As you mentioned in #10, blkdev_issue_zeroout (the function that prints 'WRITE SAME failed. Manually zeroing.'), still causes the test to show failures even if we should be manually zeroing out the block device when the hardware write_same fails. A test I could try is to short circuit BLKZEROOUT to always use the manual case and see if there are still failures.
As you mentioned in #10, blkdev_ issue_zeroout (the function that prints 'WRITE SAME failed. Manually zeroing.'), still causes the test to show failures even if we should be manually zeroing out the block device when the hardware write_same fails. A test I could try is to short circuit BLKZEROOUT to always use the manual case and see if there are still failures.