[1/2] block: Honour BDRV_REQ_NO_SERIALISING in copy range

Commit Message

Fam Zheng May 31, 2018, 2:34 a.m. UTC

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

Signed-off-by: Fam Zheng <[e-mail]>
---
 block/io.c            | 6 ++++--
 include/block/block.h | 5 +++--
 2 files changed, 7 insertions(+), 4 deletions(-)

Patch

diff --git a/block/io.c b/block/io.c
index b7beaeeb9f..f55e0c39fe 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2920,8 +2920,10 @@  int coroutine_fn bdrv_co_copy_range(BdrvChild *src, uint64_t src_offset,
     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);
+    }
     ret = bdrv_co_copy_range_from(src, src_offset,
                                   dst, dst_offset,
                                   bytes, flags);
diff --git a/include/block/block.h b/include/block/block.h
index 6cc6c7e699..6d3d156927 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -630,13 +630,14 @@  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.
  **/