linux-kernel - Re: [PATCH] rbd: Remove VLA usage

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Date:   Mon, 12 Mar 2018 10:45:53 +0100
From:   Ilya Dryomov <idryomov@...il.com>
To:     Kyle Spiers <kyle@...ers.me>
Cc:     Sage Weil <sage@...hat.com>, Alex Elder <elder@...nel.org>,
        Ceph Development <ceph-devel@...r.kernel.org>,
        linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] rbd: Remove VLA usage

On Sat, Mar 10, 2018 at 6:14 AM, Kyle Spiers <kyle@...ers.me> wrote:
> From 4198ebe2e8058ff676d8e2f993d8806d6ca29c11 Mon Sep 17 00:00:00 2001
> From: Kyle Spiers <kyle@...ers.me>
> Date: Fri, 9 Mar 2018 12:34:15 -0800
> Subject: [PATCH] rbd: Remove VLA usage
>
> As part of the effort to remove VLAs from the kernel[1], this moves
> the literal values into the stack array calculation instead of using a
> variable for the sizing. The resulting size can be found from
> sizeof(buf).
>
> [1] https://lkml.org/lkml/2018/3/7/621
>
> Signed-off-by: Kyle Spiers <kyle@...ers.me>
>
> ---
>  drivers/block/rbd.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> index 8e40da0..0e94e1f 100644
> --- a/drivers/block/rbd.c
> +++ b/drivers/block/rbd.c
> @@ -3100,8 +3100,8 @@ static int __rbd_notify_op_lock(struct rbd_device
> *rbd_dev,
>  {
>      struct ceph_osd_client *osdc = &rbd_dev->rbd_client->client->osdc;
>      struct rbd_client_id cid = rbd_get_cid(rbd_dev);
> -    int buf_size = 4 + 8 + 8 + CEPH_ENCODING_START_BLK_LEN;
> -    char buf[buf_size];
> +    char buf[4 + 4 + 8 + 8 + CEPH_ENCODING_START_BLK_LEN];
> +    int buf_size = sizeof(buf);
>      void *p = buf;
>
>      dout("%s rbd_dev %p notify_op %d\n", __func__, rbd_dev, notify_op);
> @@ -3619,8 +3619,8 @@ static void __rbd_acknowledge_notify(struct
> rbd_device *rbd_dev,
>                       u64 notify_id, u64 cookie, s32 *result)
>  {
>      struct ceph_osd_client *osdc = &rbd_dev->rbd_client->client->osdc;
> -    int buf_size = 4 + CEPH_ENCODING_START_BLK_LEN;
> -    char buf[buf_size];
> +    char buf[4 + CEPH_ENCODING_START_BLK_LEN];
> +    int buf_size = sizeof(buf);
>      int ret;
>
>      if (result) {

This patch is mangled -- tabs, etc.  See

  https://www.kernel.org/doc/html/v4.15/process/email-clients.html

Thanks,

                Ilya