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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 d2da5e288a)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Kevin Wolf 2019-07-22 17:44:27 +02:00 committed by Michael Roth
parent 088f1e8fd9
commit e092a17d38
1 changed files with 5 additions and 1 deletions
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6
block/mirror.c
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@ -661,7 +661,10 @@ 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);
@ -729,6 +732,7 @@ 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);