linux-kernel - Re: [PATCH v5 07/13] mm: khugepaged: collapse_pte_mapped_thp() use pte_offset_map_rw

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Message-Id: <3418680E-14B2-4098-8730-6F569ABF51DD@linux.dev>
Date: Thu, 26 Sep 2024 15:07:12 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: Qi Zheng <zhengqi.arch@...edance.com>
Cc: david@...hat.com,
 hughd@...gle.com,
 willy@...radead.org,
 vbabka@...nel.org,
 akpm@...ux-foundation.org,
 rppt@...nel.org,
 vishal.moola@...il.com,
 peterx@...hat.com,
 ryan.roberts@....com,
 christophe.leroy2@...soprasteria.com,
 linux-kernel@...r.kernel.org,
 linux-mm@...ck.org,
 linux-arm-kernel@...ts.infradead.org,
 linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v5 07/13] mm: khugepaged: collapse_pte_mapped_thp() use
 pte_offset_map_rw_nolock()



> On Sep 26, 2024, at 14:46, Qi Zheng <zhengqi.arch@...edance.com> wrote:
> 
> In collapse_pte_mapped_thp(), we may modify the pte and pmd entry after
> acquring the ptl, so convert it to using pte_offset_map_rw_nolock(). At
> this time, the pte_same() check is not performed after the PTL held. So we
> should get pgt_pmd and do pmd_same() check after the ptl held.
> 
> Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>

Reviewed-by: Muchun Song <muchun.song@...ux.dev>

Thanks.