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block: add dma alignment and padding support to blk_rq_map_kern

Browse source 
This patch adds bio_copy_kern similar to
bio_copy_user. blk_rq_map_kern uses bio_copy_kern instead of
bio_map_kern if necessary.

bio_copy_kern uses temporary pages and the bi_end_io callback frees
these pages. bio_copy_kern saves the original kernel buffer at
bio->bi_private it doesn't use something like struct bio_map_data to
store the information about the caller.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
FUJITA Tomonori 2008-04-25 12:47:50 +02:00 committed by Jens Axboe
parent 657e93be35
commit 68154e90c9
3 changed files with 112 additions and 1 deletions
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21
block/blk-map.c
View file

@ -255,10 +255,18 @@ EXPORT_SYMBOL(blk_rq_unmap_user);
* @kbuf: the kernel buffer
* @len: length of user data
* @gfp_mask: memory allocation flags
*
* Description:
* Data will be mapped directly if possible. Otherwise a bounce
* buffer is used.
*/
int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
unsigned int len, gfp_t gfp_mask)
{
unsigned long kaddr;
unsigned int alignment;
int reading = rq_data_dir(rq) == READ;
int do_copy = 0;
struct bio *bio;
if (len > (q->max_hw_sectors << 9))
@ -266,13 +274,24 @@ int blk_rq_map_kern(struct request_queue *q, struct request *rq, void *kbuf,
if (!len || !kbuf)
return -EINVAL;
bio = bio_map_kern(q, kbuf, len, gfp_mask);
kaddr = (unsigned long)kbuf;
alignment = queue_dma_alignment(q) | q->dma_pad_mask;
do_copy = ((kaddr & alignment) || (len & alignment));
if (do_copy)
bio = bio_copy_kern(q, kbuf, len, gfp_mask, reading);
else
bio = bio_map_kern(q, kbuf, len, gfp_mask);
if (IS_ERR(bio))
return PTR_ERR(bio);
if (rq_data_dir(rq) == WRITE)
bio->bi_rw |= (1 << BIO_RW);
if (do_copy)
rq->cmd_flags |= REQ_COPY_USER;
blk_rq_bio_prep(q, rq, bio);
blk_queue_bounce(q, &rq->bio);
rq->buffer = rq->data = NULL;

90
fs/bio.c
View file

@ -937,6 +937,95 @@ struct bio *bio_map_kern(struct request_queue *q, void *data, unsigned int len,
return ERR_PTR(-EINVAL);
}
static void bio_copy_kern_endio(struct bio *bio, int err)
{
struct bio_vec *bvec;
const int read = bio_data_dir(bio) == READ;
char *p = bio->bi_private;
int i;
__bio_for_each_segment(bvec, bio, i, 0) {
char *addr = page_address(bvec->bv_page);
if (read && !err)
memcpy(p, addr, bvec->bv_len);
__free_page(bvec->bv_page);
p += bvec->bv_len;
}
bio_put(bio);
}
/**
* bio_copy_kern - copy kernel address into bio
* @q: the struct request_queue for the bio
* @data: pointer to buffer to copy
* @len: length in bytes
* @gfp_mask: allocation flags for bio and page allocation
*
* copy the kernel address into a bio suitable for io to a block
* device. Returns an error pointer in case of error.
*/
struct bio *bio_copy_kern(struct request_queue *q, void *data, unsigned int len,
gfp_t gfp_mask, int reading)
{
unsigned long kaddr = (unsigned long)data;
unsigned long end = (kaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
unsigned long start = kaddr >> PAGE_SHIFT;
const int nr_pages = end - start;
struct bio *bio;
struct bio_vec *bvec;
int i, ret;
bio = bio_alloc(gfp_mask, nr_pages);
if (!bio)
return ERR_PTR(-ENOMEM);
while (len) {
struct page *page;
unsigned int bytes = PAGE_SIZE;
if (bytes > len)
bytes = len;
page = alloc_page(q->bounce_gfp | gfp_mask);
if (!page) {
ret = -ENOMEM;
goto cleanup;
}
if (bio_add_pc_page(q, bio, page, bytes, 0) < bytes) {
ret = -EINVAL;
goto cleanup;
}
len -= bytes;
}
if (!reading) {
void *p = data;
bio_for_each_segment(bvec, bio, i) {
char *addr = page_address(bvec->bv_page);
memcpy(addr, p, bvec->bv_len);
p += bvec->bv_len;
}
}
bio->bi_private = data;
bio->bi_end_io = bio_copy_kern_endio;
return bio;
cleanup:
bio_for_each_segment(bvec, bio, i)
__free_page(bvec->bv_page);
bio_put(bio);
return ERR_PTR(ret);
}
/*
* bio_set_pages_dirty() and bio_check_pages_dirty() are support functions
* for performing direct-IO in BIOs.
@ -1273,6 +1362,7 @@ EXPORT_SYMBOL(bio_get_nr_vecs);
EXPORT_SYMBOL(bio_map_user);
EXPORT_SYMBOL(bio_unmap_user);
EXPORT_SYMBOL(bio_map_kern);
EXPORT_SYMBOL(bio_copy_kern);
EXPORT_SYMBOL(bio_pair_release);
EXPORT_SYMBOL(bio_split);
EXPORT_SYMBOL(bio_split_pool);

2
include/linux/bio.h
View file

@ -324,6 +324,8 @@ extern struct bio *bio_map_user_iov(struct request_queue *,
extern void bio_unmap_user(struct bio *);
extern struct bio *bio_map_kern(struct request_queue *, void *, unsigned int,
gfp_t);
extern struct bio *bio_copy_kern(struct request_queue *, void *, unsigned int,
gfp_t, int);
extern void bio_set_pages_dirty(struct bio *bio);
extern void bio_check_pages_dirty(struct bio *bio);
extern struct bio *bio_copy_user(struct request_queue *, unsigned long, unsigned int, int);