linux-kernel - Re: [PATCH v6 10/16] mm: replace vm_lock and detached flag with a reference count

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Message-ID: <CAJuCfpFeUU0hDdfyn+qUKGnnciRH2dAAVWL5A5FdWHa0UW_RaQ@mail.gmail.com>
Date: Thu, 19 Dec 2024 08:08:52 -0800
From: Suren Baghdasaryan <surenb@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: "Liam R. Howlett" <Liam.Howlett@...cle.com>, akpm@...ux-foundation.org, willy@...radead.org, 
	lorenzo.stoakes@...cle.com, mhocko@...e.com, vbabka@...e.cz, 
	hannes@...xchg.org, mjguzik@...il.com, oliver.sang@...el.com, 
	mgorman@...hsingularity.net, david@...hat.com, peterx@...hat.com, 
	oleg@...hat.com, dave@...olabs.net, paulmck@...nel.org, brauner@...nel.org, 
	dhowells@...hat.com, hdanton@...a.com, hughd@...gle.com, 
	lokeshgidra@...gle.com, minchan@...gle.com, jannh@...gle.com, 
	shakeel.butt@...ux.dev, souravpanda@...gle.com, pasha.tatashin@...een.com, 
	klarasmodin@...il.com, corbet@....net, linux-doc@...r.kernel.org, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, kernel-team@...roid.com
Subject: Re: [PATCH v6 10/16] mm: replace vm_lock and detached flag with a
 reference count

On Thu, Dec 19, 2024 at 12:55 AM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Wed, Dec 18, 2024 at 11:29:23AM -0800, Suren Baghdasaryan wrote:
>
> > Yeah, I think we can simply do this:
> >
> > vms_complete_munmap_vmas
> >            vms_clear_ptes
> >            remove_vma
> >                vma_mark_detached
> >            mmap_write_downgrade
> >
> > If my assumption is incorrect, assertion inside vma_mark_detached()
> > should trigger. I tried a quick test and so far nothing exploded.
>
> I think that would be unfortunate and could cause regressions. I think
> we want to keep vms_clear_ptes() under the read-lock.

Ok, I'll stop considering this option.