When removeing support for qemu-img being able to create backing chains without embedded backing formats, we caused a poor error message as caught by iotest 114. Improve the situation to inform the user what went wrong. Suggested-by: Kevin Wolf <kwolf(a)redhat.com&gt; Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- qemu-img.c | 3 +++ tests/qemu-iotests/114.out | 2 +- 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/qemu-img.c b/qemu-img.c index 7c0e73882dd4..b017734c255a 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -3786,6 +3786,9 @@ static int img_rebase(int argc, char **argv) if (ret == -ENOSPC) { error_report("Could not change the backing file to '%s': No " "space left in the file header", out_baseimg); + } else if (ret == -EINVAL && out_baseimg && !out_basefmt) { + error_report("Could not change the backing file to '%s': backing " + "format must be specified", out_baseimg); } else if (ret < 0) { error_report("Could not change the backing file to '%s': %s", out_baseimg, strerror(-ret)); diff --git a/tests/qemu-iotests/114.out b/tests/qemu-iotests/114.out index 172454401257..016e9ce3ecfb 100644 --- a/tests/qemu-iotests/114.out +++ b/tests/qemu-iotests/114.out @@ -14,7 +14,7 @@ qemu-io: can't open device TEST_DIR/t.qcow2: Could not open backing file: Unknow no file open, try 'help open' read 4096/4096 bytes at offset 0 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) -qemu-img: Could not change the backing file to '/home/eblake/qemu/build/tests/qemu-iotests/scratch/t.qcow2.base': Invalid argument +qemu-img: Could not change the backing file to '/home/eblake/qemu/build/tests/qemu-iotests/scratch/t.qcow2.base': backing format must be specified read 4096/4096 bytes at offset 0 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) *** done -- 2.31.1