linux-kernel - Re: [PATCH 1/3] mm/memcg: revise the using condition of lock_page

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Message-ID: <be915778-2f0e-17a3-c44e-889bda0bc12d@linux.alibaba.com>
Date:   Tue, 22 Dec 2020 13:23:06 +0800
From:   Alex Shi <alex.shi@...ux.alibaba.com>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] mm/memcg: revise the using condition of
 lock_page_lruvec function series



在 2020/12/22 上午11:01, Hugh Dickins 写道:
> On Thu, 17 Dec 2020, Alex Shi wrote:
> 
>> The series function could be used under lock_page_memcg(), add this and
>> a bit style changes following commit_charge().
>>
>> Signed-off-by: Alex Shi <alex.shi@...ux.alibaba.com>
>> Cc: Hugh Dickins <hughd@...gle.com>
> 
> This patch, or its intention,
> Acked-by: Hugh Dickins <hughd@...gle.com>
> but rewording suggested below, and requested above -
> which left me very puzzled before eventually I understood it.
> I don't think we need to talk about "a bit style changes",
> but the cross-reference to commit_charge() is helpful.
> 
> "
> lock_page_lruvec() and its variants are safe to use under the same
> conditions as commit_charge(): add lock_page_memcg() to the comment.
> "

Thanks a lot, Hugh. Yes, your commit log are far more better than mine. :)

I will resent with your changes and Ack.

Thanks!
Alex

> 
>> Cc: Johannes Weiner <hannes@...xchg.org>
>> Cc: Michal Hocko <mhocko@...nel.org>
>> Cc: Vladimir Davydov <vdavydov.dev@...il.com>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: cgroups@...r.kernel.org
>> Cc: linux-mm@...ck.org
>> Cc: linux-kernel@...r.kernel.org
>> ---
>>  mm/memcontrol.c | 9 +++++----
>>  1 file changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index b80328f52fb4..e6b50d068b2f 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -1345,10 +1345,11 @@ void lruvec_memcg_debug(struct lruvec *lruvec, struct page *page)
>>   * lock_page_lruvec - lock and return lruvec for a given page.
>>   * @page: the page
>>   *
>> - * This series functions should be used in either conditions:
>> - * PageLRU is cleared or unset
>> - * or page->_refcount is zero
>> - * or page is locked.
>> + * This series functions should be used in any one of following conditions:
> 
> These functions are safe to use under any of the following conditions:
> 
>> + * - PageLRU is cleared or unset
>> + * - page->_refcount is zero
>> + * - page is locked.
> 
> Remove that full stop...
> 
>> + * - lock_page_memcg()
> 
> ... and, if you wish (I don't care), add full stop at the end of that line.
> 
> Maybe reorder those to the same order as listed in commit_charge().
> Copy its text exactly? I don't think so, actually, I find your wording
> (e.g. _refcount is zero) more explicit: good to have both descriptions.
> 
>>   */
>>  struct lruvec *lock_page_lruvec(struct page *page)
>>  {
>> -- 
>> 2.29.GIT