[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-block] [PATCH 02/18] block: BDS deletion during bdrv_drain_recurse
From: |
Max Reitz |
Subject: |
[Qemu-block] [PATCH 02/18] block: BDS deletion during bdrv_drain_recurse |
Date: |
Wed, 13 Sep 2017 20:18:54 +0200 |
Drainined a BDS child may lead to both the original BDS and/or its other
children being deleted (e.g. if the original BDS represents a block
job). We should prepare for this in both bdrv_drain_recurse() and
bdrv_drained_begin() by monitoring whether the BDS we are about to drain
still exists at all.
Signed-off-by: Max Reitz <address@hidden>
---
block/io.c | 72 +++++++++++++++++++++++++++++++++++++++++++++-----------------
1 file changed, 52 insertions(+), 20 deletions(-)
diff --git a/block/io.c b/block/io.c
index 4378ae4c7d..8ec1a564ad 100644
--- a/block/io.c
+++ b/block/io.c
@@ -182,33 +182,57 @@ static void bdrv_drain_invoke(BlockDriverState *bs)
static bool bdrv_drain_recurse(BlockDriverState *bs)
{
- BdrvChild *child, *tmp;
+ BdrvChild *child;
bool waited;
+ struct BDSToDrain {
+ BlockDriverState *bs;
+ BdrvDeletedStatus del_stat;
+ QLIST_ENTRY(BDSToDrain) next;
+ };
+ QLIST_HEAD(, BDSToDrain) bs_list = QLIST_HEAD_INITIALIZER(bs_list);
+ bool in_main_loop =
+ qemu_get_current_aio_context() == qemu_get_aio_context();
waited = BDRV_POLL_WHILE(bs, atomic_read(&bs->in_flight) > 0);
/* Ensure any pending metadata writes are submitted to bs->file. */
bdrv_drain_invoke(bs);
- QLIST_FOREACH_SAFE(child, &bs->children, next, tmp) {
- BlockDriverState *bs = child->bs;
- bool in_main_loop =
- qemu_get_current_aio_context() == qemu_get_aio_context();
- assert(bs->refcnt > 0);
- if (in_main_loop) {
- /* In case the recursive bdrv_drain_recurse processes a
- * block_job_defer_to_main_loop BH and modifies the graph,
- * let's hold a reference to bs until we are done.
- *
- * IOThread doesn't have such a BH, and it is not safe to call
- * bdrv_unref without BQL, so skip doing it there.
- */
- bdrv_ref(bs);
- }
- waited |= bdrv_drain_recurse(bs);
- if (in_main_loop) {
- bdrv_unref(bs);
+ /* Draining children may result in other children being removed and maybe
+ * even deleted, so copy the children list first */
+ QLIST_FOREACH(child, &bs->children, next) {
+ struct BDSToDrain *bs2d = g_new0(struct BDSToDrain, 1);
+
+ bs2d->bs = child->bs;
+ QLIST_INSERT_HEAD(&bs->deleted_status, &bs2d->del_stat, next);
+
+ QLIST_INSERT_HEAD(&bs_list, bs2d, next);
+ }
+
+ while (!QLIST_EMPTY(&bs_list)) {
+ struct BDSToDrain *bs2d = QLIST_FIRST(&bs_list);
+ QLIST_REMOVE(bs2d, next);
+
+ if (!bs2d->del_stat.deleted) {
+ QLIST_REMOVE(&bs2d->del_stat, next);
+
+ if (in_main_loop) {
+ /* In case the recursive bdrv_drain_recurse processes a
+ * block_job_defer_to_main_loop BH and modifies the graph,
+ * let's hold a reference to the BDS until we are done.
+ *
+ * IOThread doesn't have such a BH, and it is not safe to call
+ * bdrv_unref without BQL, so skip doing it there.
+ */
+ bdrv_ref(bs2d->bs);
+ }
+ waited |= bdrv_drain_recurse(bs2d->bs);
+ if (in_main_loop) {
+ bdrv_unref(bs2d->bs);
+ }
}
+
+ g_free(bs2d);
}
return waited;
@@ -252,17 +276,25 @@ static void coroutine_fn
bdrv_co_yield_to_drain(BlockDriverState *bs)
void bdrv_drained_begin(BlockDriverState *bs)
{
+ BdrvDeletedStatus del_stat = { .deleted = false };
+
if (qemu_in_coroutine()) {
bdrv_co_yield_to_drain(bs);
return;
}
+ QLIST_INSERT_HEAD(&bs->deleted_status, &del_stat, next);
+
if (atomic_fetch_inc(&bs->quiesce_counter) == 0) {
aio_disable_external(bdrv_get_aio_context(bs));
bdrv_parent_drained_begin(bs);
}
- bdrv_drain_recurse(bs);
+ if (!del_stat.deleted) {
+ QLIST_REMOVE(&del_stat, next);
+
+ bdrv_drain_recurse(bs);
+ }
}
void bdrv_drained_end(BlockDriverState *bs)
--
2.13.5
- [Qemu-block] [PATCH 00/18] block/mirror: Add active-sync mirroring, Max Reitz, 2017/09/13
- [Qemu-block] [PATCH 01/18] block: Add BdrvDeletedStatus, Max Reitz, 2017/09/13
- [Qemu-block] [PATCH 02/18] block: BDS deletion during bdrv_drain_recurse,
Max Reitz <=
- [Qemu-block] [PATCH 03/18] blockjob: Make drained_{begin, end} public, Max Reitz, 2017/09/13
- [Qemu-block] [PATCH 04/18] block/mirror: Pull out mirror_perform(), Max Reitz, 2017/09/13
- [Qemu-block] [PATCH 05/18] block/mirror: Convert to coroutines, Max Reitz, 2017/09/13