From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53731) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dIf6M-00021K-TQ for qemu-devel@nongnu.org; Wed, 07 Jun 2017 13:50:39 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dIf6M-0005xR-3w for qemu-devel@nongnu.org; Wed, 07 Jun 2017 13:50:38 -0400 From: Kevin Wolf Date: Wed, 7 Jun 2017 19:50:19 +0200 Message-Id: <1496857819-12466-9-git-send-email-kwolf@redhat.com> In-Reply-To: <1496857819-12466-1-git-send-email-kwolf@redhat.com> References: <1496857819-12466-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PULL 8/8] block: fix external snapshot abort permission error List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org From: Jeff Cody In external_snapshot_abort(), we try to undo what was done in external_snapshot_prepare() calling bdrv_replace_node() to swap the nodes back. However, we receive a permissions error as writers are blocked on the old node, which is now the new node backing file. An easy fix (initially suggested by Kevin Wolf) is to call bdrv_set_backing_hd() on the new node, to set the backing node to NULL. Signed-off-by: Jeff Cody Reviewed-by: Eric Blake Signed-off-by: Kevin Wolf --- blockdev.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/blockdev.c b/blockdev.c index 892d768..6472548 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1803,7 +1803,11 @@ static void external_snapshot_abort(BlkActionState *common) DO_UPCAST(ExternalSnapshotState, common, common); if (state->new_bs) { if (state->overlay_appended) { + bdrv_ref(state->old_bs); /* we can't let bdrv_set_backind_hd() + close state->old_bs; we need it */ + bdrv_set_backing_hd(state->new_bs, NULL, &error_abort); bdrv_replace_node(state->new_bs, state->old_bs, &error_abort); + bdrv_unref(state->old_bs); /* bdrv_replace_node() ref'ed old_bs */ } } } -- 1.8.3.1