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| author | Konstantin Khlebnikov <khlebnikov@yandex-team.ru> | 2019-09-24 01:34:45 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-09-25 01:54:08 +0300 |
| commit | c3aab9a0bd91b696a852169479b7db1ece6cbf8c (patch) | |
| tree | d23029d8d038a4485f8f71f5c62f0543b84f74e6 | |
| parent | 8974558f49a6a41b4a74db672e13bca616eff6d8 (diff) | |
| download | linux-c3aab9a0bd91b696a852169479b7db1ece6cbf8c.tar.xz | |
mm/filemap.c: don't initiate writeback if mapping has no dirty pages
Functions like filemap_write_and_wait_range() should do nothing if inode
has no dirty pages or pages currently under writeback. But they anyway
construct struct writeback_control and this does some atomic operations if
CONFIG_CGROUP_WRITEBACK=y - on fast path it locks inode->i_lock and
updates state of writeback ownership, on slow path might be more work.
Current this path is safely avoided only when inode mapping has no pages.
For example generic_file_read_iter() calls filemap_write_and_wait_range()
at each O_DIRECT read - pretty hot path.
This patch skips starting new writeback if mapping has no dirty tags set.
If writeback is already in progress filemap_write_and_wait_range() will
wait for it.
Link: http://lkml.kernel.org/r/156378816804.1087.8607636317907921438.stgit@buzz
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | mm/filemap.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index 5f30aedd7363..82f3b9a3a940 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -408,7 +408,8 @@ int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start, .range_end = end, }; - if (!mapping_cap_writeback_dirty(mapping)) + if (!mapping_cap_writeback_dirty(mapping) || + !mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) return 0; wbc_attach_fdatawrite_inode(&wbc, mapping->host); |