Re: [PATCH 12/13] loop: remove lo_refcount and avoid lo_mutex in ->open / ->release

[Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>]

On 2022/03/24 23:13, Jan Kara wrote:
>> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
>> index b3170e8cdbe95..e1eb925d3f855 100644
>> --- a/drivers/block/loop.c
>> +++ b/drivers/block/loop.c
>> @@ -1244,7 +1244,7 @@ static int loop_clr_fd(struct loop_device *lo)
>>  	 * <dev>/do something like mkfs/losetup -d <dev> causing the losetup -d
>>  	 * command to fail with EBUSY.
>>  	 */
>> -	if (atomic_read(&lo->lo_refcnt) > 1) {
>> +	if (disk_openers(lo->lo_disk) > 1) {

This is sometimes "if (0) {" due to not holding disk->open_mutex.

>>  		lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
>>  		mutex_unlock(&lo->lo_mutex);
>>  		return 0;