Commit e5e886ba authored by Josef Bacik's avatar Josef Bacik Committed by David Sterba
Browse files

btrfs: add cached_state to read_extent_buffer_subpage 



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: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 123a7f00

fs/btrfs/extent_io.c

+10 −5
Original line number Diff line number Diff line
@@ -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;