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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

drivers/block/ll_rw_blk.c

+58 −6
Original line number Diff line number Diff line
@@ -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;

drivers/block/scsi_ioctl.c

+23 −11
Original line number Diff line number Diff line
@@ -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) {

	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

fs/bio.c

+105 −45
Original line number Diff line number Diff line
@@ -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
@@ -549,23 +550,35 @@ struct bio *bio_copy_user(request_queue_t *q, unsigned long uaddr, 
	return ERR_PTR(ret);

}



static struct bio *__bio_map_user(request_queue_t *q, struct block_device *bdev,

				  unsigned long uaddr, unsigned int len,

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;



	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);

	if (!bio)
@@ -576,18 +589,28 @@ static struct bio *__bio_map_user(request_queue_t *q, struct block_device *bdev, 
	if (!pages)

		goto out;



	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, nr_pages,

						write_to_vm, 0, pages, NULL);

		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 < nr_pages)

		goto out;

		if (ret < local_nr_pages)

			goto out_unmap;



	bio->bi_bdev = bdev;



		offset = uaddr & ~PAGE_MASK;

	for (i = 0; i < nr_pages; i++) {

		for (j = cur_page; j < page_limit; j++) {

			unsigned int bytes = PAGE_SIZE - offset;



			if (len <= 0)
@@ -599,18 +622,20 @@ static struct bio *__bio_map_user(request_queue_t *q, struct block_device *bdev, 
			/*

			 * sorry...

			 */

		if (__bio_add_page(q, bio, pages[i], bytes, offset) < bytes)

			if (__bio_add_page(q, bio, pages[j], bytes, offset) < bytes)

				break;



			len -= bytes;

			offset = 0;

		}



		cur_page = j;

		/*

		 * release the pages we didn't map into the bio, if any

		 */

	while (i < nr_pages)

		page_cache_release(pages[i++]);

		while (j < page_limit)

			page_cache_release(pages[j++]);

	}



	kfree(pages);
@@ -620,8 +645,16 @@ 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_unmap:

	for (i = 0; i < nr_pages; i++) {

		if(!pages[i])

			break;

		page_cache_release(pages[i]);

	}

 out:

	kfree(pages);

	bio_put(bio);
@@ -641,10 +674,34 @@ static struct bio *__bio_map_user(request_queue_t *q, struct block_device *bdev, 
 */

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;

include/linux/bio.h

+4 −0
Original line number Diff line number Diff line
@@ -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);

include/linux/blkdev.h

+1 −0
Original line number Diff line number Diff line
@@ -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)