Re: [PATCH 1/2] mm, slob: Prevent false positive trace upon allocation failure

[Pekka Enberg <penberg@kernel.org>]

Hi Ezequiel,

On Tue, Aug 14, 2012 at 5:38 PM, Ezequiel Garcia <elezegarcia@gmail.com> wrote:
> This patch changes the __kmalloc_node() logic to return NULL
> if alloc_pages() fails to return valid pages.
> This is done to avoid to trace a false positive kmalloc event.
>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Glauber Costa <glommer@parallels.com>
> Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
> ---
>  mm/slob.c |   11 ++++++-----
>  1 files changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/mm/slob.c b/mm/slob.c
> index 45d4ca7..686e98b 100644
> --- a/mm/slob.c
> +++ b/mm/slob.c
> @@ -450,15 +450,16 @@ void *__kmalloc_node(size_t size, gfp_t gfp, int node)
>                                    size, size + align, gfp, node);
>         } else {
>                 unsigned int order = get_order(size);
> +               struct page *page;
>
>                 if (likely(order))
>                         gfp |= __GFP_COMP;
>                 ret = slob_new_pages(gfp, order, node);
> -               if (ret) {
> -                       struct page *page;
> -                       page = virt_to_page(ret);
> -                       page->private = size;
> -               }
> +               if (!ret)
> +                       return NULL;
> +
> +               page = virt_to_page(ret);
> +               page->private = size;
>
>                 trace_kmalloc_node(_RET_IP_, ret,
>                                    size, PAGE_SIZE << order, gfp, node);

As mentioned earlier, I think it's valuable for the userspace to be
able to trace allocation failures as well. So I'm not applying this
patch.

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