[PATCH] lockdep: avoid lockdep warning in md
md_open takes ->reconfig_mutex which causes lockdep to complain. This
(normally) doesn't have deadlock potential as the possible conflict is with a
reconfig_mutex in a different device.
I say "normally" because if a loop were created in the array->member hierarchy
a deadlock could happen. However that causes bigger problems than a deadlock
and should be fixed independently.
So we flag the lock in md_open as a nested lock. This requires defining
mutex_lock_interruptible_nested.
Cc: Ingo Molnar <mingo@elte.hu>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index d2bcb41..3ce7a5d 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4423,7 +4423,7 @@
mddev_t *mddev = inode->i_bdev->bd_disk->private_data;
int err;
- if ((err = mddev_lock(mddev)))
+ if ((err = mutex_lock_interruptible_nested(&mddev->reconfig_mutex, 1)))
goto out;
err = 0;
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index b2b91c4..a7544af 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -125,8 +125,10 @@
#ifdef CONFIG_DEBUG_LOCK_ALLOC
extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
+extern int mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass);
#else
# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
+# define mutex_lock_interruptible_nested(lock, subclass) mutex_lock_interruptible(lock)
#endif
/*
diff --git a/kernel/mutex.c b/kernel/mutex.c
index 8c71cf7..e7cbbb8 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -206,6 +206,15 @@
}
EXPORT_SYMBOL_GPL(mutex_lock_nested);
+
+int __sched
+mutex_lock_interruptible_nested(struct mutex *lock, unsigned int subclass)
+{
+ might_sleep();
+ return __mutex_lock_common(lock, TASK_INTERRUPTIBLE, subclass);
+}
+
+EXPORT_SYMBOL_GPL(mutex_lock_interruptible_nested);
#endif
/*