diff options
| author | Tejun Heo | 2008-02-19 11:35:38 +0100 |
|---|---|---|
| committer | Jens Axboe | 2008-02-19 11:35:38 +0100 |
| commit | 40b01b9bbdf51ae543a04744283bf2d56c4a6afa (patch) | |
| tree | 0f81015c01834b97fdb5646a63c3fe1a24936d81 /block | |
| parent | 56c819df77f96c3fc0c2a979e12b478403728790 (diff) | |
block: update bio according to DMA alignment padding
DMA start address and transfer size alignment for PC requests are
achieved using bio_copy_user() instead of bio_map_user(). This works
because bio_copy_user() always uses full pages and block DMA alignment
isn't allowed to go over PAGE_SIZE.
However, the implementation didn't update the last bio of the request
to make this padding visible to lower layers. This patch makes
blk_rq_map_user() extend the last bio such that it includes the
padding area and the size of area pointed to by the request is
properly aligned.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-map.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/block/blk-map.c b/block/blk-map.c index bc5ce60691c3..a7cf63ccb5cf 100644 --- a/block/blk-map.c +++ b/block/blk-map.c @@ -139,6 +139,23 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq, ubuf += ret; } + /* + * __blk_rq_map_user() copies the buffers if starting address + * or length isn't aligned. As the copied buffer is always + * page aligned, we know that there's enough room for padding. + * Extend the last bio and update rq->data_len accordingly. + * + * On unmap, bio_uncopy_user() will use unmodified + * bio_map_data pointed to by bio->bi_private. + */ + if (len & queue_dma_alignment(q)) { + unsigned int pad_len = (queue_dma_alignment(q) & ~len) + 1; + struct bio *bio = rq->biotail; + + bio->bi_io_vec[bio->bi_vcnt - 1].bv_len += pad_len; + bio->bi_size += pad_len; + } + rq->buffer = rq->data = NULL; return 0; unmap_rq: |