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Commit 16ac3d63 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

block: Add bio_copy_data() 



This gets open coded quite a bit and it's tricky to get right, so make a
generic version and convert some existing users over to it instead.

Signed-off-by: default avatarKent Overstreet <koverstreet@google.com>
CC: Jens Axboe <axboe@kernel.dk>
parent b783863f

fs/bio.c

+70 −0
Original line number Diff line number Diff line
@@ -829,6 +829,76 @@ void bio_advance(struct bio *bio, unsigned bytes) 
}

EXPORT_SYMBOL(bio_advance);



/**

 * bio_copy_data - copy contents of data buffers from one chain of bios to

 * another

 * @src: source bio list

 * @dst: destination bio list

 *

 * If @src and @dst are single bios, bi_next must be NULL - otherwise, treats

 * @src and @dst as linked lists of bios.

 *

 * Stops when it reaches the end of either @src or @dst - that is, copies

 * min(src->bi_size, dst->bi_size) bytes (or the equivalent for lists of bios).

 */

void bio_copy_data(struct bio *dst, struct bio *src)

{

	struct bio_vec *src_bv, *dst_bv;

	unsigned src_offset, dst_offset, bytes;

	void *src_p, *dst_p;



	src_bv = bio_iovec(src);

	dst_bv = bio_iovec(dst);



	src_offset = src_bv->bv_offset;

	dst_offset = dst_bv->bv_offset;



	while (1) {

		if (src_offset == src_bv->bv_offset + src_bv->bv_len) {

			src_bv++;

			if (src_bv == bio_iovec_idx(src, src->bi_vcnt)) {

				src = src->bi_next;

				if (!src)

					break;



				src_bv = bio_iovec(src);

			}



			src_offset = src_bv->bv_offset;

		}



		if (dst_offset == dst_bv->bv_offset + dst_bv->bv_len) {

			dst_bv++;

			if (dst_bv == bio_iovec_idx(dst, dst->bi_vcnt)) {

				dst = dst->bi_next;

				if (!dst)

					break;



				dst_bv = bio_iovec(dst);

			}



			dst_offset = dst_bv->bv_offset;

		}



		bytes = min(dst_bv->bv_offset + dst_bv->bv_len - dst_offset,

			    src_bv->bv_offset + src_bv->bv_len - src_offset);



		src_p = kmap_atomic(src_bv->bv_page);

		dst_p = kmap_atomic(dst_bv->bv_page);



		memcpy(dst_p + dst_bv->bv_offset,

		       src_p + src_bv->bv_offset,

		       bytes);



		kunmap_atomic(dst_p);

		kunmap_atomic(src_p);



		src_offset += bytes;

		dst_offset += bytes;

	}

}

EXPORT_SYMBOL(bio_copy_data);



struct bio_map_data {

	struct bio_vec *iovecs;

	struct sg_iovec *sgvecs;

include/linux/bio.h

+2 −0
Original line number Diff line number Diff line
@@ -286,6 +286,8 @@ static inline void bio_flush_dcache_pages(struct bio *bi) 
}

#endif



extern void bio_copy_data(struct bio *dst, struct bio *src);



extern struct bio *bio_copy_user(struct request_queue *, struct rq_map_data *,

				 unsigned long, unsigned int, int, gfp_t);

extern struct bio *bio_copy_user_iov(struct request_queue *,