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: Kent Overstreet <koverstreet@xxxxxxxxxx>
CC: Jens Axboe <axboe@xxxxxxxxx>
---
fs/bio.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/bio.h | 2 ++
2 files changed, 72 insertions(+)
diff --git a/fs/bio.c b/fs/bio.c
index 1342a16..7fb9f4e 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -827,6 +827,76 @@ 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;
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 949c48a..92015ce 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -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 *,
--
1.7.12
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