linux-kernel - Re: [PATCH v4 2/3] mm/rmap: integrate PMD-mapped folio splitting into pagewalk loop

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Message-ID: <a8f7a8da-c2e1-443c-9220-a224d97b1c81@redhat.com>
Date: Tue, 7 May 2024 10:17:07 +0200
From: David Hildenbrand <david@...hat.com>
To: Lance Yang <ioworker0@...il.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org, willy@...radead.org, sj@...nel.org,
 maskray@...gle.com, ziy@...dia.com, ryan.roberts@....com, 21cnbao@...il.com,
 mhocko@...e.com, fengwei.yin@...el.com, zokeefe@...gle.com,
 shy828301@...il.com, xiehuan09@...il.com, libang.li@...group.com,
 wangkefeng.wang@...wei.com, songmuchun@...edance.com, peterx@...hat.com,
 minchan@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/3] mm/rmap: integrate PMD-mapped folio splitting into
 pagewalk loop

>>>
>>> +             if (!pvmw.pte && (flags & TTU_SPLIT_HUGE_PMD)) {
>>> +                     /*
>>> +                      * We temporarily have to drop the PTL and start once
>>> +                      * again from that now-PTE-mapped page table.
>>> +                      */
>>> +                     split_huge_pmd_locked(vma, range.start, pvmw.pmd, false,
>>> +                                           folio);
>>> +                     pvmw.pmd = NULL;
>>> +                     spin_unlock(pvmw.ptl);
>>
>> IMO, you should also make the 'pvmw.ptl = NULL;' after unlocking as
>> page_vma_mapped_walk() did, in case some corner case met.
> 
> Yep, I'll also set pvmw.ptl to NULL here if any corner cases arise.
> 

This series already resides in mm-stable. I asked Andrew to remove it 
for now. If that doesn't work, we'll need fixup patches to address any 
review feedback.

-- 
Cheers,

David / dhildenb