linux-kernel - Re: [PATCH v3 05/12] rust: xarray: use `xas_load` instead of `xa

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <hq46fcdy6zvwcwlbtbjynqadiwy3wjs7raxioime2et5amzez6@wvzzlkiijwvf>
Date: Wed, 11 Feb 2026 09:32:36 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Tamir Duberstein <tamird@...nel.org>,
        Andreas Hindborg <a.hindborg@...nel.org>,
        Tamir Duberstein <tamird@...il.com>, Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>,
        Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        Benno Lossin <lossin@...nel.org>, Trevor Gross <tmgross@...ch.edu>,
        Danilo Krummrich <dakr@...nel.org>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Lameter <cl@...two.org>,
        David Rientjes <rientjes@...gle.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Harry Yoo <harry.yoo@...cle.com>, Daniel Gomez <da.gomez@...nel.org>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v3 05/12] rust: xarray: use `xas_load` instead of
 `xa_load` in `Guard::load`

* Alice Ryhl <aliceryhl@...gle.com> [260210 16:34]:
> On Tue, Feb 10, 2026 at 10:23 PM Tamir Duberstein <tamird@...nel.org> wrote:
> >
> > On Tue, Feb 10, 2026 at 12:59 PM Liam R. Howlett
> > <Liam.Howlett@...cle.com> wrote:
> > > Is this a temporary limitation?
> >
> > Maybe? I don't think RfL has good abstractions for RCU yet. For
> > example, exposing load directly on the xarray using xa_load would
> > require a way to guarantee that the returned pointer's target isn't
> > being concurrently mutated (e.g. under the xarray lock). I'm not aware
> > of anyone asking for this, though.
> 
> It's relatively easy to add an rcu-backed load using the RCU
> abstractions we have today. I already shared an RFC containing such a
> method for the maple tree, and it would not be much different for
> xarray.
> https://lore.kernel.org/all/20260116-rcu-box-v1-0-38ebfbcd53f0@google.com/
> 

It would probably be worth having two loads then, one that does
rcu_read_lock()/unlock() and one for writer/advanced users like we have
on the C side of things.

Or at least name the load() function to indicate which is implemented
today?

At least on the maple tree side, we have both interfaces and users for
both.  I just found the change to remove the rcu safety odd because I
assumed both are needed.

Thanks,
Liam