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 efd1ebe879cc..5de56a2182bb 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);
 }