€•P.      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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h¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒM/var/lib/git/docbuild/linux/Documentation/admin-guide/device-mapper/dm-io.rst”h KubhŒ	paragraph”“”)”}”(hŒ™Dm-io provides synchronous and asynchronous I/O services. There are three
types of I/O services available, and each type has a sync and an async
version.”h]”hŒ™Dm-io provides synchronous and asynchronous I/O services. There are three
types of I/O services available, and each type has a sync and an async
version.”…””}”(hh¹hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(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hÇhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K	hh£hžhubhŒliteral_block”“”)”}”(hŒZstruct io_region {
   struct block_device *bdev;
   sector_t sector;
   sector_t count;
};”h]”hŒZstruct io_region {
   struct block_device *bdev;
   sector_t sector;
   sector_t count;
};”…””}”hh×sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1hÕhŸh¶h Khh£hžhubh¸)”}”(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hçhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¸)”}”(hŒ‚The first I/O service type takes a list of memory pages as the data buffer for
the I/O, along with an offset into the first page::”h]”hŒThe first I/O service type takes a list of memory pages as the data buffer for
the I/O, along with an offset into the first page:”…””}”(hhõhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubhÖ)”}”(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$]”h&]”håhæuh1hÕhŸh¶h Khh£hžhubh¸)”}”(hŒãThe second I/O service type takes an array of bio vectors as the data buffer
for the I/O. This service can be handy if the caller has a pre-assembled bio,
but wants to direct different portions of the bio to different devices::”h]”hŒâThe second I/O service type takes an array of bio vectors as the data buffer
for the I/O. This service can be handy if the caller has a pre-assembled bio,
but wants to direct different portions of the bio to different devices:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K%hh£hžhubhÖ)”}”(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j  sbah}”(h]”h ]”h"]”h$]”h&]”håhæuh1hÕhŸh¶h K)hh£hžhubh¸)”}”(hŒúThe third I/O service type takes a pointer to a vmalloc'd memory buffer as the
data buffer for the I/O. This service can be handy if the caller needs to do
I/O to a large region but doesn't want to allocate a large number of individual
memory pages::”h]”hŒýThe third I/O service type takes a pointer to a vmallocâ€™d memory buffer as the
data buffer for the I/O. This service can be handy if the caller needs to do
I/O to a large region but doesnâ€™t want to allocate a large number of individual
memory pages:”…””}”(hj-  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K0hh£hžhubhÖ)”}”(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j;  sbah}”(h]”h ]”h"]”h$]”h&]”håhæuh1hÕhŸh¶h K5hh£hžhubh¸)”}”(hŒCallers of the asynchronous I/O services must include the name of a completion
callback routine and a pointer to some context data for the I/O::”h]”hŒCallers of the asynchronous I/O services must include the name of a completion
callback routine and a pointer to some context data for the I/O:”…””}”(hjI  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K:hh£hžhubhÖ)”}”(hŒAtypedef void (*io_notify_fn)(unsigned long error, void *context);”h]”hŒAtypedef void (*io_notify_fn)(unsigned long error, void *context);”…””}”hjW  sbah}”(h]”h ]”h"]”h$]”h&]”håhæuh1hÕhŸh¶h K=hh£hžhubh¸)”}”(hX   The "error" parameter in this callback, as well as the `*error` parameter in
all of the synchronous versions, is a bitset (instead of a simple error value).
In the case of an write-I/O to multiple regions, this bitset allows dm-io to
indicate success or failure on each individual region.”h]”(hŒ;The â€œerrorâ€ parameter in this callback, as well as the ”…””}”(hje  hžhhŸNh NubhŒtitle_reference”“”)”}”(hŒ`*error`”h]”hŒ*error”…””}”(hjo  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jm  hje  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je  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K?hh£hžhubh¸)”}”(hX(  Before using any of the dm-io services, the user should call dm_io_get()
and specify the number of pages they expect to perform I/O on concurrently.
Dm-io will attempt to resize its mempool to make sure enough pages are
always available in order to avoid unnecessary waiting while performing I/O.”h]”hX(  Before using any of the dm-io services, the user should call dm_io_get()
and specify the number of pages they expect to perform I/O on concurrently.
Dm-io will attempt to resize its mempool to make sure enough pages are
always available in order to avoid unnecessary waiting while performing I/O.”…””}”(hj‡  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KDhh£hžhubh¸)”}”(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•  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h KIhh£hžhubeh}”(h]”Œdm-io”ah ]”h"]”Œdm-io”ah$]”h&]”uh1h¡hhhžhhŸh¶h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h¶uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¦NŒ	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”jÎ  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”h¶Œ_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¥  sŒ	nametypes”}”j¨  ‰sh}”j¥  h£sŒ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
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