diff mbox

[1/2] loop: fix LO_FLAGS_PARTSCAN hang

Message ID 7e888cad9e6c35835559281d3ab9e05ea48836d0.1488393750.git.osandov@fb.com (mailing list archive)
State New, archived
Headers show

Commit Message

Omar Sandoval March 1, 2017, 6:42 p.m. UTC 
From: Omar Sandoval <osandov@fb.com>

loop_reread_partitions() needs to do I/O, but we just froze the queue,
so we end up waiting forever. This can easily be reproduced with losetup
-P. Fix it by moving the reread to after we unfreeze the queue.

Fixes: ecdd09597a57 ("block/loop: fix race between I/O and set_status")
Reported-by: Tejun Heo <tj@kernel.org>
Cc: Ming Lei <tom.leiming@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 drivers/block/loop.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

Comments

Ming Lei March 2, 2017, 1:57 a.m. UTC | #1 
On Thu, Mar 2, 2017 at 2:42 AM, Omar Sandoval <osandov@osandov.com> wrote:
> From: Omar Sandoval <osandov@fb.com>
>
> loop_reread_partitions() needs to do I/O, but we just froze the queue,
> so we end up waiting forever. This can easily be reproduced with losetup
> -P. Fix it by moving the reread to after we unfreeze the queue.
>
> Fixes: ecdd09597a57 ("block/loop: fix race between I/O and set_status")
> Reported-by: Tejun Heo <tj@kernel.org>
> Cc: Ming Lei <tom.leiming@gmail.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Omar Sandoval <osandov@fb.com>

Reviewed-by: Ming Lei <tom.leiming@gmail.com>

Thanks,
Ming
Jens Axboe March 2, 2017, 2:26 a.m. UTC | #2 
On 03/01/2017 11:42 AM, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> loop_reread_partitions() needs to do I/O, but we just froze the queue,
> so we end up waiting forever. This can easily be reproduced with losetup
> -P. Fix it by moving the reread to after we unfreeze the queue.

Thanks Omar, applied. That's a brown paper bag bug.
diff mbox

Patch

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 4b52a1690329..132c9f371dce 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1142,13 +1142,6 @@  loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 	     (info->lo_flags & LO_FLAGS_AUTOCLEAR))
 		lo->lo_flags ^= LO_FLAGS_AUTOCLEAR;
 
-	if ((info->lo_flags & LO_FLAGS_PARTSCAN) &&
-	     !(lo->lo_flags & LO_FLAGS_PARTSCAN)) {
-		lo->lo_flags |= LO_FLAGS_PARTSCAN;
-		lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN;
-		loop_reread_partitions(lo, lo->lo_device);
-	}
-
 	lo->lo_encrypt_key_size = info->lo_encrypt_key_size;
 	lo->lo_init[0] = info->lo_init[0];
 	lo->lo_init[1] = info->lo_init[1];
@@ -1163,6 +1156,14 @@  loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
 
  exit:
 	blk_mq_unfreeze_queue(lo->lo_queue);
+
+	if (!err && (info->lo_flags & LO_FLAGS_PARTSCAN) &&
+	     !(lo->lo_flags & LO_FLAGS_PARTSCAN)) {
+		lo->lo_flags |= LO_FLAGS_PARTSCAN;
+		lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN;
+		loop_reread_partitions(lo, lo->lo_device);
+	}
+
 	return err;
 }