From dcf94a23b1add0f856db51e9ff5ba0774e096076 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 23 Mar 2018 15:57:20 +0100 Subject: block: Don't poll in parent drain callbacks bdrv_do_drained_begin() is only safe if we have a single BDRV_POLL_WHILE() after quiescing all affected nodes. We cannot allow that parent callbacks introduce a nested polling loop that could cause graph changes while we're traversing the graph. Split off bdrv_do_drained_begin_quiesce(), which only quiesces a single node without waiting for its requests to complete. These requests will be waited for in the BDRV_POLL_WHILE() call down the call chain. Signed-off-by: Kevin Wolf --- include/block/block.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include') diff --git a/include/block/block.h b/include/block/block.h index 254ed2e..067d24c 100644 --- a/include/block/block.h +++ b/include/block/block.h @@ -591,6 +591,15 @@ bool bdrv_drain_poll(BlockDriverState *bs, bool recursive, void bdrv_drained_begin(BlockDriverState *bs); /** + * bdrv_do_drained_begin_quiesce: + * + * Quiesces a BDS like bdrv_drained_begin(), but does not wait for already + * running requests to complete. + */ +void bdrv_do_drained_begin_quiesce(BlockDriverState *bs, + BdrvChild *parent); + +/** * Like bdrv_drained_begin, but recursively begins a quiesced section for * exclusive access to all child nodes as well. */ -- cgit v1.1