[PATCH AUTOSEL 4.9 17/30] dm: change max_io_len() to use blk_max_size_offset()

[Sasha Levin]

From: Mike Snitzer <snitzer@xxxxxxxxxx>

[ Upstream commit 5091cdec56faeaefa79de4b6cb3c3c55e50d1ac3 ]

Using blk_max_size_offset() enables DM core's splitting to impose
ti->max_io_len (via q->limits.chunk_sectors) and also fallback to
respecting q->limits.max_sectors if chunk_sectors isn't set.

Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/md/dm.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index dd154027adc9d..1fb44d18f3c72 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -872,22 +872,18 @@ static sector_t max_io_len_target_boundary(sector_t sector, struct dm_target *ti
 static sector_t max_io_len(sector_t sector, struct dm_target *ti)
 {
 	sector_t len = max_io_len_target_boundary(sector, ti);
-	sector_t offset, max_len;
+	sector_t max_len;
 
 	/*
 	 * Does the target need to split even further?
+	 * - q->limits.chunk_sectors reflects ti->max_io_len so
+	 *   blk_max_size_offset() provides required splitting.
+	 * - blk_max_size_offset() also respects q->limits.max_sectors
 	 */
-	if (ti->max_io_len) {
-		offset = dm_target_offset(ti, sector);
-		if (unlikely(ti->max_io_len & (ti->max_io_len - 1)))
-			max_len = sector_div(offset, ti->max_io_len);
-		else
-			max_len = offset & (ti->max_io_len - 1);
-		max_len = ti->max_io_len - max_len;
-
-		if (len > max_len)
-			len = max_len;
-	}
+	max_len = blk_max_size_offset(dm_table_get_md(ti->table)->queue,
+				      dm_target_offset(ti, sector));
+	if (len > max_len)
+		len = max_len;
 
 	return len;
 }
-- 
2.25.1