[Qemu-block] [PATCH v5 16/42] block: Use child access functions when flushing

[Max Reitz]

If the driver does not support .bdrv_co_flush() so bdrv_co_flush()
itself has to flush the children of the given node, it should not flush
just bs->file->bs, but in fact both the child that stores data, and the
one that stores metadata (if they are separate).

In any case, the BLKDBG_EVENT() should be emitted on the primary child,
because that is where a blkdebug node would be if there is any.

Signed-off-by: Max Reitz <address@hidden>
---
 block/io.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/block/io.c b/block/io.c
index 53aabf86b5..64408cf19a 100644
--- a/block/io.c
+++ b/block/io.c
@@ -2533,6 +2533,8 @@ static void coroutine_fn bdrv_flush_co_entry(void *opaque)
 
 int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
 {
+    BdrvChild *primary_child = bdrv_primary_child(bs);
+    BlockDriverState *storage_bs, *metadata_bs;
     int current_gen;
     int ret = 0;
 
@@ -2562,7 +2564,7 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
     }
 
     /* Write back cached data to the OS even with cache=unsafe */
-    BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_OS);
+    BLKDBG_EVENT(primary_child, BLKDBG_FLUSH_TO_OS);
     if (bs->drv->bdrv_co_flush_to_os) {
         ret = bs->drv->bdrv_co_flush_to_os(bs);
         if (ret < 0) {
@@ -2580,7 +2582,7 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
         goto flush_parent;
     }
 
-    BLKDBG_EVENT(bs->file, BLKDBG_FLUSH_TO_DISK);
+    BLKDBG_EVENT(primary_child, BLKDBG_FLUSH_TO_DISK);
     if (!bs->drv) {
         /* bs->drv->bdrv_co_flush() might have ejected the BDS
          * (even in case of apparent success) */
@@ -2625,7 +2627,20 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
      * in the case of cache=unsafe, so there are no useless flushes.
      */
 flush_parent:
-    ret = bs->file ? bdrv_co_flush(bs->file->bs) : 0;
+    storage_bs = bdrv_storage_bs(bs);
+    metadata_bs = bdrv_metadata_bs(bs);
+
+    ret = 0;
+    if (storage_bs) {
+        ret = bdrv_co_flush(storage_bs);
+    }
+    if (metadata_bs && metadata_bs != storage_bs) {
+        int ret_metadata = bdrv_co_flush(metadata_bs);
+        if (!ret) {
+            ret = ret_metadata;
+        }
+    }
+
 out:
     /* Notify any pending flushes that we have completed */
     if (ret == 0) {
-- 
2.21.0