mirror: Keep mirror_top_bs drained after dropping permissions
mirror_top_bs is currently implicitly drained through its connection to
the source or the target node. However, the drain section for target_bs
ends early after moving mirror_top_bs from src to target_bs, so that
requests can already be restarted while mirror_top_bs is still present
in the chain, but has dropped all permissions and therefore runs into an
assertion failure like this:
qemu-system-x86_64: block/io.c:1634: bdrv_co_write_req_prepare:
Assertion `child->perm & BLK_PERM_WRITE' failed.
Keep mirror_top_bs drained until all graph changes have completed.
Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
(cherry picked from commit d2da5e288a2e71e82866c8fdefd41b5727300124)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
diff --git a/block/mirror.c b/block/mirror.c
index 0e3f792..681b305 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -661,7 +661,10 @@
s->target = NULL;
/* We don't access the source any more. Dropping any WRITE/RESIZE is
- * required before it could become a backing file of target_bs. */
+ * required before it could become a backing file of target_bs. Not having
+ * these permissions any more means that we can't allow any new requests on
+ * mirror_top_bs from now on, so keep it drained. */
+ bdrv_drained_begin(mirror_top_bs);
bs_opaque->stop = true;
bdrv_child_refresh_perms(mirror_top_bs, mirror_top_bs->backing,
&error_abort);
@@ -729,6 +732,7 @@
bs_opaque->job = NULL;
bdrv_drained_end(src);
+ bdrv_drained_end(mirror_top_bs);
s->in_drain = false;
bdrv_unref(mirror_top_bs);
bdrv_unref(src);
