€•2/      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”Œ3/translations/zh_CN/admin-guide/device-mapper/dm-io”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$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ3/translations/zh_TW/admin-guide/device-mapper/dm-io”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ3/translations/it_IT/admin-guide/device-mapper/dm-io”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ3/translations/ja_JP/admin-guide/device-mapper/dm-io”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ3/translations/ko_KR/admin-guide/device-mapper/dm-io”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒPortuguese (Brazilian)”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ3/translations/pt_BR/admin-guide/device-mapper/dm-io”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh–sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ3/translations/sp_SP/admin-guide/device-mapper/dm-io”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒdm-io”h]”hŒdm-io”…””}”(hh¼h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhh·h²hh³ŒM/var/lib/git/docbuild/linux/Documentation/admin-guide/device-mapper/dm-io.rst”h´KubhŒ	paragraph”“”)”}”(hŒ™Dm-io provides synchronous and asynchronous I/O services. There are three
types of I/O services available, and each type has a sync and an async
version.”h]”hŒ™Dm-io provides synchronous and asynchronous I/O services. There are three
types of I/O services available, and each type has a sync and an async
version.”…””}”(hhÍh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´Khh·h²hubhÌ)”}”(hŒ¸The user must set up an io_region structure to describe the desired location
of the I/O. Each io_region indicates a block-device along with the starting
sector and size of the region::”h]”hŒ·The user must set up an io_region structure to describe the desired location
of the I/O. Each io_region indicates a block-device along with the starting
sector and size of the region:”…””}”(hhÛh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K	hh·h²hubhŒliteral_block”“”)”}”(hŒZstruct io_region {
   struct block_device *bdev;
   sector_t sector;
   sector_t count;
};”h]”hŒZstruct io_region {
   struct block_device *bdev;
   sector_t sector;
   sector_t count;
};”…””}”hhësbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1héh³hÊh´Khh·h²hubhÌ)”}”(hŒ“Dm-io can read from one io_region or write to one or more io_regions. Writes
to multiple regions are specified by an array of io_region structures.”h]”hŒ“Dm-io can read from one io_region or write to one or more io_regions. Writes
to multiple regions are specified by an array of io_region structures.”…””}”(hhûh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´Khh·h²hubhÌ)”}”(hŒ‚The first I/O service type takes a list of memory pages as the data buffer for
the I/O, along with an offset into the first page::”h]”hŒThe first I/O service type takes a list of memory pages as the data buffer for
the I/O, along with an offset into the first page:”…””}”(hj	  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´Khh·h²hubhê)”}”(hX­  struct page_list {
   struct page_list *next;
   struct page *page;
};

int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw,
               struct page_list *pl, unsigned int offset,
               unsigned long *error_bits);
int dm_io_async(unsigned int num_regions, struct io_region *where, int rw,
                struct page_list *pl, unsigned int offset,
                io_notify_fn fn, void *context);”h]”hX­  struct page_list {
   struct page_list *next;
   struct page *page;
};

int dm_io_sync(unsigned int num_regions, struct io_region *where, int rw,
               struct page_list *pl, unsigned int offset,
               unsigned long *error_bits);
int dm_io_async(unsigned int num_regions, struct io_region *where, int rw,
                struct page_list *pl, unsigned int offset,
                io_notify_fn fn, void *context);”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”hùhúuh1héh³hÊh´Khh·h²hubhÌ)”}”(hŒãThe second I/O service type takes an array of bio vectors as the data buffer
for the I/O. This service can be handy if the caller has a pre-assembled bio,
but wants to direct different portions of the bio to different devices::”h]”hŒâThe second I/O service type takes an array of bio vectors as the data buffer
for the I/O. This service can be handy if the caller has a pre-assembled bio,
but wants to direct different portions of the bio to different devices:”…””}”(hj%  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K%hh·h²hubhê)”}”(hXY  int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where,
                    int rw, struct bio_vec *bvec,
                    unsigned long *error_bits);
int dm_io_async_bvec(unsigned int num_regions, struct io_region *where,
                     int rw, struct bio_vec *bvec,
                     io_notify_fn fn, void *context);”h]”hXY  int dm_io_sync_bvec(unsigned int num_regions, struct io_region *where,
                    int rw, struct bio_vec *bvec,
                    unsigned long *error_bits);
int dm_io_async_bvec(unsigned int num_regions, struct io_region *where,
                     int rw, struct bio_vec *bvec,
                     io_notify_fn fn, void *context);”…””}”hj3  sbah}”(h]”h ]”h"]”h$]”h&]”hùhúuh1héh³hÊh´K)hh·h²hubhÌ)”}”(hŒúThe third I/O service type takes a pointer to a vmalloc'd memory buffer as the
data buffer for the I/O. This service can be handy if the caller needs to do
I/O to a large region but doesn't want to allocate a large number of individual
memory pages::”h]”hŒýThe third I/O service type takes a pointer to a vmallocâ€™d memory buffer as the
data buffer for the I/O. This service can be handy if the caller needs to do
I/O to a large region but doesnâ€™t want to allocate a large number of individual
memory pages:”…””}”(hjA  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K0hh·h²hubhê)”}”(hX  int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw,
                  void *data, unsigned long *error_bits);
int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw,
                   void *data, io_notify_fn fn, void *context);”h]”hX  int dm_io_sync_vm(unsigned int num_regions, struct io_region *where, int rw,
                  void *data, unsigned long *error_bits);
int dm_io_async_vm(unsigned int num_regions, struct io_region *where, int rw,
                   void *data, io_notify_fn fn, void *context);”…””}”hjO  sbah}”(h]”h ]”h"]”h$]”h&]”hùhúuh1héh³hÊh´K5hh·h²hubhÌ)”}”(hŒCallers of the asynchronous I/O services must include the name of a completion
callback routine and a pointer to some context data for the I/O::”h]”hŒCallers of the asynchronous I/O services must include the name of a completion
callback routine and a pointer to some context data for the I/O:”…””}”(hj]  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K:hh·h²hubhê)”}”(hŒAtypedef void (*io_notify_fn)(unsigned long error, void *context);”h]”hŒAtypedef void (*io_notify_fn)(unsigned long error, void *context);”…””}”hjk  sbah}”(h]”h ]”h"]”h$]”h&]”hùhúuh1héh³hÊh´K=hh·h²hubhÌ)”}”(hX   The "error" parameter in this callback, as well as the `*error` parameter in
all of the synchronous versions, is a bitset (instead of a simple error value).
In the case of an write-I/O to multiple regions, this bitset allows dm-io to
indicate success or failure on each individual region.”h]”(hŒ;The â€œerrorâ€ parameter in this callback, as well as the ”…””}”(hjy  h²hh³Nh´NubhŒtitle_reference”“”)”}”(hŒ`*error`”h]”hŒ*error”…””}”(hjƒ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hjy  ubhŒá parameter in
all of the synchronous versions, is a bitset (instead of a simple error value).
In the case of an write-I/O to multiple regions, this bitset allows dm-io to
indicate success or failure on each individual region.”…””}”(hjy  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K?hh·h²hubhÌ)”}”(hX(  Before using any of the dm-io services, the user should call dm_io_get()
and specify the number of pages they expect to perform I/O on concurrently.
Dm-io will attempt to resize its mempool to make sure enough pages are
always available in order to avoid unnecessary waiting while performing I/O.”h]”hX(  Before using any of the dm-io services, the user should call dm_io_get()
and specify the number of pages they expect to perform I/O on concurrently.
Dm-io will attempt to resize its mempool to make sure enough pages are
always available in order to avoid unnecessary waiting while performing I/O.”…””}”(hj›  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´KDhh·h²hubhÌ)”}”(hŒžWhen the user is finished using the dm-io services, they should call
dm_io_put() and specify the same number of pages that were given on the
dm_io_get() call.”h]”hŒžWhen the user is finished using the dm-io services, they should call
dm_io_put() and specify the same number of pages that were given on the
dm_io_get() call.”…””}”(hj©  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´KIhh·h²hubeh}”(h]”Œdm-io”ah ]”h"]”Œdm-io”ah$]”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
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id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nh²hub.