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| author | Guo Chao <yan@linux.vnet.ibm.com> | 2013-02-21 15:16:45 -0800 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2013-03-20 15:03:40 +0000 |
| commit | 54d75ff2c7caec91a8cd14b25c3fcf7256601184 (patch) | |
| tree | e6e122edb483763ee5dc4e1c8ce363dc5537ad60 /drivers/block/loop.c | |
| parent | c1a782a5c7a83f4aa3239533619e93b1fc3ab79d (diff) | |
| download | linux-rt-54d75ff2c7caec91a8cd14b25c3fcf7256601184.tar.gz | |
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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'drivers/block/loop.c')
| -rw-r--r-- | drivers/block/loop.c | 2 |
1 files changed, 0 insertions, 2 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 1e888c9e85b3..954be47e246f 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; |