linux-kernel - Re: [PATCH v2] kcov: don't generate a warning on vm_insert

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Message-ID: <CANpmjNO=qjoY+8m9Nf-8vanFZTgsiDwfchv_JsLoksFKwU98BQ@mail.gmail.com>
Date:   Fri, 1 Apr 2022 11:46:24 +0200
From:   Marco Elver <elver@...gle.com>
To:     Aleksandr Nogikh <nogikh@...gle.com>
Cc:     kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, dvyukov@...gle.com,
        andreyknvl@...il.com, glider@...gle.com, tarasmadan@...gle.com,
        bigeasy@...utronix.de
Subject: Re: [PATCH v2] kcov: don't generate a warning on vm_insert_page()'s failure

On Fri, 1 Apr 2022 at 10:43, Aleksandr Nogikh <nogikh@...gle.com> wrote:
>
> vm_insert_page()'s failure is not an unexpected condition, so don't do
> WARN_ONCE() in such a case.
>
> Instead, print a kernel message and just return an error code.
>
> Signed-off-by: Aleksandr Nogikh <nogikh@...gle.com>

Acked-by: Marco Elver <elver@...gle.com>


Just minor "process" comments:
1) There should be a '---' so that the below doesn't appear in the
commit message on 'git am' and maintainers don't have to manually
remove it.

> PATCH v2:
> * Added a newline at the end of pr_warn_once().
>
> PATCH v1: https://lkml.org/lkml/2022/3/31/909

2) We should use lore permalinks, because lkml.org isn't official and
was actually down most of this week. v1 was
https://lore.kernel.org/all/20220331180501.4130549-1-nogikh@google.com/

> ---
>  kernel/kcov.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/kcov.c b/kernel/kcov.c
> index 475524bd900a..b3732b210593 100644
> --- a/kernel/kcov.c
> +++ b/kernel/kcov.c
> @@ -475,8 +475,11 @@ static int kcov_mmap(struct file *filep, struct vm_area_struct *vma)
>         vma->vm_flags |= VM_DONTEXPAND;
>         for (off = 0; off < size; off += PAGE_SIZE) {
>                 page = vmalloc_to_page(kcov->area + off);
> -               if (vm_insert_page(vma, vma->vm_start + off, page))
> -                       WARN_ONCE(1, "vm_insert_page() failed");
> +               res = vm_insert_page(vma, vma->vm_start + off, page);
> +               if (res) {
> +                       pr_warn_once("kcov: vm_insert_page() failed\n");
> +                       return res;
> +               }
>         }
>         return 0;
>  exit:
> --
> 2.35.1.1094.g7c7d902a7c-goog
>