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

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Message-ID: <20241216220007.GE9803@noisy.programming.kicks-ass.net>
Date: Mon, 16 Dec 2024 23:00:07 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: akpm@...ux-foundation.org, willy@...radead.org, liam.howlett@...cle.com,
	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,
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	hughd@...gle.com, lokeshgidra@...gle.com, minchan@...gle.com,
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	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 Mon, Dec 16, 2024 at 01:53:06PM -0800, Suren Baghdasaryan wrote:

> > That is, should this not live in vma_iter_store*(), right before
> > mas_store_gfp() ?
> 
> Currently it's done right *after* mas_store_gfp() but I was debating
> with myself if it indeed should be *before* insertion into the tree...

The moment it goes into the tree it becomes visible to RCU lookups, it's
a bit weird to have them with !refcnt at that point, but I don't suppose
it harms.