btrfs: always read the entire extent_buffer

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[ Upstream commit e95382834c ]

Currently read_extent_buffer_pages skips pages that are already uptodate
when reading in an extent_buffer.  While this reduces the amount of data
read, it increases the number of I/O operations as we now need to do
multiple I/Os when reading an extent buffer with one or more uptodate
pages in the middle of it.  On any modern storage device, be that hard
drives or SSDs this actually decreases I/O performance.  Fortunately
this case is pretty rare as the pages are always initially read together
and then aged the same way.  Besides simplifying the code a bit as-is
this will allow for major simplifications to the I/O completion handler
later on.

Note that the case where all pages are uptodate is still handled by an
optimized fast path that does not read any data from disk.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Stable-dep-of: 7027f87108 ("btrfs: don't treat zoned writeback as being from an async helper thread")
Signed-off-by: Sasha Levin <sashal@kernel.org>

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This commit is contained in:

Christoph Hellwig 2023-05-03 17:24:25 +02:00 • committed by Greg Kroah-Hartman

parent 19920ea770

commit 110b32eea2

1 changed files with 5 additions and 12 deletions

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fs/btrfs/extent_io.c

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