linux-kernel - Re: [PATCH 0/7] remove SLOB and allow kfree() with kmem_cache

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Message-ID: <3018fb77-68d0-fb67-2595-7c58c6cf7a76@suse.cz>
Date:   Wed, 15 Mar 2023 14:53:14 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Mike Rapoport <mike.rapoport@...il.com>
Cc:     Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Pekka Enberg <penberg@...nel.org>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        rcu@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        netdev@...r.kernel.org, linux-doc@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Jonathan Corbet <corbet@....net>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Mike Rapoport <rppt@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Paolo Abeni <pabeni@...hat.com>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH 0/7] remove SLOB and allow kfree() with kmem_cache_alloc()


On 3/13/23 17:31, Steven Rostedt wrote:
> Just remove that comment. And you could even add:
> 
> Suggested-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> Fixes: e4c2ce82ca27 ("ring_buffer: allocate buffer page pointer")

Thanks for the analysis. Want to take the following patch to your tree or
should I make it part of the series?

----8<----
>From 297a8c8fda98dc5499cfe0eac6ffabfb19d1b70f Mon Sep 17 00:00:00 2001
From: Vlastimil Babka <vbabka@...e.cz>
Date: Wed, 15 Mar 2023 14:45:15 +0100
Subject: [PATCH] ring-buffer: remove obsolete comment for free_buffer_page()

The comment refers to mm/slob.o which is being removed. It comes from
commit ed56829cb319 ("ring_buffer: reset buffer page when freeing") and
according to Steven the borrowed code was a page mapcount and mapping
reset, which was later removed by commit e4c2ce82ca27 ("ring_buffer:
allocate buffer page pointer"). Thus the comment is not accurate anyway,
remove it.

Reported-by: Mike Rapoport <mike.rapoport@...il.com>
Suggested-by: Steven Rostedt (Google) <rostedt@...dmis.org>
Fixes: e4c2ce82ca27 ("ring_buffer: allocate buffer page pointer")
Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 kernel/trace/ring_buffer.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index af50d931b020..c6f47b6cfd5f 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -354,10 +354,6 @@ static void rb_init_page(struct buffer_data_page *bpage)
 	local_set(&bpage->commit, 0);
 }
 
-/*
- * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
- * this issue out.
- */
 static void free_buffer_page(struct buffer_page *bpage)
 {
 	free_page((unsigned long)bpage->page);
-- 
2.39.2