---

yaml
---
r: 200614
b: refs/heads/master
c: 57439f8
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 5904b3b81d25166e5e39b9727645bb47937618e3
+refs/heads/master: 57439f878afafefad8836ebf5c49da2a0a746105

trunk/fs/dcache.c

@@ -590,6 +590,8 @@ static void prune_dcache(int count)
 			up_read(&sb->s_umount);
 		}
 		spin_lock(&sb_lock);
+		/* lock was dropped, must reset next */
+		list_safe_reset_next(sb, n, s_list);
 		count -= pruned;
 		__put_super(sb);
 		/* more work left to do? */

trunk/fs/super.c

@@ -374,6 +374,8 @@ void sync_supers(void)
 			up_read(&sb->s_umount);
 
 			spin_lock(&sb_lock);
+			/* lock was dropped, must reset next */
+			list_safe_reset_next(sb, n, s_list);
 			__put_super(sb);
 		}
 	}
@@ -405,6 +407,8 @@ void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
 		up_read(&sb->s_umount);
 
 		spin_lock(&sb_lock);
+		/* lock was dropped, must reset next */
+		list_safe_reset_next(sb, n, s_list);
 		__put_super(sb);
 	}
 	spin_unlock(&sb_lock);
@@ -585,6 +589,8 @@ static void do_emergency_remount(struct work_struct *work)
 		}
 		up_write(&sb->s_umount);
 		spin_lock(&sb_lock);
+		/* lock was dropped, must reset next */
+		list_safe_reset_next(sb, n, s_list);
 		__put_super(sb);
 	}
 	spin_unlock(&sb_lock);

trunk/include/linux/list.h

@@ -544,6 +544,21 @@ static inline void list_splice_tail_init(struct list_head *list,
 	     &pos->member != (head); 					\
 	     pos = n, n = list_entry(n->member.prev, typeof(*n), member))
 
+/**
+ * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
+ * @pos:	the loop cursor used in the list_for_each_entry_safe loop
+ * @n:		temporary storage used in list_for_each_entry_safe
+ * @member:	the name of the list_struct within the struct.
+ *
+ * list_safe_reset_next is not safe to use in general if the list may be
+ * modified concurrently (eg. the lock is dropped in the loop body). An
+ * exception to this is if the cursor element (pos) is pinned in the list,
+ * and list_safe_reset_next is called after re-taking the lock and before
+ * completing the current iteration of the loop body.
+ */
+#define list_safe_reset_next(pos, n, member)				\
+	n = list_entry(pos->member.next, typeof(*pos), member)
+
 /*
  * Double linked lists with a single pointer list head.
  * Mostly useful for hash tables where the two pointer list head is