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block: make blk_rq_map_user take a NULL user-space buffer

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This patch changes blk_rq_map_user to accept a NULL user-space buffer
with a READ command if rq_map_data is not NULL. Thus a caller can pass
page frames to lk_rq_map_user to just set up a request and bios with
page frames propely. bio_uncopy_user (called via blk_rq_unmap_user)
doesn't copy data to user space with such request.

Signed-off-by: FUJITA Tomonori <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
FUJITA Tomonori 2008-09-02 16:20:19 +09:00 • committed by Jens Axboe
commit 818827669d
3 changed files with 17 additions and 8 deletions
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16
block/blk-map.c
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@ -42,7 +42,7 @@ static int __blk_rq_unmap_user(struct bio *bio)
static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
struct rq_map_data *map_data, void __user *ubuf,
unsigned int len, gfp_t gfp_mask)
unsigned int len, int null_mapped, gfp_t gfp_mask)
{
unsigned long uaddr;
struct bio *bio, *orig_bio;
@ -63,6 +63,9 @@ static int __blk_rq_map_user(struct request_queue *q, struct request *rq,
if (IS_ERR(bio))
return PTR_ERR(bio);
if (null_mapped)
bio->bi_flags |= (1 << BIO_NULL_MAPPED);
orig_bio = bio;
blk_queue_bounce(q, &bio);
@ -111,12 +114,17 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq,
{
unsigned long bytes_read = 0;
struct bio *bio = NULL;
int ret;
int ret, null_mapped = 0;
if (len > (q->max_hw_sectors << 9))
return -EINVAL;
if (!len || !ubuf)
if (!len)
return -EINVAL;
if (!ubuf) {
if (!map_data || rq_data_dir(rq) != READ)
return -EINVAL;
null_mapped = 1;
}
while (bytes_read != len) {
unsigned long map_len, end, start;
@ -135,7 +143,7 @@ int blk_rq_map_user(struct request_queue *q, struct request *rq,
map_len -= PAGE_SIZE;
ret = __blk_rq_map_user(q, rq, map_data, ubuf, map_len,
gfp_mask);
null_mapped, gfp_mask);
if (ret < 0)
goto unmap_rq;
if (!bio)