€•Ð1      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/nfs/pnfs”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$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/zh_TW/filesystems/nfs/pnfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/it_IT/filesystems/nfs/pnfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/ja_JP/filesystems/nfs/pnfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/ko_KR/filesystems/nfs/pnfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒPortuguese (Brazilian)”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/pt_BR/filesystems/nfs/pnfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh–sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/sp_SP/filesystems/nfs/pnfs”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒReference counting in pnfs”h]”hŒReference counting in pnfs”…””}”(hh¼h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhh·h²hh³ŒB/var/lib/git/docbuild/linux/Documentation/filesystems/nfs/pnfs.rst”h´KubhŒ	paragraph”“”)”}”(hX5  The are several inter-related caches.  We have layouts which can
reference multiple devices, each of which can reference multiple data servers.
Each data server can be referenced by multiple devices.  Each device
can be referenced by multiple layouts. To keep all of this straight,
we need to reference count.”h]”hX5  The are several inter-related caches.  We have layouts which can
reference multiple devices, each of which can reference multiple data servers.
Each data server can be referenced by multiple devices.  Each device
can be referenced by multiple layouts. To keep all of this straight,
we need to reference count.”…””}”(hhÍh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´Khh·h²hubh¶)”}”(hhh]”(h»)”}”(hŒstruct pnfs_layout_hdr”h]”hŒstruct pnfs_layout_hdr”…””}”(hhÞh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhhÛh²hh³hÊh´KubhÌ)”}”(hŒòThe on-the-wire command LAYOUTGET corresponds to struct
pnfs_layout_segment, usually referred to by the variable name lseg.
Each nfs_inode may hold a pointer to a cache of these layout
segments in nfsi->layout, of type struct pnfs_layout_hdr.”h]”hŒòThe on-the-wire command LAYOUTGET corresponds to struct
pnfs_layout_segment, usually referred to by the variable name lseg.
Each nfs_inode may hold a pointer to a cache of these layout
segments in nfsi->layout, of type struct pnfs_layout_hdr.”…””}”(hhìh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´KhhÛh²hubhÌ)”}”(hŒ±We reference the header for the inode pointing to it, across each
outstanding RPC call that references it (LAYOUTGET, LAYOUTRETURN,
LAYOUTCOMMIT), and for each lseg held within.”h]”hŒ±We reference the header for the inode pointing to it, across each
outstanding RPC call that references it (LAYOUTGET, LAYOUTRETURN,
LAYOUTCOMMIT), and for each lseg held within.”…””}”(hhúh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´KhhÛh²hubhÌ)”}”(hŒáEach header is also (when non-empty) put on a list associated with
struct nfs_client (cl_layouts).  Being put on this list does not bump
the reference count, as the layout is kept around by the lseg that
keeps it in the list.”h]”hŒáEach header is also (when non-empty) put on a list associated with
struct nfs_client (cl_layouts).  Being put on this list does not bump
the reference count, as the layout is kept around by the lseg that
keeps it in the list.”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´KhhÛh²hubeh}”(h]”Œstruct-pnfs-layout-hdr”ah ]”h"]”Œstruct pnfs_layout_hdr”ah$]”h&]”uh1hµhh·h²hh³hÊh´Kubh¶)”}”(hhh]”(h»)”}”(hŒdeviceid_cache”h]”hŒdeviceid_cache”…””}”(hj!  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhj  h²hh³hÊh´KubhÌ)”}”(hX9  lsegs reference device ids, which are resolved per nfs_client and
layout driver type.  The device ids are held in a RCU cache (struct
nfs4_deviceid_cache).  The cache itself is referenced across each
mount.  The entries (struct nfs4_deviceid) themselves are held across
the lifetime of each lseg referencing them.”h]”hX9  lsegs reference device ids, which are resolved per nfs_client and
layout driver type.  The device ids are held in a RCU cache (struct
nfs4_deviceid_cache).  The cache itself is referenced across each
mount.  The entries (struct nfs4_deviceid) themselves are held across
the lifetime of each lseg referencing them.”…””}”(hj/  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K hj  h²hubhÌ)”}”(hX  RCU is used because the deviceid is basically a write once, read many
data structure.  The hlist size of 32 buckets needs better
justification, but seems reasonable given that we can have multiple
deviceid's per filesystem, and multiple filesystems per nfs_client.”h]”hX
  RCU is used because the deviceid is basically a write once, read many
data structure.  The hlist size of 32 buckets needs better
justification, but seems reasonable given that we can have multiple
deviceidâ€™s per filesystem, and multiple filesystems per nfs_client.”…””}”(hj=  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K&hj  h²hubhÌ)”}”(hŒÓThe hash code is copied from the nfsd code base.  A discussion of
hashing and variations of this algorithm can be found `here.
<http://groups.google.com/group/comp.lang.c/browse_thread/thread/9522965e2b8d3809>`_”h]”(hŒxThe hash code is copied from the nfsd code base.  A discussion of
hashing and variations of this algorithm can be found ”…””}”(hjK  h²hh³Nh´NubhŒ	reference”“”)”}”(hŒ[`here.
<http://groups.google.com/group/comp.lang.c/browse_thread/thread/9522965e2b8d3809>`_”h]”hŒhere.”…””}”(hjU  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”Œname”Œhere.”Œrefuri”ŒPhttp://groups.google.com/group/comp.lang.c/browse_thread/thread/9522965e2b8d3809”uh1jS  hjK  ubhŒtarget”“”)”}”(hŒS
<http://groups.google.com/group/comp.lang.c/browse_thread/thread/9522965e2b8d3809>”h]”h}”(h]”Œhere”ah ]”h"]”Œhere.”ah$]”h&]”Œrefuri”jf  uh1jg  Œ
referenced”KhjK  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K+hj  h²hubeh}”(h]”Œdeviceid-cache”ah ]”h"]”Œdeviceid_cache”ah$]”h&]”uh1hµhh·h²hh³hÊh´Kubh¶)”}”(hhh]”(h»)”}”(hŒdata server cache”h]”hŒdata server cache”…””}”(hjˆ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhj…  h²hh³hÊh´K0ubhÌ)”}”(hŒ›file driver devices refer to data servers, which are kept in a module
level cache.  Its reference is held over the lifetime of the deviceid
pointing to it.”h]”hŒ›file driver devices refer to data servers, which are kept in a module
level cache.  Its reference is held over the lifetime of the deviceid
pointing to it.”…””}”(hj–  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K2hj…  h²hubeh}”(h]”Œdata-server-cache”ah ]”h"]”Œdata server cache”ah$]”h&]”uh1hµhh·h²hh³hÊh´K0ubh¶)”}”(hhh]”(h»)”}”(hŒlseg”h]”hŒlseg”…””}”(hj¯  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhj¬  h²hh³hÊh´K7ubhÌ)”}”(hX  lseg maintains an extra reference corresponding to the NFS_LSEG_VALID
bit which holds it in the pnfs_layout_hdr's list.  When the final lseg
is removed from the pnfs_layout_hdr's list, the NFS_LAYOUT_DESTROYED
bit is set, preventing any new lsegs from being added.”h]”hX  lseg maintains an extra reference corresponding to the NFS_LSEG_VALID
bit which holds it in the pnfs_layout_hdrâ€™s list.  When the final lseg
is removed from the pnfs_layout_hdrâ€™s list, the NFS_LAYOUT_DESTROYED
bit is set, preventing any new lsegs from being added.”…””}”(hj½  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K9hj¬  h²hubeh}”(h]”Œlseg”ah ]”h"]”Œlseg”ah$]”h&]”uh1hµhh·h²hh³hÊh´K7ubh¶)”}”(hhh]”(h»)”}”(hŒlayout drivers”h]”hŒlayout drivers”…””}”(hjÖ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhjÓ  h²hh³hÊh´K?ubhÌ)”}”(hX-  PNFS utilizes what is called layout drivers. The STD defines 4 basic
layout types: "files", "objects", "blocks", and "flexfiles". For each
of these types there is a layout-driver with a common function-vectors
table which are called by the nfs-client pnfs-core to implement the
different layout types.”h]”hX=  PNFS utilizes what is called layout drivers. The STD defines 4 basic
layout types: â€œfilesâ€, â€œobjectsâ€, â€œblocksâ€, and â€œflexfilesâ€. For each
of these types there is a layout-driver with a common function-vectors
table which are called by the nfs-client pnfs-core to implement the
different layout types.”…””}”(hjä  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´KAhjÓ  h²hubhÌ)”}”(hŒÆFiles-layout-driver code is in: fs/nfs/filelayout/.. directory
Blocks-layout-driver code is in: fs/nfs/blocklayout/.. directory
Flexfiles-layout-driver code is in: fs/nfs/flexfilelayout/.. directory”h]”hŒÆFiles-layout-driver code is in: fs/nfs/filelayout/.. directory
Blocks-layout-driver code is in: fs/nfs/blocklayout/.. directory
Flexfiles-layout-driver code is in: fs/nfs/flexfilelayout/.. directory”…””}”(hjò  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´KGhjÓ  h²hubeh}”(h]”Œlayout-drivers”ah ]”h"]”Œlayout drivers”ah$]”h&]”uh1hµhh·h²hh³hÊh´K?ubh¶)”}”(hhh]”(h»)”}”(hŒblocks-layout setup”h]”hŒblocks-layout setup”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhj  h²hh³hÊh´KLubhÌ)”}”(hŒ:TODO: Document the setup needs of the blocks layout driver”h]”hŒ:TODO: Document the setup needs of the blocks layout driver”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´KNhj  h²hubeh}”(h]”Œblocks-layout-setup”ah ]”h"]”Œblocks-layout setup”ah$]”h&]”uh1hµhh·h²hh³hÊh´KLubeh}”(h]”Œreference-counting-in-pnfs”ah ]”h"]”Œreference counting in pnfs”ah$]”h&]”uh1hµhhh²hh³hÊh´Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”hÊuh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(hºNŒ	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”jZ  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”hÊŒ_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”}”(j4  j1  j  j  j‚  j  jr  jo  j©  j¦  jÐ  jÍ  j  j  j,  j)  uŒ	nametypes”}”(j4  ‰j  ‰j‚  ‰jr  ˆj©  ‰jÐ  ‰j  ‰j,  ‰uh}”(j1  h·j  hÛj  j  jo  ji  j¦  j…  jÍ  j¬  j  jÓ  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”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nh²hub.