[Devel] [PATCH VZ10 4/6] drivers/md/dm-qcow2: fix seek skip to the next L2 table

[Andrey Zhadchenko]

get_next_l2() adds the number of remaining clusters to the current
sector, so for a position which is not cluster aligned (e.g. the
llseek offset itself) the result overshoots the L2 table boundary by
the in-cluster offset.

Compute the boundary from the cluster index instead of adding to the
current position.

https://virtuozzo.atlassian.net/browse/VSTOR-139407
Feature: dm-qcow2: block device over QCOW2 files driver
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
---
 drivers/md/dm-qcow2-map.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-qcow2-map.c b/drivers/md/dm-qcow2-map.c
index d6d15b04215c6..776e89fc4eb1b 100644
--- a/drivers/md/dm-qcow2-map.c
+++ b/drivers/md/dm-qcow2-map.c
@@ -4405,12 +4405,12 @@ static struct qio *free_seek_qio_ret_higher(struct qio *qio)
 static inline sector_t get_next_l2(struct qio *qio)
 {
 	struct qcow2 *qcow2 = qio->qcow2;
-	loff_t start, add;
+	u64 base_l2, add;
 
-	start = to_bytes(qio->bi_iter.bi_sector);
-	add = qcow2->l2_entries - (start / qcow2->clu_size) % qcow2->l2_entries;
+	base_l2 = to_bytes(qio->bi_iter.bi_sector) / qcow2->clu_size;
+	add = qcow2->l2_entries - base_l2 % qcow2->l2_entries;
 
-	return qio->bi_iter.bi_sector + (qcow2->clu_size / to_bytes(1)) * add;
+	return to_sector((base_l2 + add) * qcow2->clu_size);
 }
 
 static inline sector_t get_next_clu(struct qio *qio)
-- 
2.43.5