Commit d2da5e28 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

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: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarMax Reitz <mreitz@redhat.com>
parent 421919d7

block/mirror.c

+5 −1
Original line number Diff line number Diff line
@@ -656,7 +656,10 @@ static int mirror_exit_common(Job *job) 
    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);
@@ -724,6 +727,7 @@ static int mirror_exit_common(Job *job) 
    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);