diff options
| -rw-r--r-- | block.c | 49 |
1 files changed, 33 insertions, 16 deletions
diff --git a/block.c b/block.c index df3407934b..66e8602e68 100644 --- a/block.c +++ b/block.c @@ -2230,13 +2230,27 @@ static void bdrv_replace_child_noperm(BdrvChild *child, BlockDriverState *new_bs) { BlockDriverState *old_bs = child->bs; - int i; + int new_bs_quiesce_counter; + int drain_saldo; assert(!child->frozen); if (old_bs && new_bs) { assert(bdrv_get_aio_context(old_bs) == bdrv_get_aio_context(new_bs)); } + + new_bs_quiesce_counter = (new_bs ? new_bs->quiesce_counter : 0); + drain_saldo = new_bs_quiesce_counter - child->parent_quiesce_counter; + + /* + * If the new child node is drained but the old one was not, flush + * all outstanding requests to the old child node. + */ + while (drain_saldo > 0 && child->role->drained_begin) { + bdrv_parent_drained_begin_single(child, true); + drain_saldo--; + } + if (old_bs) { /* Detach first so that the recursive drain sections coming from @child * are already gone and we only end the drain sections that came from @@ -2244,28 +2258,22 @@ static void bdrv_replace_child_noperm(BdrvChild *child, if (child->role->detach) { child->role->detach(child); } - while (child->parent_quiesce_counter) { - bdrv_parent_drained_end_single(child); - } QLIST_REMOVE(child, next_parent); - } else { - assert(child->parent_quiesce_counter == 0); } child->bs = new_bs; if (new_bs) { QLIST_INSERT_HEAD(&new_bs->parents, child, next_parent); - if (new_bs->quiesce_counter) { - int num = new_bs->quiesce_counter; - if (child->role->parent_is_bds) { - num -= bdrv_drain_all_count; - } - assert(num >= 0); - for (i = 0; i < num; i++) { - bdrv_parent_drained_begin_single(child, true); - } - } + + /* + * Detaching the old node may have led to the new node's + * quiesce_counter having been decreased. Not a problem, we + * just need to recognize this here and then invoke + * drained_end appropriately more often. + */ + assert(new_bs->quiesce_counter <= new_bs_quiesce_counter); + drain_saldo += new_bs->quiesce_counter - new_bs_quiesce_counter; /* Attach only after starting new drained sections, so that recursive * drain sections coming from @child don't get an extra .drained_begin @@ -2274,6 +2282,15 @@ static void bdrv_replace_child_noperm(BdrvChild *child, child->role->attach(child); } } + + /* + * If the old child node was drained but the new one is not, allow + * requests to come in only after the new node has been attached. + */ + while (drain_saldo < 0 && child->role->drained_end) { + bdrv_parent_drained_end_single(child); + drain_saldo++; + } } /* |