blockdev: reduce aio_context locked sections in bitmap add/remove

Commit 0a6c86d returned these locks back to add/remove
functionality, to protect from intersection of persistent bitmap
related IO with other IO. But other bitmap-related functions called
here are unrelated to the problem, and there are no needs to keep these
calls inside critical sections.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20190708220502.12977-2-jsnow@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>

blockdev.c

@@ -2813,7 +2813,6 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
 {
     BlockDriverState *bs;
     BdrvDirtyBitmap *bitmap;
-    AioContext *aio_context = NULL;
 
     if (!name || name[0] == '\0') {
         error_setg(errp, "Bitmap name cannot be empty");
@@ -2849,36 +2848,34 @@ void qmp_block_dirty_bitmap_add(const char *node, const char *name,
     }
 
     if (persistent) {
-        aio_context = bdrv_get_aio_context(bs);
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+        bool ok;
+
         aio_context_acquire(aio_context);
-        if (!bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp)) {
-            goto out;
+        ok = bdrv_can_store_new_dirty_bitmap(bs, name, granularity, errp);
+        aio_context_release(aio_context);
+        if (!ok) {
+            return;
         }
     }
 
     bitmap = bdrv_create_dirty_bitmap(bs, granularity, name, errp);
     if (bitmap == NULL) {
-        goto out;
+        return;
     }
 
     if (disabled) {
         bdrv_disable_dirty_bitmap(bitmap);
     }
 
     bdrv_dirty_bitmap_set_persistence(bitmap, persistent);
- out:
-    if (aio_context) {
-        aio_context_release(aio_context);
-    }
 }
 
 void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
                                    Error **errp)
 {
     BlockDriverState *bs;
     BdrvDirtyBitmap *bitmap;
-    Error *local_err = NULL;
-    AioContext *aio_context = NULL;
 
     bitmap = block_dirty_bitmap_lookup(node, name, &bs, errp);
     if (!bitmap || !bs) {
@@ -2891,20 +2888,19 @@ void qmp_block_dirty_bitmap_remove(const char *node, const char *name,
     }
 
     if (bdrv_dirty_bitmap_get_persistence(bitmap)) {
-        aio_context = bdrv_get_aio_context(bs);
+        AioContext *aio_context = bdrv_get_aio_context(bs);
+        Error *local_err = NULL;
+
         aio_context_acquire(aio_context);
         bdrv_remove_persistent_dirty_bitmap(bs, name, &local_err);
+        aio_context_release(aio_context);
         if (local_err != NULL) {
             error_propagate(errp, local_err);
-            goto out;
+            return;
         }
     }
 
     bdrv_release_dirty_bitmap(bs, bitmap);
- out:
-    if (aio_context) {
-        aio_context_release(aio_context);
-    }
 }
 
 /**