xfs: Correctly invert xfs_buftarg LRU isolation logic

Due to an inverted logic mistake in xfs_buftarg_isolate()
the xfs_buffers with zero b_lru_ref will take another trip
around LRU, while isolating buffers with non-zero b_lru_ref.

Additionally those isolated buffers end up right back on the LRU
once they are released, because b_lru_ref remains elevated.

Fix that circuitous route by leaving them on the LRU
as originally intended.

Signed-off-by: Vratislav Bendel <vbendel@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index d1da2ee..ac669a1 100644 (file)
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1708,7 +1708,7 @@ xfs_buftarg_isolate(
         * zero. If the value is already zero, we need to reclaim the
         * buffer, otherwise it gets another trip through the LRU.
         */
-       if (!atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
+       if (atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
                spin_unlock(&bp->b_lock);
                return LRU_ROTATE;
        }