block/qcow2: proper locking on bitmap add/remove paths

qmp_block_dirty_bitmap_add and do_block_dirty_bitmap_remove do acquire
aio context since 0a6c86d024c52b. But this is not enough: we also must
lock qcow2 mutex when access in-image metadata. Especially it concerns
freeing qcow2 clusters.

To achieve this, move qcow2_can_store_new_dirty_bitmap and
qcow2_remove_persistent_dirty_bitmap to coroutine context.

Since we work in coroutines in correct aio context, we don't need
context acquiring in blockdev.c anymore, drop it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20190920082543.23444-4-vsementsov@virtuozzo.com
Signed-off-by: John Snow <jsnow@redhat.com>

1 files changed, 7 insertions, 20 deletions

diff --git a/blockdev.c b/blockdev.c
index a45458a..7e12919 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2898,16 +2898,10 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
         disabled = false;
     }
 
-    if (persistent) {
-        AioContext *aio_context = bdrv_get_aio_context(bs);
-        bool ok;
-
-        aio_context_acquire(aio_context);
-        ok = bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp);
-        aio_context_release(aio_context);
-        if (!ok) {
-            return;
-        }
+    if (persistent &&
+        !bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp))
+    {
+        return;
     }
 
     bitmap = bdrv_create_dirty_bitmap(bs, granularity, name, errp);
@@ -2939,17 +2933,10 @@ static BdrvDirtyBitmap *do_block_dirty_bitmap_remove(
         return NULL;
     }
 
-    if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
-        int ret;
-        AioContext *aio_context = bdrv_get_aio_context(bs);
-
-        aio_context_acquire(aio_context);
-        ret = bdrv_remove_persistent_dirty_bitmap(bs, name, errp);
-        aio_context_release(aio_context);
-
-        if (ret < 0) {
+    if (bdrv_dirty_bitmap_get_persistence(bitmap) &&
+        bdrv_remove_persistent_dirty_bitmap(bs, name, errp) < 0)
+    {
             return NULL;
-        }
     }
 
     if (release) {