linux-kernel - Re: [PATCH 1/2] mm: remove redundant check in page_vma_mapped

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Message-ID: <5e3bebd2-9144-ed51-9e57-36da0a5de3fd@huaweicloud.com>
Date:   Thu, 6 Jul 2023 10:37:08 +0800
From:   Kemeng Shi <shikemeng@...weicloud.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] mm: remove redundant check in page_vma_mapped_walk



on 7/5/2023 1:05 AM, Andrew Morton wrote:
> On Wed,  5 Jul 2023 05:39:31 +0800 Kemeng Shi <shikemeng@...weicloud.com> wrote:
> 
>> For PVMW_SYNC case, we always take pte lock when get first pte of
>> PTE-mapped THP in map_pte and hold it until:
>> 1. scan of pmd range finished or
>> 2. scan of user input range finished or
>> 3. user stop walk with page_vma_mapped_walk_done.
>> In each case. pte lock will not be freed during middle scan of PTE-mapped
>> THP.
>>
>> ...
>>
>> --- a/mm/page_vma_mapped.c
>> +++ b/mm/page_vma_mapped.c
>> @@ -275,10 +275,6 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>>  				goto restart;
>>  			}
>>  			pvmw->pte++;
>> -			if ((pvmw->flags & PVMW_SYNC) && !pvmw->ptl) {
>> -				pvmw->ptl = pte_lockptr(mm, pvmw->pmd);
>> -				spin_lock(pvmw->ptl);
>> -			}
>>  		} while (pte_none(*pvmw->pte));
>>  
>>  		if (!pvmw->ptl) {
> 
> This code has changed significantly since 6.4.  Please develop against
> the mm-unstable branch at
> git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm, thanks.
> 
> 
Thanks for reminding me of this, I will check my changes in updated code.

-- 
Best wishes
Kemeng Shi