linux-kernel - Re: [PATCH] mmc: block: copy resp[] data on err for MMC_IOC_MULTI

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Date:	Mon, 5 Oct 2015 12:55:47 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Grant Grundler <grundler@...omium.org>
Cc:	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jon Hunter <jonathanh@...dia.com>,
	Hyung Taek Ryoo <hryoo@...dia.com>,
	Gwendal Grignou <gwendal@...omium.org>
Subject: Re: [PATCH] mmc: block: copy resp[] data on err for MMC_IOC_MULTI_CMD

On 24 September 2015 at 03:30, Grant Grundler <grundler@...omium.org> wrote:
> MMC_IOC_CMD and MMC_IOC_MULTI_CMD ioctl() code currently bails on
> any eMMC errors. However, in case there is any resp[] data, we
> should attempt to copy resp[] back to user space. The user app
> can then determine which command(s) failed in the MMC_IOC_MULTI_CMD
> case AND/OR report better diagnostics in both cases.
>
> Gwendal Grignou provided the idea and it was previously implemented
> and tested on v3.18 ChromeOS kernel:
>     https://chromium-review.googlesource.com/#/c/299956
>
> Signed-off-by: Grant Grundler <grundler@...omium.org>
> Reviewed-by: Hyung Taek Ryoo <hryoo@...dia.com>
> Reviewed-by: Gwendal Grignou <gwendal@...omium.org>
> Tested-by: David Riley <davidriley@...omium.org>

Thanks, applied for next!

Kind regards
Uffe

> ---
> I believe the patch applied correctly to Ulf's mmc.git on linaro.org.
> I would have warm fuzzies if Jon or Hyung (Nvidia) could review/test this.
>
> I made one change from the chromium.org version:
>   initialize err and ioc_err to zero in mmc_blk_ioctl_cmd()
>
>  drivers/mmc/card/block.c | 27 +++++++++------------------
>  1 file changed, 9 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index f6acf0f..23b6c8e 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -595,7 +595,7 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>         struct mmc_blk_ioc_data *idata;
>         struct mmc_blk_data *md;
>         struct mmc_card *card;
> -       int err;
> +       int err = 0, ioc_err = 0;
>
>         idata = mmc_blk_ioctl_copy_from_user(ic_ptr);
>         if (IS_ERR(idata))
> @@ -615,19 +615,18 @@ static int mmc_blk_ioctl_cmd(struct block_device *bdev,
>
>         mmc_get_card(card);
>
> -       err = __mmc_blk_ioctl_cmd(card, md, idata);
> +       ioc_err = __mmc_blk_ioctl_cmd(card, md, idata);
>
>         mmc_put_card(card);
>
> -       if (!err)
> -               err = mmc_blk_ioctl_copy_to_user(ic_ptr, idata);
> +       err = mmc_blk_ioctl_copy_to_user(ic_ptr, idata);
>
>  cmd_done:
>         mmc_blk_put(md);
>  cmd_err:
>         kfree(idata->buf);
>         kfree(idata);
> -       return err;
> +       return ioc_err ? ioc_err : err;
>  }
>
>  static int mmc_blk_ioctl_multi_cmd(struct block_device *bdev,
> @@ -637,7 +636,7 @@ static int mmc_blk_ioctl_multi_cmd(struct block_device *bdev,
>         struct mmc_ioc_cmd __user *cmds = user->cmds;
>         struct mmc_card *card;
>         struct mmc_blk_data *md;
> -       int i, err = -EFAULT;
> +       int i, err = 0, ioc_err = 0;
>         __u64 num_of_cmds;
>
>         if (copy_from_user(&num_of_cmds, &user->num_of_cmds,
> @@ -672,22 +671,14 @@ static int mmc_blk_ioctl_multi_cmd(struct block_device *bdev,
>
>         mmc_get_card(card);
>
> -       for (i = 0; i < num_of_cmds; i++) {
> -               err = __mmc_blk_ioctl_cmd(card, md, idata[i]);
> -               if (err) {
> -                       mmc_put_card(card);
> -                       goto cmd_done;
> -               }
> -       }
> +       for (i = 0; i < num_of_cmds && !ioc_err; i++)
> +               ioc_err = __mmc_blk_ioctl_cmd(card, md, idata[i]);
>
>         mmc_put_card(card);
>
>         /* copy to user if data and response */
> -       for (i = 0; i < num_of_cmds; i++) {
> +       for (i = 0; i < num_of_cmds && !err; i++)
>                 err = mmc_blk_ioctl_copy_to_user(&cmds[i], idata[i]);
> -               if (err)
> -                       break;
> -       }
>
>  cmd_done:
>         mmc_blk_put(md);
> @@ -697,7 +688,7 @@ cmd_err:
>                 kfree(idata[i]);
>         }
>         kfree(idata);
> -       return err;
> +       return ioc_err ? ioc_err : err;
>  }
>
>  static int mmc_blk_ioctl(struct block_device *bdev, fmode_t mode,
> --
> 2.6.0.rc2.230.g3dd15c0
>
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