linux-kernel - Re: [PATCH RESEND] mmc: block: Fix request completion in the CQE timeout path

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Message-ID: <CAPDyKFqAuxDhxpMOJSWut3YbE=p0w53KStDn1JAbizJMoWeDBQ@mail.gmail.com>
Date:   Fri, 8 May 2020 10:17:55 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     linux-mmc <linux-mmc@...r.kernel.org>,
        Veerabhadrarao Badiganti <vbadigan@...eaurora.org>,
        Sahitya Tummala <stummala@...eaurora.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Sarthak Garg <sartgarg@...eaurora.org>,
        Baolin Wang <baolin.wang@...aro.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH RESEND] mmc: block: Fix request completion in the CQE
 timeout path

On Fri, 8 May 2020 at 08:22, Adrian Hunter <adrian.hunter@...el.com> wrote:
>
> First, it should be noted that the CQE timeout (60 seconds) is substantial
> so a CQE request that times out is really stuck, and the race between
> timeout and completion is extremely unlikely. Nevertheless this patch
> fixes an issue with it.
>
> Commit ad73d6feadbd7b ("mmc: complete requests from ->timeout")
> preserved the existing functionality, to complete the request.
> However that had only been necessary because the block layer
> timeout handler had been marking the request to prevent it from being
> completed normally. That restriction was removed at the same time, the
> result being that a request that has gone will have been completed anyway.
> That is, the completion was unnecessary.
>
> At the time, the unnecessary completion was harmless because the block
> layer would ignore it, although that changed in kernel v5.0.
>
> Note for stable, this patch will not apply cleanly without patch "mmc:
> core: Fix recursive locking issue in CQE recovery path"
>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> Fixes: ad73d6feadbd7b ("mmc: complete requests from ->timeout")
> Cc: stable@...r.kernel.org

Applied for fixes, thanks!

Kind regards
Uffe

> ---
>  drivers/mmc/core/queue.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
> index 72bef39d7011..10ea67892b5f 100644
> --- a/drivers/mmc/core/queue.c
> +++ b/drivers/mmc/core/queue.c
> @@ -110,8 +110,7 @@ static enum blk_eh_timer_return mmc_cqe_timed_out(struct request *req)
>                                 mmc_cqe_recovery_notifier(mrq);
>                         return BLK_EH_RESET_TIMER;
>                 }
> -               /* No timeout (XXX: huh? comment doesn't make much sense) */
> -               blk_mq_complete_request(req);
> +               /* The request has gone already */
>                 return BLK_EH_DONE;
>         default:
>                 /* Timeout is handled by mmc core */
> --
> 2.17.1
>