diff options
| -rw-r--r-- | block/mirror.c | 32 |
1 files changed, 25 insertions, 7 deletions
diff --git a/block/mirror.c b/block/mirror.c index 6af02a57c4..d7e54c0ff7 100644 --- a/block/mirror.c +++ b/block/mirror.c @@ -89,6 +89,7 @@ typedef struct MirrorBlockJob { typedef struct MirrorBDSOpaque { MirrorBlockJob *job; bool stop; + bool is_commit; } MirrorBDSOpaque; struct MirrorOp { @@ -1522,13 +1523,27 @@ static void bdrv_mirror_top_child_perm(BlockDriverState *bs, BdrvChild *c, return; } - /* Must be able to forward guest writes to the real image */ - *nperm = 0; - if (perm & BLK_PERM_WRITE) { - *nperm |= BLK_PERM_WRITE; - } + bdrv_default_perms(bs, c, role, reopen_queue, + perm, shared, nperm, nshared); - *nshared = BLK_PERM_ALL; + if (s->is_commit) { + /* + * For commit jobs, we cannot take CONSISTENT_READ, because + * that permission is unshared for everything above the base + * node (except for filters on the base node). + * We also have to force-share the WRITE permission, or + * otherwise we would block ourselves at the base node (if + * writes are blocked for a node, they are also blocked for + * its backing file). + * (We could also share RESIZE, because it may be needed for + * the target if its size is less than the top node's; but + * bdrv_default_perms_for_cow() automatically shares RESIZE + * for backing nodes if WRITE is shared, so there is no need + * to do it here.) + */ + *nperm &= ~BLK_PERM_CONSISTENT_READ; + *nshared |= BLK_PERM_WRITE; + } } /* Dummy node that provides consistent read to its users without requiring it @@ -1591,6 +1606,8 @@ static BlockJob *mirror_start_job( return NULL; } + target_is_backing = bdrv_chain_contains(bs, target); + /* In the case of active commit, add dummy driver to provide consistent * reads on the top, while disabling it in the intermediate nodes, and make * the backing chain writable. */ @@ -1613,6 +1630,8 @@ static BlockJob *mirror_start_job( bs_opaque = g_new0(MirrorBDSOpaque, 1); mirror_top_bs->opaque = bs_opaque; + bs_opaque->is_commit = target_is_backing; + /* bdrv_append takes ownership of the mirror_top_bs reference, need to keep * it alive until block_job_create() succeeds even if bs has no parent. */ bdrv_ref(mirror_top_bs); @@ -1653,7 +1672,6 @@ static BlockJob *mirror_start_job( target_perms = BLK_PERM_WRITE; target_shared_perms = BLK_PERM_WRITE_UNCHANGED; - target_is_backing = bdrv_chain_contains(bs, target); if (target_is_backing) { int64_t bs_size, target_size; bs_size = bdrv_getlength(bs); |