fs: move i_sb_list out from under inode_lock

Protect the per-sb inode list with a new global lock
inode_sb_list_lock and use it to protect the list manipulations and
traversals. This lock replaces the inode_lock as the inodes on the
list can be validity checked while holding the inode->i_lock and
hence the inode_lock is no longer needed to protect the list.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 11 insertions, 10 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index efd1ebe879c..5de56a2182b 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -1123,7 +1123,7 @@ static void wait_sb_inodes(struct super_block *sb)
 	 */
 	WARN_ON(!rwsem_is_locked(&sb->s_umount));
 
-	spin_lock(&inode_lock);
+	spin_lock(&inode_sb_list_lock);
 
 	/*
 	 * Data integrity sync. Must wait for all pages under writeback,
@@ -1143,14 +1143,15 @@ static void wait_sb_inodes(struct super_block *sb)
 		}
 		__iget(inode);
 		spin_unlock(&inode->i_lock);
-		spin_unlock(&inode_lock);
+		spin_unlock(&inode_sb_list_lock);
+
 		/*
-		 * We hold a reference to 'inode' so it couldn't have
-		 * been removed from s_inodes list while we dropped the
-		 * inode_lock.  We cannot iput the inode now as we can
-		 * be holding the last reference and we cannot iput it
-		 * under inode_lock. So we keep the reference and iput
-		 * it later.
+		 * We hold a reference to 'inode' so it couldn't have been
+		 * removed from s_inodes list while we dropped the
+		 * inode_sb_list_lock.  We cannot iput the inode now as we can
+		 * be holding the last reference and we cannot iput it under
+		 * inode_sb_list_lock. So we keep the reference and iput it
+		 * later.
 		 */
 		iput(old_inode);
 		old_inode = inode;
@@ -1159,9 +1160,9 @@ static void wait_sb_inodes(struct super_block *sb)
 
 		cond_resched();
 
-		spin_lock(&inode_lock);
+		spin_lock(&inode_sb_list_lock);
 	}
-	spin_unlock(&inode_lock);
+	spin_unlock(&inode_sb_list_lock);
 	iput(old_inode);
 }