Re: [RFC PATCH] filelock: new helper: vfs_file_has_locks

[Jeff Layton <jlayton@kernel.org>]

On Wed, 2022-11-16 at 19:16 +0800, Xiubo Li wrote:
> On 16/11/2022 18:55, Jeff Layton wrote:
> > On Wed, 2022-11-16 at 14:49 +0800, Xiubo Li wrote:
> > > On 15/11/2022 22:40, Jeff Layton wrote:
> > > 
> ...
> > > > +	spin_lock(&ctx->flc_lock);
> > > > +	ret = !list_empty(&ctx->flc_posix) || !list_empty(&ctx->flc_flock);
> > > > +	spin_unlock(&ctx->flc_lock);
> > > BTW, is the spin_lock/spin_unlock here really needed ?
> > > 
> > We could probably achieve the same effect with barriers, but I doubt
> > it's worth it. The flc_lock only protects the lists in the
> > file_lock_context, so it should almost always be uncontended.
> > 
> I just see some other places where are also checking this don't use the 
> spin lock.
> 
> 

True.

There are a number of places that don't and that use list_empty_careful.
Some of those  We could convert to that here, but again, I'm not sure
it's worth it. Let's stick with using the spinlocks here, since this
isn't a performance-critical codepath anyway.

> 
> > > > +	return ret;
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(vfs_inode_has_locks);
> > > > +
> > > >    #ifdef CONFIG_PROC_FS
> > > >    #include <linux/proc_fs.h>
> > > >    #include <linux/seq_file.h>
> > > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > > index e654435f1651..d6cb42b7e91c 100644
> > > > --- a/include/linux/fs.h
> > > > +++ b/include/linux/fs.h
> > > > @@ -1170,6 +1170,7 @@ extern int locks_delete_block(struct file_lock *);
> > > >    extern int vfs_test_lock(struct file *, struct file_lock *);
> > > >    extern int vfs_lock_file(struct file *, unsigned int, struct file_lock *, struct file_lock *);
> > > >    extern int vfs_cancel_lock(struct file *filp, struct file_lock *fl);
> > > > +bool vfs_inode_has_locks(struct inode *inode);
> > > >    extern int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl);
> > > >    extern int __break_lease(struct inode *inode, unsigned int flags, unsigned int type);
> > > >    extern void lease_get_mtime(struct inode *, struct timespec64 *time);
> > > All the others LGTM.
> > > 
> > > Thanks.
> > > 
> > > - Xiubo
> > > 
> > > 
> > Thanks. I'll re-post it "officially" in a bit and will queue it up for
> > v6.2.
> 

-- 
Jeff Layton <jlayton@kernel.org>