On Thu, Mar 16, 2017 at 05:23:50PM -0400, John Snow wrote:
> Allow block backends to forward drain requests to their devices/users.
> The initial intended purpose for this patch is to allow BBs to forward
> requests along to BlockJobs, which will want to pause if their associated
> BB has entered a drained region.
>
> Signed-off-by: John Snow <js...@redhat.com>
> ---
> block/block-backend.c | 24 ++++++++++++++++++++++--
> include/sysemu/block-backend.h | 8 ++++++++
> 2 files changed, 30 insertions(+), 2 deletions(-)
>
> diff --git a/block/block-backend.c b/block/block-backend.c
> index 5742c09..dec4a1c 100644
> --- a/block/block-backend.c
> +++ b/block/block-backend.c
> @@ -65,6 +65,8 @@ struct BlockBackend {
> bool allow_write_beyond_eof;
>
> NotifierList remove_bs_notifiers, insert_bs_notifiers;
> +
> + int quiesce_counter;
> };
>
> typedef struct BlockBackendAIOCB {
> @@ -699,12 +701,17 @@ void blk_set_dev_ops(BlockBackend *blk, const
> BlockDevOps *ops,
> void *opaque)
> {
> /* All drivers that use blk_set_dev_ops() are qdevified and we want to
> keep
> - * it that way, so we can assume blk->dev is a DeviceState if
> blk->dev_ops
> - * is set. */
> + * it that way, so we can assume blk->dev, if present, is a DeviceState
> if
> + * blk->dev_ops is set. Non-device users may use dev_ops without device.
> */
> assert(!blk->legacy_dev);
>
> blk->dev_ops = ops;
> blk->dev_opaque = opaque;
> +
> + /* Are we currently quiesced? Should we enforce this right now? */
> + if (blk->quiesce_counter && ops->drained_begin) {
> + ops->drained_begin(opaque);
> + }
> }
>
> /*
> @@ -1870,6 +1877,12 @@ static void blk_root_drained_begin(BdrvChild *child)
> {
> BlockBackend *blk = child->opaque;
>
> + if (++blk->quiesce_counter == 1) {
> + if (blk->dev_ops && blk->dev_ops->drained_begin) {
> + blk->dev_ops->drained_begin(blk->dev_opaque);
> + }
> + }
> +
> /* Note that blk->root may not be accessible here yet if we are just
> * attaching to a BlockDriverState that is drained. Use child instead. */
>
> @@ -1881,7 +1894,14 @@ static void blk_root_drained_begin(BdrvChild *child)
> static void blk_root_drained_end(BdrvChild *child)
> {
> BlockBackend *blk = child->opaque;
> + assert(blk->quiesce_counter);
>
> assert(blk->public.io_limits_disabled);
> --blk->public.io_limits_disabled;
> +
> + if (--blk->quiesce_counter == 0) {
> + if (blk->dev_ops && blk->dev_ops->drained_end) {
> + blk->dev_ops->drained_end(blk->dev_opaque);
> + }
> + }
> }
> diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
> index 096c17f..7462228 100644
> --- a/include/sysemu/block-backend.h
> +++ b/include/sysemu/block-backend.h
> @@ -58,6 +58,14 @@ typedef struct BlockDevOps {
> * Runs when the size changed (e.g. monitor command block_resize)
> */
> void (*resize_cb)(void *opaque);
> + /*
> + * Runs when the backend receives a drain request.
> + */
> + void (*drained_begin)(void *opaque);
> + /*
> + * Runs when the backend's last drain request ends.
> + */
> + void (*drained_end)(void *opaque);
> } BlockDevOps;
>
> /* This struct is embedded in (the private) BlockBackend struct and contains
> --
> 2.9.3
>
Reviewed-by: Jeff Cody <jc...@redhat.com>
