09.08.2019 19:13, Max Reitz wrote:
> 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 all children.
>
> 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.
>
> Suggested-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
> Signed-off-by: Max Reitz <mre...@redhat.com>
> ---
> block/io.c | 23 +++++++++++++++++------
> 1 file changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/block/io.c b/block/io.c
> index c5a8e3e6a3..bcc770d336 100644
> --- a/block/io.c
> +++ b/block/io.c
> @@ -2572,6 +2572,8 @@ 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);
> + BdrvChild *child;
> int current_gen;
> int ret = 0;
>
> @@ -2601,7 +2603,7 @@ 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) {
> @@ -2611,15 +2613,15 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
>
> /* But don't actually force it to the disk with cache=unsafe */
> if (bs->open_flags & BDRV_O_NO_FLUSH) {
> - goto flush_parent;
> + goto flush_children;
> }
>
> /* Check if we really need to flush anything */
> if (bs->flushed_gen == current_gen) {
> - goto flush_parent;
> + goto flush_children;
> }
>
> - 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) */
> @@ -2663,8 +2665,17 @@ int coroutine_fn bdrv_co_flush(BlockDriverState *bs)
> /* Now flush the underlying protocol. It will also have BDRV_O_NO_FLUSH
> * in the case of cache=unsafe, so there are no useless flushes.
> */
> -flush_parent:
> - ret = bs->file ? bdrv_co_flush(bs->file->bs) : 0;
> +flush_children:
> + ret = 0; > + QLIST_FOREACH(child, &bs->children, next) {
> + int this_child_ret;
> +
> + this_child_ret = bdrv_co_flush(child->bs);
> + if (!ret) {
> + ret = this_child_ret;
> + }
> + }
Hmm, you said that we want to flush only children with write-access from
parent..
Shouldn't we check it? Or we assume that it's always safe to call bdrv_co_flush
on
a node?
> +
> out:
> /* Notify any pending flushes that we have completed */
> if (ret == 0) {
>
--
Best regards,
Vladimir
