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-rw-r--r--block/blk-merge.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index d3b84bbb776a..7506c4fe0264 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -220,7 +220,10 @@ new_segment:
bvprv = bvec;
} /* segments in rq */
- if (q->dma_drain_size) {
+ if (q->dma_drain_size && q->dma_drain_needed(rq)) {
+ if (rq->cmd_flags & REQ_RW)
+ memset(q->dma_drain_buffer, 0, q->dma_drain_size);
+
sg->page_link &= ~0x02;
sg = sg_next(sg);
sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
@@ -228,6 +231,7 @@ new_segment:
((unsigned long)q->dma_drain_buffer) &
(PAGE_SIZE - 1));
nsegs++;
+ rq->data_len += q->dma_drain_size;
}
if (sg)