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 <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Guo Chao <[email protected]>
Cc: M. Hindess <[email protected]>
Cc: Nikanth Karthikesan <[email protected]>
Cc: Jens Axboe <[email protected]>
Cc: [email protected] # 3.0 3.2 3.4 3.8 d646a02a block: use i_size_write()
in bd_set_size()
Cc: [email protected] # 3.0 3.2 3.4 3.8
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
Acked-by: Jeff Mahoney <[email protected]>
---
drivers/block/loop.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index ae12512..7f80653 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1285,11 +1285,9 @@ 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;
--
Jeff Mahoney
SUSE Labs
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