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Commit 6346c939 authored by Josef Bacik's avatar Josef Bacik Committed by Chris Mason
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Btrfs: fix data allocation hint start 



Sometimes our start allocation hint when we cow a file can be either
EXTENT_HOLE or some other such place holder, which is not optimal.  So if we
find that our em->block_start is one of these special values, check to see
where the first block of the inode is stored, and use that as a hint.  If that
block is also a special value, just fallback on a hint of 0 and let the
allocator figure out a good place to put the data.

Signed-off-by: default avatarJosef Bacik <josef@redhat.com>
Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 444528b3

fs/btrfs/inode.c

+16 −2
Original line number Original line Diff line number Diff line
@@ -743,9 +743,23 @@ static noinline int cow_file_range(struct inode *inode, 
	em = search_extent_mapping(&BTRFS_I(inode)->extent_tree,

	em = search_extent_mapping(&BTRFS_I(inode)->extent_tree,

				   start, num_bytes);

				   start, num_bytes);

	if (em) {

	if (em) {

		/*

		 * if block start isn't an actual block number then find the

		 * first block in this inode and use that as a hint.  If that

		 * block is also bogus then just don't worry about it.

		 */

		if (em->block_start >= EXTENT_MAP_LAST_BYTE) {

			free_extent_map(em);

			em = search_extent_mapping(em_tree, 0, 0);

			if (em && em->block_start < EXTENT_MAP_LAST_BYTE)

				alloc_hint = em->block_start;

			if (em)

				free_extent_map(em);

		} else {

			alloc_hint = em->block_start;

			alloc_hint = em->block_start;

			free_extent_map(em);

			free_extent_map(em);

		}

		}

	}

	read_unlock(&BTRFS_I(inode)->extent_tree.lock);

	read_unlock(&BTRFS_I(inode)->extent_tree.lock);

	btrfs_drop_extent_cache(inode, start, start + num_bytes - 1, 0);

	btrfs_drop_extent_cache(inode, start, start + num_bytes - 1, 0);