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

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Message-ID: <b3cdb5fe-40df-41df-ae10-0b7be4dcd7a6@gmail.com>
Date:   Thu, 01 Oct 2020 20:47:29 +0200
From:   Vicente Bergas <vicencb@...il.com>
To:     Coly Li <colyli@...e.de>
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 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>