From 1ffa7d12a15fdc4f1bbed59bf5d3292ac2b574b3 Mon Sep 17 00:00:00 2001 From: Jeffrey Cody Date: Mon, 12 Jun 2017 14:46:56 +0200 Subject: [PATCH 11/13] block: fix external snapshot abort permission error RH-Author: Jeffrey Cody Message-id: <14e6e82657b93fb6bec16eddce051ced36db5ff9.1497278737.git.jcody@redhat.com> Patchwork-id: 75593 O-Subject: [RHEV-7.4 qemu-kvm-rhev PATCH 1/1] block: fix external snapshot abort permission error Bugzilla: 1447184 RH-Acked-by: Kevin Wolf RH-Acked-by: Max Reitz RH-Acked-by: John Snow 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 (cherry picked from commit 719fc28c80a22ab9f1533d775bae09c14442bbbe) Signed-off-by: Jeff Cody Signed-off-by: Miroslav Rezanina --- blockdev.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/blockdev.c b/blockdev.c index 4432143..a3a0731 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1847,7 +1847,11 @@ 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