From 54d75ff2c7caec91a8cd14b25c3fcf7256601184 Mon Sep 17 00:00:00 2001 From: Guo Chao Date: Thu, 21 Feb 2013 15:16:45 -0800 Subject: loopdev: fix a deadlock commit 5370019dc2d2c2ff90e95d181468071362934f3a upstream. bd_mutex and lo_ctl_mutex can be held in different order. Path #1: blkdev_open blkdev_get __blkdev_get (hold bd_mutex) lo_open (hold lo_ctl_mutex) Path #2: blkdev_ioctl lo_ioctl (hold lo_ctl_mutex) lo_set_capacity (hold bd_mutex) Lockdep does not report it, because path #2 actually holds a subclass of lo_ctl_mutex. This subclass seems creep into the code by mistake. The patch author actually just mentioned it in the changelog, see commit f028f3b2 ("loop: fix circular locking in loop_clr_fd()"), also see: http://marc.info/?l=linux-kernel&m=123806169129727&w=2 Path #2 hold bd_mutex to call bd_set_size(), I've protected it with i_mutex in a previous patch, so drop bd_mutex at this site. Signed-off-by: Guo Chao Cc: Alexander Viro Cc: Guo Chao Cc: M. Hindess Cc: Nikanth Karthikesan Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Jens Axboe Signed-off-by: Ben Hutchings --- drivers/block/loop.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'drivers/block') diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 1e888c9..954be47 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1262,11 +1262,9 @@ static int loop_set_capacity(struct loop_device *lo, struct block_device *bdev) /* the width of sector_t may be narrow for bit-shift */ sz = sec; sz <<= 9; - mutex_lock(&bdev->bd_mutex); bd_set_size(bdev, sz); /* let user-space know about the new size */ kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE); - mutex_unlock(&bdev->bd_mutex); out: return err; -- cgit v1.1