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Date:   Wed, 16 Oct 2019 17:49:55 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     zhong jiang <zhongjiang@huawei.com>
Cc:     John Hubbard <jhubbard@nvidia.com>,
        Vlastimil Babka <vbabka@suse.cz>, <mhocko@kernel.org>,
        <anshuman.khandual@arm.com>, <linux-mm@kvack.org>,
        <linux-kernel@vger.kernel.org>, Ira Weiny <ira.weiny@intel.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Subject: Re: [PATCH] mm: Unsigned 'nr_pages' always larger than zero
Message-Id: <20191016174955.300d5fd4968537151d3ad43f@linux-foundation.org>
In-Reply-To: <5DA6DDE0.6000804@huawei.com>
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        <20190904114820.42d9c4daf445ded3d0da52ab@linux-foundation.org>
        <73c49a1b-4f42-c21d-ccd8-2b063cdf1293@nvidia.com>
        <5DA6DDE0.6000804@huawei.com>
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On Wed, 16 Oct 2019 17:07:44 +0800 zhong jiang <zhongjiang@huawei.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?