linux-kernel - Re: [PATCH] mmc: inline the first mmc_scan() on mmc_start

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Date:   Tue, 13 Jun 2023 16:25:11 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Dennis Zhou <dennis@...nel.org>
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc: inline the first mmc_scan() on mmc_start_host()

On Wed, 29 Mar 2023 at 22:21, Dennis Zhou <dennis@...nel.org> wrote:
>
> When using dm-verity with a data partition on an emmc device, dm-verity
> races with the discovery of attached emmc devices. This is because mmc's
> probing code sets up the host data structure then a work item is
> scheduled to do discovery afterwards. To prevent this race on init,
> let's inline the first call to detection, __mm_scan(), and let
> subsequent detect calls be handled via the workqueue.
>
> Signed-off-by: Dennis Zhou <dennis@...nel.org>

Along with the patch for the mmci driver, this one applied too, for
next, thanks!

Note also that I took the liberty to clarify the commit message a bit.

Moreover, if we want this to be applied for stable kernels, we need to
manage that separately, as then the mmci patch is needed too. Please
ping if you need some pointers in regards to this.

Kind regards
Uffe

> ---
>  drivers/mmc/core/core.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 368f10405e13..c0fdc438c882 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -2185,10 +2185,8 @@ int mmc_card_alternative_gpt_sector(struct mmc_card *card, sector_t *gpt_sector)
>  }
>  EXPORT_SYMBOL(mmc_card_alternative_gpt_sector);
>
> -void mmc_rescan(struct work_struct *work)
> +void __mmc_rescan(struct mmc_host *host)
>  {
> -       struct mmc_host *host =
> -               container_of(work, struct mmc_host, detect.work);
>         int i;
>
>         if (host->rescan_disable)
> @@ -2249,6 +2247,14 @@ void mmc_rescan(struct work_struct *work)
>                 mmc_schedule_delayed_work(&host->detect, HZ);
>  }
>
> +void mmc_rescan(struct work_struct *work)
> +{
> +       struct mmc_host *host =
> +               container_of(work, struct mmc_host, detect.work);
> +
> +       __mmc_rescan(host);
> +}
> +
>  void mmc_start_host(struct mmc_host *host)
>  {
>         host->f_init = max(min(freqs[0], host->f_max), host->f_min);
> @@ -2261,7 +2267,8 @@ void mmc_start_host(struct mmc_host *host)
>         }
>
>         mmc_gpiod_request_cd_irq(host);
> -       _mmc_detect_change(host, 0, false);
> +       host->detect_change = 1;
> +       __mmc_rescan(host);
>  }
>
>  void __mmc_stop_host(struct mmc_host *host)
> --
> 2.40.0
>