On Tue, Jul 19, 2016 at 02:22:47PM -0700, Calvin Owens wrote: > On 07/18/2016 07:05 PM, Calvin Owens wrote: > >On 07/17/2016 11:02 PM, Dave Chinner wrote: > >>On Sun, Jul 17, 2016 at 10:00:03AM +1000, Dave Chinner wrote: > >>>On Fri, Jul 15, 2016 at 05:18:02PM -0700, Calvin Owens wrote: > >>>>Hello all, > >>>> > >>>>I've found a nasty source of slab corruption. Based on seeing similar symptoms > >>>>on boxes at Facebook, I suspect it's been around since at least 3.10. > >>>> > >>>>It only reproduces under memory pressure so far as I can tell: the issue seems > >>>>to be that XFS reclaims pages from buffers that are still in use by > >>>>scsi/block. I'm not sure which side the bug lies on, but I've only observed it > >>>>with XFS. > >>[....] > >>>But this indicates that the page is under writeback at this point, > >>>so that tends to indicate that the above freeing was incorrect. > >>> > >>>Hmmm - it's clear we've got direct reclaim involved here, and the > >>>suspicion of a dirty page that has had it's bufferheads cleared. > >>>Are there any other warnings in the log from XFS prior to kasan > >>>throwing the error? > >> > >>Can you try the patch below? > > > >Thanks for getting this out so quickly :) > > > >So far so good: I booted Linus' tree as of this morning and reproduced the ASAN > >splat. After applying your patch I haven't triggered it. > > > >I'm a bit wary since it was hard to trigger reliably in the first place... so I > >lined up a few dozen boxes to run the test case overnight. I'll confirm in the > >morning (-0700) they look good. > > All right, my testcase ran 2099 times overnight without triggering anything. > > For the overnight tests, I booted the boxes with "mem=" to artificially limit RAM, > which makes my repro *much* more reliable (I feel silly for not thinking of that > in the first place). With that setup, I hit the ASAN splat 21 times in 98 runs on > vanilla 4.7-rc7. So I'm sold. > > Tested-by: Calvin Owens <calvinowens@xxxxxx> Thanks for testing, Calvin. I'll update the patch and get it reviewed and committed. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
