https://bugzilla.kernel.org/show_bug.cgi?id=102731 --- Comment #17 from Theodore Tso <tytso@xxxxxxx> --- I just realized something which I forgot to ask you --- what file system are you using on the *host*? You said that on the guest you are using ext3 file systems with the ext4 driver --- but what about on the host OS side? I will say that using a full ext4 file system is far more stable on 3.18.21 than using an ext3 file system in compatibility mode. Ext4 with the 4.2 kernel will support ext3 with zero unexpected test failures, but there are a handful of test failures that are showing up with the 3.18.21 kernel. I've backported a few bug fixes, but they haven't shown up in the stable kernel series yet, and there are still a half-dozen test failures that I haven't had time to characterized yet. (Note: support for long-term stable kernel is something I do as a very low priority background task. My priority is upstream regressions and upstream development, and ideally someone would help with testing the stable kernels and identifying patches that require manual backports, but I haven't found a sucker yet.) One of the reasons why I ask is that the PUNCH hole functionality was relatively new in the 3.18 kernel, and KVM uses it --- and I am suspicious that there might be some bug fixes that didn't land in the 3.18 kernel. So one thing that might be worth trying is to get a 4.2.3 kernel for both your Host and Guest kernels, and see what that does for you. -- You are receiving this mail because: You are watching the assignee of the bug. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html