bdrv_is_read_only() only checks if the node is configured to be
read-only eventually, but even if it returns false, writing to the node
may not be permitted at the moment (because it's inactive).
bdrv_is_writable() checks that the node can be written to right now, and
this is what the snapshot operations really need.
Change bdrv_can_snapshot() to use bdrv_is_writable() to fix crashes like
the following:
$ ./qemu-system-x86_64 -hda /tmp/test.qcow2 -loadvm foo -incoming defer
qemu-system-x86_64: ../block/io.c:1990: int bdrv_co_write_req_prepare(BdrvChild
*, int64_t, int64_t, BdrvTrackedRequest *, int): Assertion `!(bs->open_flags &
BDRV_O_INACTIVE)' failed.
The resulting error message after this patch isn't perfect yet, but at
least it doesn't crash any more:
$ ./qemu-system-x86_64 -hda /tmp/test.qcow2 -loadvm foo -incoming defer
qemu-system-x86_64: Device 'ide0-hd0' is writable but does not support snapshots
Signed-off-by: Kevin Wolf <kw...@redhat.com>
Message-ID: <20231201142520.32255-2-kw...@redhat.com>
Signed-off-by: Kevin Wolf <kw...@redhat.com>
---
block/snapshot.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/block/snapshot.c b/block/snapshot.c
index ec8cf4810b..c4d40e80dd 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -196,8 +196,10 @@ bdrv_snapshot_fallback(BlockDriverState *bs)
int bdrv_can_snapshot(BlockDriverState *bs)
{
BlockDriver *drv = bs->drv;
+
GLOBAL_STATE_CODE();
- if (!drv || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
+
+ if (!drv || !bdrv_is_inserted(bs) || !bdrv_is_writable(bs)) {
return 0;
}
--
2.43.0
