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authorNeilBrown <neilb@suse.de>2022-03-22 14:38:51 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-22 15:57:00 -0700
commit84dacdbd5352bfef82423760fa2e8bffaeef9e05 (patch)
tree2492d4ebb01d4fcd1928b530c84621f1bd1ba179 /Documentation/core-api
parentbf507030f312c68fdbb17c2d33f317cda109a484 (diff)
mm: document and polish read-ahead code
Add some "big-picture" documentation for read-ahead and polish the code to make it fit this documentation. The meaning of ->async_size is clarified to match its name. i.e. Any request to ->readahead() has a sync part and an async part. The caller will wait for the sync pages to complete, but will not wait for the async pages. The first async page is still marked PG_readahead Note that the current function names page_cache_sync_ra() and page_cache_async_ra() are misleading. All ra request are partly sync and partly async, so either part can be empty. A page_cache_sync_ra() request will usually set ->async_size non-zero, implying it is not all synchronous. When a non-zero req_count is passed to page_cache_async_ra(), the implication is that some prefix of the request is synchronous, though the calculation made there is incorrect - I haven't tried to fix it. Link: https://lkml.kernel.org/r/164549983734.9187.11586890887006601405.stgit@noble.brown Signed-off-by: NeilBrown <neilb@suse.de> Cc: Anna Schumaker <Anna.Schumaker@Netapp.com> Cc: Chao Yu <chao@kernel.org> Cc: Darrick J. Wong <djwong@kernel.org> Cc: Ilya Dryomov <idryomov@gmail.com> Cc: Jaegeuk Kim <jaegeuk@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: Jeff Layton <jlayton@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Lars Ellenberg <lars.ellenberg@linbit.com> Cc: Miklos Szeredi <miklos@szeredi.hu> Cc: Paolo Valente <paolo.valente@linaro.org> Cc: Philipp Reisner <philipp.reisner@linbit.com> Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com> Cc: Trond Myklebust <trond.myklebust@hammerspace.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/core-api')
-rw-r--r--Documentation/core-api/mm-api.rst19
1 files changed, 17 insertions, 2 deletions
diff --git a/Documentation/core-api/mm-api.rst b/Documentation/core-api/mm-api.rst
index 395835f9289f..f5b2f92822c8 100644
--- a/Documentation/core-api/mm-api.rst
+++ b/Documentation/core-api/mm-api.rst
@@ -58,15 +58,30 @@ Virtually Contiguous Mappings
File Mapping and Page Cache
===========================
-.. kernel-doc:: mm/readahead.c
- :export:
+Filemap
+-------
.. kernel-doc:: mm/filemap.c
:export:
+Readahead
+---------
+
+.. kernel-doc:: mm/readahead.c
+ :doc: Readahead Overview
+
+.. kernel-doc:: mm/readahead.c
+ :export:
+
+Writeback
+---------
+
.. kernel-doc:: mm/page-writeback.c
:export:
+Truncate
+--------
+
.. kernel-doc:: mm/truncate.c
:export: