Messages in this thread | | | Date | Wed, 25 Aug 2021 04:53:32 -0700 | From | Michel Lespinasse <> | Subject | Re: [PATCH] rbtree: stop iteration early in rb_find_first |
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On Wed, Aug 25, 2021 at 01:39:26PM +0200, Peter Zijlstra wrote: > On Wed, Aug 25, 2021 at 05:59:48PM +0800, Li RongQing wrote: > > stop iteration if match is not NULL and result of cmp is > > not zero, this means the matched node has been found, and > > the node with same key has been passed > > > > Signed-off-by: Li RongQing <lirongqing@baidu.com> > > --- > > include/linux/rbtree.h | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/include/linux/rbtree.h b/include/linux/rbtree.h > > index d31ecaf4fdd3..2689771df9bb 100644 > > --- a/include/linux/rbtree.h > > +++ b/include/linux/rbtree.h > > @@ -324,6 +324,9 @@ rb_find_first(const void *key, const struct rb_root *tree, > > } else if (c > 0) { > > node = node->rb_right; > > } > > + > > + if (match && c) > > + break; > > } > > > > return match; > > Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
NAK. This looked slightly wrong before, and is more wrong after.
Before: there was this weird condition if (c <= 0) {} else if (c > 0) {} , making you wonder what the third possibility may be. Easy fix would be to remove the second condition.
After: say the key is equal the root, so the code sets match=root and goes left. Then it stops searching because match is set and c<0. This doesn't work, the code needs to keep searching for the leftmost match.
-- Michel "walken" Lespinasse
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