> On Mar 15, 2021, at 7:29 PM, Xiao Ni <xni@redhat.com> wrote:
> 
> Hi all
> 
> The atomic_t r10_bio->remaining starts at 1 in raid10_handle_discard. It means
> raid10_handle_discard uses it and sets it to 1. So in fact it starts at 0 and sets to 1
> when it's used at first time. Then r10_bio->remaining is added by atomic_inc per usage.
> 
> It decrements the value when leaving raid10_handle_discard and in every callback function.
> So the count of r10_bio->remaining in this patch is right.
> 
> Regards
> Xiao

It does look like a false alarm, as we set r10bio to first_r10bio after
the free. 

Thanks,
Song

> 
> On 03/16/2021 08:29 AM, kernel test robot wrote:
>> tree:   git://git.kernel.org/pub/scm/linux/kernel/git/song/md.git md-next
>> head:   49c4d345c81f149a29b3db6e521e5191e55f02b6
>> commit: f3cf8c2b2caf6ae77b7c786218d3b060faef63a6 [5/6] md/raid10: improve discard request for far layout
>> config: x86_64-allyesconfig (attached as .config)
>> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
>> 
>> If you fix the issue, kindly add following tag as appropriate
>> Reported-by: kernel test robot <lkp@intel.com>
>> 
>> 
>> "coccinelle warnings: (new ones prefixed by >>)"
>>>> drivers/md/raid10.c:1526:8-27: atomic_dec_and_test variation before object free at line 1532.
>>    drivers/md/raid10.c:1526:8-27: atomic_dec_and_test variation before object free at line 1537.
>> 
>> vim +1526 drivers/md/raid10.c
>> 
>>   1520	
>>   1521	static void raid_end_discard_bio(struct r10bio *r10bio)
>>   1522	{
>>   1523		struct r10conf *conf = r10bio->mddev->private;
>>   1524		struct r10bio *first_r10bio;
>>   1525	
>>> 1526		while (atomic_dec_and_test(&r10bio->remaining)) {
>>   1527	
>>   1528			allow_barrier(conf);
>>   1529	
>>   1530			if (!test_bit(R10BIO_Discard, &r10bio->state)) {
>>   1531				first_r10bio = (struct r10bio *)r10bio->master_bio;
>>> 1532				free_r10bio(r10bio);
>>   1533				r10bio = first_r10bio;
>>   1534			} else {
>>   1535				md_write_end(r10bio->mddev);
>>   1536				bio_endio(r10bio->master_bio);
>>   1537				free_r10bio(r10bio);
>>   1538				break;
>>   1539			}
>>   1540		}
>>   1541	}
>>   1542	
>> 
>> ---
>> 0-DAY CI Kernel Test Service, Intel Corporation
>> https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org