linux-kernel - Re: [PATCH] mmc: host: Fix data stomping during mmc recovery

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Message-ID: <CAPDyKFqNJzwizZduMj_ig=aEXAgssQM8AzbYxa_T9XEqNXeWPw@mail.gmail.com>
Date:   Tue, 20 Sep 2022 11:32:45 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Wenchao Chen <wenchao.chen666@...il.com>
Cc:     baolin.wang@...ux.alibaba.com, zhang.lyra@...il.com,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        megoo.tang@...il.com, lzx.stg@...il.com,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH] mmc: host: Fix data stomping during mmc recovery

+ Adrian

On Fri, 16 Sept 2022 at 11:05, Wenchao Chen <wenchao.chen666@...il.com> wrote:
>
> From: Wenchao Chen <wenchao.chen@...soc.com>
>
> The block device uses multiple queues to access emmc. There will be up to 3
> requests in the hsq of the host. The current code will check whether there
> is a request doing recovery before entering the queue, but it will not check
> whether there is a request when the lock is issued. The request is in recovery
> mode. If there is a request in recovery, then a read and write request is
> initiated at this time, and the conflict between the request and the recovery
> request will cause the data to be trampled.
>
> Signed-off-by: Wenchao Chen <wenchao.chen@...soc.com>

Looks like we should consider tagging this for stable kernels too, right?

> ---
>  drivers/mmc/host/mmc_hsq.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/mmc_hsq.c b/drivers/mmc/host/mmc_hsq.c
> index a5e05ed0fda3..9d35453e7371 100644
> --- a/drivers/mmc/host/mmc_hsq.c
> +++ b/drivers/mmc/host/mmc_hsq.c
> @@ -34,7 +34,7 @@ static void mmc_hsq_pump_requests(struct mmc_hsq *hsq)
>         spin_lock_irqsave(&hsq->lock, flags);
>
>         /* Make sure we are not already running a request now */
> -       if (hsq->mrq) {
> +       if (hsq->mrq || hsq->recovery_halt) {

This still looks a bit odd to me, but I may not fully understand the
code, as it's been a while since I looked at this.

In particular, I wonder why the callers of mmc_hsq_pump_requests()
need to release the spin_lock before they call
mmc_hsq_pump_requests()? Is it because we want to allow some other
code that may be waiting for the spin_lock to be released, to run too?

If that isn't the case, it seems better to let the callers of
mmc_hsq_pump_requests() to keep holding the lock - and thus we can
avoid the additional check(s). In that case, it means the
"recovery_halt" flag has already been checked, for example.

>                 spin_unlock_irqrestore(&hsq->lock, flags);
>                 return;
>         }
> --
> 2.17.1
>

Kind regards
Uffe