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block-backend: add drained_poll 

Allow block backends to poll their devices/users to check if they have
been quiesced when entering a drained section.

This will be used in the next patch to wait for the NBD server to be
completely quiesced.

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Sergio Lopez <slp@redhat.com>
Message-Id: <20210602060552.17433-2-slp@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Sergio Lopez 2021-06-02 08:05:51 +02:00 committed by Kevin Wolf
parent 30ebb9aa92
commit 095cc4d0f6
2 changed files with 10 additions and 1 deletions

7
block/block-backend.c
View File

@ -2386,8 +2386,13 @@ static void blk_root_drained_begin(BdrvChild *child)
static bool blk_root_drained_poll(BdrvChild *child)
{
BlockBackend *blk = child->opaque;
bool busy = false;
assert(blk->quiesce_counter);
return !!blk->in_flight;
if (blk->dev_ops && blk->dev_ops->drained_poll) {
busy = blk->dev_ops->drained_poll(blk->dev_opaque);
}
return busy || !!blk->in_flight;
}
static void blk_root_drained_end(BdrvChild *child, int *drained_end_counter)

4
include/sysemu/block-backend.h
View File

@ -66,6 +66,10 @@ typedef struct BlockDevOps {
* Runs when the backend's last drain request ends.
*/
void (*drained_end)(void *opaque);
/*
* Is the device still busy?
*/
bool (*drained_poll)(void *opaque);
} BlockDevOps;
/* This struct is embedded in (the private) BlockBackend struct and contains