From: zhong jiang <zhongjiang@huawei.com>
To: John Hubbard <jhubbard@nvidia.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
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
Date: Wed, 16 Oct 2019 17:07:44 +0800 [thread overview]
Message-ID: <5DA6DDE0.6000804@huawei.com> (raw)
In-Reply-To: <73c49a1b-4f42-c21d-ccd8-2b063cdf1293@nvidia.com>
On 2019/9/5 14:19, John Hubbard wrote:
> On 9/4/19 11:48 AM, Andrew Morton wrote:
>> On Wed, 4 Sep 2019 13:24:58 +0200 Vlastimil Babka <vbabka@suse.cz> wrote:
>>
>>> On 9/4/19 12:26 PM, zhong jiang wrote:
>>>> With the help of unsigned_lesser_than_zero.cocci. Unsigned 'nr_pages"'
>>>> compare with zero. And __get_user_pages_locked will return an long value.
>>>> Hence, Convert the long to compare with zero is feasible.
>>>
>>> It would be nicer if the parameter nr_pages was long again instead of unsigned
>>> long (note there are two variants of the function, so both should be changed).
>>
>> nr_pages should be unsigned - it's a count of pages!
>>
>
> Yes!
>
>> The bug is that __get_user_pages_locked() returns a signed long which
>> can be a -ve errno.
>>
>> I think it's best if __get_user_pages_locked() is to get itself a new
>> local with the same type as its return value. Something like:
>>
>> --- 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 ?
Thanks,
zhogn jiang
next prev parent reply other threads:[~2019-10-16 9:07 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-04 10:26 [PATCH] mm: Unsigned 'nr_pages' always larger than zero zhong jiang
2019-09-04 11:24 ` Vlastimil Babka
2019-09-04 18:25 ` Weiny, Ira
2019-09-04 18:39 ` Matthew Wilcox
2019-09-04 18:48 ` Andrew Morton
2019-09-04 20:20 ` Weiny, Ira
2019-09-04 20:40 ` Vlastimil Babka
2019-09-05 6:18 ` zhong jiang
2019-09-05 7:19 ` Vlastimil Babka
2019-09-05 6:19 ` John Hubbard
2019-10-16 9:07 ` zhong jiang [this message]
2019-10-17 0:49 ` Andrew Morton
2019-10-17 1:38 ` zhong jiang
2019-09-04 19:01 ` Andrew Morton
2019-09-04 20:44 ` Vlastimil Babka
2019-09-05 2:05 ` zhong jiang
2019-10-17 3:19 zhong jiang
2019-10-17 18:01 ` Ira Weiny
2019-10-18 2:01 ` zhong jiang
2019-10-17 20:42 ` John Hubbard
2019-10-18 2:15 ` zhong jiang
2019-10-18 14:00 ` zhong jiang
2019-10-18 16:07 ` Alexander Duyck
2019-10-21 15:11 ` zhong jiang
2019-10-21 12:57 ` Vlastimil Babka
2019-10-21 13:47 ` zhong jiang
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