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 08:46:42 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: 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,
	Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH 05/14] tracefs: replace call_rcu by kfree_rcu for simple
 kmem_cache_free callback

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.  ;-)

							Thanx, Paul

> -- Steve
> 
> 
> > -}
> > -
> >  static void tracefs_free_inode(struct inode *inode)
> >  {
> >  	struct tracefs_inode *ti = get_tracefs(inode);
> > @@ -70,7 +62,7 @@ static void tracefs_free_inode(struct inode *inode)
> >  	list_del_rcu(&ti->list);
> >  	spin_unlock_irqrestore(&tracefs_inode_lock, flags);
> >  
> > -	call_rcu(&ti->rcu, tracefs_free_inode_rcu);
> > +	kfree_rcu(ti, rcu);
> >  }
> >  
> >  static ssize_t default_read_file(struct file *file, char __user *buf,
>