They will be used for backup.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 include/block/block-copy.h |  6 ++++++
 block/block-copy.c         | 11 +++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/block/block-copy.h b/include/block/block-copy.h
index 3566827599..57806e8a49 100644
--- a/include/block/block-copy.h
+++ b/include/block/block-copy.h
@@ -49,9 +49,15 @@ int coroutine_fn block_copy(BlockCopyState *s, int64_t offset, int64_t bytes,
  *
  * Caller is responsible to call block_copy_call_free() to free
  * BlockCopyCallState object.
+ *
+ * @max_workers means maximum of parallel coroutines to execute sub-requests,
+ * must be > 0.
+ *
+ * @max_chunk means maximum length for one IO operation. Zero means unlimited.
  */
 BlockCopyCallState *block_copy_async(BlockCopyState *s,
                                      int64_t offset, int64_t bytes,
+                                     int max_workers, int64_t max_chunk,
                                      BlockCopyAsyncCallbackFunc cb,
                                      void *cb_opaque);
 
diff --git a/block/block-copy.c b/block/block-copy.c
index 74655b86f8..35213bd832 100644
--- a/block/block-copy.c
+++ b/block/block-copy.c
@@ -34,6 +34,8 @@ typedef struct BlockCopyCallState {
     BlockCopyState *s;
     int64_t offset;
     int64_t bytes;
+    int max_workers;
+    int64_t max_chunk;
     BlockCopyAsyncCallbackFunc cb;
     void *cb_opaque;
 
@@ -148,10 +150,11 @@ static BlockCopyTask *block_copy_task_create(BlockCopyState *s,
                                              int64_t offset, int64_t bytes)
 {
     BlockCopyTask *task;
+    int64_t max_chunk = MIN_NON_ZERO(s->copy_size, call_state->max_chunk);
 
     if (!bdrv_dirty_bitmap_next_dirty_area(s->copy_bitmap,
                                            offset, offset + bytes,
-                                           s->copy_size, &offset, &bytes))
+                                           max_chunk, &offset, &bytes))
     {
         return NULL;
     }
@@ -623,7 +626,7 @@ block_copy_dirty_clusters(BlockCopyCallState *call_state)
         bytes = end - offset;
 
         if (!aio && bytes) {
-            aio = aio_task_pool_new(BLOCK_COPY_MAX_WORKERS);
+            aio = aio_task_pool_new(call_state->max_workers);
         }
 
         ret = block_copy_task_run(aio, task);
@@ -701,6 +704,7 @@ int coroutine_fn block_copy(BlockCopyState *s, int64_t start, int64_t bytes,
         .s = s,
         .offset = start,
         .bytes = bytes,
+        .max_workers = BLOCK_COPY_MAX_WORKERS,
     };
 
     int ret = block_copy_common(&call_state);
@@ -719,6 +723,7 @@ static void coroutine_fn block_copy_async_co_entry(void *opaque)
 
 BlockCopyCallState *block_copy_async(BlockCopyState *s,
                                      int64_t offset, int64_t bytes,
+                                     int max_workers, int64_t max_chunk,
                                      BlockCopyAsyncCallbackFunc cb,
                                      void *cb_opaque)
 {
@@ -728,6 +733,8 @@ BlockCopyCallState *block_copy_async(BlockCopyState *s,
         .s = s,
         .offset = offset,
         .bytes = bytes,
+        .max_workers = max_workers,
+        .max_chunk = max_chunk,
         .cb = cb,
         .cb_opaque = cb_opaque,
 
-- 
2.21.3

On 26.10.20 18:17, Vladimir Sementsov-Ogievskiy wrote:
> They will be used for backup.
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>   include/block/block-copy.h |  6 ++++++
>   block/block-copy.c         | 11 +++++++++--
>   2 files changed, 15 insertions(+), 2 deletions(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>