Re: [PATCH v2 1/2] kernfs: Make it possible to use RCU for kernfs_node::name lookup.

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2024-11-14 14:48:16 [+0100], Michal Koutný wrote:
> On Tue, Nov 12, 2024 at 04:52:38PM GMT, Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> > --- a/include/linux/kernfs.h
> > +++ b/include/linux/kernfs.h
> > @@ -147,6 +147,11 @@ enum kernfs_root_flag {
> >  	 * Support user xattrs to be written to nodes rooted at this root.
> >  	 */
> >  	KERNFS_ROOT_SUPPORT_USER_XATTR		= 0x0008,
> > +
> > +	/*
> > +	 * Renames must not change the parent node.
> > +	 */
> > +	KERNFS_ROOT_SAME_PARENT			= 0x0010,
> 
> FTR, cgroup v2 doesn't even define renames and the full rename
> (different parent) is only used by resctrl filesystem AFAICS.
> I'm only mentioning it in the case you wanted to replace the flag with
> two different rename methods in kernfs_syscall_ops.

Thanks. I think I have enough clues for a v3 now. I wanted to do
something today but didn't manage it yet.

> Thanks for fixing this locking situation in general,
> Michal

Sebastian