On Tue 12-11-19 09:59:41, Sascha Hauer wrote:
> On Mon, Nov 11, 2019 at 05:34:46PM +0100, Jan Kara wrote:
> > Hi Sascha!
> >
> > On Mon 11-11-19 09:57:45, Sascha Hauer wrote:
> > > On Wed, Nov 06, 2019 at 11:14:28AM +0100, Jan Kara wrote:
> > > > > +/**
> > > > > + * ubifs_dqblk_find_next - find the next qid
> > > > > + * @c: UBIFS file-system description object
> > > > > + * @qid: The qid to look for
> > > > > + *
> > > > > + * Find the next dqblk entry with a qid that is bigger or equally big than the
> > > > > + * given qid. Returns the next dqblk entry if found or NULL if no dqblk exists
> > > > > + * with a qid that is at least equally big.
> > > > > + */
> > > > > +static struct ubifs_dqblk *ubifs_dqblk_find_next(struct ubifs_info *c,
> > > > > + struct kqid qid)
> > > > > +{
> > > > > + struct rb_node *node = c->dqblk_tree[qid.type].rb_node;
> > > > > + struct ubifs_dqblk *next = NULL;
> > > > > +
> > > > > + while (node) {
> > > > > + struct ubifs_dqblk *ud = rb_entry(node, struct ubifs_dqblk, rb);
> > > > > +
> > > > > + if (qid_eq(qid, ud->kqid))
> > > > > + return ud;
> > > > > +
> > > > > + if (qid_lt(qid, ud->kqid)) {
> > > > > + if (!next || qid_lt(ud->kqid, next->kqid))
> > ^^^
> > This condition looks superfluous as it should be always true. The last node
> > where you went left should be the least greater node if you didn't find the
> > exact match...
>
> You are right. I can't say why I thought this is necessary when I wrote
> this.
>
> >
> > > > > + next = ud;
> > > > > +
> > > > > + node = node->rb_left;
> > > > > + } else {
> > > > > + node = node->rb_right;
> > > > > + }
> > > > > + }
> > > > > +
> > > > > + return next;
> > > > > +}
> > > >
> > > > Why not use rb_next() here? It should do what you need, shouldn't it?
> > >
> > > I could use rb_next(), but it defeats the purpose of a tree to iterate
> > > over the whole tree to find an entry. If I wanted that I would have used
> > > a list.
> >
> > I wasn't quite clear in my suggestion and now that I look at it it was
> > actually misleading. I'm sorry for that. So a second try :):
> >
> > You have ubifs_dqblk_find() and ubifs_dqblk_find_next() doing very similar
> > rbtree traversal. I think you could remove that duplication by using
> > ubifs_dqblk_find_next() from ubifs_dqblk_find()?
>
> Ok, with this the two functions can be simplified to:
>
> /**
> * ubifs_dqblk_find_next - find the next qid
> * @c: UBIFS file-system description object
> * @qid: The qid to look for
> *
> * Find the next dqblk entry with a qid that is bigger or equally big than the
> * given qid. Returns the next dqblk entry if found or NULL if no dqblk exists
> * with a qid that is at least equally big.
> */
> static struct ubifs_dqblk *ubifs_dqblk_find_next(struct ubifs_info *c,
> struct kqid qid)
> {
> struct rb_node *node = c->dqblk_tree[qid.type].rb_node;
> struct ubifs_dqblk *next = NULL;
>
> while (node) {
> struct ubifs_dqblk *ud = rb_entry(node, struct ubifs_dqblk, rb);
>
> if (qid_eq(qid, ud->kqid))
> return ud;
>
> if (qid_lt(qid, ud->kqid)) {
> next = ud;
> node = node->rb_left;
> } else {
> node = node->rb_right;
> }
> }
>
> return next;
> }
>
> /**
> * ubifs_dqblk_find - find qid in tree
> * @c: UBIFS file-system description object
> * @qid: The qid to look for
> *
> * This walks the dqblk tree and searches a given qid. Returns the dqblk entry
> * when found or NULL otherwise.
> */
> static struct ubifs_dqblk *ubifs_dqblk_find(struct ubifs_info *c,
> struct kqid qid)
> {
> struct ubifs_dqblk *next = NULL;
>
> next = ubifs_dqblk_find_next(c, qid);
>
> if (next && qid_eq(qid, next->kqid))
> return next;
>
> return NULL;
> }
Yep, look good to me. Thanks!
> If this looks good now I'll integrate it for the next round. I'll delay
> sending a new version until Richard has had a look into this series.
Sure.
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
