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block: separate out padding from alignment

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Block layer alignment was used for two different purposes - memory
alignment and padding.  This causes problems in lower layers because
drivers which only require memory alignment ends up with adjusted
rq->data_len.  Separate out padding such that padding occurs iff
driver explicitly requests it.

Tomo: restorethe code to update bio in blk_rq_map_user
      introduced by the commit 40b01b9bbd
      according to padding alignment.

Signed-off-by: Tejun Heo <[email protected]>
Signed-off-by: FUJITA Tomonori <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Tejun Heo 2008-03-04 11:18:17 +01:00 • committed by Jens Axboe
commit e3790c7d42
4 changed files with 34 additions and 8 deletions
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20
block/blk-map.c
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@ -43,6 +43,7 @@ static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
void __user *ubuf, unsigned int len)
{
unsigned long uaddr;
unsigned int alignment;
struct bio *bio, *orig_bio;
int reading, ret;
@ -53,8 +54,8 @@ static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
* direct dma. else, set up kernel bounce buffers
*/
uaddr = (unsigned long) ubuf;
if (!(uaddr & queue_dma_alignment(q)) &&
!(len & queue_dma_alignment(q)))
alignment = queue_dma_alignment(q) | q->dma_pad_mask;
if (!(uaddr & alignment) && !(len & alignment))
bio = bio_map_user(q, NULL, uaddr, len, reading);
else
bio = bio_copy_user(q, uaddr, len, reading);
@ -141,15 +142,20 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq,
/*
* __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.
* or length isn't aligned to dma_pad_mask. 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;
if (len & q->dma_pad_mask) {
unsigned int pad_len = (q->dma_pad_mask & ~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->extra_len += pad_len;
}