[BUG REPORT] Incorrect adaptation of 7e49538288e5 ("loop: Avoid updating block size under exclusive owner") for stable 6.6

[BUG REPORT] Incorrect adaptation of 7e49538288e5 ("loop: Avoid updating block size under exclusive owner") for stable 6.6

[yangerkun]

Error path for blk_validate_block_size is wrong, we should goto unlock, 
or lo_mutex won't be release, and bdev will keep claimed.

...

-static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
+static int loop_set_block_size(struct loop_device *lo, blk_mode_t mode,
+                              struct block_device *bdev, unsigned long arg)
  {
         int err = 0;

-       if (lo->lo_state != Lo_bound)
-               return -ENXIO;
+       /*
+        * If we don't hold exclusive handle for the device, upgrade to it
+        * here to avoid changing device under exclusive owner.
+        */
+       if (!(mode & BLK_OPEN_EXCL)) {
+               err = bd_prepare_to_claim(bdev, loop_set_block_size, NULL);
+               if (err)
+                       return err;
+       }
+
+       err = mutex_lock_killable(&lo->lo_mutex);
+       if (err)
+               goto abort_claim;
+
+       if (lo->lo_state != Lo_bound) {
+               err = -ENXIO;
+               goto unlock;
+       }

         err = blk_validate_block_size(arg);
         if (err)
                 return err;
                 ^^^^^^^^^^^^^
                 should goto unlock

         if (lo->lo_queue->limits.logical_block_size == arg)
-               return 0;
+               goto unlock;

         sync_blockdev(lo->lo_device);
         invalidate_bdev(lo->lo_device);

         blk_mq_freeze_queue(lo->lo_queue);
         blk_queue_logical_block_size(lo->lo_queue, arg);
         blk_queue_physical_block_size(lo->lo_queue, arg);
         blk_queue_io_min(lo->lo_queue, arg);
         loop_update_dio(lo);
         blk_mq_unfreeze_queue(lo->lo_queue);

+unlock:
+       mutex_unlock(&lo->lo_mutex);
+abort_claim:
+       if (!(mode & BLK_OPEN_EXCL))
+               bd_abort_claiming(bdev, loop_set_block_size);
         return err;
  }

Re: [BUG REPORT] Incorrect adaptation of 7e49538288e5 ("loop: Avoid updating block size under exclusive owner") for stable 6.6

[Greg KH]

On Wed, Sep 24, 2025 at 10:36:19AM +0800, yangerkun wrote:
> Error path for blk_validate_block_size is wrong, we should goto unlock, or
> lo_mutex won't be release, and bdev will keep claimed.

Can you provide a working patch we can apply?

thanks,

greg k-h

Re: [BUG REPORT] Incorrect adaptation of 7e49538288e5 ("loop: Avoid updating block size under exclusive owner") for stable 6.6

[yangerkun]

在 2025/9/29 21:28, Greg KH 写道:
> On Wed, Sep 24, 2025 at 10:36:19AM +0800, yangerkun wrote:
>> Error path for blk_validate_block_size is wrong, we should goto unlock, or
>> lo_mutex won't be release, and bdev will keep claimed.
> 
> Can you provide a working patch we can apply?

My colleague Zheng Qixing has already made the correct adaptation, and
she might release it in a week (we are about to start the National Day
holiday).

> 
> thanks,
> 
> greg k-h
>