xfs: speed up write operations by using non-overlapped lookups when possible

Reverse mapping on a reflink-capable filesystem has some pretty high
overhead when performing file operations.  This is because the rmap
records for logically and physically adjacent extents might not be
adjacent in the rmap index due to data block sharing.  As a result, we
use expensive overlapped-interval btree search, which walks every record
that overlaps with the supplied key in the hopes of finding the record.

However, profiling data shows that when the index contains a record that
is an exact match for a query key, the non-overlapped btree search
function can find the record much faster than the overlapped version.
Try the non-overlapped lookup first when we're trying to find the left
neighbor rmap record for a given file mapping, which makes unwritten
extent conversion and remap operations run faster if data block sharing
is minimal in this part of the filesystem.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 0 insertions, 3 deletions

diff --git a/fs/xfs/libxfs/xfs_rmap.h b/fs/xfs/libxfs/xfs_rmap.h
index 11ec9406a0ea..54741a591a17 100644
--- a/fs/xfs/libxfs/xfs_rmap.h
+++ b/fs/xfs/libxfs/xfs_rmap.h
@@ -184,9 +184,6 @@ int xfs_rmap_finish_one(struct xfs_trans *tp, enum xfs_rmap_intent_type type,
 		xfs_fsblock_t startblock, xfs_filblks_t blockcount,
 		xfs_exntst_t state, struct xfs_btree_cur **pcur);
 
-int xfs_rmap_find_left_neighbor(struct xfs_btree_cur *cur, xfs_agblock_t bno,
-		uint64_t owner, uint64_t offset, unsigned int flags,
-		struct xfs_rmap_irec *irec, int	*stat);
 int xfs_rmap_lookup_le_range(struct xfs_btree_cur *cur, xfs_agblock_t bno,
 		uint64_t owner, uint64_t offset, unsigned int flags,
 		struct xfs_rmap_irec *irec, int	*stat);