block: Use BdrvChild callbacks for change_media/resize

We want to get rid of BlockDriverState.blk in order to allow multiple
BlockBackends per BDS. Converting the device callbacks in block.c (which
assume a single BlockBackend) to per-child callbacks gets us rid of the
first few instances.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>

block.c

@@ -1214,6 +1214,27 @@ void bdrv_unref_child(BlockDriverState *parent, BdrvChild *child)
     bdrv_root_unref_child(child);
 }
 
+
+static void bdrv_parent_cb_change_media(BlockDriverState *bs, bool load)
+{
+    BdrvChild *c;
+    QLIST_FOREACH(c, &bs->parents, next_parent) {
+        if (c->role->change_media) {
+            c->role->change_media(c, load);
+        }
+    }
+}
+
+static void bdrv_parent_cb_resize(BlockDriverState *bs)
+{
+    BdrvChild *c;
+    QLIST_FOREACH(c, &bs->parents, next_parent) {
+        if (c->role->resize) {
+            c->role->resize(c);
+        }
+    }
+}
+
 /*
  * Sets the backing file link of a BDS. A new reference is created; callers
  * which don't need their own reference any more must call bdrv_unref().
@@ -1673,9 +1694,7 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
     }
 
     if (!bdrv_key_required(bs)) {
-        if (bs->blk) {
+        bdrv_parent_cb_change_media(bs, true);
-            blk_dev_change_media_cb(bs->blk, true);
-        }
     } else if (!runstate_check(RUN_STATE_PRELAUNCH)
                && !runstate_check(RUN_STATE_INMIGRATE)
                && !runstate_check(RUN_STATE_PAUSED)) { /* HACK */
@@ -2121,9 +2140,7 @@ static void bdrv_close(BlockDriverState *bs)
     bdrv_release_named_dirty_bitmaps(bs);
     assert(QLIST_EMPTY(&bs->dirty_bitmaps));
 
-    if (bs->blk) {
+    bdrv_parent_cb_change_media(bs, false);
-        blk_dev_change_media_cb(bs->blk, false);
-    }
 
     if (bs->drv) {
         BdrvChild *child, *next;
@@ -2574,9 +2591,7 @@ int bdrv_truncate(BlockDriverState *bs, int64_t offset)
     if (ret == 0) {
         ret = refresh_total_sectors(bs, offset >> BDRV_SECTOR_BITS);
         bdrv_dirty_bitmap_truncate(bs);
-        if (bs->blk) {
+        bdrv_parent_cb_resize(bs);
-            blk_dev_resize_cb(bs->blk);
-        }
     }
     return ret;
 }
@@ -2686,11 +2701,9 @@ int bdrv_set_key(BlockDriverState *bs, const char *key)
     if (ret < 0) {
         bs->valid_key = 0;
     } else if (!bs->valid_key) {
+        /* call the change callback now, we skipped it on open */
         bs->valid_key = 1;
-        if (bs->blk) {
+        bdrv_parent_cb_change_media(bs, true);
-            /* call the change callback now, we skipped it on open */
-            blk_dev_change_media_cb(bs->blk, true);
-        }
     }
     return ret;
 }

block/block-backend.c

@@ -94,9 +94,15 @@ static void blk_root_inherit_options(int *child_flags, QDict *child_options,
 static void blk_root_drained_begin(BdrvChild *child);
 static void blk_root_drained_end(BdrvChild *child);
 
+static void blk_root_change_media(BdrvChild *child, bool load);
+static void blk_root_resize(BdrvChild *child);
+
 static const BdrvChildRole child_root = {
     .inherit_options    = blk_root_inherit_options,
 
+    .change_media       = blk_root_change_media,
+    .resize             = blk_root_resize,
+
     .drained_begin      = blk_root_drained_begin,
     .drained_end        = blk_root_drained_end,
 };
@@ -556,6 +562,11 @@ void blk_dev_change_media_cb(BlockBackend *blk, bool load)
     }
 }
 
+static void blk_root_change_media(BdrvChild *child, bool load)
+{
+    blk_dev_change_media_cb(child->opaque, load);
+}
+
 /*
  * Does @blk's attached device model have removable media?
  * %true if no device model is attached.
@@ -610,8 +621,10 @@ bool blk_dev_is_medium_locked(BlockBackend *blk)
 /*
  * Notify @blk's attached device model of a backend size change.
  */
-void blk_dev_resize_cb(BlockBackend *blk)
+static void blk_root_resize(BdrvChild *child)
 {
+    BlockBackend *blk = child->opaque;
+
     if (blk->dev_ops && blk->dev_ops->resize_cb) {
         blk->dev_ops->resize_cb(blk->dev_opaque);
     }

include/block/block_int.h

@@ -365,6 +365,9 @@ struct BdrvChildRole {
     void (*inherit_options)(int *child_flags, QDict *child_options,
                             int parent_flags, QDict *parent_options);
 
+    void (*change_media)(BdrvChild *child, bool load);
+    void (*resize)(BdrvChild *child);
+
     /*
      * If this pair of functions is implemented, the parent doesn't issue new
      * requests after returning from .drained_begin() until .drained_end() is
@@ -722,7 +725,6 @@ bool blk_dev_has_tray(BlockBackend *blk);
 void blk_dev_eject_request(BlockBackend *blk, bool force);
 bool blk_dev_is_tray_open(BlockBackend *blk);
 bool blk_dev_is_medium_locked(BlockBackend *blk);
-void blk_dev_resize_cb(BlockBackend *blk);
 
 void bdrv_set_dirty(BlockDriverState *bs, int64_t cur_sector, int nr_sectors);
 bool bdrv_requests_pending(BlockDriverState *bs);