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References: <20201001071824.24995-1-colyli@suse.de>
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From:   Vicente Bergas <vicencb@gmail.com>
Date:   Thu, 1 Oct 2020 10:38:18 +0200
Message-ID: <CAAMcf8Ao8Go7GdB2XFXAHsWrcxb0VqtDRpHReOGTsjegq2XP0Q@mail.gmail.com>
Subject: Re: [PATCH v3] mmc: core: don't set limits.discard_granularity as 0
To:     Coly Li <colyli@suse.de>, Adrian Hunter <adrian.hunter@intel.com>
Cc:     linux-mmc@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-block@vger.kernel.org, Ulf Hansson <ulf.hansson@linaro.org>
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On Thu, Oct 1, 2020 at 9:18 AM Coly Li <colyli@suse.de> 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=3D--)
> pc : __blkdev_issue_discard+0x200/0x294
> lr : __blkdev_issue_discard+0x54/0x294
> sp : ffff800011dd3b10
> x29: ffff800011dd3b10 x28: 0000000000000000 x27: ffff800011dd3cc4 x26: ff=
ff800011dd3e18 x25: 000000000004e69b x24: 0000000000000c40 x23: ffff0000f1d=
eaaf0 x22: ffff0000f2849200 x21: 00000000002734d8 x20: 0000000000000008 x19=
: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000=
000000000 x15: 0000000000000000 x14: 0000000000000394 x13: 0000000000000000=
 x12: 0000000000000000 x11: 0000000000000000 x10: 00000000000008b0 x9 : fff=
f800011dd3cb0 x8 : 000000000004e69b x7 : 0000000000000000 x6 : ffff0000f192=
6400 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 di=
scard timeout")
> Fixes: b35fd7422c2f ("block: check queue's limits.discard_granularity in =
__blkdev_issue_discard()").
> Reported-by: Vicente Bergas <vicencb@gmail.com>

Hi Coly, Adrian,
would you like me to reply with a tested-by?
before testing it: what are the chances of losing data?
Regards,
  Vicente.

> Signed-off-by: Coly Li <colyli@suse.de>
> Acked-by: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Ulf Hansson <ulf.hansson@linaro.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_qu=
eue *q,
>         q->limits.discard_granularity =3D card->pref_erase << 9;
>         /* granularity must not be greater than max. discard */
>         if (card->pref_erase > max_discard)
> -               q->limits.discard_granularity =3D 0;
> +               q->limits.discard_granularity =3D SECTOR_SIZE;
>         if (mmc_can_secure_erase_trim(card))
>                 blk_queue_flag_set(QUEUE_FLAG_SECERASE, q);
>  }
> --
> 2.26.2
>