vfs: Set special lockdep map for dirs only if not set by fs

Some filesystems need to set lockdep map for i_mutex differently for
different directories. For example OCFS2 has system directories (for
orphan inode tracking and for gathering all system files like journal
or quota files into a single place) which have different locking
locking rules than standard directories. For a filesystem setting
lockdep map is naturaly done when the inode is read but we have to
modify unlock_new_inode() not to overwrite the lockdep map the filesystem
has set.

Acked-by: peterz@infradead.org
CC: mingo@redhat.com
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Joel Becker <joel.becker@oracle.com>

1 files changed, 11 insertions, 6 deletions

diff --git a/fs/inode.c b/fs/inode.c
index f643be5..04c785b 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -665,12 +665,17 @@ void unlock_new_inode(struct inode *inode)
 	if (inode->i_mode & S_IFDIR) {
 		struct file_system_type *type = inode->i_sb->s_type;
 
-		/*
-		 * ensure nobody is actually holding i_mutex
-		 */
-		mutex_destroy(&inode->i_mutex);
-		mutex_init(&inode->i_mutex);
-		lockdep_set_class(&inode->i_mutex, &type->i_mutex_dir_key);
+		/* Set new key only if filesystem hasn't already changed it */
+		if (!lockdep_match_class(&inode->i_mutex,
+		    &type->i_mutex_key)) {
+			/*
+			 * ensure nobody is actually holding i_mutex
+			 */
+			mutex_destroy(&inode->i_mutex);
+			mutex_init(&inode->i_mutex);
+			lockdep_set_class(&inode->i_mutex,
+					  &type->i_mutex_dir_key);
+		}
 	}
 #endif
 	/*