Re: [PATCH 05/14] tracefs: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

Vlastimil Babka
2024-06-10T20:42:32Z

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@inria.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/

> 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,
>>