ublk: use rq_for_each_segment() for user copy

ublk_advance_io_iter() and ublk_copy_io_pages() currently open-code the
iteration over the request's bvecs. Switch to the rq_for_each_segment()
macro provided by blk-mq to avoid reaching into the bio internals and
simplify the code.

Suggested-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 40eee3e15a4c8ca9c5c89330d0c7a9b215146b0f..5cf288809226b2b8c7fe308f76b361640866af31 100644 (file)
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -913,22 +913,29 @@ static const struct block_device_operations ub_fops = {
        .report_zones = ublk_report_zones,
 };
 
-struct ublk_io_iter {
-       struct bio *bio;
-       struct bvec_iter iter;
-};
-
-/* return how many bytes are copied */
-static size_t ublk_copy_io_pages(struct ublk_io_iter *data,
-               struct iov_iter *uiter, int dir)
+/*
+ * Copy data between request pages and io_iter, and 'offset'
+ * is the start point of linear offset of request.
+ */
+static size_t ublk_copy_user_pages(const struct request *req,
+               unsigned offset, struct iov_iter *uiter, int dir)
 {
+       struct req_iterator iter;
+       struct bio_vec bv;
        size_t done = 0;
 
-       for (;;) {
-               struct bio_vec bv = bio_iter_iovec(data->bio, data->iter);
-               void *bv_buf = bvec_kmap_local(&bv);
+       rq_for_each_segment(bv, req, iter) {
+               void *bv_buf;
                size_t copied;
 
+               if (offset >= bv.bv_len) {
+                       offset -= bv.bv_len;
+                       continue;
+               }
+
+               bv.bv_offset += offset;
+               bv.bv_len -= offset;
+               bv_buf = bvec_kmap_local(&bv);
                if (dir == ITER_DEST)
                        copied = copy_to_iter(bv_buf, bv.bv_len, uiter);
                else
@@ -940,50 +947,11 @@ static size_t ublk_copy_io_pages(struct ublk_io_iter *data,
                if (copied < bv.bv_len)
                        break;
 
-               /* advance bio */
-               bio_advance_iter_single(data->bio, &data->iter, copied);
-               if (!data->iter.bi_size) {
-                       data->bio = data->bio->bi_next;
-                       if (data->bio == NULL)
-                               break;
-                       data->iter = data->bio->bi_iter;
-               }
+               offset = 0;
        }
        return done;
 }
 
-static bool ublk_advance_io_iter(const struct request *req,
-               struct ublk_io_iter *iter, unsigned int offset)
-{
-       struct bio *bio = req->bio;
-
-       for_each_bio(bio) {
-               if (bio->bi_iter.bi_size > offset) {
-                       iter->bio = bio;
-                       iter->iter = bio->bi_iter;
-                       bio_advance_iter(iter->bio, &iter->iter, offset);
-                       return true;
-               }
-               offset -= bio->bi_iter.bi_size;
-       }
-       return false;
-}
-
-/*
- * Copy data between request pages and io_iter, and 'offset'
- * is the start point of linear offset of request.
- */
-static size_t ublk_copy_user_pages(const struct request *req,
-               unsigned offset, struct iov_iter *uiter, int dir)
-{
-       struct ublk_io_iter iter;
-
-       if (!ublk_advance_io_iter(req, &iter, offset))
-               return 0;
-
-       return ublk_copy_io_pages(&iter, uiter, dir);
-}
-
 static inline bool ublk_need_map_req(const struct request *req)
 {
        return ublk_rq_has_data(req) && req_op(req) == REQ_OP_WRITE;