On Thu, Sep 24, 2020 at 09:13:11PM -0400, Theodore Y. Ts'o wrote: > On Thu, Sep 24, 2020 at 10:33:45AM -0400, Theodore Y. Ts'o wrote: > > HOWEVER, thanks to a hint from a colleague at $WORK, and realizing > > that one of the stack traces had virtio balloon in the trace, I > > realized that when I switched the GCE VM type from e1-standard-2 to > > n1-standard-2 (where e1 VM's are cheaper because they use > > virtio-balloon to better manage host OS memory utilization), problem > > has become, much, *much* rarer (and possibly has gone away, although > > I'm going to want to run a lot more tests before I say that > > conclusively) on my test setup. At the very least, using an n1 VM > > (which doesn't have virtio-balloon enabled in the hypervisor) is > > enough to unblock ext4 development. > > .... and I spoke too soon. A number of runs using -rc6 are now > failing even with the n1-standard-2 VM, so virtio-ballon may not be an > indicator. > > This is why debugging this is frustrating; it is very much a heisenbug > --- although 5.8 seems to work completely reliably, as does commits > before 37f4a24c2469. Anything after that point will show random > failures. :-( It does not make sense to mention 37f4a24c2469, which is reverted in 4e2f62e566b5. Later the patch in 37f4a24c2469 is fixed and re-commited as 568f27006577. However, I can _not_ reproduce the issue by running the same test on kernel built from 568f27006577 directly. Also you have confirmed that the issue can't be fixed after reverting 568f27006577 against v5.9-rc4. Looks the real issue(slab list corruption) should be introduced between 568f27006577 and v5.9-rc4. thanks, Ming
