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Message-ID: <214ca3ac-45b7-4131-86e5-ac134ab0bcbd@kernel.org>
Date: Wed, 22 Apr 2026 16:30:07 +0200
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Subject: Re: [RFC PATCH v2 0/8] kvfree_rcu() improvements
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To: "Harry Yoo (Oracle)" <harry@kernel.org>,
 Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Lameter <cl@gentwo.org>, David Rientjes <rientjes@google.com>,
 Roman Gushchin <roman.gushchin@linux.dev>, Hao Li <hao.li@linux.dev>,
 Alexei Starovoitov <ast@kernel.org>, Uladzislau Rezki <urezki@gmail.com>,
 "Paul E . McKenney" <paulmck@kernel.org>,
 Frederic Weisbecker <frederic@kernel.org>,
 Neeraj Upadhyay <neeraj.upadhyay@kernel.org>,
 Joel Fernandes <joelagnelf@nvidia.com>, Josh Triplett
 <josh@joshtriplett.org>, Boqun Feng <boqun@kernel.org>,
 Zqiang <qiang.zhang@linux.dev>, Steven Rostedt <rostedt@goodmis.org>,
 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
 Lai Jiangshan <jiangshanlai@gmail.com>, rcu@vger.kernel.org,
 linux-mm@kvack.org, Alexander Viro <viro@zeniv.linux.org.uk>,
 Christian Brauner <brauner@kernel.org>
References: <20260416091022.36823-1-harry@kernel.org>
From: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>
In-Reply-To: <20260416091022.36823-1-harry@kernel.org>
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On 4/16/26 11:10, Harry Yoo (Oracle) wrote:
> # Part 1. Allow an 8-byte field to be used as an alternative to
>   struct rcu_head for 2-argument kvfree_rcu()
>   (patches 1-2)
> 
> Technically, objects that are freed with k[v]free_rcu() need
> only one pointer to link objects, because we already know that
> the callback function is always kvfree(). For this purpose,
> struct rcu_head is unnecessarily large (16 bytes on 64-bit).
> 
> Allow a smaller, 8-byte field (of struct rcu_ptr type) to be used
> with k[v]free_rcu(). Let's save one pointer per slab object.
> 
> I have to admit that my naming skill isn't great; hopefully
> we'll come up with a better name than `struct rcu_ptr`.

"rcu_ptr" sounds too generic to me. Things like rcu_dereference() talk about
"RCU-protected pointer" and it could be misleading that "rcu_ptr" has
something to do with this. Only if Paul think it's ok :)
But maybe just "kvfree_rcu_head"? As IMHO It's an rcu_head specialized for
kvfree.