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block: Drain source node in bdrv_replace_node()

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Instead of just asserting that no requests are in flight in
bdrv_replace_node(), which is a requirement that most callers ignore, we
can just drain the source node right there. This fixes at least starting
a commit job while I/O is active on the backing chain, but probably
other callers, too.

Having requests in flight on the target node isn't a problem because the
target just gets new parents, but the call path of running requests
isn't modified. So we can just drop this assertion without a replacement.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1711643
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Kevin Wolf 2019-05-21 19:00:25 +02:00
parent e2a58ff493
commit f871abd60f
1 changed files with 4 additions and 3 deletions
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7
block.c
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@ -4017,13 +4017,13 @@ void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
uint64_t perm = 0, shared = BLK_PERM_ALL;
int ret;
assert(!atomic_read(&from->in_flight));
assert(!atomic_read(&to->in_flight));
/* Make sure that @from doesn't go away until we have successfully attached
* all of its parents to @to. */
bdrv_ref(from);
assert(qemu_get_current_aio_context() == qemu_get_aio_context());
bdrv_drained_begin(from);
/* Put all parents into @list and calculate their cumulative permissions */
QLIST_FOREACH_SAFE(c, &from->parents, next_parent, next) {
assert(c->bs == from);
@ -4064,6 +4064,7 @@ void bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
out:
g_slist_free(list);
bdrv_drained_end(from);
bdrv_unref(from);
}