block: Drain individual nodes during reopen

bdrv_reopen() and friends use subtree drains as a lazy way of covering
all the nodes they touch. Turns out that this lazy way is a lot more
complicated than just draining the nodes individually, even not
accounting for the additional complexity in the drain mechanism itself.

Simplify the code by switching to draining the individual nodes that are
already managed in the BlockReopenQueue anyway.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20221118174110.55183-8-kwolf@redhat.com>
Reviewed-by: Hanna Reitz <hreitz@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/block.c b/block.c
index 32665194551c636fd704700a9b9d381013c4e9ec..dd329a16ce696d431b9258e63152159bc5ca121f 100644 (file)
--- a/block.c
+++ b/block.c
@@ -4173,7 +4173,7 @@ static bool bdrv_recurse_has_child(BlockDriverState *bs,
  * returns a pointer to bs_queue, which is either the newly allocated
  * bs_queue, or the existing bs_queue being used.
  *
- * bs must be drained between bdrv_reopen_queue() and bdrv_reopen_multiple().
+ * bs is drained here and undrained by bdrv_reopen_queue_free().
  *
  * To be called with bs->aio_context locked.
  */
@@ -4195,12 +4195,10 @@ static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue,
     int flags;
     QemuOpts *opts;
 
-    /* Make sure that the caller remembered to use a drained section. This is
-     * important to avoid graph changes between the recursive queuing here and
-     * bdrv_reopen_multiple(). */
-    assert(bs->quiesce_counter > 0);
     GLOBAL_STATE_CODE();
 
+    bdrv_drained_begin(bs);
+
     if (bs_queue == NULL) {
         bs_queue = g_new0(BlockReopenQueue, 1);
         QTAILQ_INIT(bs_queue);
@@ -4351,6 +4349,12 @@ void bdrv_reopen_queue_free(BlockReopenQueue *bs_queue)
     if (bs_queue) {
         BlockReopenQueueEntry *bs_entry, *next;
         QTAILQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
+            AioContext *ctx = bdrv_get_aio_context(bs_entry->state.bs);
+
+            aio_context_acquire(ctx);
+            bdrv_drained_end(bs_entry->state.bs);
+            aio_context_release(ctx);
+
             qobject_unref(bs_entry->state.explicit_options);
             qobject_unref(bs_entry->state.options);
             g_free(bs_entry);
@@ -4494,7 +4498,6 @@ int bdrv_reopen(BlockDriverState *bs, QDict *opts, bool keep_old_opts,
 
     GLOBAL_STATE_CODE();
 
-    bdrv_subtree_drained_begin(bs);
     queue = bdrv_reopen_queue(NULL, bs, opts, keep_old_opts);
 
     if (ctx != qemu_get_aio_context()) {
@@ -4505,7 +4508,6 @@ int bdrv_reopen(BlockDriverState *bs, QDict *opts, bool keep_old_opts,
     if (ctx != qemu_get_aio_context()) {
         aio_context_acquire(ctx);
     }
-    bdrv_subtree_drained_end(bs);
 
     return ret;
 }

diff --git a/block/replication.c b/block/replication.c
index f1eed25e43ab8e5f8aefae798d0d5e0bc8d2b0e0..c62f48a87465ca439d015cf1b8340d408410ccbf 100644 (file)
--- a/block/replication.c
+++ b/block/replication.c
@@ -374,9 +374,6 @@ static void reopen_backing_file(BlockDriverState *bs, bool writable,
         s->orig_secondary_read_only = bdrv_is_read_only(secondary_disk->bs);
     }
 
-    bdrv_subtree_drained_begin(hidden_disk->bs);
-    bdrv_subtree_drained_begin(secondary_disk->bs);
-
     if (s->orig_hidden_read_only) {
         QDict *opts = qdict_new();
         qdict_put_bool(opts, BDRV_OPT_READ_ONLY, !writable);
@@ -401,9 +398,6 @@ static void reopen_backing_file(BlockDriverState *bs, bool writable,
             aio_context_acquire(ctx);
         }
     }
-
-    bdrv_subtree_drained_end(hidden_disk->bs);
-    bdrv_subtree_drained_end(secondary_disk->bs);
 }
 
 static void backup_job_cleanup(BlockDriverState *bs)

diff --git a/blockdev.c b/blockdev.c
index 75eef8535ebdd636301e9927ab00f1df7871f54a..d2f80b0386ffbc7a1c875250859d93806616e488 100644 (file)
--- a/blockdev.c
+++ b/blockdev.c
@@ -3515,8 +3515,6 @@ fail:
 void qmp_blockdev_reopen(BlockdevOptionsList *reopen_list, Error **errp)
 {
     BlockReopenQueue *queue = NULL;
-    GSList *drained = NULL;
-    GSList *p;
 
     /* Add each one of the BDS that we want to reopen to the queue */
     for (; reopen_list != NULL; reopen_list = reopen_list->next) {
@@ -3553,9 +3551,7 @@ void qmp_blockdev_reopen(BlockdevOptionsList *reopen_list, Error **errp)
         ctx = bdrv_get_aio_context(bs);
         aio_context_acquire(ctx);
 
-        bdrv_subtree_drained_begin(bs);
         queue = bdrv_reopen_queue(queue, bs, qdict, false);
-        drained = g_slist_prepend(drained, bs);
 
         aio_context_release(ctx);
     }
@@ -3566,15 +3562,6 @@ void qmp_blockdev_reopen(BlockdevOptionsList *reopen_list, Error **errp)
 
 fail:
     bdrv_reopen_queue_free(queue);
-    for (p = drained; p; p = p->next) {
-        BlockDriverState *bs = p->data;
-        AioContext *ctx = bdrv_get_aio_context(bs);
-
-        aio_context_acquire(ctx);
-        bdrv_subtree_drained_end(bs);
-        aio_context_release(ctx);
-    }
-    g_slist_free(drained);
 }
 
 void qmp_blockdev_del(const char *node_name, Error **errp)