block: Print its file name if backing file opening failed
If backing file doesn't exist, the error message is confusing and
misleading:
$ qemu /tmp/a.qcow2
qemu: could not open disk image /tmp/a.qcow2: Could not open file: No
such file or directory
But...
$ ls /tmp/a.qcow2
/tmp/a.qcow2
$ qemu-img info /tmp/a.qcow2
image: /tmp/a.qcow2
file format: qcow2
virtual size: 8.0G (8589934592 bytes)
disk size: 196K
cluster_size: 65536
backing file: /tmp/b.qcow2
Because...
$ ls /tmp/b.qcow2
ls: cannot access /tmp/b.qcow2: No such file or directory
This is not intuitive. It's better to have the missing file's name in
the error message. With this patch:
$ qemu-io -c 'read 0 512' /tmp/a.qcow2
qemu-io: can't open device /tmp/a.qcow2: Could not open backing
file: Could not open '/stor/vm/arch.raw': No such file or directory
no file open, try 'help open'
Which is a little bit better.
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/block.c b/block.c
index 6d5c804..38078f7 100644
--- a/block.c
+++ b/block.c
@@ -1009,7 +1009,9 @@
bdrv_unref(bs->backing_hd);
bs->backing_hd = NULL;
bs->open_flags |= BDRV_O_NO_BACKING;
- error_propagate(errp, local_err);
+ error_setg(errp, "Could not open backing file: %s",
+ error_get_pretty(local_err));
+ error_free(local_err);
return ret;
}
pstrcpy(bs->backing_file, sizeof(bs->backing_file),
