Re: [PATCH 2/3] erofs: convert to use kobject_is_added()

[Gao Xiang]

Hi Greg,

On 2023/4/6 18:03, Greg KH wrote:
> On Thu, Apr 06, 2023 at 05:30:55PM +0800, Yangtao Li wrote:
> > Use kobject_is_added() instead of directly accessing the internal
> > variables of kobject. BTW kill kobject_del() directly, because
> > kobject_put() actually covers kobject removal automatically.
> >
> > Signed-off-by: Yangtao Li <frank.li@xxxxxxxx>
> > ---
> >   fs/erofs/sysfs.c | 3 +--
> >   1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> > index 435e515c0792..daac23e32026 100644
> > --- a/fs/erofs/sysfs.c
> > +++ b/fs/erofs/sysfs.c
> > @@ -240,8 +240,7 @@ void erofs_unregister_sysfs(struct super_block *sb)
> >   {
> >   	struct erofs_sb_info *sbi = EROFS_SB(sb);
> >   
> > -	if (sbi->s_kobj.state_in_sysfs) {
> > -		kobject_del(&sbi->s_kobj);
> > +	if (kobject_is_added(&sbi->s_kobj)) {
>
> I do not understand why this check is even needed, I do not think it
> should be there at all as obviously the kobject was registered if it now
> needs to not be registered.

I think Yangtao sent a new patchset which missed the whole previous
background discussions as below:
https://lore.kernel.org/r/028a1b56-72c9-75f6-fb68-1dc5181bf2e8@xxxxxxxxxxxxxxxxx

It's needed because once a syzbot complaint as below:
https://lore.kernel.org/r/CAD-N9QXNx=p3-QoWzk6pCznF32CZy8kM3vvo8mamfZZ9CpUKdw@xxxxxxxxxxxxxx

I'd suggest including the previous backgrounds at least in the newer patchset,
otherwise it makes me explain again and again...

Thanks,
Gao Xiang

> Meta-comment, we need to come up with a "filesystem kobject type" to get
> rid of lots of the boilerplate filesystem kobject logic as it's
> duplicated in every filesystem in tiny different ways and lots of times
> (like here), it's wrong.
>
> kobjects were not designed to be "used raw" like this, ideally they
> would be wrapped in a subsystem that makes them easier to be used (like
> the driver model), but filesystems decided to use them and that usage
> just grew over the years.  That's evolution for you...> 
> thanks,
>
> greg k-h