linux-kernel - Re: [PATCH 05/14] tracefs: replace call_rcu by kfree_rcu for simple kmem_cache

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Date: Mon, 10 Jun 2024 17:18:26 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: paulmck@...nel.org, Julia Lawall <Julia.Lawall@...ia.fr>,
 kernel-janitors@...r.kernel.org, Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 05/14] tracefs: replace call_rcu by kfree_rcu for simple
 kmem_cache_free callback

On Mon, 10 Jun 2024 22:42:30 +0200
Vlastimil Babka <vbabka@...e.cz> wrote:

> On 6/10/24 5:46 PM, Paul E. McKenney wrote:
> > On Mon, Jun 10, 2024 at 11:22:23AM -0400, Steven Rostedt wrote:  
> >> On Sun,  9 Jun 2024 10:27:17 +0200
> >> Julia Lawall <Julia.Lawall@...ia.fr> wrote:
> >>   
> >> > diff --git a/fs/tracefs/inode.c b/fs/tracefs/inode.c
> >> > index 7c29f4afc23d..338c52168e61 100644
> >> > --- a/fs/tracefs/inode.c
> >> > +++ b/fs/tracefs/inode.c
> >> > @@ -53,14 +53,6 @@ static struct inode *tracefs_alloc_inode(struct super_block *sb)
> >> >  	return &ti->vfs_inode;
> >> >  }
> >> >  
> >> > -static void tracefs_free_inode_rcu(struct rcu_head *rcu)
> >> > -{
> >> > -	struct tracefs_inode *ti;
> >> > -
> >> > -	ti = container_of(rcu, struct tracefs_inode, rcu);
> >> > -	kmem_cache_free(tracefs_inode_cachep, ti);  
> >> 
> >> Does this work?
> >> 
> >> tracefs needs to be freed via the tracefs_inode_cachep. Does
> >> kfree_rcu() handle specific frees for objects that were not allocated
> >> via kmalloc()?  
> > 
> > A recent change to kfree() allows it to correctly handle memory allocated
> > via kmem_cache_alloc().  News to me as of a few weeks ago.  ;-)  
> 
> Hey, I did try not to keep that a secret :)
> https://lore.kernel.org/all/20230310103210.22372-8-vbabka@suse.cz/
> 

Heh, I didn't look at that patch very deeply.

-- Steve