linux-kernel - Re: [PATCH v4 07/10] mm/gup: change index type to long as it counts pages

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Message-ID: <20201218095058.GV32193@dhcp22.suse.cz>
Date:   Fri, 18 Dec 2020 10:50:58 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Pavel Tatashin <pasha.tatashin@...een.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, vbabka@...e.cz, david@...hat.com,
        osalvador@...e.de, dan.j.williams@...el.com, sashal@...nel.org,
        tyhicks@...ux.microsoft.com, iamjoonsoo.kim@....com,
        mike.kravetz@...cle.com, rostedt@...dmis.org, mingo@...hat.com,
        jgg@...pe.ca, peterz@...radead.org, mgorman@...e.de,
        willy@...radead.org, rientjes@...gle.com, jhubbard@...dia.com,
        linux-doc@...r.kernel.org, ira.weiny@...el.com,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v4 07/10] mm/gup: change index type to long as it counts
 pages

On Thu 17-12-20 13:52:40, Pavel Tatashin wrote:
> In __get_user_pages_locked() i counts number of pages which should be
> long.

Do we know of any caller who would like to pin so many pages it wouldn't
fit into an int? I suspect this is more to sync types of nr_pages and
the iterator right. It would be better to be explicit about this in the
changelog.

> Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>

Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  mm/gup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index 591d8e2dfc70..1ebb7cc2fbe4 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1481,7 +1481,7 @@ static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start,
>  {
>  	struct vm_area_struct *vma;
>  	unsigned long vm_flags;
> -	int i;
> +	long i;
>  
>  	/* calculate required read or write permissions.
>  	 * If FOLL_FORCE is set, we only require the "MAY" flags.
> -- 
> 2.25.1

-- 
Michal Hocko
SUSE Labs