block: Honour BDRV_REQ_NO_SERIALISING in copy range

This semantics is needed by drive-backup so implement it before using
this API there.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Message-id: 20180703023758.14422-3-famz@redhat.com
Signed-off-by: Jeff Cody <jcody@redhat.com>

diff --git a/block/io.c b/block/io.c
index b8845708d70b112f7ee016a113895ec558061476..1a2272fad318b14d576b3e71c1a768212fff3f91 100644 (file)
--- a/block/io.c
+++ b/block/io.c
@@ -2930,8 +2930,10 @@ static int coroutine_fn bdrv_co_copy_range_internal(BdrvChild *src,
     tracked_request_begin(&dst_req, dst->bs, dst_offset,
                           bytes, BDRV_TRACKED_WRITE);
 
-    wait_serialising_requests(&src_req);
-    wait_serialising_requests(&dst_req);
+    if (!(flags & BDRV_REQ_NO_SERIALISING)) {
+        wait_serialising_requests(&src_req);
+        wait_serialising_requests(&dst_req);
+    }
     if (recurse_src) {
         ret = src->bs->drv->bdrv_co_copy_range_from(src->bs,
                                                     src, src_offset,

diff --git a/include/block/block.h b/include/block/block.h
index 2ffc1c64c66d3e0c14396f0b4a698cc5a1b6bd8f..e5c7759a0c4c1f5966b5b306b2d3b0c393ae94c6 100644 (file)
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -659,13 +659,14 @@ void bdrv_unregister_buf(BlockDriverState *bs, void *host);
  * @dst: Destination child to copy data to
  * @dst_offset: offset in @dst image to write data
  * @bytes: number of bytes to copy
- * @flags: request flags. Must be one of:
- *         0 - actually read data from src;
+ * @flags: request flags. Supported flags:
  *         BDRV_REQ_ZERO_WRITE - treat the @src range as zero data and do zero
  *                               write on @dst as if bdrv_co_pwrite_zeroes is
  *                               called. Used to simplify caller code, or
  *                               during BlockDriver.bdrv_co_copy_range_from()
  *                               recursion.
+ *         BDRV_REQ_NO_SERIALISING - do not serialize with other overlapping
+ *                                   requests currently in flight.
  *
  * Returns: 0 if succeeded; negative error code if failed.
  **/