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block: add bio_copy_user_iov support to blk_rq_map_user_iov

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With this patch, blk_rq_map_user_iov uses bio_copy_user_iov when a low
level driver needs padding or a buffer in sg_iovec isn't aligned. That
is, it uses temporary kernel buffers instead of mapping user pages
directly.

When a LLD needs padding, later blk_rq_map_sg needs to extend the last
entry of a scatter list. bio_copy_user_iov guarantees that there is
enough space for padding by using temporary kernel buffers instead of
user pages.

blk_rq_map_user_iov needs buffers in sg_iovec to be aligned. The
comment in blk_rq_map_user_iov indicates that drivers/scsi/sg.c also
needs buffers in sg_iovec to be aligned. Actually, drivers/scsi/sg.c
works with unaligned buffers in sg_iovec (it always uses temporary
kernel buffers).

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
FUJITA Tomonori 2008-04-11 12:56:51 +02:00 committed by Jens Axboe
parent c5dec1c303
commit afdc1a780e
1 changed files with 17 additions and 5 deletions
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22
block/blk-map.c
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@ -5,6 +5,7 @@
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <scsi/sg.h> /* for struct sg_iovec */
#include "blk.h"
@ -194,15 +195,26 @@ int blk_rq_map_user_iov(struct request_queue *q, struct request *rq,
struct sg_iovec *iov, int iov_count, unsigned int len)
{
struct bio *bio;
int i, read = rq_data_dir(rq) == READ;
int unaligned = 0;
if (!iov || iov_count <= 0)
return -EINVAL;
/* we don't allow misaligned data like bio_map_user() does. If the
* user is using sg, they're expected to know the alignment constraints
* and respect them accordingly */
bio = bio_map_user_iov(q, NULL, iov, iov_count,
rq_data_dir(rq) == READ);
for (i = 0; i < iov_count; i++) {
unsigned long uaddr = (unsigned long)iov[i].iov_base;
if (uaddr & queue_dma_alignment(q)) {
unaligned = 1;
break;
}
}
if (unaligned || (q->dma_pad_mask & len))
bio = bio_copy_user_iov(q, iov, iov_count, read);
else
bio = bio_map_user_iov(q, NULL, iov, iov_count, read);
if (IS_ERR(bio))
return PTR_ERR(bio);