[PATCH 2/2] xfs: convert pag_ici_lock to a spin lock

[Dave Chinner <david@fromorbit.com>]

From: Dave Chinner <dchinner@redhat.com>

now that we are using RCU protection for the inode cache lookups,
the lock is only needed on the modification side. Hence it is not
necessary for the lock to be a rwlock as there are no read side
holders anymore. Convert it to a spin lock to reflect it's exclusive
nature.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/linux-2.6/xfs_sync.c |   14 +++++++-------
 fs/xfs/xfs_ag.h             |    2 +-
 fs/xfs/xfs_iget.c           |   10 +++++-----
 fs/xfs/xfs_mount.c          |    2 +-
 4 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index 5ee02d7..d3b3b4f 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -602,12 +602,12 @@ xfs_inode_set_reclaim_tag(
 	struct xfs_perag *pag;
 
 	pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino));
-	write_lock(&pag->pag_ici_lock);
+	spin_lock(&pag->pag_ici_lock);
 	spin_lock(&ip->i_flags_lock);
 	__xfs_inode_set_reclaim_tag(pag, ip);
 	__xfs_iflags_set(ip, XFS_IRECLAIMABLE);
 	spin_unlock(&ip->i_flags_lock);
-	write_unlock(&pag->pag_ici_lock);
+	spin_unlock(&pag->pag_ici_lock);
 	xfs_perag_put(pag);
 }
 
@@ -808,12 +808,12 @@ reclaim:
 	 * added to the tree assert that it's been there before to catch
 	 * problems with the inode life time early on.
 	 */
-	write_lock(&pag->pag_ici_lock);
+	spin_lock(&pag->pag_ici_lock);
 	if (!radix_tree_delete(&pag->pag_ici_root,
 				XFS_INO_TO_AGINO(ip->i_mount, ip->i_ino)))
 		ASSERT(0);
 	__xfs_inode_clear_reclaim(pag, ip);
-	write_unlock(&pag->pag_ici_lock);
+	spin_unlock(&pag->pag_ici_lock);
 
 	/*
 	 * Here we do an (almost) spurious inode lock in order to coordinate
@@ -877,14 +877,14 @@ restart:
 			struct xfs_inode *batch[XFS_LOOKUP_BATCH];
 			int	i;
 
-			write_lock(&pag->pag_ici_lock);
+			spin_lock(&pag->pag_ici_lock);
 			nr_found = radix_tree_gang_lookup_tag(
 					&pag->pag_ici_root,
 					(void **)batch, first_index,
 					XFS_LOOKUP_BATCH,
 					XFS_ICI_RECLAIM_TAG);
 			if (!nr_found) {
-				write_unlock(&pag->pag_ici_lock);
+				spin_unlock(&pag->pag_ici_lock);
 				break;
 			}
 
@@ -911,7 +911,7 @@ restart:
 			}
 
 			/* unlock now we've grabbed the inodes. */
-			write_unlock(&pag->pag_ici_lock);
+			spin_unlock(&pag->pag_ici_lock);
 
 			for (i = 0; i < nr_found; i++) {
 				if (!batch[i])
diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index 63c7a1a..58632cc 100644
--- a/fs/xfs/xfs_ag.h
+++ b/fs/xfs/xfs_ag.h
@@ -227,7 +227,7 @@ typedef struct xfs_perag {
 
 	atomic_t        pagf_fstrms;    /* # of filestreams active in this AG */
 
-	rwlock_t	pag_ici_lock;	/* incore inode lock */
+	spinlock_t	pag_ici_lock;	/* incore inode cache lock */
 	struct radix_tree_root pag_ici_root;	/* incore inode cache root */
 	int		pag_ici_reclaimable;	/* reclaimable inodes */
 	struct mutex	pag_ici_reclaim_lock;	/* serialisation point */
diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index 0d2b6d2..f6845e1 100644
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -236,14 +236,14 @@ xfs_iget_cache_hit(
 			goto out_error;
 		}
 
-		write_lock(&pag->pag_ici_lock);
+		spin_lock(&pag->pag_ici_lock);
 		spin_lock(&ip->i_flags_lock);
 		ip->i_flags &= ~(XFS_IRECLAIMABLE | XFS_IRECLAIM);
 		ip->i_flags |= XFS_INEW;
 		__xfs_inode_clear_reclaim_tag(mp, pag, ip);
 		inode->i_state = I_NEW;
 		spin_unlock(&ip->i_flags_lock);
-		write_unlock(&pag->pag_ici_lock);
+		spin_unlock(&pag->pag_ici_lock);
 	} else {
 		/* If the VFS inode is being torn down, pause and try again. */
 		if (!igrab(inode)) {
@@ -321,7 +321,7 @@ xfs_iget_cache_miss(
 			BUG();
 	}
 
-	write_lock(&pag->pag_ici_lock);
+	spin_lock(&pag->pag_ici_lock);
 
 	/* insert the new inode */
 	error = radix_tree_insert(&pag->pag_ici_root, agino, ip);
@@ -336,14 +336,14 @@ xfs_iget_cache_miss(
 	ip->i_udquot = ip->i_gdquot = NULL;
 	xfs_iflags_set(ip, XFS_INEW);
 
-	write_unlock(&pag->pag_ici_lock);
+	spin_unlock(&pag->pag_ici_lock);
 	radix_tree_preload_end();
 
 	*ipp = ip;
 	return 0;
 
 out_preload_end:
-	write_unlock(&pag->pag_ici_lock);
+	spin_unlock(&pag->pag_ici_lock);
 	radix_tree_preload_end();
 	if (lock_flags)
 		xfs_iunlock(ip, lock_flags);
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 98cb266..a33ab94 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -634,7 +634,7 @@ xfs_initialize_perag(
 			goto out_unwind;
 		pag->pag_agno = index;
 		pag->pag_mount = mp;
-		rwlock_init(&pag->pag_ici_lock);
+		spin_lock_init(&pag->pag_ici_lock);
 		mutex_init(&pag->pag_ici_reclaim_lock);
 		INIT_RADIX_TREE(&pag->pag_ici_root, GFP_ATOMIC);
 		spin_lock_init(&pag->pag_buf_lock);
-- 
1.7.2.3

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