On Wed, Apr 12, 2023 at 12:04:40PM +0200, Jan Kara wrote:
> Hi Carlos!
>
> On Wed 12-04-23 11:44:32, Carlos Maiolino wrote:
> > > > > +static int shmem_release_dquot(struct dquot *dquot)
> > > > > +{
> > > > > + struct mem_dqinfo *info = sb_dqinfo(dquot->dq_sb, dquot->dq_id.type);
> > > > > + struct rb_node *node = ((struct rb_root *)info->dqi_priv)->rb_node;
> > > > > + qid_t id = from_kqid(&init_user_ns, dquot->dq_id);
> > > > > + struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);
> > > > > + struct quota_id *entry = NULL;
> > > > > +
> > > > > + mutex_lock(&dquot->dq_lock);
> > > > > + /* Check whether we are not racing with some other dqget() */
> > > > > + if (dquot_is_busy(dquot))
> > > > > + goto out_dqlock;
> > > > > +
> > > > > + down_write(&dqopt->dqio_sem);
> > > > > + while (node) {
> > > > > + entry = rb_entry(node, struct quota_id, node);
> > > > > +
> > > > > + if (id < entry->id)
> > > > > + node = node->rb_left;
> > > > > + else if (id > entry->id)
> > > > > + node = node->rb_right;
> > > > > + else
> > > > > + goto found;
> > > > > + }
> > > > > +
> > > > > + up_write(&dqopt->dqio_sem);
> > > > > + mutex_unlock(&dquot->dq_lock);
> > > >
> > > > We should report some kind of error here, shouldn't we? We do expect to
> > > > have the quota_id allocated from shmem_acquire_dquot() and we will be
> > > > possibly loosing set limits here.
> > > >
> >
> > I've been looking into this today, and I'm not sure if there is any error we
> > should be reporting here, as there isn't anything to really go wrong here. I was
> > comparing it with other filesystems, and most of them uses dquot_release()
> > return value, as a return value for .release_dquot. And on such cases, the error
> > could be other than zero, if something failed while writing the dquot to disk.
> > In the case here, we just write to the RB tree in memory, and it has already
> > been allocated, so, I don't think there is any error we could be returning here.
> > Does it sound right to you?
>
> My point is that it should never happen that we don't find the entry in the
> rbtree in shmem_release_dquot(). So we should rather WARN_ON_ONCE() and
> bail or something like that, rather then silently return success. Not a big
> deal but for initial debugging it might be useful.
>
I see. Thanks Honza. What you think about something like this:
while (node) {
entry = rb_entry(node, struct quota_id, node);
if (id < entry->id)
node = node->rb_left;
else if (id > entry->id)
node = node->rb_right;
else
goto found;
}
/* We should always find the entry in the rb tree */
WARN_ONCE(1, "quota id not in rb tree!\n", __func__)
return -ENOENT;
I am not sure if -ENOENT is the best error here though. It seems the most
logical one, as -ENOMEM wouldn't make much sense, any suggestions if you don't
agree with ENOENT?
> Honza
> --
> Jan Kara <jack@xxxxxxxx>
> SUSE Labs, CR
--
Carlos Maiolino
