linux-kernel - Re: [PATCH] mm: remove unnecessary page_table

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Message-ID: <CAHk-=whhiQtzQ4L80rQg7uQzM1cPcNh9nE9U=Bn=iSVaYXPi2g@mail.gmail.com>
Date: Fri, 1 Nov 2024 08:59:58 -1000
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, "Liam R . Howlett" <Liam.Howlett@...cle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: remove unnecessary page_table_lock on stack expansion

On Fri, 1 Nov 2024 at 08:46, Lorenzo Stoakes <lorenzo.stoakes@...cle.com> wrote:
>
> Each of which acquire the mmap write lock before doing so. Despite this, we
> maintain code that acquires a page table lock in the expand_upwards() and
> expand_downwards() code, stating that we hold a shared mmap lock and thus
> this is necessary.
>
> It is not, we do not have to worry about concurrent VMA expansions so we
> can simply drop this, and update comments accordingly.
>
> We do not even need be concerned with racing page faults, as
> vma_start_write() is invoked in both cases.

Ack, seems ObviouslyCorrect(tm).

           Linus