qcow2_alloc_compressed_cluster_offset() used to return the cluster
offset for success and 0 for error. This doesn't only conflict with 0 as
a valid host offset, but also loses the error code.
Similar to the change made to qcow2_alloc_cluster_offset() for
uncompressed clusters in commit 148da7ea9d, make the function return
0/-errno and return the allocated cluster offset in a by-reference
parameter.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
If you have a capable file system (tmpfs is good, ext4 not so much;
run ./check with TEST_DIR pointing to a good location so as not
to skip the test), it's actually possible to create a qcow2 file
that expands to a sparse 512T image with just over 38M of content.
The test is not the world's fastest (qemu crawling through 256M
bits of refcount table to find the next cluster to allocate takes
several seconds, as does qemu-img check reporting millions of
leaked clusters); but it DOES catch the problem that the previous
patch just fixed where writing a compressed cluster to a full
image ended up overwriting the wrong cluster.
Suggested-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Kevin Wolf
Eric Blake