This tests that qemu-img rebase doesn't assume that the backing file has
the same size as the image, but considers that it can be smaller.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
The io_pattern style functions have the following loop:
for i in `seq 1 $count`; do
echo ... $(( start + i * step )) ...
done
Offsets are 1-based so start=1024, step=512, count=4 yields:
1536, 2048, 2560, 3072
Normally we expect:
1024, 1536, 2048, 2560
Most tests ignore this detail, which means that they perform I/O to a
slightly different range than expected by the test author.
Later on things got less innocent and tests started trying to compensate
for the 1-based indexing. This included negative start values in test
024 and my own attempt with count-1 in test 028!
The end result is that tests that use io_pattern are hard to reason
about and don't work the way you'd expect. It's time to clean this mess
up.
This patch switches io_pattern to 0-based offsets. This requires
adjusting the golden outputs since I/O ranges are now shifted and output
differs.
Verifying these output diffs is easy, however. Each diff hunk moves one
I/O from beyond the end of the pattern range to the beginning.
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Some image formats support backing images that are smaller than the
image file. This patch adds a test that verifies that reads and writes
beyond the end of backing image work.
Unallocated reads beyond the end of the backing file should produce
zeroes.
Writes beyond the end of the backing file should copy-on-write using
zeroes.
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
