From: Vlastimil Babka <vbabka@suse.cz>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: zhong jiang <zhongjiang@huawei.com>,
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, 4 Sep 2019 22:44:51 +0200 [thread overview]
Message-ID: <8817c107-71d9-e47c-8dba-5f7eea30a140@suse.cz> (raw)
In-Reply-To: <20190904120159.d4026b573f419838d77e991d@linux-foundation.org>
On 9/4/19 9:01 PM, 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).
>>
>>> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
>>
>> Fixes: 932f4a630a69 ("mm/gup: replace get_user_pages_longterm() with FOLL_LONGTERM")
>>
>> (which changed long to unsigned long)
>>
>> AFAICS... stable shouldn't be needed as the only "risk" is that we goto
>> check_again even when we fail, which should be harmless.
>>
>
> Really? If nr_pages gets a value of -EFAULT from the
> __get_user_pages_locked() call, check_and_migrate_cma_pages() will go
> berzerk?
Hmm it should only reach that goto when it migrated something, which
means it won't have to be migrated again, so eventually it should
terminate. But it's very subtle, so I might be wrong.
> And does __get_user_pages_locked() correctly handle a -ve errno
> returned by __get_user_pages()? It's hard to see how...
I think it does, but agree.
next prev parent reply other threads:[~2019-09-04 20:44 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
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 [this message]
2019-09-05 2:05 ` zhong jiang
-- strict thread matches above, loose matches on Subject: below --
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=8817c107-71d9-e47c-8dba-5f7eea30a140@suse.cz \
--to=vbabka@suse.cz \
--cc=akpm@linux-foundation.org \
--cc=aneesh.kumar@linux.vnet.ibm.com \
--cc=anshuman.khandual@arm.com \
--cc=ira.weiny@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=zhongjiang@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).