dm: change max_io_len() to use blk_max_size_offset()

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@redhat.com>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 977a962..82886b4 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1051,22 +1051,18 @@ 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;
 }