[v2,07/15] block: Drain invidual nodes during reopen

Commit Message

Kevin Wolf Nov. 18, 2022, 5:41 p.m. UTC

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 <[e-mail]>
---
 block.c             | 16 +++++++++-------
 block/replication.c |  6 ------
 blockdev.c          | 13 -------------
 3 files changed, 9 insertions(+), 26 deletions(-)

Comments

Vladimir Sementsov-Ogievskiy Nov. 25, 2022, 1:10 p.m. UTC | #1

in subject: s/invidual/individual/

On 11/18/22 20:41, Kevin Wolf wrote:
> 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<[e-mail]>

Reviewed-by: Vladimir Sementsov-Ogievskiy <[e-mail]>

Patch

diff --git a/block.c b/block.c
index 191dfc5d0c..59eafcc54c 100644
--- a/block.c
+++ b/block.c
@@ -4152,7 +4152,7 @@  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.
  */
@@ -4174,12 +4174,10 @@  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);
@@ -4330,6 +4328,12 @@  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);
@@ -4477,7 +4481,6 @@  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()) {
@@ -4488,7 +4491,6 @@  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 f1eed25e43..c62f48a874 100644
--- 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 3f1dec6242..8ffb3d9537 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -3547,8 +3547,6 @@  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) {
@@ -3585,9 +3583,7 @@  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);
     }
@@ -3598,15 +3594,6 @@  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)