From: Dave Chinner <dchinner@xxxxxxxxxx>
Currently on the slow path insert we repeat the initial hash table
lookup before we attempt the insert, resulting in a two traversals
of the hash table to ensure the insert is valid. The rhashtable API
provides a method for an atomic lookup and insert operation, so we
can avoid one of the hash table traversals by using this method.
Adapted from a large patch containing this optimisation by Christoph
Hellwig.
Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
fs/xfs/xfs_buf.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 374c4e508b12..1a6542e01bec 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -623,8 +623,15 @@ xfs_buf_find_insert(
}
spin_lock(&pag->pag_buf_lock);
- bp = rhashtable_lookup(&pag->pag_buf_hash, cmap, xfs_buf_hash_params);
+ bp = rhashtable_lookup_get_insert_fast(&pag->pag_buf_hash,
+ &new_bp->b_rhash_head, xfs_buf_hash_params);
+ if (IS_ERR(bp)) {
+ error = PTR_ERR(bp);
+ spin_unlock(&pag->pag_buf_lock);
+ goto out_free_buf;
+ }
if (bp) {
+ /* found an existing buffer */
atomic_inc(&bp->b_hold);
spin_unlock(&pag->pag_buf_lock);
error = xfs_buf_find_lock(bp, flags);
@@ -635,10 +642,8 @@ xfs_buf_find_insert(
goto out_free_buf;
}
- /* The buffer keeps the perag reference until it is freed. */
+ /* The new buffer keeps the perag reference until it is freed. */
new_bp->b_pag = pag;
- rhashtable_insert_fast(&pag->pag_buf_hash, &new_bp->b_rhash_head,
- xfs_buf_hash_params);
spin_unlock(&pag->pag_buf_lock);
*bpp = new_bp;
return 0;
--
2.36.1
