ublk: support to copy any part of request pages

Add 'offset' to 'struct ublk_map_data', so that ublk_copy_user_pages()
can be used to copy any sub-buffer(linear mapped) of the request.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230519065030.351216-6-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 353ccdb60729c1a280dd722e070ec86a5b4d4307..13523c37a165d64eea629b81599d516a6063dbda 100644 (file)
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -505,19 +505,36 @@ static void ublk_copy_io_pages(struct ublk_io_iter *data,
        }
 }
 
+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,
-               struct iov_iter *uiter, int dir)
+               unsigned offset, struct iov_iter *uiter, int dir)
 {
-       struct ublk_io_iter iter = {
-               .bio    = req->bio,
-               .iter   = req->bio->bi_iter,
-       };
+       struct ublk_io_iter iter;
        size_t done = 0;
 
+       if (!ublk_advance_io_iter(req, &iter, offset))
+               return 0;
+
        while (iov_iter_count(uiter) && iter.bio) {
                unsigned nr_pages;
                size_t len, off;
@@ -570,7 +587,7 @@ static int ublk_map_io(const struct ublk_queue *ubq, const struct request *req,
                import_single_range(dir, u64_to_user_ptr(io->addr), rq_bytes,
                                &iov, &iter);
 
-               return ublk_copy_user_pages(req, &iter, dir);
+               return ublk_copy_user_pages(req, 0, &iter, dir);
        }
        return rq_bytes;
 }
@@ -590,7 +607,7 @@ static int ublk_unmap_io(const struct ublk_queue *ubq,
 
                import_single_range(dir, u64_to_user_ptr(io->addr), io->res,
                                &iov, &iter);
-               return ublk_copy_user_pages(req, &iter, dir);
+               return ublk_copy_user_pages(req, 0, &iter, dir);
        }
        return rq_bytes;
 }