindable  |
|-------------|------------|--------------|--------------|-------------|
|unbindable   |shared      |**unbindable  |    private   | unbindable  |
------------------------------------------------------------------------

* if the shared mount is the only mount in its peer group, making it
slave, makes it private automatically. Note that there is no master to
which it can be slaved to.

** slaving a non-shared mount has no effect on the mount.”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´MGhjº  ubhý)”}”(hŒ¥Apart from the commands listed below, the 'move' operation also changes
the state of a mount depending on type of the destination mount. Its
explained in section 5d.”h]”hŒ©Apart from the commands listed below, the â€˜moveâ€™ operation also changes
the state of a mount depending on type of the destination mount. Its
explained in section 5d.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M^hjº  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj9  ubeh}”(h]”h ]”h"]”h$]”h&]”jÔ  Œarabic”jÖ  Œ(”j×  jØ  uh1jO  hjÙ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjÖ  h²hh³Nh´NubjU  )”}”(hXæ  Bind semantics

Consider the following command::

  mount --bind A/a  B/b

where 'A' is the source mount, 'a' is the dentry in the mount 'A', 'B'
is the destination mount and 'b' is the dentry in the destination mount.

The outcome depends on the type of mount of 'A' and 'B'. The table
below contains quick reference::

         --------------------------------------------------------------------------
         |         BIND MOUNT OPERATION                                           |
         |************************************************************************|
         |source(A)->| shared      |       private  |       slave    | unbindable |
         | dest(B)  |              |                |                |            |
         |   |      |              |                |                |            |
         |   v      |              |                |                |            |
         |************************************************************************|
         |  shared  | shared       |     shared     | shared & slave |  invalid   |
         |          |              |                |                |            |
         |non-shared| shared       |      private   |      slave     |  invalid   |
         **************************************************************************

Details:

1. 'A' is a shared mount and 'B' is a shared mount. A new mount 'C'
   which is clone of 'A', is created. Its root dentry is 'a' . 'C' is
   mounted on mount 'B' at dentry 'b'. Also new mount 'C1', 'C2', 'C3' ...
   are created and mounted at the dentry 'b' on all mounts where 'B'
   propagates to. A new propagation tree containing 'C1',..,'Cn' is
   created. This propagation tree is identical to the propagation tree of
   'B'.  And finally the peer-group of 'C' is merged with the peer group
   of 'A'.

2. 'A' is a private mount and 'B' is a shared mount. A new mount 'C'
   which is clone of 'A', is created. Its root dentry is 'a'. 'C' is
   mounted on mount 'B' at dentry 'b'. Also new mount 'C1', 'C2', 'C3' ...
   are created and mounted at the dentry 'b' on all mounts where 'B'
   propagates to. A new propagation tree is set containing all new mounts
   'C', 'C1', .., 'Cn' with exactly the same configuration as the
   propagation tree for 'B'.

3. 'A' is a slave mount of mount 'Z' and 'B' is a shared mount. A new
   mount 'C' which is clone of 'A', is created. Its root dentry is 'a' .
   'C' is mounted on mount 'B' at dentry 'b'. Also new mounts 'C1', 'C2',
   'C3' ... are created and mounted at the dentry 'b' on all mounts where
   'B' propagates to. A new propagation tree containing the new mounts
   'C','C1',..  'Cn' is created. This propagation tree is identical to the
   propagation tree for 'B'. And finally the mount 'C' and its peer group
   is made the slave of mount 'Z'.  In other words, mount 'C' is in the
   state 'slave and shared'.

4. 'A' is a unbindable mount and 'B' is a shared mount. This is a
   invalid operation.

5. 'A' is a private mount and 'B' is a non-shared(private or slave or
   unbindable) mount. A new mount 'C' which is clone of 'A', is created.
   Its root dentry is 'a'. 'C' is mounted on mount 'B' at dentry 'b'.

6. 'A' is a shared mount and 'B' is a non-shared mount. A new mount 'C'
   which is a clone of 'A' is created. Its root dentry is 'a'. 'C' is
   mounted on mount 'B' at dentry 'b'.  'C' is made a member of the
   peer-group of 'A'.

7. 'A' is a slave mount of mount 'Z' and 'B' is a non-shared mount. A
   new mount 'C' which is a clone of 'A' is created. Its root dentry is
   'a'.  'C' is mounted on mount 'B' at dentry 'b'. Also 'C' is set as a
   slave mount of 'Z'. In other words 'A' and 'C' are both slave mounts of
   'Z'.  All mount/unmount events on 'Z' propagates to 'A' and 'C'. But
   mount/unmount on 'A' do not propagate anywhere else. Similarly
   mount/unmount on 'C' do not propagate anywhere else.

8. 'A' is a unbindable mount and 'B' is a non-shared mount. This is a
   invalid operation. A unbindable mount cannot be bind mounted.
”h]”(hý)”}”(hŒBind semantics”h]”hŒBind semantics”…””}”(hj<  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mbhj8  ubhý)”}”(hŒ Consider the following command::”h]”hŒConsider the following command:”…””}”(hjJ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mdhj8  ubj™  )”}”(hŒmount --bind A/a  B/b”h]”hŒmount --bind A/a  B/b”…””}”hjX  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Mfhj8  ubhý)”}”(hŒwhere 'A' is the source mount, 'a' is the dentry in the mount 'A', 'B'
is the destination mount and 'b' is the dentry in the destination mount.”h]”hŒ£where â€˜Aâ€™ is the source mount, â€˜aâ€™ is the dentry in the mount â€˜Aâ€™, â€˜Bâ€™
is the destination mount and â€˜bâ€™ is the dentry in the destination mount.”…””}”(hjf  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhhj8  ubhý)”}”(hŒcThe outcome depends on the type of mount of 'A' and 'B'. The table
below contains quick reference::”h]”hŒjThe outcome depends on the type of mount of â€˜Aâ€™ and â€˜Bâ€™. The table
below contains quick reference:”…””}”(hjt  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mkhj8  ubj™  )”}”(hXƒ  --------------------------------------------------------------------------
|         BIND MOUNT OPERATION                                           |
|************************************************************************|
|source(A)->| shared      |       private  |       slave    | unbindable |
| dest(B)  |              |                |                |            |
|   |      |              |                |                |            |
|   v      |              |                |                |            |
|************************************************************************|
|  shared  | shared       |     shared     | shared & slave |  invalid   |
|          |              |                |                |            |
|non-shared| shared       |      private   |      slave     |  invalid   |
**************************************************************************”h]”hXƒ  --------------------------------------------------------------------------
|         BIND MOUNT OPERATION                                           |
|************************************************************************|
|source(A)->| shared      |       private  |       slave    | unbindable |
| dest(B)  |              |                |                |            |
|   |      |              |                |                |            |
|   v      |              |                |                |            |
|************************************************************************|
|  shared  | shared       |     shared     | shared & slave |  invalid   |
|          |              |                |                |            |
|non-shared| shared       |      private   |      slave     |  invalid   |
**************************************************************************”…””}”hj‚  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Mnhj8  ubhý)”}”(hŒDetails:”h]”hŒDetails:”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M{hj8  ubjP  )”}”(hhh]”(jU  )”}”(hXä  'A' is a shared mount and 'B' is a shared mount. A new mount 'C'
which is clone of 'A', is created. Its root dentry is 'a' . 'C' is
mounted on mount 'B' at dentry 'b'. Also new mount 'C1', 'C2', 'C3' ...
are created and mounted at the dentry 'b' on all mounts where 'B'
propagates to. A new propagation tree containing 'C1',..,'Cn' is
created. This propagation tree is identical to the propagation tree of
'B'.  And finally the peer-group of 'C' is merged with the peer group
of 'A'.
”h]”hý)”}”(hXã  'A' is a shared mount and 'B' is a shared mount. A new mount 'C'
which is clone of 'A', is created. Its root dentry is 'a' . 'C' is
mounted on mount 'B' at dentry 'b'. Also new mount 'C1', 'C2', 'C3' ...
are created and mounted at the dentry 'b' on all mounts where 'B'
propagates to. A new propagation tree containing 'C1',..,'Cn' is
created. This propagation tree is identical to the propagation tree of
'B'.  And finally the peer-group of 'C' is merged with the peer group
of 'A'.”h]”hX+  â€˜Aâ€™ is a shared mount and â€˜Bâ€™ is a shared mount. A new mount â€˜Câ€™
which is clone of â€˜Aâ€™, is created. Its root dentry is â€˜aâ€™ . â€˜Câ€™ is
mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™. Also new mount â€˜C1â€™, â€˜C2â€™, â€˜C3â€™ ...
are created and mounted at the dentry â€˜bâ€™ on all mounts where â€˜Bâ€™
propagates to. A new propagation tree containing â€˜C1â€™,..,â€™Cnâ€™ is
created. This propagation tree is identical to the propagation tree of
â€˜Bâ€™.  And finally the peer-group of â€˜Câ€™ is merged with the peer group
of â€˜Aâ€™.”…””}”(hj¥  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M}hj¡  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjž  ubjU  )”}”(hX®  'A' is a private mount and 'B' is a shared mount. A new mount 'C'
which is clone of 'A', is created. Its root dentry is 'a'. 'C' is
mounted on mount 'B' at dentry 'b'. Also new mount 'C1', 'C2', 'C3' ...
are created and mounted at the dentry 'b' on all mounts where 'B'
propagates to. A new propagation tree is set containing all new mounts
'C', 'C1', .., 'Cn' with exactly the same configuration as the
propagation tree for 'B'.
”h]”hý)”}”(hX­  'A' is a private mount and 'B' is a shared mount. A new mount 'C'
which is clone of 'A', is created. Its root dentry is 'a'. 'C' is
mounted on mount 'B' at dentry 'b'. Also new mount 'C1', 'C2', 'C3' ...
are created and mounted at the dentry 'b' on all mounts where 'B'
propagates to. A new propagation tree is set containing all new mounts
'C', 'C1', .., 'Cn' with exactly the same configuration as the
propagation tree for 'B'.”h]”hXñ  â€˜Aâ€™ is a private mount and â€˜Bâ€™ is a shared mount. A new mount â€˜Câ€™
which is clone of â€˜Aâ€™, is created. Its root dentry is â€˜aâ€™. â€˜Câ€™ is
mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™. Also new mount â€˜C1â€™, â€˜C2â€™, â€˜C3â€™ ...
are created and mounted at the dentry â€˜bâ€™ on all mounts where â€˜Bâ€™
propagates to. A new propagation tree is set containing all new mounts
â€˜Câ€™, â€˜C1â€™, .., â€˜Cnâ€™ with exactly the same configuration as the
propagation tree for â€˜Bâ€™.”…””}”(hj½  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M†hj¹  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjž  ubjU  )”}”(hXI  'A' is a slave mount of mount 'Z' and 'B' is a shared mount. A new
mount 'C' which is clone of 'A', is created. Its root dentry is 'a' .
'C' is mounted on mount 'B' at dentry 'b'. Also new mounts 'C1', 'C2',
'C3' ... are created and mounted at the dentry 'b' on all mounts where
'B' propagates to. A new propagation tree containing the new mounts
'C','C1',..  'Cn' is created. This propagation tree is identical to the
propagation tree for 'B'. And finally the mount 'C' and its peer group
is made the slave of mount 'Z'.  In other words, mount 'C' is in the
state 'slave and shared'.
”h]”hý)”}”(hXH  'A' is a slave mount of mount 'Z' and 'B' is a shared mount. A new
mount 'C' which is clone of 'A', is created. Its root dentry is 'a' .
'C' is mounted on mount 'B' at dentry 'b'. Also new mounts 'C1', 'C2',
'C3' ... are created and mounted at the dentry 'b' on all mounts where
'B' propagates to. A new propagation tree containing the new mounts
'C','C1',..  'Cn' is created. This propagation tree is identical to the
propagation tree for 'B'. And finally the mount 'C' and its peer group
is made the slave of mount 'Z'.  In other words, mount 'C' is in the
state 'slave and shared'.”h]”hX   â€˜Aâ€™ is a slave mount of mount â€˜Zâ€™ and â€˜Bâ€™ is a shared mount. A new
mount â€˜Câ€™ which is clone of â€˜Aâ€™, is created. Its root dentry is â€˜aâ€™ .
â€˜Câ€™ is mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™. Also new mounts â€˜C1â€™, â€˜C2â€™,
â€˜C3â€™ ... are created and mounted at the dentry â€˜bâ€™ on all mounts where
â€˜Bâ€™ propagates to. A new propagation tree containing the new mounts
â€˜Câ€™,â€™C1â€™,..  â€˜Cnâ€™ is created. This propagation tree is identical to the
propagation tree for â€˜Bâ€™. And finally the mount â€˜Câ€™ and its peer group
is made the slave of mount â€˜Zâ€™.  In other words, mount â€˜Câ€™ is in the
state â€˜slave and sharedâ€™.”…””}”(hjÕ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MŽhjÑ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjž  ubjU  )”}”(hŒR'A' is a unbindable mount and 'B' is a shared mount. This is a
invalid operation.
”h]”hý)”}”(hŒQ'A' is a unbindable mount and 'B' is a shared mount. This is a
invalid operation.”h]”hŒYâ€˜Aâ€™ is a unbindable mount and â€˜Bâ€™ is a shared mount. This is a
invalid operation.”…””}”(hjí  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M˜hjé  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjž  ubjU  )”}”(hŒÌ'A' is a private mount and 'B' is a non-shared(private or slave or
unbindable) mount. A new mount 'C' which is clone of 'A', is created.
Its root dentry is 'a'. 'C' is mounted on mount 'B' at dentry 'b'.
”h]”hý)”}”(hŒË'A' is a private mount and 'B' is a non-shared(private or slave or
unbindable) mount. A new mount 'C' which is clone of 'A', is created.
Its root dentry is 'a'. 'C' is mounted on mount 'B' at dentry 'b'.”h]”hŒëâ€˜Aâ€™ is a private mount and â€˜Bâ€™ is a non-shared(private or slave or
unbindable) mount. A new mount â€˜Câ€™ which is clone of â€˜Aâ€™, is created.
Its root dentry is â€˜aâ€™. â€˜Câ€™ is mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™.”…””}”(hj	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M›hj	  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjž  ubjU  )”}”(hŒÜ'A' is a shared mount and 'B' is a non-shared mount. A new mount 'C'
which is a clone of 'A' is created. Its root dentry is 'a'. 'C' is
mounted on mount 'B' at dentry 'b'.  'C' is made a member of the
peer-group of 'A'.
”h]”hý)”}”(hŒÛ'A' is a shared mount and 'B' is a non-shared mount. A new mount 'C'
which is a clone of 'A' is created. Its root dentry is 'a'. 'C' is
mounted on mount 'B' at dentry 'b'.  'C' is made a member of the
peer-group of 'A'.”h]”hX  â€˜Aâ€™ is a shared mount and â€˜Bâ€™ is a non-shared mount. A new mount â€˜Câ€™
which is a clone of â€˜Aâ€™ is created. Its root dentry is â€˜aâ€™. â€˜Câ€™ is
mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™.  â€˜Câ€™ is made a member of the
peer-group of â€˜Aâ€™.”…””}”(hj	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MŸhj	  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjž  ubjU  )”}”(hXÏ  'A' is a slave mount of mount 'Z' and 'B' is a non-shared mount. A
new mount 'C' which is a clone of 'A' is created. Its root dentry is
'a'.  'C' is mounted on mount 'B' at dentry 'b'. Also 'C' is set as a
slave mount of 'Z'. In other words 'A' and 'C' are both slave mounts of
'Z'.  All mount/unmount events on 'Z' propagates to 'A' and 'C'. But
mount/unmount on 'A' do not propagate anywhere else. Similarly
mount/unmount on 'C' do not propagate anywhere else.
”h]”hý)”}”(hXÎ  'A' is a slave mount of mount 'Z' and 'B' is a non-shared mount. A
new mount 'C' which is a clone of 'A' is created. Its root dentry is
'a'.  'C' is mounted on mount 'B' at dentry 'b'. Also 'C' is set as a
slave mount of 'Z'. In other words 'A' and 'C' are both slave mounts of
'Z'.  All mount/unmount events on 'Z' propagates to 'A' and 'C'. But
mount/unmount on 'A' do not propagate anywhere else. Similarly
mount/unmount on 'C' do not propagate anywhere else.”h]”hX  â€˜Aâ€™ is a slave mount of mount â€˜Zâ€™ and â€˜Bâ€™ is a non-shared mount. A
new mount â€˜Câ€™ which is a clone of â€˜Aâ€™ is created. Its root dentry is
â€˜aâ€™.  â€˜Câ€™ is mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™. Also â€˜Câ€™ is set as a
slave mount of â€˜Zâ€™. In other words â€˜Aâ€™ and â€˜Câ€™ are both slave mounts of
â€˜Zâ€™.  All mount/unmount events on â€˜Zâ€™ propagates to â€˜Aâ€™ and â€˜Câ€™. But
mount/unmount on â€˜Aâ€™ do not propagate anywhere else. Similarly
mount/unmount on â€˜Câ€™ do not propagate anywhere else.”…””}”(hj5	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¤hj1	  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjž  ubjU  )”}”(hŒ'A' is a unbindable mount and 'B' is a non-shared mount. This is a
invalid operation. A unbindable mount cannot be bind mounted.
”h]”hý)”}”(hŒ€'A' is a unbindable mount and 'B' is a non-shared mount. This is a
invalid operation. A unbindable mount cannot be bind mounted.”h]”hŒˆâ€˜Aâ€™ is a unbindable mount and â€˜Bâ€™ is a non-shared mount. This is a
invalid operation. A unbindable mount cannot be bind mounted.”…””}”(hjM	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¬hjI	  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjž  ubeh}”(h]”h ]”h"]”h$]”h&]”jÔ  j0  jÖ  hj×  Œ.”uh1jO  hj8  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjÖ  h²hh³Nh´NubjU  )”}”(hXe  Rbind semantics

rbind is same as bind. Bind replicates the specified mount.  Rbind
replicates all the mounts in the tree belonging to the specified mount.
Rbind mount is bind mount applied to all the mounts in the tree.

If the source tree that is rbind has some unbindable mounts,
then the subtree under the unbindable mount is pruned in the new
location.

eg:

let's say we have the following mount tree::

             A
           /   \
           B   C
          / \ / \
          D E F G

Let's say all the mount except the mount C in the tree are
of a type other than unbindable.

If this tree is rbound to say Z

We will have the following tree at the new location::

             Z
             |
             A'
            /
           B'                Note how the tree under C is pruned
          / \                in the new location.
         D' E'


”h]”(hý)”}”(hŒRbind semantics”h]”hŒRbind semantics”…””}”(hjr	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¯hjn	  ubhý)”}”(hŒËrbind is same as bind. Bind replicates the specified mount.  Rbind
replicates all the mounts in the tree belonging to the specified mount.
Rbind mount is bind mount applied to all the mounts in the tree.”h]”hŒËrbind is same as bind. Bind replicates the specified mount.  Rbind
replicates all the mounts in the tree belonging to the specified mount.
Rbind mount is bind mount applied to all the mounts in the tree.”…””}”(hj€	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M±hjn	  ubhý)”}”(hŒ‡If the source tree that is rbind has some unbindable mounts,
then the subtree under the unbindable mount is pruned in the new
location.”h]”hŒ‡If the source tree that is rbind has some unbindable mounts,
then the subtree under the unbindable mount is pruned in the new
location.”…””}”(hjŽ	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mµhjn	  ubhý)”}”(hŒeg:”h]”hŒeg:”…””}”(hjœ	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¹hjn	  ubhý)”}”(hŒ,let's say we have the following mount tree::”h]”hŒ-letâ€™s say we have the following mount tree:”…””}”(hjª	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M»hjn	  ubj™  )”}”(hŒ"   A
 /   \
 B   C
/ \ / \
D E F G”h]”hŒ"   A
 /   \
 B   C
/ \ / \
D E F G”…””}”hj¸	  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´M½hjn	  ubhý)”}”(hŒ[Let's say all the mount except the mount C in the tree are
of a type other than unbindable.”h]”hŒ]Letâ€™s say all the mount except the mount C in the tree are
of a type other than unbindable.”…””}”(hjÆ	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÃhjn	  ubhý)”}”(hŒIf this tree is rbound to say Z”h]”hŒIf this tree is rbound to say Z”…””••     }”(hjÔ	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÆhjn	  ubhý)”}”(hŒ5We will have the following tree at the new location::”h]”hŒ4We will have the following tree at the new location:”…””}”(hjâ	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÈhjn	  ubj™  )”}”(hŒ~    Z
    |
    A'
   /
  B'                Note how the tree under C is pruned
 / \                in the new location.
D' E'”h]”hŒ~    Z
    |
    A'
   /
  B'                Note how the tree under C is pruned
 / \                in the new location.
D' E'”…””}”hjð	  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´MÊhjn	  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjÖ  h²hh³hÇh´NubjU  )”}”(hXH  Move semantics

Consider the following command::

  mount --move A  B/b

where 'A' is the source mount, 'B' is the destination mount and 'b' is
the dentry in the destination mount.

The outcome depends on the type of the mount of 'A' and 'B'. The table
below is a quick reference::

         ---------------------------------------------------------------------------
         |                   MOVE MOUNT OPERATION                                 |
         |**************************************************************************
         | source(A)->| shared      |       private  |       slave    | unbindable |
         | dest(B)  |               |                |                |            |
         |   |      |               |                |                |            |
         |   v      |               |                |                |            |
         |**************************************************************************
         |  shared  | shared        |     shared     |shared and slave|  invalid   |
         |          |               |                |                |            |
         |non-shared| shared        |      private   |    slave       | unbindable |
         ***************************************************************************

.. Note:: moving a mount residing under a shared mount is invalid.

Details follow:

1. 'A' is a shared mount and 'B' is a shared mount.  The mount 'A' is
   mounted on mount 'B' at dentry 'b'.  Also new mounts 'A1', 'A2'...'An'
   are created and mounted at dentry 'b' on all mounts that receive
   propagation from mount 'B'. A new propagation tree is created in the
   exact same configuration as that of 'B'. This new propagation tree
   contains all the new mounts 'A1', 'A2'...  'An'.  And this new
   propagation tree is appended to the already existing propagation tree
   of 'A'.

2. 'A' is a private mount and 'B' is a shared mount. The mount 'A' is
   mounted on mount 'B' at dentry 'b'. Also new mount 'A1', 'A2'... 'An'
   are created and mounted at dentry 'b' on all mounts that receive
   propagation from mount 'B'. The mount 'A' becomes a shared mount and a
   propagation tree is created which is identical to that of
   'B'. This new propagation tree contains all the new mounts 'A1',
   'A2'...  'An'.

3. 'A' is a slave mount of mount 'Z' and 'B' is a shared mount.  The
   mount 'A' is mounted on mount 'B' at dentry 'b'.  Also new mounts 'A1',
   'A2'... 'An' are created and mounted at dentry 'b' on all mounts that
   receive propagation from mount 'B'. A new propagation tree is created
   in the exact same configuration as that of 'B'. This new propagation
   tree contains all the new mounts 'A1', 'A2'...  'An'.  And this new
   propagation tree is appended to the already existing propagation tree of
   'A'.  Mount 'A' continues to be the slave mount of 'Z' but it also
   becomes 'shared'.

4. 'A' is a unbindable mount and 'B' is a shared mount. The operation
   is invalid. Because mounting anything on the shared mount 'B' can
   create new mounts that get mounted on the mounts that receive
   propagation from 'B'.  And since the mount 'A' is unbindable, cloning
   it to mount at other mountpoints is not possible.

5. 'A' is a private mount and 'B' is a non-shared(private or slave or
   unbindable) mount. The mount 'A' is mounted on mount 'B' at dentry 'b'.

6. 'A' is a shared mount and 'B' is a non-shared mount.  The mount 'A'
   is mounted on mount 'B' at dentry 'b'.  Mount 'A' continues to be a
   shared mount.

7. 'A' is a slave mount of mount 'Z' and 'B' is a non-shared mount.
   The mount 'A' is mounted on mount 'B' at dentry 'b'.  Mount 'A'
   continues to be a slave mount of mount 'Z'.

8. 'A' is a unbindable mount and 'B' is a non-shared mount. The mount
   'A' is mounted on mount 'B' at dentry 'b'. Mount 'A' continues to be a
   unbindable mount.
”h]”(hý)”}”(hŒMove semantics”h]”hŒMove semantics”…””}”(hj
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÔhj
  ubhý)”}”(hŒ Consider the following command::”h]”hŒConsider the following command:”…””}”(hj
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÖhj
  ubj™  )”}”(hŒmount --move A  B/b”h]”hŒmount --move A  B/b”…””}”hj$
  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´MØhj
  ubhý)”}”(hŒkwhere 'A' is the source mount, 'B' is the destination mount and 'b' is
the dentry in the destination mount.”h]”hŒwwhere â€˜Aâ€™ is the source mount, â€˜Bâ€™ is the destination mount and â€˜bâ€™ is
the dentry in the destination mount.”…””}”(hj2
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÚhj
  ubhý)”}”(hŒcThe outcome depends on the type of the mount of 'A' and 'B'. The table
below is a quick reference::”h]”hŒjThe outcome depends on the type of the mount of â€˜Aâ€™ and â€˜Bâ€™. The table
below is a quick reference:”…””}”(hj@
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÝhj
  ubj™  )”}”(hXŽ  ---------------------------------------------------------------------------
|                   MOVE MOUNT OPERATION                                 |
|**************************************************************************
| source(A)->| shared      |       private  |       slave    | unbindable |
| dest(B)  |               |                |                |            |
|   |      |               |                |                |            |
|   v      |               |                |                |            |
|**************************************************************************
|  shared  | shared        |     shared     |shared and slave|  invalid   |
|          |               |                |                |            |
|non-shared| shared        |      private   |    slave       | unbindable |
***************************************************************************”h]”hXŽ  ---------------------------------------------------------------------------
|                   MOVE MOUNT OPERATION                                 |
|**************************************************************************
| source(A)->| shared      |       private  |       slave    | unbindable |
| dest(B)  |               |                |                |            |
|   |      |               |                |                |            |
|   v      |               |                |                |            |
|**************************************************************************
|  shared  | shared        |     shared     |shared and slave|  invalid   |
|          |               |                |                |            |
|non-shared| shared        |      private   |    slave       | unbindable |
***************************************************************************”…””}”hjN
  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Màhj
  ubj©  )”}”(hŒ8moving a mount residing under a shared mount is invalid.”h]”hý)”}”(hj^
  h]”hŒ8moving a mount residing under a shared mount is invalid.”…””}”(hj`
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Míhj\
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j¨  hj
  ubhý)”}”(hŒDetails follow:”h]”hŒDetails follow:”…””}”(hjs
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mïhj
  ubjP  )”}”(hhh]”(jU  )”}”(hXà  'A' is a shared mount and 'B' is a shared mount.  The mount 'A' is
mounted on mount 'B' at dentry 'b'.  Also new mounts 'A1', 'A2'...'An'
are created and mounted at dentry 'b' on all mounts that receive
propagation from mount 'B'. A new propagation tree is created in the
exact same configuration as that of 'B'. This new propagation tree
contains all the new mounts 'A1', 'A2'...  'An'.  And this new
propagation tree is appended to the already existing propagation tree
of 'A'.
”h]”hý)”}”(hXß  'A' is a shared mount and 'B' is a shared mount.  The mount 'A' is
mounted on mount 'B' at dentry 'b'.  Also new mounts 'A1', 'A2'...'An'
are created and mounted at dentry 'b' on all mounts that receive
propagation from mount 'B'. A new propagation tree is created in the
exact same configuration as that of 'B'. This new propagation tree
contains all the new mounts 'A1', 'A2'...  'An'.  And this new
propagation tree is appended to the already existing propagation tree
of 'A'.”h]”hX  â€˜Aâ€™ is a shared mount and â€˜Bâ€™ is a shared mount.  The mount â€˜Aâ€™ is
mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™.  Also new mounts â€˜A1â€™, â€˜A2â€™...â€™Anâ€™
are created and mounted at dentry â€˜bâ€™ on all mounts that receive
propagation from mount â€˜Bâ€™. A new propagation tree is created in the
exact same configuration as that of â€˜Bâ€™. This new propagation tree
contains all the new mounts â€˜A1â€™, â€˜A2â€™...  â€˜Anâ€™.  And this new
propagation tree is appended to the already existing propagation tree
of â€˜Aâ€™.”…””}”(hjˆ
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mñhj„
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj
  ubjU  )”}”(hX›  'A' is a private mount and 'B' is a shared mount. The mount 'A' is
mounted on mount 'B' at dentry 'b'. Also new mount 'A1', 'A2'... 'An'
are created and mounted at dentry 'b' on all mounts that receive
propagation from mount 'B'. The mount 'A' becomes a shared mount and a
propagation tree is created which is identical to that of
'B'. This new propagation tree contains all the new mounts 'A1',
'A2'...  'An'.
”h]”hý)”}”(hXš  'A' is a private mount and 'B' is a shared mount. The mount 'A' is
mounted on mount 'B' at dentry 'b'. Also new mount 'A1', 'A2'... 'An'
are created and mounted at dentry 'b' on all mounts that receive
propagation from mount 'B'. The mount 'A' becomes a shared mount and a
propagation tree is created which is identical to that of
'B'. This new propagation tree contains all the new mounts 'A1',
'A2'...  'An'.”h]”hXÖ  â€˜Aâ€™ is a private mount and â€˜Bâ€™ is a shared mount. The mount â€˜Aâ€™ is
mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™. Also new mount â€˜A1â€™, â€˜A2â€™... â€˜Anâ€™
are created and mounted at dentry â€˜bâ€™ on all mounts that receive
propagation from mount â€˜Bâ€™. The mount â€˜Aâ€™ becomes a shared mount and a
propagation tree is created which is identical to that of
â€˜Bâ€™. This new propagation tree contains all the new mounts â€˜A1â€™,
â€˜A2â€™...  â€˜Anâ€™.”…””}”(hj 
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Múhjœ
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj
  ubjU  )”}”(hX=  'A' is a slave mount of mount 'Z' and 'B' is a shared mount.  The
mount 'A' is mounted on mount 'B' at dentry 'b'.  Also new mounts 'A1',
'A2'... 'An' are created and mounted at dentry 'b' on all mounts that
receive propagation from mount 'B'. A new propagation tree is created
in the exact same configuration as that of 'B'. This new propagation
tree contains all the new mounts 'A1', 'A2'...  'An'.  And this new
propagation tree is appended to the already existing propagation tree of
'A'.  Mount 'A' continues to be the slave mount of 'Z' but it also
becomes 'shared'.
”h]”hý)”}”(hX<  'A' is a slave mount of mount 'Z' and 'B' is a shared mount.  The
mount 'A' is mounted on mount 'B' at dentry 'b'.  Also new mounts 'A1',
'A2'... 'An' are created and mounted at dentry 'b' on all mounts that
receive propagation from mount 'B'. A new propagation tree is created
in the exact same configuration as that of 'B'. This new propagation
tree contains all the new mounts 'A1', 'A2'...  'An'.  And this new
propagation tree is appended to the already existing propagation tree of
'A'.  Mount 'A' continues to be the slave mount of 'Z' but it also
becomes 'shared'.”h]”hXˆ  â€˜Aâ€™ is a slave mount of mount â€˜Zâ€™ and â€˜Bâ€™ is a shared mount.  The
mount â€˜Aâ€™ is mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™.  Also new mounts â€˜A1â€™,
â€˜A2â€™... â€˜Anâ€™ are created and mounted at dentry â€˜bâ€™ on all mounts that
receive propagation from mount â€˜Bâ€™. A new propagation tree is created
in the exact same configuration as that of â€˜Bâ€™. This new propagation
tree contains all the new mounts â€˜A1â€™, â€˜A2â€™...  â€˜Anâ€™.  And this new
propagation tree is appended to the already existing propagation tree of
â€˜Aâ€™.  Mount â€˜Aâ€™ continues to be the slave mount of â€˜Zâ€™ but it also
becomes â€˜sharedâ€™.”…””}”(hj¸
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhj´
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj
  ubjU  )”}”(hX;  'A' is a unbindable mount and 'B' is a shared mount. The operation
is invalid. Because mounting anything on the shared mount 'B' can
create new mounts that get mounted on the mounts that receive
propagation from 'B'.  And since the mount 'A' is unbindable, cloning
it to mount at other mountpoints is not possible.
”h]”hý)”}”(hX:  'A' is a unbindable mount and 'B' is a shared mount. The operation
is invalid. Because mounting anything on the shared mount 'B' can
create new mounts that get mounted on the mounts that receive
propagation from 'B'.  And since the mount 'A' is unbindable, cloning
it to mount at other mountpoints is not possible.”h]”hXN  â€˜Aâ€™ is a unbindable mount and â€˜Bâ€™ is a shared mount. The operation
is invalid. Because mounting anything on the shared mount â€˜Bâ€™ can
create new mounts that get mounted on the mounts that receive
propagation from â€˜Bâ€™.  And since the mount â€˜Aâ€™ is unbindable, cloning
it to mount at other mountpoints is not possible.”…””}”(hjÐ
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MhjÌ
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj
  ubjU  )”}”(hŒ‹'A' is a private mount and 'B' is a non-shared(private or slave or
unbindable) mount. The mount 'A' is mounted on mount 'B' at dentry 'b'.
”h]”hý)”}”(hŒŠ'A' is a private mount and 'B' is a non-shared(private or slave or
unbindable) mount. The mount 'A' is mounted on mount 'B' at dentry 'b'.”h]”hŒžâ€˜Aâ€™ is a private mount and â€˜Bâ€™ is a non-shared(private or slave or
unbindable) mount. The mount â€˜Aâ€™ is mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™.”…””}”(hjè
  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhjä
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj
  ubjU  )”}”(hŒ–'A' is a shared mount and 'B' is a non-shared mount.  The mount 'A'
is mounted on mount 'B' at dentry 'b'.  Mount 'A' continues to be a
shared mount.
”h]”hý)”}”(hŒ•'A' is a shared mount and 'B' is a non-shared mount.  The mount 'A'
is mounted on mount 'B' at dentry 'b'.  Mount 'A' continues to be a
shared mount.”h]”hŒ­â€˜Aâ€™ is a shared mount and â€˜Bâ€™ is a non-shared mount.  The mount â€˜Aâ€™
is mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™.  Mount â€˜Aâ€™ continues to be a
shared mount.”…””}”(hj   h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhjü
  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj
  ubjU  )”}”(hŒ­'A' is a slave mount of mount 'Z' and 'B' is a non-shared mount.
The mount 'A' is mounted on mount 'B' at dentry 'b'.  Mount 'A'
continues to be a slave mount of mount 'Z'.
”h]”hý)”}”(hŒ¬'A' is a slave mount of mount 'Z' and 'B' is a non-shared mount.
The mount 'A' is mounted on mount 'B' at dentry 'b'.  Mount 'A'
continues to be a slave mount of mount 'Z'.”h]”hŒÌâ€˜Aâ€™ is a slave mount of mount â€˜Zâ€™ and â€˜Bâ€™ is a non-shared mount.
The mount â€˜Aâ€™ is mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™.  Mount â€˜Aâ€™
continues to be a slave mount of mount â€˜Zâ€™.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj
  ubjU  )”}”(hŒœ'A' is a unbindable mount and 'B' is a non-shared mount. The mount
'A' is mounted on mount 'B' at dentry 'b'. Mount 'A' continues to be a
unbindable mount.
”h]”hý)”}”(hŒ›'A' is a unbindable mount and 'B' is a non-shared mount. The mount
'A' is mounted on mount 'B' at dentry 'b'. Mount 'A' continues to be a
unbindable mount.”h]”hŒ³â€˜Aâ€™ is a unbindable mount and â€˜Bâ€™ is a non-shared mount. The mount
â€˜Aâ€™ is mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™. Mount â€˜Aâ€™ continues to be a
unbindable mount.”…””}”(hj0  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhj,  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj
  ubeh}”(h]”h ]”h"]”h$]”h&]”jÔ  j0  jÖ  hj×  jg	  uh1jO  hj
  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjÖ  h²hh³Nh´NubjU  )”}”(hX  Mount semantics

Consider the following command::

  mount device  B/b

'B' is the destination mount and 'b' is the dentry in the destination
mount.

The above operation is the same as bind operation with the exception
that the source mount is always a private mount.

”h]”(hý)”}”(hŒMount semantics”h]”hŒMount semantics”…””}”(hjT  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M!hjP  ubhý)”}”(hŒ Consider the following command::”h]”hŒConsider the following command:”…””}”(hjb  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M#hjP  ubj™  )”}”(hŒmount device  B/b”h]”hŒmount device  B/b”…””}”hjp  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´M%hjP  ubhý)”}”(hŒL'B' is the destination mount and 'b' is the dentry in the destination
mount.”h]”hŒTâ€˜Bâ€™ is the destination mount and â€˜bâ€™ is the dentry in the destination
mount.”…””}”(hj~  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M'hjP  ubhý)”}”(hŒuThe above operation is the same as bind operation with the exception
that the source mount is always a private mount.”h]”hŒuThe above operation is the same as bind operation with the exception
that the source mount is always a private mount.”…””}”(hjŒ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M*hjP  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjÖ  h²hh³hÇh´NubjU  )”}”(hX9  Unmount semantics

Consider the following command::

  umount A

where 'A' is a mount mounted on mount 'B' at dentry 'b'.

If mount 'B' is shared, then all most-recently-mounted mounts at dentry
'b' on mounts that receive propagation from mount 'B' are unmounted as
well, if every mount below them is also unmounted.

Example: Let's say 'B1', 'B2', 'B3' are shared mounts that propagate to
each other.

let's say 'A1', 'A2', 'A3' are first mounted at dentry 'b' on mount
'B1', 'B2' and 'B3' respectively.

let's say 'C1', 'C2', 'C3' are next mounted at the same dentry 'b' on
mount 'B1', 'B2' and 'B3' respectively.

if 'C1' is unmounted, all the mounts that are most-recently-mounted on
'B1' and on the mounts that 'B1' propagates-to are unmounted.

'B1' propagates to 'B2' and 'B3'. And the most recently mounted mount
on 'B2' at dentry 'b' is 'C2', and that of mount 'B3' is 'C3'.

So all 'C1', 'C2' and 'C3' should be unmounted.

If any of 'C2' or 'C3' has a child mount that cannot be unmounted
then that mount is not unmounted. But all other mounts are unmounted.
A child mount that is itself unmounted by the same unmount
propagation does not keep its parent mounted. However if 'C1' is
supposed to be unmounted and 'C1' has some sub-mounts, the unmount
fails.

A lazy umount (MNT_DETACH) takes a whole tree. Every mount of the
tree then propagates its unmount from its own parent as described
above, so the mounts that receive propagation lose the corresponding
trees as well. Documentation/filesystems/propagate_umount.txt has the
precise rules, including the ones for locked mounts.
”h]”(hý)”}”(hŒUnmount semantics”h]”hŒUnmount semantics”…””}”(hj¤  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M.hj   ubhý)”}”(hŒ Consider the following command::”h]”hŒConsider the following command:”…””}”(hj²  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M0hj   ubj™  )”}”(hŒumount A”h]”hŒumount A”…””}”hjÀ  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´M2hj   ubhý)”}”(hŒ8where 'A' is a mount mounted on mount 'B' at dentry 'b'.”h]”hŒDwhere â€˜Aâ€™ is a mount mounted on mount â€˜Bâ€™ at dentry â€˜bâ€™.”…””}”(hjÎ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M4hj   ubhý)”}”(hŒÁIf mount 'B' is shared, then all most-recently-mounted mounts at dentry
'b' on mounts that receive propagation from mount 'B' are unmounted as
well, if every mount below them is also unmounted.”h]”hŒÍIf mount â€˜Bâ€™ is shared, then all most-recently-mounted mounts at dentry
â€˜bâ€™ on mounts that receive propagation from mount â€˜Bâ€™ are unmounted as
well, if every mount below them is also unmounted.”…””}”(hjÜ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M6hj   ubhý)”}”(hŒSExample: Let's say 'B1', 'B2', 'B3' are shared mounts that propagate to
each other.”h]”hŒaExample: Letâ€™s say â€˜B1â€™, â€˜B2â€™, â€˜B3â€™ are shared mounts that propagate to
each other.”…””}”(hjê  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M:hj   ubhý)”}”(hŒelet's say 'A1', 'A2', 'A3' are first mounted at dentry 'b' on mount
'B1', 'B2' and 'B3' respectively.”h]”hŒƒletâ€™s say â€˜A1â€™, â€˜A2â€™, â€˜A3â€™ are first mounted at dentry â€˜bâ€™ on mount
â€˜B1â€™, â€˜B2â€™ and â€˜B3â€™ respectively.”…””}”(hjø  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M=hj   ubhý)”}”(hŒmlet's say 'C1', 'C2', 'C3' are next mounted at the same dentry 'b' on
mount 'B1', 'B2' and 'B3' respectively.”h]”hŒ‹letâ€™s say â€˜C1â€™, â€˜C2â€™, â€˜C3â€™ are next mounted at the same dentry â€˜bâ€™ on
mount â€˜B1â€™, â€˜B2â€™ and â€˜B3â€™ respectively.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M@hj   ubhý)”}”(hŒ„if 'C1' is unmounted, all the mounts that are most-recently-mounted on
'B1' and on the mounts that 'B1' propagates-to are unmounted.”h]”hŒif â€˜C1â€™ is unmounted, all the mounts that are most-recently-mounted on
â€˜B1â€™ and on the mounts that â€˜B1â€™ propagates-to are unmounted.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MChj   ubhý)”}”(hŒ„'B1' propagates to 'B2' and 'B3'. And the most recently mounted mount
on 'B2' at dentry 'b' is 'C2', and that of mount 'B3' is 'C3'.”h]”hŒ¤â€˜B1â€™ propagates to â€˜B2â€™ and â€˜B3â€™. And the most recently mounted mount
on â€˜B2â€™ at dentry â€˜bâ€™ is â€˜C2â€™, and that of mount â€˜B3â€™ is â€˜C3â€™.”…””}”(hj"  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MFhj   ubhý)”}”(hŒ/So all 'C1', 'C2' and 'C3' should be unmounted.”h]”hŒ;So all â€˜C1â€™, â€˜C2â€™ and â€˜C3â€™ should be unmounted.”…””}”(hj0  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MIhj   ubhý)”}”(hXM  If any of 'C2' or 'C3' has a child mount that cannot be unmounted
then that mount is not unmounted. But all other mounts are unmounted.
A child mount that is itself unmounted by the same unmount
propagation does not keep its parent mounted. However if 'C1' is
supposed to be unmounted and 'C1' has some sub-mounts, the unmount
fails.”h]”hX]  If any of â€˜C2â€™ or â€˜C3â€™ has a child mount that cannot be unmounted
then that mount is not unmounted. But all other mounts are unmounted.
A child mount that is itself unmounted by the same unmount
propagation does not keep its parent mounted. However if â€˜C1â€™ is
supposed to be unmounted and â€˜C1â€™ has some sub-mounts, the unmount
fails.”…””}”(hj>  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MKhj   ubhý)”}”(hXC  A lazy umount (MNT_DETACH) takes a whole tree. Every mount of the
tree then propagates its unmount from its own parent as described
above, so the mounts that receive propagation lose the corresponding
trees as well. Documentation/filesystems/propagate_umount.txt has the
precise rules, including the ones for locked mounts.”h]”hXC  A lazy umount (MNT_DETACH) takes a whole tree. Every mount of the
tree then propagates its unmount from its own parent as described
above, so the mounts that receive propagation lose the corresponding
trees as well. Documentation/filesystems/propagate_umount.txt has the
precise rules, including the ones for locked mounts.”…””}”(hjL  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MRhj   ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjÖ  h²hh³hÇh´NubjU  )”}”(hXÕ  Clone Namespace

A cloned namespace contains all the mounts as that of the parent
namespace.

Let's say 'A' and 'B' are the corresponding mounts in the parent and the
child namespace.

If 'A' is shared, then 'B' is also shared and 'A' and 'B' propagate to
each other.

If 'A' is a slave mount of 'Z', then 'B' is also the slave mount of
'Z'.

If 'A' is a private mount, then 'B' is a private mount too.

If 'A' is unbindable mount, then 'B' is a unbindable mount too.

”h]”(hý)”}”(hŒClone Namespace”h]”hŒClone Namespace”…””}”(hjd  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MXhj`  ubhý)”}”(hŒKA cloned namespace contains all the mounts as that of the parent
namespace.”h]”hŒKA cloned namespace contains all the mounts as that of the parent
namespace.”…””}”(hjr  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MZhj`  ubhý)”}”(hŒYLet's say 'A' and 'B' are the corresponding mounts in the parent and the
child namespace.”h]”hŒcLetâ€™s say â€˜Aâ€™ and â€˜Bâ€™ are the corresponding mounts in the parent and the
child namespace.”…””}”(hj€  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M]hj`  ubhý)”}”(hŒRIf 'A' is shared, then 'B' is also shared and 'A' and 'B' propagate to
each other.”h]”hŒbIf â€˜Aâ€™ is shared, then â€˜Bâ€™ is also shared and â€˜Aâ€™ and â€˜Bâ€™ propagate to
each other.”…””}”(hjŽ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M`hj`  ubhý)”}”(hŒHIf 'A' is a slave mount of 'Z', then 'B' is also the slave mount of
'Z'.”h]”hŒXIf â€˜Aâ€™ is a slave mount of â€˜Zâ€™, then â€˜Bâ€™ is also the slave mount of
â€˜Zâ€™.”…””}”(hjœ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mchj`  ubhý)”}”(hŒ;If 'A' is a private mount, then 'B' is a private mount too.”h]”hŒCIf â€˜Aâ€™ is a private mount, then â€˜Bâ€™ is a private mount too.”…””}”(hjª  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mfhj`  ubhý)”}”(hŒ?If 'A' is unbindable mount, then 'B' is a unbindable mount too.”h]”hŒGIf â€˜Aâ€™ is unbindable mount, then â€˜Bâ€™ is a unbindable mount too.”…””}”(hj¸  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhhj`  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjÖ  h²hh³hÇh´Nubeh}”(h]”h ]”h"]”h$]”h&]”jÔ  jÕ  jÖ  hj×  jØ  uh1jO  hjŸ  h²hh³hÇh´Kúubeh}”(h]”Œdetailed-semantics”ah ]”h"]”Œ5) detailed semantics”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´KòubhÉ)”}”(hhh]”(hÎ)”}”(hŒ6) Quiz”h]”hŒ6) Quiz”…””}”(hjÝ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhjÚ  h²hh³hÇh´MlubjP  )”}”(hhh]”(jU  )”}”(hX7  What is the result of the following command sequence?

::

    mount --bind /mnt /mnt
    mount --make-shared /mnt
    mount --bind /mnt /tmp
    mount --move /tmp /mnt/1

what should be the contents of /mnt /mnt/1 /mnt/1/1 should be?
Should they all be identical? or should /mnt and /mnt/1 be
identical only?

”h]”(hý)”}”(hŒ5What is the result of the following command sequence?”h]”hŒ5What is the result of the following command sequence?”…””}”(hjò  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mnhjî  ubj™  )”}”(hŒ_mount --bind /mnt /mnt
mount --make-shared /mnt
mount --bind /mnt /tmp
mount --move /tmp /mnt/1”h]”hŒ_mount --bind /mnt /mnt
mount --make-shared /mnt
mount --bind /mnt /tmp
mount --move /tmp /mnt/1”…””}”hj   sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Mrhjî  ubhý)”}”(hŒ‰what should be the contents of /mnt /mnt/1 /mnt/1/1 should be?
Should they all be identical? or should /mnt and /mnt/1 be
identical only?”h]”hŒ‰what should be the contents of /mnt /mnt/1 /mnt/1/1 should be?
Should they all be identical? or should /mnt and /mnt/1 be
identical only?”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mwhjî  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjë  h²hh³hÇh´NubjU  )”}”(hŒ®What is the result of the following command sequence?

::

    mount --make-rshared /
    mkdir -p /v/1
    mount --rbind / /v/1

what should be the content of /v/1/v/1 be?

”h]”(hý)”}”(hŒ5What is the result of the following command sequence?”h]”hŒ5What is the result of the following command sequence?”…””}”(hj&  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M|hj"  ubj™  )”}”(hŒ9mount --make-rshared /
mkdir -p /v/1
mount --rbind / /v/1”h]”hŒ9mount --make-rshared /
mkdir -p /v/1
mount --rbind / /v/1”…””}”hj4  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´M€hj"  ubhý)”}”(hŒ*what should be the content of /v/1/v/1 be?”h]”hŒ*what should be the content of /v/1/v/1 be?”…””}”(hjB  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M„hj"  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjë  h²hh³hÇh´NubjU  )”}”(hXB  What is the result of the following command sequence?

::

    mount --bind /mnt /mnt
    mount --make-shared /mnt
    mkdir -p /mnt/1/2/3 /mnt/1/test
    mount --bind /mnt/1 /tmp
    mount --make-slave /mnt
    mount --make-shared /mnt
    mount --bind /mnt/1/2 /tmp1
    mount --make-slave /mnt

At this point we have the first mount at /tmp and
its root dentry is 1. Let's call this mount 'A'
And then we have a second mount at /tmp1 with root
dentry 2. Let's call this mount 'B'
Next we have a third mount at /mnt with root dentry
mnt. Let's call this mount 'C'

'B' is the slave of 'A' and 'C' is a slave of 'B'
A -> B -> C

at this point if we execute the following command::

  mount --bind /bin /tmp/test

The mount is attempted on 'A'

will the mount propagate to 'B' and 'C' ?

what would be the contents of
/mnt/1/test be?
”h]”(hý)”}”(hŒ5What is the result of the following command sequence?”h]”hŒ5What is the result of the following command sequence?”…””}”(hjZ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M‡hjV  ubj™  )”}”(hŒÍmount --bind /mnt /mnt
mount --make-shared /mnt
mkdir -p /mnt/1/2/3 /mnt/1/test
mount --bind /mnt/1 /tmp
mount --make-slave /mnt
mount --make-shared /mnt
mount --bind /mnt/1/2 /tmp1
mount --make-slave /mnt”h]”hŒÍmount --bind /mnt /mnt
mount --make-shared /mnt
mkdir -p /mnt/1/2/3 /mnt/1/test
mount --bind /mnt/1 /tmp
mount --make-slave /mnt
mount --make-shared /mnt
mount --bind /mnt/1/2 /tmp1
mount --make-slave /mnt”…””}”hjh  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´M‹hjV  ubhý)”}”(hX  At this point we have the first mount at /tmp and
its root dentry is 1. Let's call this mount 'A'
And then we have a second mount at /tmp1 with root
dentry 2. Let's call this mount 'B'
Next we have a third mount at /mnt with root dentry
mnt. Let's call this mount 'C'”h]”hX  At this point we have the first mount at /tmp and
its root dentry is 1. Letâ€™s call this mount â€˜Aâ€™
And then we have a second mount at /tmp1 with root
dentry 2. Letâ€™s call this mount â€˜Bâ€™
Next we have a third mount at /mnt with root dentry
mnt. Letâ€™s call this mount â€˜Câ€™”…””}”(hjv  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M”hjV  ubhý)”}”(hŒ='B' is the slave of 'A' and 'C' is a slave of 'B'
A -> B -> C”h]”hŒMâ€˜Bâ€™ is the slave of â€˜Aâ€™ and â€˜Câ€™ is a slave of â€˜Bâ€™
A -> B -> C”…””}”(hj„  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M›hjV  ubhý)”}”(hŒ3at this point if we execute the following command::”h]”hŒ2at this point if we execute the following command:”…””}”(hj’  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MžhjV  ubj™  )”}”(hŒmount --bind /bin /tmp/test”h]”hŒmount --bind /bin /tmp/test”…””}”hj   sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´M hjV  ubhý)”}”(hŒThe mount is attempted on 'A'”h]”hŒ!The mount is attempted on â€˜Aâ€™”…””}”(hj®  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¢hjV  ubhý)”}”(hŒ)will the mount propagate to 'B' and 'C' ?”h]”hŒ1will the mount propagate to â€˜Bâ€™ and â€˜Câ€™ ?”…””}”(hj¼  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¤hjV  ubhý)”}”(hŒ-what would be the contents of
/mnt/1/test be?”h]”hŒ-what would be the contents of
/mnt/1/test be?”…””}”(hjÊ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¦hjV  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjë  h²hh³hÇh´Nubeh}”(h]”h ]”h"]”h$]”h&]”jÔ  jú  jÖ  hj×  jg	  uh1jO  hjÚ  h²hh³hÇh´Mnubeh}”(h]”Œquiz”ah ]”h"]”Œ6) quiz”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´MlubhÉ)”}”(hhh]”(hÎ)”}”(hŒ7) FAQ”h]”hŒ7) FAQ”…””}”(hjï  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhjì  h²hh³hÇh´MªubjP  )”}”(hhh]”(jU  )”}”(hŒàWhy is bind mount needed? How is it different from symbolic links?

symbolic links can get stale if the destination mount gets
unmounted or moved. Bind mounts continue to exist even if the
other mount is unmounted or moved.
”h]”(hý)”}”(hŒBWhy is bind mount needed? How is it different from symbolic links?”h]”hŒBWhy is bind mount needed? How is it different from symbolic links?”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¬hj   ubhý)”}”(hŒ›symbolic links can get stale if the destination mount gets
unmounted or moved. Bind mounts continue to exist even if the
other mount is unmounted or moved.”h]”hŒ›symbolic links can get stale if the destination mount gets
unmounted or moved. Bind mounts continue to exist even if the
other mount is unmounted or moved.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M®hj   ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjý  h²hh³hÇh´NubjU  )”}”(hŒáWhy can't the shared subtree be implemented using exportfs?

exportfs is a heavyweight way of accomplishing part of what
shared subtree can do. I cannot imagine a way to implement the
semantics of slave mount using exportfs?
”h]”(hý)”}”(hŒ;Why can't the shared subtree be implemented using exportfs?”h]”hŒ=Why canâ€™t the shared subtree be implemented using exportfs?”…””}”(hj*  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M²hj&  ubhý)”}”(hŒ£exportfs is a heavyweight way of accomplishing part of what
shared subtree can do. I cannot imagine a way to implement the
semantics of slave mount using exportfs?”h]”hŒ£exportfs is a heavyweight way of accomplishing part of what
shared subtree can do. I cannot imagine a way to implement the
semantics of slave mount using exportfs?”…””}”(hj8  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M´hj&  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjý  h²hh³hÇh´NubjU  )”}”(hX{  Why is unbindable mount needed?

Let's say we want to replicate the mount tree at multiple
locations within the same subtree.

if one rbind mounts a tree within the same subtree 'n' times
the number of mounts created is an exponential function of 'n'.
Having unbindable mount can help prune the unneeded bind
mounts. Here is an example.

step 1:
   let's say the root tree has just two directories with
   one vfsmount::

                                 root
                                /    \
                               tmp    usr

   And we want to replicate the tree at multiple
   mountpoints under /root/tmp

step 2:
   ::


                     mount --make-shared /root

                     mkdir -p /tmp/m1

                     mount --rbind /root /tmp/m1

   the new tree now looks like this::

                                 root
                                /    \
                              tmp    usr
                             /
                            m1
                           /  \
                          tmp  usr
                          /
                         m1

   it has two vfsmounts

step 3:
   ::

                         mkdir -p /tmp/m2
                         mount --rbind /root /tmp/m2

   the new tree now looks like this::

                                   root
                                  /    \
                                tmp     usr
                               /    \
                             m1       m2
                            / \       /  \
                          tmp  usr   tmp  usr
                          / \          /
                         m1  m2      m1
                             / \     /  \
                           tmp usr  tmp   usr
                           /        / \
                          m1       m1  m2
                         /  \
                       tmp   usr
                       /  \
                      m1   m2

                 it has 6 vfsmounts

step 4:
   ::

                       mkdir -p /tmp/m3
                       mount --rbind /root /tmp/m3

   I won't draw the tree..but it has 24 vfsmounts


at step i the number of vfsmounts is V[i] = i*V[i-1].
This is an exponential function. And this tree has way more
mounts than what we really needed in the first place.

One could use a series of umount at each step to prune
out the unneeded mounts. But there is a better solution.
Unclonable mounts come in handy here.

step 1:
   let's say the root tree has just two directories with
   one vfsmount::

                                 root
                                /    \
                               tmp    usr

      How do we set up the same tree at multiple locations under
      /root/tmp

step 2:
   ::


                     mount --bind /root/tmp /root/tmp

                     mount --make-rshared /root
                     mount --make-unbindable /root/tmp

                     mkdir -p /tmp/m1

                     mount --rbind /root /tmp/m1

   the new tree now looks like this::

                                 root
                                /    \
                              tmp    usr
                             /
                            m1
                           /  \
                          tmp  usr

step 3:
   ::

                         mkdir -p /tmp/m2
                         mount --rbind /root /tmp/m2

   the new tree now looks like this::

                                 root
                                /    \
                              tmp    usr
                             /   \
                            m1     m2
                           /  \     / \
                          tmp  usr tmp usr

step 4:
   ::

                         mkdir -p /tmp/m3
                         mount --rbind /root /tmp/m3

   the new tree now looks like this::

                                       root
                                   /           \
                                  tmp           usr
                              /    \    \
                            m1     m2     m3
                           /  \     / \    /  \
                          tmp  usr tmp usr tmp usr
”h]”(hý)”}”(hŒWhy is unbindable mount needed?”h]”hŒWhy is unbindable mount needed?”…””}”(hjP  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¸hjL  ubhý)”}”(hŒ\Let's say we want to replicate the mount tree at multiple
locations within the same subtree.”h]”hŒ^Letâ€™s say we want to replicate the mount tree at multiple
locations within the same subtree.”…””}”(hj^  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MºhjL  ubhý)”}”(hŒÑif one rbind mounts a tree within the same subtree 'n' times
the number of mounts created is an exponential function of 'n'.
Having unbindable mount can help prune the unneeded bind
mounts. Here is an example.”h]”hŒÙif one rbind mounts a tree within the same subtree â€˜nâ€™ times
the number of mounts created is an exponential function of â€˜nâ€™.
Having unbindable mount can help prune the unneeded bind
mounts. Here is an example.”…””}”(hjl  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M½hjL  ubhŒdefinition_list”“”)”}”(hhh]”(hŒdefinition_list_item”“”)”}”(hX  step 1:
let's say the root tree has just two directories with
one vfsmount::

                              root
                             /    \
                            tmp    usr

And we want to replicate the tree at multiple
mountpoints under /root/tmp
”h]”(hŒterm”“”)”}”(hŒstep 1:”h]”hŒstep 1:”…””}”(hj‡  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´MËhj  ubhŒ
definition”“”)”}”(hhh]”(hý)”}”(hŒDlet's say the root tree has just two directories with
one vfsmount::”h]”hŒEletâ€™s say the root tree has just two directories with
one vfsmount:”…””}”(hjš  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÃhj—  ubj™  )”}”(hŒ  root
 /    \
tmp    usr”h]”hŒ  root
 /    \
tmp    usr”…””}”hj¨  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´MÆhj—  ubhý)”}”(hŒIAnd we want to replicate the tree at multiple
mountpoints under /root/tmp”h]”hŒIAnd we want to replicate the tree at multiple
mountpoints under /root/tmp”…””}”(hj¶  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÊhj—  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j•  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´MËhj|  ubj€  )”}”(hXÛ  step 2:
::


                  mount --make-shared /root

                  mkdir -p /tmp/m1

                  mount --rbind /root /tmp/m1

the new tree now looks like this::

                              root
                             /    \
                           tmp    usr
                          /
                         m1
                        /  \
                       tmp  usr
                       /
                      m1

it has two vfsmounts
”h]”(j†  )”}”(hŒstep 2:”h]”hŒstep 2:”…””}”(hjÔ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´MãhjÐ  ubj–  )”}”(hhh]”(j™  )”}”(hŒHmount --make-shared /root

mkdir -p /tmp/m1

mount --rbind /root /tmp/m1”h]”hŒHmount --make-shared /root

mkdir -p /tmp/m1

mount --rbind /root /tmp/m1”…””}”hjå  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´MÑhjâ  ubhý)”}”(hŒ"the new tree now looks like this::”h]”hŒ!the new tree now looks like this:”…””}”(hjó  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M×hjâ  ubj™  )”}”(hŒM        root
       /    \
     tmp    usr
    /
   m1
  /  \
 tmp  usr
 /
m1”h]”hŒM        root
       /    \
     tmp    usr
    /
   m1
  /  \
 tmp  usr
 /
m1”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´MÙhjâ  ubhý)”}”(hŒit has two vfsmounts”h]”hŒit has two vfsmounts”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mãhjâ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j•  hjÐ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´Mãhj|  ubj€  )”}”(hX  step 3:
::

                      mkdir -p /tmp/m2
                      mount --rbind /root /tmp/m2

the new tree now looks like this::

                                root
                               /    \
                             tmp     usr
                            /    \
                          m1       m2
                         / \       /  \
                       tmp  usr   tmp  usr
                       / \          /
                      m1  m2      m1
                          / \     /  \
                        tmp usr  tmp   usr
                        /        / \
                       m1       m1  m2
                      /  \
                    tmp   usr
                    /  \
                   m1   m2

              it has 6 vfsmounts
”h]”(j†  )”}”(hŒstep 3:”h]”hŒstep 3:”…””}”(hj-  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´Mÿhj)  ubj–  )”}”(hhh]”(j™  )”}”(hŒ,mkdir -p /tmp/m2
mount --rbind /root /tmp/m2”h]”hŒ,mkdir -p /tmp/m2
mount --rbind /root /tmp/m2”…””}”hj>  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Mèhj;  ubhý)”}”(hŒ"the new tree now looks like this::”h]”hŒ!the new tree now looks like this:”…””}”(hjL  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mëhj;  ubj™  )”}”(hX‹                    root
                 /    \
               tmp     usr
              /    \
            m1       m2
           / \       /  \
         tmp  usr   tmp  usr
         / \          /
        m1  m2      m1
            / \     /  \
          tmp usr  tmp   usr
          /        / \
         m1       m1  m2
        /  \
      tmp   usr
      /  \
     m1   m2

it has 6 vfsmounts”h]”hX‹                    root
                 /    \
               tmp     usr
              /    \
            m1       m2
           / \       /  \
         tmp  usr   tmp  usr
         / \          /
        m1  m2      m1
            / \     /  \
          tmp usr  tmp   usr
          /        / \
         m1       m1  m2
        /  \
      tmp   usr
      /  \
     m1   m2

it has 6 vfsmounts”…””}”hjZ  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Míhj;  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j•  hj)  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´Mÿhj|  ubj€  )”}”(hŒ’step 4:
::

                    mkdir -p /tmp/m3
                    mount --rbind /root /tmp/m3

I won't draw the tree..but it has 24 vfsmounts

”h]”(j†  )”}”(hŒstep 4:”h]”hŒstep 4:”…””}”(hjx  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´Mhjt  ubj–  )”}”(hhh]”(j™  )”}”(hŒ,mkdir -p /tmp/m3
mount --rbind /root /tmp/m3”h]”hŒ,mkdir -p /tmp/m3
mount --rbind /root /tmp/m3”…””}”hj‰  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Mhj†  ubhý)”}”(hŒ.I won't draw the tree..but it has 24 vfsmounts”h]”hŒ0I wonâ€™t draw the tree..but it has 24 vfsmounts”…””}”(hj—  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhj†  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j•  hjt  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´Mhj|  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jz  hjL  ubhý)”}”(hŒ§at step i the number of vfsmounts is V[i] = i*V[i-1].
This is an exponential function. And this tree has way more
mounts than what we really needed in the first place.”h]”hŒ§at step i the number of vfsmounts is V[i] = i*V[i-1].
This is an exponential function. And this tree has way more
mounts than what we really needed in the first place.”…””}”(hj·  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M
hjL  ubhý)”}”(hŒ•One could use a series of umount at each step to prune
out the unneeded mounts. But there is a better solution.
Unclonable mounts come in handy here.”h]”hŒ•One could use a series of umount at each step to prune
out the unneeded mounts. But there is a better solution.
Unclonable mounts come in handy here.”…””}”(hjÅ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MhjL  ubj{  )”}”(hhh]”(j€  )”}”(hX  step 1:
let's say the root tree has just two directories with
one vfsmount::

                              root
                             /    \
                            tmp    usr

   How do we set up the same tree at multiple locations under
   /root/tmp
”h]”(j†  )”}”(hŒstep 1:”h]”hŒstep 1:”…””}”(hjÚ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´MhjÖ  ubj–  )”}”(hhh]”(hý)”}”(hŒDlet's say the root tree has just two directories with
one vfsmount::”h]”hŒEletâ€™s say the root tree has just two directories with
one vfsmount:”…””}”(hjë  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhjè  ubj™  )”}”(hŒª                           root
                          /    \
                         tmp    usr

How do we set up the same tree at multiple locations under
/root/tmp”h]”hŒª                           root
                          /    \
                         tmp    usr

How do we set up the same tree at multiple locations under
/root/tmp”…””}”hjù  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´Mhjè  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j•  hjÖ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´MhjÓ  ubj€  )”}”(hXü  step 2:
::


                  mount --bind /root/tmp /root/tmp

                  mount --make-rshared /root
                  mount --make-unbindable /root/tmp

                  mkdir -p /tmp/m1

                  mount --rbind /root /tmp/m1

the new tree now looks like this::

                              root
                             /    \
                           tmp    usr
                          /
                         m1
                        /  \
                       tmp  usr
”h]”(j†  )”}”(hŒstep 2:”h]”hŒstep 2:”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´M2hj  ubj–  )”}”(hhh]”(j™  )”}”(hŒmount --bind /root/tmp /root/tmp

mount --make-rshared /root
mount --make-unbindable /root/tmp

mkdir -p /tmp/m1

mount --rbind /root /tmp/m1”h]”hŒmount --bind /root/tmp /root/tmp

mount --make-rshared /root
mount --make-unbindable /root/tmp

mkdir -p /tmp/m1

mount --rbind /root /tmp/m1”…””}”hj(  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´M!hj%  ubhý)”}”(hŒ"the new tree now looks like this::”h]”hŒ!the new tree now looks like this:”…””}”(hj6  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M*hj%  ubj™  )”}”(hŒ@       root
      /    \
    tmp    usr
   /
  m1
 /  \
tmp  usr”h]”hŒ@       root
      /    \
    tmp    usr
   /
  m1
 /  \
tmp  usr”…””}”hjD  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´M,hj%  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j•  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´M2hjÓ  ubj€  )”}”(hX‡  step 3:
::

                      mkdir -p /tmp/m2
                      mount --rbind /root /tmp/m2

the new tree now looks like this::

                              root
                             /    \
                           tmp    usr
                          /   \
                         m1     m2
                        /  \     / \
                       tmp  usr tmp usr
”h]”(j†  )”}”(hŒstep 3:”h]”hŒstep 3:”…””}”(hjb  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´MBhj^  ubj–  )”}”(hhh]”(j™  )”}”(hŒ,mkdir -p /tmp/m2
mount --rbind /root /tmp/m2”h]”hŒ,mkdir -p /tmp/m2
mount --rbind /root /tmp/m2”…””}”hjs  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´M7hjp  ubhý)”}”(hŒ"the new tree now looks like this::”h]”hŒ!the new tree now looks like this:”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M:hjp  ubj™  )”}”(hŒ[       root
      /    \
    tmp    usr
   /   \
  m1     m2
 /  \     / \
tmp  usr tmp usr”h]”hŒ[       root
      /    \
    tmp    usr
   /   \
  m1     m2
 /  \     / \
tmp  usr tmp usr”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´M<hjp  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j•  hj^  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´MBhjÓ  ubj€  )”}”(hXÀ  step 4:
::

                      mkdir -p /tmp/m3
                      mount --rbind /root /tmp/m3

the new tree now looks like this::

                                    root
                                /           \
                               tmp           usr
                           /    \    \
                         m1     m2     m3
                        /  \     / \    /  \
                       tmp  usr tmp usr tmp usr
”h]”(j†  )”}”(hŒstep 4:”h]”hŒstep 4:”…””}”(hj­  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´MRhj©  ubj–  )”}”(hhh]”(j™  )”}”(hŒ,mkdir -p /tmp/m3
mount --rbind /root /tmp/m3”h]”hŒ,mkdir -p /tmp/m3
mount --rbind /root /tmp/m3”…””}”hj¾  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´MGhj»  ubhý)”}”(hŒ"the new tree now looks like this::”h]”hŒ!the new tree now looks like this:”…””}”(hjÌ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MJhj»  ubj™  )”}”(hŒ”             root
         /           \
        tmp           usr
    /    \    \
  m1     m2     m3
 /  \     / \    /  \
tmp  usr tmp usr tmp usr”h]”hŒ”             root
         /           \
        tmp           usr
    /    \    \
  m1     m2     m3
 /  \     / \    /  \
tmp  usr tmp usr tmp usr”…””}”hjÚ  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´MLhj»  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j•  hj©  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´MRhjÓ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jz  hjL  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjý  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”jÔ  j0  jÖ  hj×  jg	  uh1jO  hjì  h²hh³hÇh´M¬ubeh}”(h]”Œfaq”ah ]”h"]”Œ7) faq”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´MªubhÉ)”}”(hhh]”(hÎ)”}”(hŒ8) Implementation”h]”hŒ8) Implementation”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÍhj  h²hh³hÇh´MUubjP  )”}”(hhh]”(jU  )”}”(hXd  Datastructure

Several new fields are introduced to struct vfsmount:

->mnt_share
        Links together all the mount to/from which this vfsmount
        send/receives propagation events.

->mnt_slave_list
        Links all the mounts to which this vfsmount propagates
        to.

->mnt_slave
        Links together all the slaves that its master vfsmount
        propagates to.

->mnt_master
        Points to the master vfsmount from which this vfsmount
        receives propagation.

->mnt_flags
        Takes two more flags to indicate the propagation status of
        the vfsmount.  MNT_SHARE indicates that the vfsmount is a shared
        vfsmount.  MNT_UNCLONABLE indicates that the vfsmount cannot be
        replicated.

All the shared vfsmounts in a peer group form a cyclic list through
->mnt_share.

All vfsmounts with the same ->mnt_master form on a cyclic list anchored
in ->mnt_master->mnt_slave_list and going through ->mnt_slave.

->mnt_master can point to arbitrary (and possibly different) members
of master peer group.  To find all immediate slaves of a peer group
you need to go through _all_ ->mnt_slave_list of its members.
Conceptually it's just a single set - distribution among the
individual lists does not affect propagation or the way propagation
tree is modified by operations.

All vfsmounts in a peer group have the same ->mnt_master.  If it is
non-NULL, they form a contiguous (ordered) segment of slave list.

A example propagation tree looks as shown in the figure below.

.. note::
   Though it looks like a forest, if we consider all the shared
   mounts as a conceptual entity called 'pnode', it becomes a tree.

::


                     A <--> B <--> C <---> D
                    /|\            /|      |\
                   / F G          J K      H I
                  /
                 E<-->K
                     /|\
                    M L N

In the above figure  A,B,C and D all are shared and propagate to each
other.   'A' has got 3 slave mounts 'E' 'F' and 'G' 'C' has got 2 slave
mounts 'J' and 'K'  and  'D' has got two slave mounts 'H' and 'I'.
'E' is also shared with 'K' and they propagate to each other.  And
'K' has 3 slaves 'M', 'L' and 'N'

A's ->mnt_share links with the ->mnt_share of 'B' 'C' and 'D'

A's ->mnt_slave_list links with ->mnt_slave of 'E', 'K', 'F' and 'G'

E's ->mnt_share links with ->mnt_share of K

'E', 'K', 'F', 'G' have their ->mnt_master point to struct vfsmount of 'A'

'M', 'L', 'N' have their ->mnt_master point to struct vfsmount of 'K'

K's ->mnt_slave_list links with ->mnt_slave of 'M', 'L' and 'N'

C's ->mnt_slave_list links with ->mnt_slave of 'J' and 'K'

J and K's ->mnt_master points to struct vfsmount of C

and finally D's ->mnt_slave_list links with ->mnt_slave of 'H' and 'I'

'H' and 'I' have their ->mnt_master pointing to struct vfsmount of 'D'.


NOTE: The propagation tree is orthogonal to the mount tree.
”h]”(hý)”}”(hŒDatastructure”h]”hŒDatastructure”…””}”(hj&  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MWhj"  ubhý)”}”(hŒ5Several new fields are introduced to struct vfsmount:”h]”hŒ5Several new fields are introduced to struct vfsmount:”…””}”(hj4  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MYhj"  ubj{  )”}”(hhh]”(j€  )”}”(hŒg->mnt_share
Links together all the mount to/from which this vfsmount
send/receives propagation events.
”h]”(j†  )”}”(hŒ->mnt_share”h]”hŒ->mnt_share”…””}”(hjI  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´M]hjE  ubj–  )”}”(hhh]”hý)”}”(hŒZLinks together all the mount to/from which this vfsmount
send/receives propagation events.”h]”hŒZLinks together all the mount to/from which this vfsmount
send/receives propagation events.”…””}”(hjZ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M\hjW  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j•  hjE  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´M]hjB  ubj€  )”}”(hŒL->mnt_slave_list
Links all the mounts to which this vfsmount propagates
to.
”h]”(j†  )”}”(hŒ->mnt_slave_list”h]”hŒ->mnt_slave_list”…””}”(hjx  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´Mahjt  ubj–  )”}”(hhh]”hý)”}”(hŒ:Links all the mounts to which this vfsmount propagates
to.”h]”hŒ:Links all the mounts to which this vfsmount propagates
to.”…””}”(hj‰  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M`hj†  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j•  hjt  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´MahjB  ubj€  )”}”(hŒR->mnt_slave
Links together all the slaves that its master vfsmount
propagates to.
”h]”(j†  )”}”(hŒ->mnt_slave”h]”hŒ->mnt_slave”…””}”(hj§  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´Mehj£  ubj–  )”}”(hhh]”hý)”}”(hŒELinks together all the slaves that its master vfsmount
propagates to.”h]”hŒELinks together all the slaves that its master vfsmount
propagates to.”…””}”(hj¸  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mdhjµ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j•  hj£  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´MehjB  ubj€  )”}”(hŒZ->mnt_master
Points to the master vfsmount from which this vfsmount
receives propagation.
”h]”(j†  )”}”(hŒ->mnt_master”h]”hŒ->mnt_master”…””}”(hjÖ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´MihjÒ  ubj–  )”}”(hhh]”hý)”}”(hŒLPoints to the master vfsmount from which this vfsmount
receives propagation.”h]”hŒLPoints to the master vfsmount from which this vfsmount
receives propagation.”…””}”(hjç  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhhjä  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j•  hjÒ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´MihjB  ubj€  )”}”(hŒÔ->mnt_flags
Takes two more flags to indicate the propagation status of
the vfsmount.  MNT_SHARE indicates that the vfsmount is a shared
vfsmount.  MNT_UNCLONABLE indicates that the vfsmount cannot be
replicated.
”h]”(j†  )”}”(hŒ->mnt_flags”h]”hŒ->mnt_flags”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j…  h³hÇh´Mohj  ubj–  )”}”(hhh]”hý)”}”(hŒÇTakes two more flags to indicate the propagation status of
the vfsmount.  MNT_SHARE indicates that the vfsmount is a shared
vfsmount.  MNT_UNCLONABLE indicates that the vfsmount cannot be
replicated.”h]”hŒÇTakes two more flags to indicate the propagation status of
the vfsmount.  MNT_SHARE indicates that the vfsmount is a shared
vfsmount.  MNT_UNCLONABLE indicates that the vfsmount cannot be
replicated.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mlhj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j•  hj  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1j  h³hÇh´MohjB  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jz  hj"  ubhý)”}”(hŒPAll the shared vfsmounts in a peer group form a cyclic list through
->mnt_share.”h]”hŒPAll the shared vfsmounts in a peer group form a cyclic list through
->mnt_share.”…””}”(hj6  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mqhj"  ubhý)”}”(hŒ†All vfsmounts with the same ->mnt_master form on a cyclic list anchored
in ->mnt_master->mnt_slave_list and going through ->mnt_slave.”h]”hŒ†All vfsmounts with the same ->mnt_master form on a cyclic list anchored
in ->mnt_master->mnt_slave_list and going through ->mnt_slave.”…””}”(hjD  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mthj"  ubhý)”}”(hXg  ->mnt_master can point to arbitrary (and possibly different) members
of master peer group.  To find all immediate slaves of a peer group
you need to go through _all_ ->mnt_slave_list of its members.
Conceptually it's just a single set - distribution among the
individual lists does not affect propagation or the way propagation
tree is modified by operations.”h]”hXi  ->mnt_master can point to arbitrary (and possibly different) members
of master peer group.  To find all immediate slaves of a peer group
you need to go through _all_ ->mnt_slave_list of its members.
Conceptually itâ€™s just a single set - distribution among the
individual lists does not affect propagation or the way propagation
tree is modified by operations.”…””}”(hjR  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mwhj"  ubhý)”}”(hŒ…All vfsmounts in a peer group have the same ->mnt_master.  If it is
non-NULL, they form a contiguous (ordered) segment of slave list.”h]”hŒ…All vfsmounts in a peer group have the same ->mnt_master.  If it is
non-NULL, they form a contiguous (ordered) segment of slave list.”…””}”(hj`  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M~hj"  ubhý)”}”(hŒ>A example propagation tree looks as shown in the figure below.”h]”hŒ>A example propagation tree looks as shown in the figure below.”…””}”(hjn  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mhj"  ubj©  )”}”(hŒ}Though it looks like a forest, if we consider all the shared
mounts as a conceptual entity called 'pnode', it becomes a tree.”h]”hý)”}”(hŒ}Though it looks like a forest, if we consider all the shared
mounts as a conceptual entity called 'pnode', it becomes a tree.”h]”hŒThough it looks like a forest, if we consider all the shared
mounts as a conceptual entity called â€˜pnodeâ€™, it becomes a tree.”…””}”(hj€  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M„hj|  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j¨  hj"  ubj™  )”}”(hŒq    A <--> B <--> C <---> D
   /|\            /|      |\
  / F G          J K      H I
 /
E<-->K
    /|\
   M L N”h]”hŒq    A <--> B <--> C <---> D
   /|\            /|      |\
  / F G          J K      H I
 /
E<-->K
    /|\
   M L N”…””}”hj”  sbah}”(h]”h ]”h"]”h$]”h&]”hÅhÆuh1j˜  h³hÇh´MŠhj"  ubhý)”}”(hX5  In the above figure  A,B,C and D all are shared and propagate to each
other.   'A' has got 3 slave mounts 'E' 'F' and 'G' 'C' has got 2 slave
mounts 'J' and 'K'  and  'D' has got two slave mounts 'H' and 'I'.
'E' is also shared with 'K' and they propagate to each other.  And
'K' has 3 slaves 'M', 'L' and 'N'”h]”hXu  In the above figure  A,B,C and D all are shared and propagate to each
other.   â€˜Aâ€™ has got 3 slave mounts â€˜Eâ€™ â€˜Fâ€™ and â€˜Gâ€™ â€˜Câ€™ has got 2 slave
mounts â€˜Jâ€™ and â€˜Kâ€™  and  â€˜Dâ€™ has got two slave mounts â€˜Hâ€™ and â€˜Iâ€™.
â€˜Eâ€™ is also shared with â€˜Kâ€™ and they propagate to each other.  And
â€˜Kâ€™ has 3 slaves â€˜Mâ€™, â€˜Lâ€™ and â€˜Nâ€™”…””}”(hj¢  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M’hj"  ubhý)”}”(hŒ=A's ->mnt_share links with the ->mnt_share of 'B' 'C' and 'D'”h]”hŒKAâ€™s ->mnt_share links with the ->mnt_share of â€˜Bâ€™ â€˜Câ€™ and â€˜Dâ€™”…””}”(hj°  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M˜hj"  ubhý)”}”(hŒDA's ->mnt_slave_list links with ->mnt_slave of 'E', 'K', 'F' and 'G'”h]”hŒVAâ€™s ->mnt_slave_list links with ->mnt_slave of â€˜Eâ€™, â€˜Kâ€™, â€˜Fâ€™ and â€˜Gâ€™”…””}”(hj¾  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mšhj"  ubhý)”}”(hŒ+E's ->mnt_share links with ->mnt_share of K”h]”hŒ-Eâ€™s ->mnt_share links with ->mnt_share of K”…””}”(hjÌ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mœhj"  ubhý)”}”(hŒJ'E', 'K', 'F', 'G' have their ->mnt_master point to struct vfsmount of 'A'”h]”hŒ^â€˜Eâ€™, â€˜Kâ€™, â€˜Fâ€™, â€˜Gâ€™ have their ->mnt_master point to struct vfsmount of â€˜Aâ€™”…””}”(hjÚ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mžhj"  ubhý)”}”(hŒE'M', 'L', 'N' have their ->mnt_master point to struct vfsmount of 'K'”h]”hŒUâ€˜Mâ€™, â€˜Lâ€™, â€˜Nâ€™ have their ->mnt_master point to struct vfsmount of â€˜Kâ€™”…””}”(hjè  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M hj"  ubhý)”}”(hŒ?K's ->mnt_slave_list links with ->mnt_slave of 'M', 'L' and 'N'”h]”hŒMKâ€™s ->mnt_slave_list links with ->mnt_slave of â€˜Mâ€™, â€˜Lâ€™ and â€˜Nâ€™”…””}”(hjö  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¢hj"  ubhý)”}”(hŒ:C's ->mnt_slave_list links with ->mnt_slave of 'J' and 'K'”h]”hŒDCâ€™s ->mnt_slave_list links with ->mnt_slave of â€˜Jâ€™ and â€˜Kâ€™”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¤hj"  ubhý)”}”(hŒ5J and K's ->mnt_master points to struct vfsmount of C”h]”hŒ7J and Kâ€™s ->mnt_master points to struct vfsmount of C”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¦hj"  ubhý)”}”(hŒFand finally D's ->mnt_slave_list links with ->mnt_slave of 'H' and 'I'”h]”hŒPand finally Dâ€™s ->mnt_slave_list links with ->mnt_slave of â€˜Hâ€™ and â€˜Iâ€™”…””}”(hj   h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¨hj"  ubhý)”}”(hŒG'H' and 'I' have their ->mnt_master pointing to struct vfsmount of 'D'.”h]”hŒSâ€˜Hâ€™ and â€˜Iâ€™ have their ->mnt_master pointing to struct vfsmount of â€˜Dâ€™.”…””}”(hj.  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mªhj"  ubhý)”}”(hŒ;NOTE: The propagation tree is orthogonal to the mount tree.”h]”hŒ;NOTE: The propagation tree is orthogonal to the mount tree.”…””}”(hj<  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M­hj"  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj  h²hh³hÇh´NubjU  )”}”(hXó  Locking:

->mnt_share, ->mnt_slave, ->mnt_slave_list, ->mnt_master are protected
by namespace_sem (exclusive for modifications, shared for reading).

Normally we have ->mnt_flags modifications serialized by vfsmount_lock.
There are two exceptions: do_add_mount() and clone_mnt().
The former modifies a vfsmount that has not been visible in any shared
data structures yet.
The latter holds namespace_sem and the only references to vfsmount
are in lists that can't be traversed without namespace_sem.
”•›.      h]”(hý)”}”(hŒLocking:”h]”hŒLocking:”…””}”(hjT  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¯hjP  ubhý)”}”(hŒŠ->mnt_share, ->mnt_slave, ->mnt_slave_list, ->mnt_master are protected
by namespace_sem (exclusive for modifications, shared for reading).”h]”hŒŠ->mnt_share, ->mnt_slave, ->mnt_slave_list, ->mnt_master are protected
by namespace_sem (exclusive for modifications, shared for reading).”…””}”(hjb  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M±hjP  ubhý)”}”(hX\  Normally we have ->mnt_flags modifications serialized by vfsmount_lock.
There are two exceptions: do_add_mount() and clone_mnt().
The former modifies a vfsmount that has not been visible in any shared
data structures yet.
The latter holds namespace_sem and the only references to vfsmount
are in lists that can't be traversed without namespace_sem.”h]”hX^  Normally we have ->mnt_flags modifications serialized by vfsmount_lock.
There are two exceptions: do_add_mount() and clone_mnt().
The former modifies a vfsmount that has not been visible in any shared
data structures yet.
The latter holds namespace_sem and the only references to vfsmount
are in lists that canâ€™t be traversed without namespace_sem.”…””}”(hjp  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M´hjP  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj  h²hh³hÇh´NubjU  )”}”(hXÞ  Algorithm:

The crux of the implementation resides in rbind/move operation.

The overall algorithm breaks the operation into 3 phases: (look at
attach_recursive_mnt() and propagate_mnt())

1. Prepare phase.

   For each mount in the source tree:

   a) Create the necessary number of mount trees to
      be attached to each of the mounts that receive
      propagation from the destination mount.
   b) Do not attach any of the trees to its destination.
      However note down its ->mnt_parent and ->mnt_mountpoint
   c) Link all the new mounts to form a propagation tree that
      is identical to the propagation tree of the destination
      mount.

   If this phase is successful, there should be 'n' new
   propagation trees; where 'n' is the number of mounts in the
   source tree.  Go to the commit phase

   Also there should be 'm' new mount trees, where 'm' is
   the number of mounts to which the destination mount
   propagates to.

   If any memory allocations fail, go to the abort phase.

2. Commit phase.

   Attach each of the mount trees to their corresponding
   destination mounts.

3. Abort phase.

   Delete all the newly created trees.

.. Note::
   all the propagation related functionality resides in the file pnode.c

”h]”(hý)”}”(hŒ
Algorithm:”h]”hŒ
Algorithm:”…””}”(hjˆ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M»hj„  ubhý)”}”(hŒ?The crux of the implementation resides in rbind/move operation.”h]”hŒ?The crux of the implementation resides in rbind/move operation.”…””}”(hj–  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M½hj„  ubhý)”}”(hŒnThe overall algorithm breaks the operation into 3 phases: (look at
attach_recursive_mnt() and propagate_mnt())”h]”hŒnThe overall algorithm breaks the operation into 3 phases: (look at
attach_recursive_mnt() and propagate_mnt())”…””}”(hj¤  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M¿hj„  ubjP  )”}”(hhh]”(jU  )”}”(hXý  Prepare phase.

For each mount in the source tree:

a) Create the necessary number of mount trees to
   be attached to each of the mounts that receive
   propagation from the destination mount.
b) Do not attach any of the trees to its destination.
   However note down its ->mnt_parent and ->mnt_mountpoint
c) Link all the new mounts to form a propagation tree that
   is identical to the propagation tree of the destination
   mount.

If this phase is successful, there should be 'n' new
propagation trees; where 'n' is the number of mounts in the
source tree.  Go to the commit phase

Also there should be 'm' new mount trees, where 'm' is
the number of mounts to which the destination mount
propagates to.

If any memory allocations fail, go to the abort phase.
”h]”(hý)”}”(hŒPrepare phase.”h]”hŒPrepare phase.”…””}”(hj¹  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÂhjµ  ubhý)”}”(hŒ"For each mount in the source tree:”h]”hŒ"For each mount in the source tree:”…””}”(hjÇ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÄhjµ  ubjP  )”}”(hhh]”(jU  )”}”(hŒ„Create the necessary number of mount trees to
be attached to each of the mounts that receive
propagation from the destination mount.”h]”hý)”}”(hŒ„Create the necessary number of mount trees to
be attached to each of the mounts that receive
propagation from the destination mount.”h]”hŒ„Create the necessary number of mount trees to
be attached to each of the mounts that receive
propagation from the destination mount.”…””}”(hjÜ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÆhjØ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjÕ  ubjU  )”}”(hŒjDo not attach any of the trees to its destination.
However note down its ->mnt_parent and ->mnt_mountpoint”h]”hý)”}”(hŒjDo not attach any of the trees to its destination.
However note down its ->mnt_parent and ->mnt_mountpoint”h]”hŒjDo not attach any of the trees to its destination.
However note down its ->mnt_parent and ->mnt_mountpoint”…””}”(hjô  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÉhjð  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjÕ  ubjU  )”}”(hŒwLink all the new mounts to form a propagation tree that
is identical to the propagation tree of the destination
mount.
”h]”hý)”}”(hŒvLink all the new mounts to form a propagation tree that
is identical to the propagation tree of the destination
mount.”h]”hŒvLink all the new mounts to form a propagation tree that
is identical to the propagation tree of the destination
mount.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MËhj  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jT  hjÕ  ubeh}”(h]”h ]”h"]”h$]”h&]”jÔ  jÕ  jÖ  hj×  jØ  uh1jO  hjµ  ubhý)”}”(hŒ•If this phase is successful, there should be 'n' new
propagation trees; where 'n' is the number of mounts in the
source tree.  Go to the commit phase”h]”hŒIf this phase is successful, there should be â€˜nâ€™ new
propagation trees; where â€˜nâ€™ is the number of mounts in the
source tree.  Go to the commit phase”…””}”(hj&  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÏhjµ  ubhý)”}”(hŒyAlso there should be 'm' new mount trees, where 'm' is
the number of mounts to which the destination mount
propagates to.”h]”hŒAlso there should be â€˜mâ€™ new mount trees, where â€˜mâ€™ is
the number of mounts to which the destination mount
propagates to.”…””}”(hj4  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÓhjµ  ubhý)”}”(hŒ6If any memory allocations fail, go to the abort phase.”h]”hŒ6If any memory allocations fail, go to the abort phase.”…””}”(hjB  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´M×hjµ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj²  ubjU  )”}”(hŒYCommit phase.

Attach each of the mount trees to their corresponding
destination mounts.
”h]”(hý)”}”(hŒCommit phase.”h]”hŒCommit phase.”…””}”(hjZ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÙhjV  ubhý)”}”(hŒIAttach each of the mount trees to their corresponding
destination mounts.”h]”hŒIAttach each of the mount trees to their corresponding
destination mounts.”…””}”(hjh  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÛhjV  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj²  ubjU  )”}”(hŒ2Abort phase.

Delete all the newly created trees.
”h]”(hý)”}”(hŒAbort phase.”h]”hŒAbort phase.”…””}”(hj€  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´MÞhj|  ubhý)”}”(hŒ#Delete all the newly created trees.”h]”hŒ#Delete all the newly created trees.”…””}”(hjŽ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Màhj|  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj²  ubeh}”(h]”h ]”h"]”h$]”h&]”jÔ  j0  jÖ  hj×  jg	  uh1jO  hj„  ubj©  )”}”(hŒEall the propagation related functionality resides in the file pnode.c”h]”hý)”}”(hjª  h]”hŒEall the propagation related functionality resides in the file pnode.c”…””}”(hj¬  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mãhj¨  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j¨  hj„  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jT  hj  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”jÔ  jú  jÖ  hj×  jØ  uh1jO  hj  h²hh³hÇh´MWubhŒ
transition”“”)”}”(hŒH------------------------------------------------------------------------”h]”h}”(h]”h ]”h"]”h$]”h&]”uh1jË  h³hÇh´Mæhj  h²hubhý)”}”(hŒHversion 0.1  (created the initial document, Ram Pai linuxram@us.ibm.com)”h]”(hŒ4version 0.1  (created the initial document, Ram Pai ”…””}”(hj×  h²hh³Nh´NubhŒ	reference”“”)”}”(hŒlinuxram@us.ibm.com”h]”hŒlinuxram@us.ibm.com”…””}”(hjá  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œmailto:linuxram@us.ibm.com”uh1jß  hj×  ubhŒ)”…””}”(hj×  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mèhj  h²hubhý)”}”(hŒ1version 0.2  (Incorporated comments from Al Viro)”h]”hŒ1version 0.2  (Incorporated comments from Al Viro)”…””}”(hjû  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hüh³hÇh´Mêhj  h²hubeh}”(h]”Œimplementation”ah ]”h"]”Œ8) implementation”ah$]”h&]”uh1hÈhhÊh²hh³hÇh´MUubeh}”(h]”Œshared-subtrees”ah ]”h"]”Œshared subtrees”ah$]”h&]”uh1hÈhhh²hh³hÇh´Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”hÇuh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(hÍNŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”j<  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”hÇŒ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(j  j  j-  j*  jÞ  jÛ  j  j  jœ  j™  j×  jÔ  jé  jæ  j  j  j  j  uŒ	nametypes”}”(j  ‰j-  ‰jÞ  ‰j  ‰jœ  ‰j×  ‰jé  ‰j  ‰j  ‰uh}”(j  hÊj*  hëjÛ  j0  j  já  j™  j  jÔ  jŸ  jæ  jÚ  j  jì  j  j  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”hŒsystem_message”“”)”}”(hhh]”hý)”}”(hŒ:Enumerated list start value not ordinal-1: "C" (ordinal 3)”h]”hŒ>Enumerated list start value not ordinal-1: â€œCâ€ (ordinal 3)”…””}”(hj£  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hühj   ubah}”(h]”h ]”h"]”h$]”h&]”Œlevel”KŒtype”ŒINFO”Œsource”hÇŒline”Kuh1jž  hj  h²hh³hÇh´KÏubaŒtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nh²hub.