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replication: Properly attach children 

The replication driver needs access to the children block-nodes of
it's child so it can issue bdrv_make_empty() and bdrv_co_pwritev()
to manage the replication. However, it does this by directly copying
the BdrvChilds, which is wrong.

Fix this by properly attaching the block-nodes with
bdrv_attach_child() and requesting the required permissions.

This ultimatively fixes a potential crash in replication_co_writev(),
because it may write to s->secondary_disk if it is in state
BLOCK_REPLICATION_FAILOVER_FAILED, without requesting write
permissions first. And now the workaround in
secondary_do_checkpoint() can be removed.

Signed-off-by: Lukas Straub <lukasstraub2@web.de>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <5d0539d729afb8072d0d7cde977c5066285591b4.1626619393.git.lukasstraub2@web.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
master
Lukas Straub 2021-07-18 16:48:33 +02:00 committed by Kevin Wolf
parent a990a42b39
commit 3b78420bb1
1 changed files with 27 additions and 3 deletions
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30
block/replication.c
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@ -165,7 +165,12 @@ static void replication_child_perm(BlockDriverState *bs, BdrvChild *c,
uint64_t perm, uint64_t shared,
uint64_t *nperm, uint64_t *nshared)
{
*nperm = BLK_PERM_CONSISTENT_READ;
if (role & BDRV_CHILD_PRIMARY) {
*nperm = BLK_PERM_CONSISTENT_READ;
} else {
*nperm = 0;
}
if ((bs->open_flags & (BDRV_O_INACTIVE | BDRV_O_RDWR)) == BDRV_O_RDWR) {
*nperm |= BLK_PERM_WRITE;
}
@ -557,8 +562,25 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
return;
}
s->hidden_disk = hidden_disk;
s->secondary_disk = secondary_disk;
bdrv_ref(hidden_disk->bs);
s->hidden_disk = bdrv_attach_child(bs, hidden_disk->bs, "hidden disk",
&child_of_bds, BDRV_CHILD_DATA,
&local_err);
if (local_err) {
error_propagate(errp, local_err);
aio_context_release(aio_context);
return;
}
bdrv_ref(secondary_disk->bs);
s->secondary_disk = bdrv_attach_child(bs, secondary_disk->bs,
"secondary disk", &child_of_bds,
BDRV_CHILD_DATA, &local_err);
if (local_err) {
error_propagate(errp, local_err);
aio_context_release(aio_context);
return;
}
/* start backup job now */
error_setg(&s->blocker,
@ -664,7 +686,9 @@ static void replication_done(void *opaque, int ret)
if (ret == 0) {
s->stage = BLOCK_REPLICATION_DONE;
bdrv_unref_child(bs, s->secondary_disk);
s->secondary_disk = NULL;
bdrv_unref_child(bs, s->hidden_disk);
s->hidden_disk = NULL;
s->error = 0;
} else {