linux-kernel - Re: [RFC PATCH v2 1/7] mm: pgtable: make pte_offset_map

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Message-ID: <0e8e0503-5796-4b61-bb5b-249e285f5d21@redhat.com>
Date: Mon, 5 Aug 2024 16:43:05 +0200
From: David Hildenbrand <david@...hat.com>
To: Qi Zheng <zhengqi.arch@...edance.com>, hughd@...gle.com,
 willy@...radead.org, mgorman@...e.de, muchun.song@...ux.dev,
 vbabka@...nel.org, akpm@...ux-foundation.org, zokeefe@...gle.com,
 rientjes@...gle.com
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 1/7] mm: pgtable: make pte_offset_map_nolock()
 return pmdval

On 05.08.24 14:55, Qi Zheng wrote:
> Make pte_offset_map_nolock() return pmdval so that we can recheck the
> *pmd once the lock is taken. This is a preparation for freeing empty
> PTE pages, no functional changes are expected.

Skimming the patches, only patch #4 updates one of the callsites 
(collapse_pte_mapped_thp).

Wouldn't we have to recheck if the PMD val changed in more cases after 
taking the PTL?

If not, would it make sense to have a separate function that returns the 
pmdval and we won't have to update each and every callsite?

-- 
Cheers,

David / dhildenb