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block: Avoid processing BDS twice in bdrv_set_aio_context_ignore()

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Some graphs may contain an indirect reference to the first BDS in the
chain that can be reached while walking it bottom->up from one its
children.

Doubling-processing of a BDS is especially problematic for the
aio_notifiers, as they might attempt to work on both the old and the
new AIO contexts.

To avoid this problem, add every child and parent to the ignore list
before actually processing them.

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Sergio Lopez <slp@redhat.com>
Message-Id: <20210201125032.44713-2-slp@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Sergio Lopez 2021-02-01 13:50:31 +01:00 committed by Kevin Wolf
parent d7beddcc02
commit 722d8e73d6
1 changed files with 27 additions and 7 deletions
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34
block.c
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@ -6439,7 +6439,10 @@ void bdrv_set_aio_context_ignore(BlockDriverState *bs,
AioContext *new_context, GSList **ignore)
{
AioContext *old_context = bdrv_get_aio_context(bs);
BdrvChild *child;
GSList *children_to_process = NULL;
GSList *parents_to_process = NULL;
GSList *entry;
BdrvChild *child, *parent;
g_assert(qemu_get_current_aio_context() == qemu_get_aio_context());
@ -6454,17 +6457,34 @@ void bdrv_set_aio_context_ignore(BlockDriverState *bs,
continue;
}
*ignore = g_slist_prepend(*ignore, child);
bdrv_set_aio_context_ignore(child->bs, new_context, ignore);
children_to_process = g_slist_prepend(children_to_process, child);
}
QLIST_FOREACH(child, &bs->parents, next_parent) {
if (g_slist_find(*ignore, child)) {
QLIST_FOREACH(parent, &bs->parents, next_parent) {
if (g_slist_find(*ignore, parent)) {
continue;
}
assert(child->klass->set_aio_ctx);
*ignore = g_slist_prepend(*ignore, child);
child->klass->set_aio_ctx(child, new_context, ignore);
*ignore = g_slist_prepend(*ignore, parent);
parents_to_process = g_slist_prepend(parents_to_process, parent);
}
for (entry = children_to_process;
entry != NULL;
entry = g_slist_next(entry)) {
child = entry->data;
bdrv_set_aio_context_ignore(child->bs, new_context, ignore);
}
g_slist_free(children_to_process);
for (entry = parents_to_process;
entry != NULL;
entry = g_slist_next(entry)) {
parent = entry->data;
assert(parent->klass->set_aio_ctx);
parent->klass->set_aio_ctx(parent, new_context, ignore);
}
g_slist_free(parents_to_process);
bdrv_detach_aio_context(bs);
/* Acquire the new context, if necessary */