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btrfs: add cached_state to read_extent_buffer_subpage

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We don't use a cached state here at all, which generally makes sense as
async reads are going to unlock at endio time.  However for blocking
reads we will call wait_extent_bit() for our range.  Since the
lock_extent() stuff will return the cached_state for the start of the
range this is a helpful optimization to have for this case, we'll have
the exact state we want to wait on.  Add a cached state here and simply
throw it away if we're a non-blocking read, otherwise we'll get a small
improvement by eliminating some tree searches.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Josef Bacik
2022-09-30 16:45:13 -04:00
committed by David Sterba
parent 123a7f008c
commit e5e886bad9
1 changed files with 10 additions and 5 deletions
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15
fs/btrfs/extent_io.c
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@@ -4949,6 +4949,7 @@ static int read_extent_buffer_subpage(struct extent_buffer *eb, int wait,
struct btrfs_fs_info *fs_info = eb->fs_info;
struct extent_io_tree *io_tree;
struct page *page = eb->pages[0];
struct extent_state *cached_state = NULL;
struct btrfs_bio_ctrl bio_ctrl = {
.mirror_num = mirror_num,
};
@@ -4960,10 +4961,11 @@ static int read_extent_buffer_subpage(struct extent_buffer *eb, int wait,
if (wait == WAIT_NONE) {
if (!try_lock_extent(io_tree, eb->start, eb->start + eb->len - 1,
NULL))
&cached_state))
return -EAGAIN;
} else {
ret = lock_extent(io_tree, eb->start, eb->start + eb->len - 1, NULL);
ret = lock_extent(io_tree, eb->start, eb->start + eb->len - 1,
&cached_state);
if (ret < 0)
return ret;
}
@@ -4973,7 +4975,8 @@ static int read_extent_buffer_subpage(struct extent_buffer *eb, int wait,
PageUptodate(page) ||
btrfs_subpage_test_uptodate(fs_info, page, eb->start, eb->len)) {
set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags);
unlock_extent(io_tree, eb->start, eb->start + eb->len - 1, NULL);
unlock_extent(io_tree, eb->start, eb->start + eb->len - 1,
&cached_state);
return ret;
}
@@ -4998,11 +5001,13 @@ static int read_extent_buffer_subpage(struct extent_buffer *eb, int wait,
atomic_dec(&eb->io_pages);
}
submit_one_bio(&bio_ctrl);
if (ret || wait != WAIT_COMPLETE)
if (ret || wait != WAIT_COMPLETE) {
free_extent_state(cached_state);
return ret;
}
wait_extent_bit(io_tree, eb->start, eb->start + eb->len - 1,
EXTENT_LOCKED, NULL);
EXTENT_LOCKED, &cached_state);
if (!test_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags))
ret = -EIO;
return ret;