linux-kernel - Re: [RFC PATCH RESEND 03/28] mm: introduce __find_vma to be used without mmap

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Message-ID: <20220901202239.tnnzlbermiyvkmih@moria.home.lan>
Date:   Thu, 1 Sep 2022 16:22:39 -0400
From:   Kent Overstreet <kent.overstreet@...ux.dev>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     akpm@...ux-foundation.org, michel@...pinasse.org,
        jglisse@...gle.com, mhocko@...e.com, vbabka@...e.cz,
        hannes@...xchg.org, mgorman@...e.de, dave@...olabs.net,
        willy@...radead.org, liam.howlett@...cle.com, peterz@...radead.org,
        ldufour@...ux.ibm.com, laurent.dufour@...ibm.com,
        paulmck@...nel.org, luto@...nel.org, songliubraving@...com,
        peterx@...hat.com, david@...hat.com, dhowells@...hat.com,
        hughd@...gle.com, bigeasy@...utronix.de, rientjes@...gle.com,
        axelrasmussen@...gle.com, joelaf@...gle.com, minchan@...gle.com,
        kernel-team@...roid.com, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH RESEND 03/28] mm: introduce __find_vma to be used
 without mmap_lock protection

On Thu, Sep 01, 2022 at 10:34:51AM -0700, Suren Baghdasaryan wrote:
> Add __find_vma function to be used for VMA lookup under rcu protection.

So it was news to me that the rb tree code can be used for lockless lookups -
not having looked at lib/rbtree.c in over 10 years :) - I still think it should
be mentioned in the commit message that that's what you're doing and why it's
safe, because it's not exactly common knowledge and lockless stuff deserves
extra scrutiny.

Probably worth a comment, too.

Reviewed-by: Kent Overstreet <kent.overstreet@...ux.dev>