linux-kernel - Re: [PATCH v3] mmc: core: don't set limits.discard

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Date:   Fri, 2 Oct 2020 09:34:57 +0800
From:   Coly Li <colyli@...e.de>
To:     Vicente Bergas <vicencb@...il.com>
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-block@...r.kernel.org,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v3] mmc: core: don't set limits.discard_granularity as 0

On 2020/10/2 02:47, Vicente Bergas wrote:
> On Thursday, October 1, 2020 9:18:24 AM CEST, Coly Li 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@...il.com>
>> Signed-off-by: Coly Li <colyli@...e.de>
>> Acked-by: Adrian Hunter <adrian.hunter@...el.com>
>> Cc: Ulf Hansson <ulf.hansson@...aro.org>
>> ---
>> 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);
>>  }
> 
> Tested on rk3399-gru-kevin with f2fs filesystem over the mmc driver, that
> is, the same setup that reproduced the issue.
> The kernel warning message is no longer reported.
> So,
> Tested-by: Vicente Bergas <vicencb@...il.com>
> 

Hi Vicente,

Thank you very much!

Coly Li