qemu-iotests: add sub-cluster allocating write test for sparse image formats

Image formats that grow the image file on demand and are organized into
clusters must handle sub-cluster allocating writes.  Such writes touch
a portion of a previously unallocated data cluster.  After the image
file is grown with the written data, reads of that cluster should work
as expected:

1. Sectors before the written region are zero.
2. The written region is present and the data is uncorrupted.
3. Sectors after the written region are zero.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 23 insertions, 0 deletions

diff --git a/tests/qemu-iotests/027.out b/tests/qemu-iotests/027.out
new file mode 100644
index 0000000000..a45c303724
--- /dev/null
+++ b/tests/qemu-iotests/027.out
@@ -0,0 +1,23 @@
+QA output created by 027
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 
+
+== writing first cluster to populate metadata ==
+wrote 65536/65536 bytes at offset 65536
+64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== writing at sub-cluster granularity ==
+wrote 2048/2048 bytes at offset 1024
+2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== verify pattern ==
+read 2048/2048 bytes at offset 1024
+2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== verify zeroes before sub-cluster pattern ==
+read 2048/2048 bytes at offset 0
+2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+== verify zeroes after sub-cluster pattern ==
+read 2560/2560 bytes at offset 1024
+2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+*** done