diff --git a/include/block/block.h b/include/block/block.h
index 86ad511..eed1330 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -468,9 +468,9 @@ int bdrv_get_flags(BlockDriverState *bs);
 int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi);
 ImageInfoSpecific *bdrv_get_specific_info(BlockDriverState *bs);
 void bdrv_round_to_clusters(BlockDriverState *bs,
-                            int64_t offset, unsigned int bytes,
+                            int64_t offset, int64_t bytes,
                             int64_t *cluster_offset,
-                            unsigned int *cluster_bytes);
+                            int64_t *cluster_bytes);

 const char *bdrv_get_encrypted_filename(BlockDriverState *bs);
 void bdrv_get_backing_filename(BlockDriverState *bs,
diff --git a/block/io.c b/block/io.c
index d61a906..07165dc 100644
--- a/block/io.c
+++ b/block/io.c
@@ -422,9 +422,9 @@ static void mark_request_serialising(BdrvTrackedRequest *req, uint64_t align)
  * Round a region to cluster boundaries
  */
 void bdrv_round_to_clusters(BlockDriverState *bs,
-                            int64_t offset, unsigned int bytes,
+                            int64_t offset, int64_t bytes,
                             int64_t *cluster_offset,
-                            unsigned int *cluster_bytes)
+                            int64_t *cluster_bytes)
 {
     BlockDriverInfo bdi;

@@ -920,7 +920,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
     struct iovec iov;
     QEMUIOVector bounce_qiov;
     int64_t cluster_offset;
-    unsigned int cluster_bytes;
+    int64_t cluster_bytes;
     size_t skip_bytes;
     int ret;

@@ -941,6 +941,7 @@ static int coroutine_fn bdrv_co_do_copy_on_readv(BdrvChild *child,
     trace_bdrv_co_do_copy_on_readv(bs, offset, bytes,
                                    cluster_offset, cluster_bytes);

+    assert(cluster_bytes < SIZE_MAX);
     iov.iov_len = cluster_bytes;
     iov.iov_base = bounce_buffer = qemu_try_blockalign(bs, iov.iov_len);
     if (bounce_buffer == NULL) {
diff --git a/block/mirror.c b/block/mirror.c
index 846e392..2510793 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -177,7 +177,7 @@ static void mirror_read_complete(void *opaque, int ret)
 /* Clip bytes relative to offset to not exceed end-of-file */
 static inline void mirror_clip_bytes(MirrorBlockJob *s,
                                      int64_t offset,
-                                     unsigned int *bytes)
+                                     int64_t *bytes)
 {
     *bytes = MIN(*bytes, s->bdev_length - offset);
 }
@@ -190,10 +190,9 @@ static int mirror_cow_align(MirrorBlockJob *s, int64_t *offset,
     bool need_cow;
     int ret = 0;
     int64_t align_offset = *offset;
-    unsigned int align_bytes = *bytes;
+    int64_t align_bytes = *bytes;
     int max_bytes = s->granularity * s->max_iov;

-    assert(*bytes < INT_MAX);
     need_cow = !test_bit(*offset / s->granularity, s->cow_bitmap);
     need_cow |= !test_bit((*offset + *bytes - 1) / s->granularity,
                           s->cow_bitmap);
@@ -384,7 +383,7 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
     while (nb_chunks > 0 && offset < s->bdev_length) {
         int64_t ret;
         int io_sectors;
-        unsigned int io_bytes;
+        int64_t io_bytes;
         int64_t io_bytes_acct;
         BlockDriverState *file;
         enum MirrorMethod {
@@ -410,7 +409,7 @@ static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
             io_bytes = s->granularity;
         } else if (ret >= 0 && !(ret & BDRV_BLOCK_DATA)) {
             int64_t target_offset;
-            unsigned int target_bytes;
+            int64_t target_bytes;
             bdrv_round_to_clusters(blk_bs(s->target), offset, io_bytes,
                                    &target_offset, &target_bytes);
             if (target_offset == offset &&
diff --git a/block/trace-events b/block/trace-events
index 04f6463..2301a50 100644
--- a/block/trace-events
+++ b/block/trace-events
@@ -15,7 +15,7 @@ bdrv_aio_writev(void *bs, int64_t sector_num, int nb_sectors, void *opaque) "bs
 bdrv_co_readv(void *bs, int64_t sector_num, int nb_sector) "bs %p sector_num %"PRId64" nb_sectors %d"
 bdrv_co_writev(void *bs, int64_t sector_num, int nb_sector) "bs %p sector_num %"PRId64" nb_sectors %d"
 bdrv_co_pwrite_zeroes(void *bs, int64_t offset, int count, int flags) "bs %p offset %"PRId64" count %d flags %#x"
-bdrv_co_do_copy_on_readv(void *bs, int64_t offset, unsigned int bytes, int64_t cluster_offset, unsigned int cluster_bytes) "bs %p offset %"PRId64" bytes %u cluster_offset %"PRId64" cluster_bytes %u"
+bdrv_co_do_copy_on_readv(void *bs, int64_t offset, int64_t bytes, int64_t cluster_offset, unsigned int cluster_bytes) "bs %p offset %"PRId64" bytes %"PRId64" cluster_offset %"PRId64" cluster_bytes %u"

 # block/stream.c
 stream_one_iteration(void *s, int64_t offset, uint64_t bytes, int is_allocated) "s %p offset %" PRId64 " bytes %" PRIu64 " is_allocated %d"
