Re: [PATCH 1/2] vfs: free vfsmount through rcu work from kern_unmount

[Al Viro]

On Sat, Feb 19, 2022 at 05:53:37AM +0000, Al Viro wrote:
> On Fri, Feb 18, 2022 at 01:31:13PM -0500, Rik van Riel wrote:
> 
> >  struct super_block;
> >  struct vfsmount;
> > @@ -73,6 +74,7 @@ struct vfsmount {
> >  	struct super_block *mnt_sb;	/* pointer to superblock */
> >  	int mnt_flags;
> >  	struct user_namespace *mnt_userns;
> > +	struct rcu_work free_rwork;
> >  } __randomize_layout;
> 
> Wait, what?  First of all, that has no business being in vfsmount -
> everything that deeply internal belongs in struct mount, not in
> its public part.  Moreover, there's already mount->mnt_rcu, so what's
> the point duplicating that?

Argh... You need rcu_work there...

OK, so make that a member of the same union mnt_rcu is.  In struct mount,
please.  And I'm not sure I like the idea of shoving that much into
struct mount, TBH...