On Mon 18-02-19 16:05:15, Mike Rapoport wrote: > On Mon, Feb 18, 2019 at 11:30:13AM +0100, Michal Hocko wrote: > > On Mon 18-02-19 18:01:39, Rong Chen wrote: > > > > > > On 2/18/19 4:55 PM, Michal Hocko wrote: > > > > [Sorry for an excessive quoting in the previous email] > > > > [Cc Pavel - the full report is > > > > http://lkml.kernel.org/r/20190218052823.GH29177@shao2-debian[] > > > > > > > > On Mon 18-02-19 08:08:44, Michal Hocko wrote: > > > > > On Mon 18-02-19 13:28:23, kernel test robot wrote: > > > > [...] > > > > > > [ 40.305212] PGD 0 P4D 0 > > > > > > [ 40.308255] Oops: 0000 [#1] PREEMPT SMP PTI > > > > > > [ 40.313055] CPU: 1 PID: 239 Comm: udevd Not tainted > > > > > > 5.0.0-rc4-00149-gefad4e4 #1 > > > > > > [ 40.321348] Hardware name: QEMU Standard PC (i440FX + PIIX, > > > > > > 1996), BIOS 1.10.2-1 04/01/2014 > > > > > > [ 40.330813] RIP: 0010:page_mapping+0x12/0x80 > > > > > > [ 40.335709] Code: 5d c3 48 89 df e8 0e ad 02 00 85 c0 75 da 89 > > > > > > e8 5b 5d c3 0f 1f 44 00 00 53 48 89 fb 48 8b 43 08 48 8d 50 ff a8 > > > > > > 01 48 0f 45 da <48> 8b 53 08 48 8d 42 ff 83 e2 01 48 0f 44 c3 48 83 > > > > > > 38 ff 74 2f 48 > > > > > > [ 40.356704] RSP: 0018:ffff88801fa87cd8 EFLAGS: 00010202 > > > > > > [ 40.362714] RAX: ffffffffffffffff RBX: fffffffffffffffe RCX: > > > > > > 000000000000000a > > > > > > [ 40.370798] RDX: fffffffffffffffe RSI: ffffffff820b9a20 RDI: > > > > > > ffff88801e5c0000 > > > > > > [ 40.378830] RBP: 6db6db6db6db6db7 R08: ffff88801e8bb000 R09: > > > > > > 0000000001b64d13 > > > > > > [ 40.386902] R10: ffff88801fa87cf8 R11: 0000000000000001 R12: > > > > > > ffff88801e640000 > > > > > > [ 40.395033] R13: ffffffff820b9a20 R14: ffff88801f145258 R15: > > > > > > 0000000000000001 > > > > > > [ 40.403138] FS: 00007fb2079817c0(0000) > > > > > > GS:ffff88801dd00000(0000) knlGS:0000000000000000 > > > > > > [ 40.412243] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > > > > [ 40.418846] CR2: 0000000000000006 CR3: 000000001fa82000 CR4: > > > > > > 00000000000006a0 > > > > > > [ 40.426951] Call Trace: > > > > > > [ 40.429843] __dump_page+0x14/0x2c0 > > > > > > [ 40.433947] is_mem_section_removable+0x24c/0x2c0 > > > > > This looks like we are stumbling over an unitialized struct page > > > > > again. > > > > > Something this patch should prevent from. Could you try to apply [1] > > > > > which will make __dump_page more robust so that we do not blow up > > > > > there > > > > > and give some more details in return. > > > > > > > > > > Btw. is this reproducible all the time? > > > > And forgot to ask whether this is reproducible with pending mmotm > > > > patches in linux-next. > > > > > > > > > Do you mean the below patch? I can reproduce the problem too. > > > > Yes, thanks for the swift response. The patch has just added a debugging > > output > > [ 0.013697] Early memory node ranges > > [ 0.013701] node 0: [mem 0x0000000000001000-0x000000000009efff] > > [ 0.013706] node 0: [mem 0x0000000000100000-0x000000001ffdffff] > > [ 0.013711] zeroying 0-1 > > > > This is the first pfn. > > > > [ 0.013715] zeroying 9f-100 > > > > this is [mem 0x9f000, 0xfffff] so it fills up the whole hole between the > > above two ranges. This is definitely good. > > > > [ 0.013722] zeroying 1ffe0-1ffe0 > > > > this is a single page at 0x1ffe0000 right after the zone end. > > > > [ 0.013727] Zeroed struct page in unavailable ranges: 98 pages > > > > Hmm, so this is getting really interesting. The whole zone range should > > be covered. So this is either some off-by-one or I something that I am > > missing right now. Could you apply the following on top please? We > > definitely need to see what pfn this is. > > > > > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > > index 124e794867c5..59bcfd934e37 100644 > > --- a/mm/memory_hotplug.c > > +++ b/mm/memory_hotplug.c > > @@ -1232,12 +1232,14 @@ static bool is_pageblock_removable_nolock(struct > > page *page) > > /* Checks if this range of memory is likely to be hot-removable. */ > > bool is_mem_section_removable(unsigned long start_pfn, unsigned long > > nr_pages) > > { > > - struct page *page = pfn_to_page(start_pfn); > > + struct page *page = pfn_to_page(start_pfn), *first_page; > > unsigned long end_pfn = min(start_pfn + nr_pages, > > zone_end_pfn(page_zone(page))); > > struct page *end_page = pfn_to_page(end_pfn); > > > > /* Check the starting page of each pageblock within the range */ > > - for (; page < end_page; page = next_active_pageblock(page)) { > > + for (first_page = page; page < end_page; page = > > next_active_pageblock(page)) { > > + if (PagePoisoned(page)) > > + pr_info("Unexpected poisoned page %px pfn:%lx\n", page, > > start_pfn + page-first_page); > > if (!is_pageblock_removable_nolock(page)) > > return false; > > cond_resched(); > > I've added more prints and somehow end_page gets too big (in brackets is > the pfn): > > [ 11.183835] ===> start: ffff88801e240000(0), end: ffff88801e400000(8000) > [ 11.188457] ===> start: ffff88801e400000(8000), end: > ffff88801e640000(10000) > [ 11.193266] ===> start: ffff88801e640000(10000), end: > ffff88801e060000(18000) > > should be ffff88801e5c0000 > > [ 11.197363] ===> start: ffff88801e060000(18000), end: > ffff88801e21f900(1ffe0) > [ 11.207547] Unexpected poisoned page ffff88801e5c0000 pfn:10000 > > > With the patch below the problem seem to disappear, although I have no idea > why... > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 91e6fef..53d15ff 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1234,7 +1234,7 @@ bool is_mem_section_removable(unsigned long start_pfn, > unsigned long nr_pages) > { > struct page *page = pfn_to_page(start_pfn); > unsigned long end_pfn = min(start_pfn + nr_pages, > zone_end_pfn(page_zone(page))); > - struct page *end_page = pfn_to_page(end_pfn); > + struct page *end_page = page + (end_pfn - start_pfn); > > /* Check the starting page of each pageblock within the range */ > for (; page < end_page; page = next_active_pageblock(page)) {
This is really interesting, because it would mean that the end_pfn is out of the section and so the page pointer arithmetic doesn't really work. But I am wondering how that could happen as nr_pages is PAGES_PER_SECTION. Another option is that pfn_to_page doesn't work properly here. It is CONFIG_SPARSEMEM. Could you print section_nr of both start_pfn and end_pfn please? -- Michal Hocko SUSE Labs
