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>

diff --git a/fs/inode.c b/fs/inode.c
index f643be5..04c785b 100644 (file)
--- 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
        /*

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index da5a5a1..b25d1b5 100644 (file)
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -258,6 +258,16 @@ extern void lockdep_init_map(struct lockdep_map *lock, const char *name,
 #define lockdep_set_subclass(lock, sub)        \
                lockdep_init_map(&(lock)->dep_map, #lock, \
                                 (lock)->dep_map.key, sub)
+/*
+ * Compare locking classes
+ */
+#define lockdep_match_class(lock, key) lockdep_match_key(&(lock)->dep_map, key)
+
+static inline int lockdep_match_key(struct lockdep_map *lock,
+                                   struct lock_class_key *key)
+{
+       return lock->key == key;
+}
 
 /*
  * Acquire a lock.
@@ -326,6 +336,11 @@ static inline void lockdep_on(void)
 #define lockdep_set_class_and_subclass(lock, key, sub) \
                do { (void)(key); } while (0)
 #define lockdep_set_subclass(lock, sub)                do { } while (0)
+/*
+ * We don't define lockdep_match_class() and lockdep_match_key() for !LOCKDEP
+ * case since the result is not well defined and the caller should rather
+ * #ifdef the call himself.
+ */
 
 # define INIT_LOCKDEP
 # define lockdep_reset()               do { debug_locks = 1; } while (0)