linux-kernel - Re: [PATCH] mm: Unsigned 'nr_pages' always larger than zero

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Message-ID: <5DA7C612.1090300@huawei.com>
Date:   Thu, 17 Oct 2019 09:38:26 +0800
From:   zhong jiang <zhongjiang@...wei.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     John Hubbard <jhubbard@...dia.com>,
        Vlastimil Babka <vbabka@...e.cz>, <mhocko@...nel.org>,
        <anshuman.khandual@....com>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, Ira Weiny <ira.weiny@...el.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: [PATCH] mm: Unsigned 'nr_pages' always larger than zero

On 2019/10/17 8:49, Andrew Morton wrote:
> On Wed, 16 Oct 2019 17:07:44 +0800 zhong jiang <zhongjiang@...wei.com> wrote:
>
>>>> --- a/mm/gup.c~a
>>>> +++ a/mm/gup.c
>>>> @@ -1450,6 +1450,7 @@ static long check_and_migrate_cma_pages(
>>>>       bool drain_allow = true;
>>>>       bool migrate_allow = true;
>>>>       LIST_HEAD(cma_page_list);
>>>> +    long ret;
>>>>     check_again:
>>>>       for (i = 0; i < nr_pages;) {
>>>> @@ -1511,17 +1512,18 @@ check_again:
>>>>            * again migrating any new CMA pages which we failed to isolate
>>>>            * earlier.
>>>>            */
>>>> -        nr_pages = __get_user_pages_locked(tsk, mm, start, nr_pages,
>>>> +        ret = __get_user_pages_locked(tsk, mm, start, nr_pages,
>>>>                              pages, vmas, NULL,
>>>>                              gup_flags);
>>>>   -        if ((nr_pages > 0) && migrate_allow) {
>>>> +        nr_pages = ret;
>>>> +        if (ret > 0 && migrate_allow) {
>>>>               drain_allow = true;
>>>>               goto check_again;
>>>>           }
>>>>       }
>>>>   -    return nr_pages;
>>>> +    return ret;
>>>>   }
>>>>   #else
>>>>   static long check_and_migrate_cma_pages(struct task_struct *tsk,
>>>>
>>> +1 for this approach, please.
>>>
>>>
>>> thanks,
>> Hi,  Andrew
>>
>> I didn't see the fix for the issue in the upstream. Your proposal should be
>> appiled to upstream. Could you appiled the patch or  repost by me ?
> Forgotten about it ;)  Please send a patch sometime?
>
> .
>
I will  repost the patch as your suggestion.  Thanks,

Sincerely,
zhong jiang