block: Add blk_add_close_notifier() for BB

Adding something like a "delete notifier" to a BlockBackend would not
make much sense, because whoever is interested in registering there will
probably hold a reference to that BlockBackend; therefore, the notifier
will never be called (or only when the notifiee already relinquished its
reference and thus most probably is no longer interested in that
notification).

Therefore, this patch just passes through the close notifier interface
of the root BDS. This will be called when the device is ejected, for
instance, and therefore does make sense.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-id: 1416309679-333-4-git-send-email-mreitz@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/block-backend.c

@@ -642,6 +642,11 @@ void blk_remove_aio_context_notifier(BlockBackend *blk,
                                      detach_aio_context, opaque);
 }
 
+void blk_add_close_notifier(BlockBackend *blk, Notifier *notify)
+{
+    bdrv_add_close_notifier(blk->bs, notify);
+}
+
 void blk_io_plug(BlockBackend *blk)
 {
     bdrv_io_plug(blk->bs);

include/sysemu/block-backend.h

@@ -143,6 +143,7 @@ void blk_remove_aio_context_notifier(BlockBackend *blk,
                                                                   void *),
                                      void (*detach_aio_context)(void *),
                                      void *opaque);
+void blk_add_close_notifier(BlockBackend *blk, Notifier *notify);
 void blk_io_plug(BlockBackend *blk);
 void blk_io_unplug(BlockBackend *blk);
 BlockAcctStats *blk_get_stats(BlockBackend *blk);