The patch titled
Subject: loopdev: fix a deadlock
has been added to the -mm tree. Its filename is
loopdev-fix-a-deadlock.patch
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------------------------------------------------------
From: Guo Chao <yan@xxxxxxxxxxxxxxxxxx>
Subject: loopdev: fix a deadlock
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@xxxxxxxxxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Guo Chao <yan@xxxxxxxxxxxxxxxxxx>
Cc: M. Hindess <hindessm@xxxxxxxxxx>
Cc: Nikanth Karthikesan <knikanth@xxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/loop.c | 2 --
1 file changed, 2 deletions(-)
diff -puN drivers/block/loop.c~loopdev-fix-a-deadlock drivers/block/loop.c
--- a/drivers/block/loop.c~loopdev-fix-a-deadlock
+++ a/drivers/block/loop.c
@@ -1285,11 +1285,9 @@ static int loop_set_capacity(struct loop
/* 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;
_
Patches currently in -mm which might be from yan@xxxxxxxxxxxxxxxxxx are
linux-next.patch
block-use-i_size_write-in-bd_set_size.patch
block-remove-redundant-check-to-bd_openers.patch
loopdev-fix-a-deadlock.patch
loopdev-update-block-device-size-in-loop_set_status.patch
loopdev-move-common-code-into-loop_figure_size.patch
loopdev-remove-an-user-triggerable-oops.patch
loopdev-ignore-negative-offset-when-calculate-loop-device-size.patch
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