[PATCH 2/2] rbtree_latch: don't need to check seq when it found a node

[Lai Jiangshan]

latch_tree_find() should be protected by caller via RCU or so.
When it find a node in an attempt, the node must be a valid one.

Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Paul E. McKenney <paul...@kernel.org>
Cc: Oleg Nesterov <o...@redhat.com>
Cc: Michel Lespinasse <wal...@google.com>
Cc: Andrea Arcangeli <aarca...@redhat.com>
Cc: David Woodhouse <david.woodho...@intel.com>
Cc: Rik van Riel <r...@redhat.com>
Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
Signed-off-by: Lai Jiangshan <la...@linux.alibaba.com>
---
 include/linux/rbtree_latch.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/rbtree_latch.h b/include/linux/rbtree_latch.h
index b012bd95eabf..09a3c05d1c5b 100644
--- a/include/linux/rbtree_latch.h
+++ b/include/linux/rbtree_latch.h
@@ -208,7 +208,7 @@ latch_tree_find(void *key, struct latch_tree_root *root,
        do {
                seq = raw_read_seqcount_latch(&root->seq);
                node = __lt_find(key, root, seq & 1, ops->comp);
-       } while (read_seqcount_retry(&root->seq, seq));
+       } while (!node && read_seqcount_retry(&root->seq, seq));
 
        return node;
 }
-- 
2.20.1