linux-kernel - Re: [PATCH 13/16] mm/migration: return errno when isolate_huge

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <8ff5c0d7-bc5b-6991-6daa-d4c62d019dbb@huawei.com>
Date:   Wed, 9 Mar 2022 16:29:06 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     "Huang, Ying" <ying.huang@...el.com>
CC:     <akpm@...ux-foundation.org>, <mike.kravetz@...cle.com>,
        <shy828301@...il.com>, <willy@...radead.org>, <ziy@...dia.com>,
        <minchan@...nel.org>, <apopple@...dia.com>,
        <ave.hansen@...ux.intel.com>, <o451686892@...il.com>,
        <almasrymina@...gle.com>, <jhubbard@...dia.com>,
        <rcampbell@...dia.com>, <peterx@...hat.com>,
        <naoya.horiguchi@....com>, <mhocko@...e.com>, <riel@...hat.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 13/16] mm/migration: return errno when isolate_huge_page
 failed

On 2022/3/9 9:00, Huang, Ying wrote:
> Miaohe Lin <linmiaohe@...wei.com> writes:
> 
>> On 2022/3/7 13:07, Huang, Ying wrote:
>>> Miaohe Lin <linmiaohe@...wei.com> writes:
>>>
>>>> We should return errno (-EBUSY here) when failed to isolate the huge page
>>>> rather than always return 1 which could confuse the user.
>>>>
>>>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>>>> ---
>>>>  mm/migrate.c | 6 ++----
>>>>  1 file changed, 2 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/mm/migrate.c b/mm/migrate.c
>>>> index 6c2dfed2ddb8..279940c0c064 100644
>>>> --- a/mm/migrate.c
>>>> +++ b/mm/migrate.c
>>>> @@ -1618,10 +1618,8 @@ static int add_page_for_migration(struct mm_struct *mm, unsigned long addr,
>>>>  		goto out_putpage;
>>>>  
>>>>  	if (PageHuge(page)) {
>>>> -		if (PageHead(page)) {
>>>> -			isolate_huge_page(page, pagelist);
>>>> -			err = 1;
>>>> -		}
>>>> +		if (PageHead(page))
>>>> +			err = isolate_huge_page(page, pagelist) ? 1 : -EBUSY;
>>>
>>> IMHO, it's better to determine the proper errno inside
>>> isolate_huge_page() instead of in the caller.  If you think it's
>>> necessary to get errno here.  How about change isolate_huge_page()
>>> instead?
>>
>> IMO, -EBUSY should be enough for the user (as they could not do much) and this
>> errno keeps consistent with the non-hugetlb page case. What do you think?
> 
> I found the prototype of isolate_lru_page() is as follows,
> 
>   int isolate_lru_page(struct page *page)
> 
> And it will return errno directly.  I think we should follow same
> convention here?
> 

I see. Sounds reasonable to me. Will try to do it. Thanks.

> Best Regards,
> Huang, Ying
> .
>