Re: [PATCH v3] mmc: core: don't set limits.discard_granularity as 0

[Adrian Hunter]

On 1/10/20 11:38 am, Vicente Bergas wrote:
> On Thu, Oct 1, 2020 at 9:18 AM Coly Li <colyli@xxxxxxx> wrote:
>>
>> In mmc_queue_setup_discard() the mmc driver queue's discard_granularity
>> might be set as 0 (when card->pref_erase > max_discard) while the mmc
>> device still declares to support discard operation. This is buggy and
>> triggered the following kernel warning message,
>>
>> WARNING: CPU: 0 PID: 135 at __blkdev_issue_discard+0x200/0x294
>> CPU: 0 PID: 135 Comm: f2fs_discard-17 Not tainted 5.9.0-rc6 #1
>> Hardware name: Google Kevin (DT)
>> pstate: 00000005 (nzcv daif -PAN -UAO BTYPE=--)
>> pc : __blkdev_issue_discard+0x200/0x294
>> lr : __blkdev_issue_discard+0x54/0x294
>> sp : ffff800011dd3b10
>> x29: ffff800011dd3b10 x28: 0000000000000000 x27: ffff800011dd3cc4 x26: ffff800011dd3e18 x25: 000000000004e69b x24: 0000000000000c40 x23: ffff0000f1deaaf0 x22: ffff0000f2849200 x21: 00000000002734d8 x20: 0000000000000008 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000394 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 00000000000008b0 x9 : ffff800011dd3cb0 x8 : 000000000004e69b x7 : 0000000000000000 x6 : ffff0000f1926400 x5 : ffff0000f1940800 x4 : 0000000000000000 x3 : 0000000000000c40 x2 : 0000000000000008 x1 : 00000000002734d8 x0 : 0000000000000000 Call trace:
>> __blkdev_issue_discard+0x200/0x294
>> __submit_discard_cmd+0x128/0x374
>> __issue_discard_cmd_orderly+0x188/0x244
>> __issue_discard_cmd+0x2e8/0x33c
>> issue_discard_thread+0xe8/0x2f0
>> kthread+0x11c/0x120
>> ret_from_fork+0x10/0x1c
>> ---[ end trace e4c8023d33dfe77a ]---
>>
>> This patch fixes the issue by setting discard_granularity as SECTOR_SIZE
>> instead of 0 when (card->pref_erase > max_discard) is true. Now no more
>> complain from __blkdev_issue_discard() for the improper value of discard
>> granularity.
>>
>> This issue is exposed after commit b35fd7422c2f ("block: check queue's
>> limits.discard_granularity in __blkdev_issue_discard()"), a "Fixes:" tag
>> is also added for the commit to make sure people won't miss this patch
>> after applying the change of __blkdev_issue_discard().
>>
>> Fixes: e056a1b5b67b ("mmc: queue: let host controllers specify maximum discard timeout")
>> Fixes: b35fd7422c2f ("block: check queue's limits.discard_granularity in __blkdev_issue_discard()").
>> Reported-by: Vicente Bergas <vicencb@xxxxxxxxx>
> 
> Hi Coly, Adrian,
> would you like me to reply with a tested-by?
> before testing it: what are the chances of losing data?

Very low I would hope, but that is no reason not to have backups :-)

> Regards,
>   Vicente.
> 
>> Signed-off-by: Coly Li <colyli@xxxxxxx>
>> Acked-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>> Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
>> ---
>> Changelog,
>> v3, add Fixes tag for both commits.
>> v2, change commit id of the Fixes tag.
>> v1, initial version.
>>
>>  drivers/mmc/core/queue.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
>> index 6c022ef0f84d..350d0cc4ee62 100644
>> --- a/drivers/mmc/core/queue.c
>> +++ b/drivers/mmc/core/queue.c
>> @@ -190,7 +190,7 @@ static void mmc_queue_setup_discard(struct request_queue *q,
>>         q->limits.discard_granularity = card->pref_erase << 9;
>>         /* granularity must not be greater than max. discard */
>>         if (card->pref_erase > max_discard)
>> -               q->limits.discard_granularity = 0;
>> +               q->limits.discard_granularity = SECTOR_SIZE;
>>         if (mmc_can_secure_erase_trim(card))
>>                 blk_queue_flag_set(QUEUE_FLAG_SECERASE, q);
>>  }
>> --
>> 2.26.2
>>