linux-kernel - Re: [PATCH V3] mmc: block: Add new ioctl to send multi commands

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Message-ID: <55FFD467.9020801@nvidia.com>
Date:	Mon, 21 Sep 2015 10:56:55 +0100
From:	Jon Hunter <jonathanh@...dia.com>
To:	Gwendal Grignou <gwendal@...omium.org>
CC:	Ulf Hansson <ulf.hansson@...aro.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Seshagiri Holi <sholi@...dia.com>,
	Arnd Bergmann <arnd@...db.de>,
	"Grant Grundler" <grundler@...gle.com>,
	Olof Johansson <olofj@...omium.org>
Subject: Re: [PATCH V3] mmc: block: Add new ioctl to send multi commands


On 16/09/15 18:54, Gwendal Grignou wrote:

[snip]

>> +static int mmc_blk_ioctl_multi_cmd(struct block_device *bdev,
>> +                                  struct mmc_ioc_multi_cmd __user *user)
>> +{
>> +       struct mmc_blk_ioc_data **idata = NULL;
>> +       struct mmc_ioc_cmd __user *cmds = user->cmds;
>> +       struct mmc_card *card;
>> +       struct mmc_blk_data *md;
>> +       int i, err = -EFAULT;
>> +       __u64 num_of_cmds;
>> +
>> +       /*
>> +        * The caller must have CAP_SYS_RAWIO, and must be calling this on the
>> +        * whole block device, not on a partition.  This prevents overspray
>> +        * between sibling partitions.
>> +        */
>> +       if ((!capable(CAP_SYS_RAWIO)) || (bdev != bdev->bd_contains))
>> +               return -EPERM;
>> +
>> +       if (copy_from_user(&num_of_cmds, &user->num_of_cmds,
>> +                          sizeof(num_of_cmds)))
>> +               return -EFAULT;
>> +
>> +       if (num_of_cmds > MMC_IOC_MAX_CMDS)
>> +               return -EINVAL;
>> +
>> +       idata = kcalloc(num_of_cmds, sizeof(*idata), GFP_KERNEL);
>> +       if (!idata)
>> +               return -ENOMEM;
>> +
>> +       for (i = 0; i < num_of_cmds; i++) {
>> +               idata[i] = mmc_blk_ioctl_copy_from_user(&cmds[i]);
>> +               if (IS_ERR(idata[i])) {
>> +                       err = PTR_ERR(idata[i]);
>> +                       num_of_cmds = i;
>> +                       goto cmd_err;
>> +               }
>> +       }
>> +
>> +       md = mmc_blk_get(bdev->bd_disk);
>> +       if (!md)
>> +               goto cmd_err;
>> +
>> +       card = md->queue.card;
>> +       if (IS_ERR(card)) {
>> +               err = PTR_ERR(card);
>> +               goto cmd_done;
>> +       }
>> +
>> +       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;
> Instead of exiting here, you should first copy to the user the data
> and response of successful commands, mark the failed command as failed
> and the remaining ones as "not executed".
> This way, it will be easier for the user space application to find out
> where the sequence failed. This especially true if some reverts are
> needed.

Yes that sounds like a sensible thing to do. I will incorporate that change.

Cheers
Jon
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