From d374d5aa4485a0c62d6b48eec64491cae2fd0873 Mon Sep 17 00:00:00 2001
From: Peter Lieven <pl@kamp.de>
Date: Thu, 13 Jan 2022 15:44:25 +0100
Subject: [PATCH 4/5] block/rbd: fix handling of holes in .bdrv_co_block_status

RH-Author: Stefano Garzarella <sgarzare@redhat.com>
RH-MergeRequest: 68: block/rbd: fix handling of holes in .bdrv_co_block_status
RH-Commit: [1/2] 8ef178b01885e3c292f7844ccff865b1a8d4faf0 (sgarzarella/qemu-kvm-c-9-s)
RH-Bugzilla: 2034791
RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Hanna Reitz <hreitz@redhat.com>

the assumption that we can't hit a hole if we do not diff against a snapshot was wrong.

We can see a hole in an image if we diff against base if there exists an older snapshot
of the image and we have discarded blocks in the image where the snapshot has data.

Fix this by simply handling a hole like an unallocated area. There are no callbacks
for unallocated areas so just bail out if we hit a hole.

Fixes: 0347a8fd4c3faaedf119be04c197804be40a384b
Suggested-by: Ilya Dryomov <idryomov@gmail.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Lieven <pl@kamp.de>
Message-Id: <20220113144426.4036493-2-pl@kamp.de>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit 9e302f64bb407a9bb097b626da97228c2654cfee)
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
---
 block/rbd.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/rbd.c b/block/rbd.c
index def96292e0..20bb896c4a 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -1279,11 +1279,11 @@ static int qemu_rbd_diff_iterate_cb(uint64_t offs, size_t len,
     RBDDiffIterateReq *req = opaque;
 
     assert(req->offs + req->bytes <= offs);
-    /*
-     * we do not diff against a snapshot so we should never receive a callback
-     * for a hole.
-     */
-    assert(exists);
+
+    /* treat a hole like an unallocated area and bail out */
+    if (!exists) {
+        return 0;
+    }
 
     if (!req->exists && offs > req->offs) {
         /*
-- 
2.27.0