[PATCH 06/18] xfs: convert pag_ici_lock to a spin lock

[Dave Chinner]

From: Dave Chinner <dchinner at 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 at redhat.com>
---
 fs/xfs/linux-2.6/xfs_sync.c |   16 ++++++++--------
 fs/xfs/xfs_ag.h             |    2 +-
 fs/xfs/xfs_iget.c           |   10 +++++-----
 fs/xfs/xfs_mount.c          |    2 +-
 4 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_sync.c b/fs/xfs/linux-2.6/xfs_sync.c
index e549d67..c093e91 100644
--- a/fs/xfs/linux-2.6/xfs_sync.c
+++ b/fs/xfs/linux-2.6/xfs_sync.c
@@ -100,13 +100,13 @@ restart:
 		xfs_inode_t	*ip;
 
 		if (exclusive)
-			write_lock(&pag->pag_ici_lock);
+			spin_lock(&pag->pag_ici_lock);
 		else
 			rcu_read_lock();
 		ip = xfs_inode_ag_lookup(mp, pag, &first_index, tag);
 		if (!ip) {
 			if (exclusive)
-				write_unlock(&pag->pag_ici_lock);
+				spin_unlock(&pag->pag_ici_lock);
 			else
 				rcu_read_unlock();
 			break;
@@ -659,12 +659,12 @@ 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);
 }
 
@@ -757,12 +757,12 @@ xfs_reclaim_inode(
 	if (__xfs_iflags_test(ip, XFS_IRECLAIM)) {
 		/* ignore as it is already under reclaim */
 		spin_unlock(&ip->i_flags_lock);
-		write_unlock(&pag->pag_ici_lock);
+		spin_unlock(&pag->pag_ici_lock);
 		return 0;
 	}
 	__xfs_iflags_set(ip, XFS_IRECLAIM);
 	spin_unlock(&ip->i_flags_lock);
-	write_unlock(&pag->pag_ici_lock);
+	spin_unlock(&pag->pag_ici_lock);
 
 	xfs_ilock(ip, XFS_ILOCK_EXCL);
 	if (!xfs_iflock_nowait(ip)) {
@@ -834,11 +834,11 @@ 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);
-	write_unlock(&pag->pag_ici_lock);
+	spin_unlock(&pag->pag_ici_lock);
 
 	/*
 	 * Here we do an (almost) spurious inode lock in order to coordinate
diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index 51c42c2..6de9128 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 */
 
diff --git a/fs/xfs/xfs_iget.c b/fs/xfs/xfs_iget.c
index f3a46b6..c46ce03 100644
--- a/fs/xfs/xfs_iget.c
+++ b/fs/xfs/xfs_iget.c
@@ -234,14 +234,14 @@ 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)) {
@@ -319,7 +319,7 @@ 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);
@@ -334,14 +334,14 @@ 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 14fc6e9..546eb1f 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -450,7 +450,7 @@ 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);
 		INIT_RADIX_TREE(&pag->pag_ici_root, GFP_ATOMIC);
 
 		if (radix_tree_preload(GFP_NOFS))
-- 
1.7.1