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authorGuo Chao <yan@linux.vnet.ibm.com>2013-02-21 15:16:45 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-03-20 13:05:01 -0700
commit187c2bd82defa4d64910eed4d8c39ac93a984306 (patch)
tree01c7ae69a8d93c59f5702762afa0acf778b3d3b2
parentd72b4f90a2b042136f74a3de50b29d6ce76b5f12 (diff)
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 <yan@linux.vnet.ibm.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Guo Chao <yan@linux.vnet.ibm.com> Cc: M. Hindess <hindessm@uk.ibm.com> Cc: Nikanth Karthikesan <knikanth@suse.de> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Jens Axboe <axboe@kernel.dk> Acked-by: Jeff Mahoney <jeffm@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/block/loop.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index bbca966f8f6..17070e2ebd7 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1263,11 +1263,9 @@ 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;