[PATCH 3.4 011/107] dm btree remove: fix bug in redistribute3

lizf
2016-03-16T08:43:29Z

From: Dennis Yang <shinrairis@gmail.com>

3.4.111-rc1 review patch. If anyone has any objections, please let me know.

------------------

commit 4c7e309340ff85072e96f529582d159002c36734 upstream.

redistribute3() shares entries out across 3 nodes. Some entries were
being moved the wrong way, breaking the ordering. This manifested as a
BUG() in dm-btree-remove.c:shift() when entries were removed from the
btree.

For additional context see:
https://www.redhat.com/archives/dm-devel/2015-May/msg00113.html

Signed-off-by: Dennis Yang <shinrairis@gmail.com>
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Zefan Li <lizefan@huawei.com>
---
drivers/md/persistent-data/dm-btree-remove.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/md/persistent-data/dm-btree-remove.c b/drivers/md/persistent-data/dm-btree-remove.c
index b88757c..a03178e 100644
--- a/drivers/md/persistent-data/dm-btree-remove.c
+++ b/drivers/md/persistent-data/dm-btree-remove.c
@@ -309,8 +309,8 @@ static void redistribute3(struct dm_btree_info *info, struct btree_node *parent,

if (s < 0 && nr_center < -s) {
/* not enough in central node */
- shift(left, center, nr_center);
- s = nr_center - target;
+ shift(left, center, -nr_center);
+ s += nr_center;
shift(left, right, s);
nr_right += s;
} else
@@ -323,7 +323,7 @@ static void redistribute3(struct dm_btree_info *info, struct btree_node *parent,
if (s > 0 && nr_center < s) {
/* not enough in central node */
shift(center, right, nr_center);
- s = target - nr_center;
+ s -= nr_center;
shift(left, right, s);
nr_left -= s;
} else
--
1.9.1