btree: fix merge logic to use btree_last() return value

[Guan-Chun.Wu]

Previously btree_merge() called btree_last() only to test existence,
then performed an extra btree_lookup() to fetch the value. This patch
changes it to directly use the value returned by btree_last(), avoiding
redundant lookups and simplifying the merge loop.

Signed-off-by: Guan-Chun.Wu <409411716@xxxxxxxxxxxxxx>
---
 lib/btree.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/btree.c b/lib/btree.c
index bb81d3393ac5..9c80c0c7bba8 100644
--- a/lib/btree.c
+++ b/lib/btree.c
@@ -653,9 +653,9 @@ int btree_merge(struct btree_head *target, struct btree_head *victim,
 	 * walks to remove a single object from the victim.
 	 */
 	for (;;) {
-		if (!btree_last(victim, geo, key))
+		val = btree_last(victim, geo, key);
+		if (!val)
 			break;
-		val = btree_lookup(victim, geo, key);
 		err = btree_insert(target, geo, key, val, gfp);
 		if (err)
 			return err;
-- 
2.34.1