Commit f1970baf authored by James Bottomley 's avatar James Bottomley Committed by Jens Axboe
Browse files

[PATCH] Add scatter-gather support for the block layer SG_IO


Signed-off-by: default avatarJens Axboe <axboe@suse.de>
parent dd1cab95
......@@ -2148,6 +2148,50 @@ int blk_rq_map_user(request_queue_t *q, struct request *rq, void __user *ubuf,
EXPORT_SYMBOL(blk_rq_map_user);
/**
* blk_rq_map_user_iov - map user data to a request, for REQ_BLOCK_PC usage
* @q: request queue where request should be inserted
* @rq: request to map data to
* @iov: pointer to the iovec
* @iov_count: number of elements in the iovec
*
* Description:
* Data will be mapped directly for zero copy io, if possible. Otherwise
* a kernel bounce buffer is used.
*
* A matching blk_rq_unmap_user() must be issued at the end of io, while
* still in process context.
*
* Note: The mapped bio may need to be bounced through blk_queue_bounce()
* before being submitted to the device, as pages mapped may be out of
* reach. It's the callers responsibility to make sure this happens. The
* original bio must be passed back in to blk_rq_unmap_user() for proper
* unmapping.
*/
int blk_rq_map_user_iov(request_queue_t *q, struct request *rq,
struct sg_iovec *iov, int iov_count)
{
struct bio *bio;
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);
if (IS_ERR(bio))
return PTR_ERR(bio);
rq->bio = rq->biotail = bio;
blk_rq_bio_prep(q, rq, bio);
rq->buffer = rq->data = NULL;
rq->data_len = bio->bi_size;
return 0;
}
EXPORT_SYMBOL(blk_rq_map_user_iov);
/**
* blk_rq_unmap_user - unmap a request with user data
* @rq: request to be unmapped
......@@ -2207,6 +2251,19 @@ int blk_rq_map_kern(request_queue_t *q, struct request *rq, void *kbuf,
EXPORT_SYMBOL(blk_rq_map_kern);
void blk_execute_rq_nowait(request_queue_t *q, struct gendisk *bd_disk,
struct request *rq, int at_head,
void (*done)(struct request *))
{
int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
rq->rq_disk = bd_disk;
rq->flags |= REQ_NOMERGE;
rq->end_io = done;
elv_add_request(q, rq, where, 1);
generic_unplug_device(q);
}
/**
* blk_execute_rq - insert a request into queue for execution
* @q: queue to insert the request in
......@@ -2224,8 +2281,6 @@ int blk_execute_rq(request_queue_t *q, struct gendisk *bd_disk,
char sense[SCSI_SENSE_BUFFERSIZE];
int err = 0;
rq->rq_disk = bd_disk;
/*
* we need an extra reference to the request, so we can look at
* it after io completion
......@@ -2238,11 +2293,8 @@ int blk_execute_rq(request_queue_t *q, struct gendisk *bd_disk,
rq->sense_len = 0;
}
rq->flags |= REQ_NOMERGE;
rq->waiting = &wait;
rq->end_io = blk_end_sync_rq;
elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 1);
generic_unplug_device(q);
blk_execute_rq_nowait(q, bd_disk, rq, 0, blk_end_sync_rq);
wait_for_completion(&wait);
rq->waiting = NULL;
......
......@@ -231,17 +231,11 @@ static int sg_io(struct file *file, request_queue_t *q,
if (verify_command(file, cmd))
return -EPERM;
/*
* we'll do that later
*/
if (hdr->iovec_count)
return -EOPNOTSUPP;
if (hdr->dxfer_len > (q->max_sectors << 9))
return -EIO;
reading = writing = 0;
if (hdr->dxfer_len) {
if (hdr->dxfer_len)
switch (hdr->dxfer_direction) {
default:
return -EINVAL;
......@@ -261,11 +255,29 @@ static int sg_io(struct file *file, request_queue_t *q,
if (!rq)
return -ENOMEM;
if (reading || writing) {
ret = blk_rq_map_user(q, rq, hdr->dxferp, hdr->dxfer_len);
if (ret)
if (hdr->iovec_count) {
const int size = sizeof(struct sg_iovec) * hdr->iovec_count;
struct sg_iovec *iov;
iov = kmalloc(size, GFP_KERNEL);
if (!iov) {
ret = -ENOMEM;
goto out;
}
}
if (copy_from_user(iov, hdr->dxferp, size)) {
kfree(iov);
ret = -EFAULT;
goto out;
}
ret = blk_rq_map_user_iov(q, rq, iov, hdr->iovec_count);
kfree(iov);
} else if (hdr->dxfer_len)
ret = blk_rq_map_user(q, rq, hdr->dxferp, hdr->dxfer_len);
if (ret)
goto out;
/*
* fill in request structure
......
......@@ -25,6 +25,7 @@
#include <linux/module.h>
#include <linux/mempool.h>
#include <linux/workqueue.h>
#include <scsi/sg.h> /* for struct sg_iovec */
#define BIO_POOL_SIZE 256
......@@ -549,22 +550,34 @@ out_bmd:
return ERR_PTR(ret);
}
static struct bio *__bio_map_user(request_queue_t *q, struct block_device *bdev,
unsigned long uaddr, unsigned int len,
int write_to_vm)
static struct bio *__bio_map_user_iov(request_queue_t *q,
struct block_device *bdev,
struct sg_iovec *iov, int iov_count,
int write_to_vm)
{
unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
unsigned long start = uaddr >> PAGE_SHIFT;
const int nr_pages = end - start;
int ret, offset, i;
int i, j;
int nr_pages = 0;
struct page **pages;
struct bio *bio;
int cur_page = 0;
int ret, offset;
/*
* transfer and buffer must be aligned to at least hardsector
* size for now, in the future we can relax this restriction
*/
if ((uaddr & queue_dma_alignment(q)) || (len & queue_dma_alignment(q)))
for (i = 0; i < iov_count; i++) {
unsigned long uaddr = (unsigned long)iov[i].iov_base;
unsigned long len = iov[i].iov_len;
unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
unsigned long start = uaddr >> PAGE_SHIFT;
nr_pages += end - start;
/*
* transfer and buffer must be aligned to at least hardsector
* size for now, in the future we can relax this restriction
*/
if ((uaddr & queue_dma_alignment(q)) || (len & queue_dma_alignment(q)))
return ERR_PTR(-EINVAL);
}
if (!nr_pages)
return ERR_PTR(-EINVAL);
bio = bio_alloc(GFP_KERNEL, nr_pages);
......@@ -576,42 +589,54 @@ static struct bio *__bio_map_user(request_queue_t *q, struct block_device *bdev,
if (!pages)
goto out;
down_read(&current->mm->mmap_sem);
ret = get_user_pages(current, current->mm, uaddr, nr_pages,
write_to_vm, 0, pages, NULL);
up_read(&current->mm->mmap_sem);
if (ret < nr_pages)
goto out;
bio->bi_bdev = bdev;
offset = uaddr & ~PAGE_MASK;
for (i = 0; i < nr_pages; i++) {
unsigned int bytes = PAGE_SIZE - offset;
if (len <= 0)
break;
if (bytes > len)
bytes = len;
memset(pages, 0, nr_pages * sizeof(struct page *));
for (i = 0; i < iov_count; i++) {
unsigned long uaddr = (unsigned long)iov[i].iov_base;
unsigned long len = iov[i].iov_len;
unsigned long end = (uaddr + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
unsigned long start = uaddr >> PAGE_SHIFT;
const int local_nr_pages = end - start;
const int page_limit = cur_page + local_nr_pages;
down_read(&current->mm->mmap_sem);
ret = get_user_pages(current, current->mm, uaddr,
local_nr_pages,
write_to_vm, 0, &pages[cur_page], NULL);
up_read(&current->mm->mmap_sem);
if (ret < local_nr_pages)
goto out_unmap;
offset = uaddr & ~PAGE_MASK;
for (j = cur_page; j < page_limit; j++) {
unsigned int bytes = PAGE_SIZE - offset;
if (len <= 0)
break;
if (bytes > len)
bytes = len;
/*
* sorry...
*/
if (__bio_add_page(q, bio, pages[j], bytes, offset) < bytes)
break;
len -= bytes;
offset = 0;
}
cur_page = j;
/*
* sorry...
* release the pages we didn't map into the bio, if any
*/
if (__bio_add_page(q, bio, pages[i], bytes, offset) < bytes)
break;
len -= bytes;
offset = 0;
while (j < page_limit)
page_cache_release(pages[j++]);
}
/*
* release the pages we didn't map into the bio, if any
*/
while (i < nr_pages)
page_cache_release(pages[i++]);
kfree(pages);
/*
......@@ -620,9 +645,17 @@ static struct bio *__bio_map_user(request_queue_t *q, struct block_device *bdev,
if (!write_to_vm)
bio->bi_rw |= (1 << BIO_RW);
bio->bi_bdev = bdev;
bio->bi_flags |= (1 << BIO_USER_MAPPED);
return bio;
out:
out_unmap:
for (i = 0; i < nr_pages; i++) {
if(!pages[i])
break;
page_cache_release(pages[i]);
}
out:
kfree(pages);
bio_put(bio);
return ERR_PTR(ret);
......@@ -641,10 +674,34 @@ out:
*/
struct bio *bio_map_user(request_queue_t *q, struct block_device *bdev,
unsigned long uaddr, unsigned int len, int write_to_vm)
{
struct sg_iovec iov;
iov.iov_base = (__user void *)uaddr;
iov.iov_len = len;
return bio_map_user_iov(q, bdev, &iov, 1, write_to_vm);
}
/**
* bio_map_user_iov - map user sg_iovec table into bio
* @q: the request_queue_t for the bio
* @bdev: destination block device
* @iov: the iovec.
* @iov_count: number of elements in the iovec
* @write_to_vm: bool indicating writing to pages or not
*
* Map the user space address into a bio suitable for io to a block
* device. Returns an error pointer in case of error.
*/
struct bio *bio_map_user_iov(request_queue_t *q, struct block_device *bdev,
struct sg_iovec *iov, int iov_count,
int write_to_vm)
{
struct bio *bio;
int len = 0, i;
bio = __bio_map_user(q, bdev, uaddr, len, write_to_vm);
bio = __bio_map_user_iov(q, bdev, iov, iov_count, write_to_vm);
if (IS_ERR(bio))
return bio;
......@@ -657,6 +714,9 @@ struct bio *bio_map_user(request_queue_t *q, struct block_device *bdev,
*/
bio_get(bio);
for (i = 0; i < iov_count; i++)
len += iov[i].iov_len;
if (bio->bi_size == len)
return bio;
......
......@@ -281,6 +281,10 @@ extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
extern int bio_get_nr_vecs(struct block_device *);
extern struct bio *bio_map_user(struct request_queue *, struct block_device *,
unsigned long, unsigned int, int);
struct sg_iovec;
extern struct bio *bio_map_user_iov(struct request_queue *,
struct block_device *,
struct sg_iovec *, int, int);
extern void bio_unmap_user(struct bio *);
extern struct bio *bio_map_kern(struct request_queue *, void *, unsigned int,
unsigned int);
......
......@@ -561,6 +561,7 @@ extern void blk_queue_activity_fn(request_queue_t *, activity_fn *, void *);
extern int blk_rq_map_user(request_queue_t *, struct request *, void __user *, unsigned int);
extern int blk_rq_unmap_user(struct bio *, unsigned int);
extern int blk_rq_map_kern(request_queue_t *, struct request *, void *, unsigned int, unsigned int);
extern int blk_rq_map_user_iov(request_queue_t *, struct request *, struct sg_iovec *, int);
extern int blk_execute_rq(request_queue_t *, struct gendisk *, struct request *);
static inline request_queue_t *bdev_get_queue(struct block_device *bdev)
......
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