linux-kernel - Re: [PATCH] md: raid10: remove VLAIS

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Date:   Thu, 5 Oct 2017 12:49:22 -0700
From:   Guenter Roeck <groeck@...gle.com>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Shaohua Li <shli@...nel.org>, linux-raid@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Michael Davidson <md@...gle.com>,
        Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH] md: raid10: remove VLAIS

On Thu, Oct 5, 2017 at 11:28 AM, Matthias Kaehlcke <mka@...omium.org> wrote:
> The raid10 driver can't be built with clang since it uses a variable
> length array in a structure (VLAIS):
>
> drivers/md/raid10.c:4583:17: error: fields must have a constant size:
>   'variable length array in structure' extension will never be supported
>
> Allocate the r10bio struct with kmalloc instead of using the VLAIS
> construct.
>
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>

Reviewed-by: Guenter Roeck <groeck@...omium.org>

> ---
>  drivers/md/raid10.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
> index 374df5796649..9616163eaf8c 100644
> --- a/drivers/md/raid10.c
> +++ b/drivers/md/raid10.c
> @@ -4578,15 +4578,16 @@ static int handle_reshape_read_error(struct mddev *mddev,
>         /* Use sync reads to get the blocks from somewhere else */
>         int sectors = r10_bio->sectors;
>         struct r10conf *conf = mddev->private;
> -       struct {
> -               struct r10bio r10_bio;
> -               struct r10dev devs[conf->copies];
> -       } on_stack;
> -       struct r10bio *r10b = &on_stack.r10_bio;
> +       struct r10bio *r10b;
>         int slot = 0;
>         int idx = 0;
>         struct page **pages;
>
> +       r10b = kmalloc(sizeof(*r10b) +
> +              sizeof(struct r10dev) * conf->copies, GFP_KERNEL);
> +       if (!r10b)
> +               return -ENOMEM;
> +
>         /* reshape IOs share pages from .devs[0].bio */
>         pages = get_resync_pages(r10_bio->devs[0].bio)->pages;
>
> @@ -4635,11 +4636,13 @@ static int handle_reshape_read_error(struct mddev *mddev,
>                         /* couldn't read this block, must give up */
>                         set_bit(MD_RECOVERY_INTR,
>                                 &mddev->recovery);
> +                       kfree(r10b);
>                         return -EIO;
>                 }
>                 sectors -= s;
>                 idx++;
>         }
> +       kfree(r10b);
>         return 0;
>  }
>
> --
> 2.14.2.920.gcf0c67979c-goog
>