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Subject: Re: [PATCH v2] mm: gup: fix comment of __get_user_pages()
To:     Liu Xiang <liuxiang_1999@126.com>, linux-mm@kvack.org
Cc:     linux-kernel@vger.kernel.org, jhubbard@nvidia.com
References: <1571929472-3091-1-git-send-email-liuxiang_1999@126.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <0839edc8-c876-1713-c753-f12e70e5a653@redhat.com>
Date:   Thu, 24 Oct 2019 18:10:08 +0200
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On 24.10.19 17:04, Liu Xiang wrote:
> Fix comment of __get_user_pages() and make it more clear.
>=20
> Suggested-by: John Hubbard <jhubbard@nvidia.com>
> Signed-off-by: Liu Xiang <liuxiang_1999@126.com>
> ---
>=20
> Changes in v2:
>   as suggested by John, rewrite the comment about return value.
>=20
>   mm/gup.c | 16 +++++++++++-----
>   1 file changed, 11 insertions(+), 5 deletions(-)
>=20
> diff --git a/mm/gup.c b/mm/gup.c
> index 8f236a3..bc6a254 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -734,11 +734,17 @@ static int check_vma_flags(struct vm_area_struct *v=
ma, unsigned long gup_flags)
>    *=09=09Or NULL if the caller does not require them.
>    * @nonblocking: whether waiting for disk IO or mmap_sem contention
>    *
> - * Returns number of pages pinned. This may be fewer than the number
> - * requested. If nr_pages is 0 or negative, returns 0. If no pages
> - * were pinned, returns -errno. Each page returned must be released
> - * with a put_page() call when it is finished with. vmas will only
> - * remain valid while mmap_sem is held.
> + * Returns either number of pages pinned (which may be less than the
> + * number requested), or an error. Details about the return value:
> + *
> + * -- If nr_pages is 0, returns 0.
> + * -- If nr_pages is >0, but no pages were pinned, returns -errno.
> + * -- If nr_pages is >0, and some pages were pinned, returns the number =
of
> + *    pages pinned. Again, this may be less than nr_pages.
> + *
> + * The caller is responsible for releasing returned @pages, via put_page=
().
> + *
> + * @vmas are valid only as long as mmap_sem is held.
>    *
>    * Must be called with mmap_sem held.  It may be released.  See below.
>    *
>=20

Reviewed-by: David Hildenbrand <david@redhat.com>

--=20

Thanks,

David / dhildenb