block: restore the meaning of rq->data_len to the true data length

The meaning of rq->data_len was changed to the length of an allocated
buffer from the true data length. It breaks SG_IO friends and
bsg. This patch restores the meaning of rq->data_len to the true data
length and adds rq->extra_len to store an extended length (due to
drain buffer and padding).

This patch also removes the code to update bio in blk_rq_map_user
introduced by the commit 40b01b9bbdf51ae543a04744283bf2d56c4a6afa.
The commit adjusts bio according to memory alignment
(queue_dma_alignment). However, memory alignment is NOT padding
alignment. This adjustment also breaks SG_IO friends and bsg. Padding
alignment needs to be fixed in a proper way (by a separate patch).

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <axboe@carl.home.kernel.dk>

1 files changed, 1 insertions, 1 deletions

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 7506c4fe0264..0f58616bcd7f 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -231,7 +231,7 @@ new_segment:
                             ((unsigned long)q->dma_drain_buffer) &
                             (PAGE_SIZE - 1));
                 nsegs++;
-                rq->data_len += q->dma_drain_size;
+                rq->extra_len += q->dma_drain_size;
         }
 
         if (sg)