LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Dan Williams <dan.j.williams@intel.com>
To: Kyle Spiers <ksspiers@google.com>
Cc: David Miller <davem@davemloft.net>,
	Kees Cook <keescook@chromium.org>,
	Vinod Koul <vinod.koul@intel.com>,
	ray.jui@broadcom.com, linux-crypto@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-raid <linux-raid@vger.kernel.org>
Subject: Re: [PATCH v2] async_pq: Remove VLA usage
Date: Tue, 29 May 2018 15:37:20 -0700	[thread overview]
Message-ID: <CAPcyv4i__AQmCxM1rVBrLqXreMxQ5u9uRHRyJ=XZjDELxxJTzw@mail.gmail.com> (raw)
In-Reply-To: <20180505075854.192237-1-ksspiers@google.com>

[ adding linux-raid ]

Apologies for the delay, the recent ping from Kees made me take a closer look.

On Sat, May 5, 2018 at 12:58 AM, Kyle Spiers <ksspiers@google.com> wrote:
> In the quest to remove VLAs from the kernel[1], this moves the
> allocation of coefs and blocks from the stack to being kmalloc()ed.
>
> [1] https://lkml.org/lkml/2018/3/7/621
>
> Signed-off-by: Kyle Spiers <ksspiers@google.com>
> ---
> Forgot to add slab.h
> ---
>  crypto/async_tx/async_pq.c  | 18 ++++++++++++++----
>  crypto/async_tx/raid6test.c |  9 ++++++++-
>  2 files changed, 22 insertions(+), 5 deletions(-)
>
> diff --git a/crypto/async_tx/async_pq.c b/crypto/async_tx/async_pq.c
> index 56bd612927ab..af1912313a23 100644
> --- a/crypto/async_tx/async_pq.c
> +++ b/crypto/async_tx/async_pq.c
> @@ -194,9 +194,9 @@ async_gen_syndrome(struct page **blocks, unsigned int offset, int disks,
>             (src_cnt <= dma_maxpq(device, 0) ||
>              dma_maxpq(device, DMA_PREP_CONTINUE) > 0) &&
>             is_dma_pq_aligned(device, offset, 0, len)) {
> -               struct dma_async_tx_descriptor *tx;
> +               struct dma_async_tx_descriptor *tx = NULL;
>                 enum dma_ctrl_flags dma_flags = 0;
> -               unsigned char coefs[src_cnt];
> +               unsigned char *coefs;
>                 int i, j;
>
>                 /* run the p+q asynchronously */
> @@ -207,6 +207,9 @@ async_gen_syndrome(struct page **blocks, unsigned int offset, int disks,
>                  * sources and update the coefficients accordingly
>                  */
>                 unmap->len = len;
> +               coefs = kmalloc_array(src_cnt, sizeof(*coefs), GFP_KERNEL);

At a minimum this needs to be GFP_NOIO since raid may be in the
page-reclaim path.

However, I think it may be better to allocate this with the rest of
the stripe resources and pass it in as a scratch buffer. See the usage
/ implementation of scribble_alloc() in drivers/md/raid5.c.

  parent reply	other threads:[~2018-05-29 22:37 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-05  7:58 Kyle Spiers
2018-05-10 20:57 ` Kees Cook
2018-05-29 22:24   ` Kees Cook
2018-05-29 22:37 ` Dan Williams [this message]
2018-05-29 22:40   ` Dan Williams
2018-05-30 21:33     ` Kees Cook
2018-05-30 22:04       ` Dan Williams

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAPcyv4i__AQmCxM1rVBrLqXreMxQ5u9uRHRyJ=XZjDELxxJTzw@mail.gmail.com' \
    --to=dan.j.williams@intel.com \
    --cc=davem@davemloft.net \
    --cc=keescook@chromium.org \
    --cc=ksspiers@google.com \
    --cc=linux-crypto@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-raid@vger.kernel.org \
    --cc=ray.jui@broadcom.com \
    --cc=vinod.koul@intel.com \
    --subject='Re: [PATCH v2] async_pq: Remove VLA usage' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).