On Tue, 29 Jan 2019 at 18:49, Michal Hocko wrote: > > On Tue 29-01-19 14:14:47, Gerald Schaefer wrote: > > On Mon, 28 Jan 2019 15:45:04 +0100 > > Michal Hocko wrote: > > > > > Hi, > > > Mikhail has posted fixes for the two bugs quite some time ago [1]. I > > > have pushed back on those fixes because I believed that it is much > > > better to plug the problem at the initialization time rather than play > > > whack-a-mole all over the hotplug code and find all the places which > > > expect the full memory section to be initialized. We have ended up with > > > 2830bf6f05fb ("mm, memory_hotplug: initialize struct pages for the full > > > memory section") merged and cause a regression [2][3]. The reason is > > > that there might be memory layouts when two NUMA nodes share the same > > > memory section so the merged fix is simply incorrect. > > > > > > In order to plug this hole we really have to be zone range aware in > > > those handlers. I have split up the original patch into two. One is > > > unchanged (patch 2) and I took a different approach for `removable' > > > crash. It would be great if Mikhail could test it still works for his > > > memory layout. > > > > > > [1] http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com > > > [2] https://bugzilla.redhat.com/show_bug.cgi?id=1666948 > > > [3] http://lkml.kernel.org/r/20190125163938.GA20411@dhcp22.suse.cz > > > > I verified that both patches fix the issues we had with valid_zones > > (with mem=2050M) and removable (with mem=3075M). > > > > However, the call trace in the description of your patch 1 is wrong. > > You basically have the same call trace for test_pages_in_a_zone in > > both patches. The "removable" patch should have the call trace for > > is_mem_section_removable from Mikhails original patches: > > Thanks for testing. Can I use you Tested-by? > > > CONFIG_DEBUG_VM_PGFLAGS=y > > kernel parameter mem=3075M > > -------------------------- > > page:000003d08300c000 is uninitialized and poisoned > > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) > > Call Trace: > > ([<000000000038596c>] is_mem_section_removable+0xb4/0x190) > > [<00000000008f12fa>] show_mem_removable+0x9a/0xd8 > > [<00000000008cf9c4>] dev_attr_show+0x34/0x70 > > [<0000000000463ad0>] sysfs_kf_seq_show+0xc8/0x148 > > [<00000000003e4194>] seq_read+0x204/0x480 > > [<00000000003b53ea>] __vfs_read+0x32/0x178 > > [<00000000003b55b2>] vfs_read+0x82/0x138 > > [<00000000003b5be2>] ksys_read+0x5a/0xb0 > > [<0000000000b86ba0>] system_call+0xdc/0x2d8 > > Last Breaking-Event-Address: > > [<000000000038596c>] is_mem_section_removable+0xb4/0x190 > > Kernel panic - not syncing: Fatal exception: panic_on_oops > > Yeah, this is c&p mistake on my end. I will use this trace instead. > Thanks for spotting. Michal, I am late? I am also tested these patches and can confirm that issue fixed again with new approach. I also attach two dmesg first when issue was reproduced and second with applied patch (problem not reproduced). -- Best Regards, Mike Gavrilov.