On Tue 22-01-19 16:44:07, Oscar Salvador wrote: > This is the same sort of error we saw in [1]. > > Gigantic hugepages crosses several memblocks, so it can be > that the page we get in scan_movable_pages() is a page-tail > belonging to a 1G-hugepage. > If that happens, page_hstate()->size_to_hstate() will return NULL, > and we will blow up in hugepage_migration_supported(). > > The splat is as follows: > > kernel: BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 > kernel: #PF error: [normal kernel read fault] > kernel: PGD 0 P4D 0 > kernel: Oops: 0000 [#1] SMP PTI > kernel: CPU: 1 PID: 1350 Comm: bash Tainted: G E 5.0.0-rc1-mm1-1-default+ #27 > kernel: Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014 > kernel: RIP: 0010:__offline_pages+0x6ae/0x900 > kernel: Code: 48 c7 c6 d0 3e a4 81 e8 44 c8 ad ff 49 8b 04 24 bf 00 10 00 00 a9 00 00 01 00 74 09 41 0f b6 4c 24 51 48 d3 e7 e8 42 2a c1 ff <8b> 40 08 83 f8 09 0f 84 b0 fc ff ff 83 f8 12 0f 84 a7 fc ff ff 83 > kernel: RSP: 0018:ffffc900008e3d20 EFLAGS: 00010246 > kernel: RAX: 0000000000000000 RBX: ffffea0000000000 RCX: 0000000000000009 > kernel: RDX: ffffffff825c64f0 RSI: 0000000000001000 RDI: 0000000000001000 > kernel: RBP: ffffc900008e3d68 R08: 0000000000200000 R09: 00000000000001e4 > kernel: R10: 0000000000000058 R11: ffffffff8254a854 R12: ffffea0004200000 > kernel: R13: 0000000000108000 R14: 0000000000110000 R15: 0000000000000000 > kernel: FS: 00007ff172339b80(0000) GS:ffff88803eb00000(0000) knlGS:0000000000000000 > kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > kernel: CR2: 0000000000000008 CR3: 0000000038d78006 CR4: 00000000003606a0 > kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > kernel: Call Trace: > kernel: ? klist_next+0x79/0xe0 > kernel: memory_subsys_offline+0x42/0x60 > kernel: device_offline+0x80/0xa0 > kernel: state_store+0xab/0xc0 > kernel: kernfs_fop_write+0x102/0x180 > kernel: __vfs_write+0x26/0x190 > kernel: ? set_close_on_exec+0x49/0x70 > kernel: vfs_write+0xad/0x1b0 > kernel: ksys_write+0x42/0x90 > kernel: do_syscall_64+0x5b/0x180 > kernel: entry_SYSCALL_64_after_hwframe+0x44/0xa9 > kernel: RIP: 0033:0x7ff1719febe4 > kernel: Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 80 00 00 00 00 8b 05 4a fc 2c 00 48 63 ff 85 c0 75 13 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 f3 c3 66 90 55 53 48 89 d5 48 89 f3 48 83 > kernel: RSP: 002b:00007ffd50b7ddc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 > kernel: RAX: ffffffffffffffda RBX: 0000000000000008 RCX: 00007ff1719febe4 > kernel: RDX: 0000000000000008 RSI: 00005556e9216b20 RDI: 0000000000000001 > kernel: RBP: 00005556e9216b20 R08: 000000000000000a R09: 0000000000000000 > kernel: R10: 000000000000000a R11: 0000000000000246 R12: 0000000000000008 > kernel: R13: 0000000000000001 R14: 00007ff171cca720 R15: 0000000000000008 > kernel: Modules linked in: af_packet(E) xt_tcpudp(E) ipt_REJECT(E) xt_conntrack(E) nf_conntrack(E) nf_defrag_ipv4(E) ip_set(E) nfnetlink(E) ebtable_nat(E) ebtable_broute(E) bridge(E) stp(E) llc(E) iptable_mangle(E) iptable_raw(E) iptable_security(E) ebtable_filter(E) ebtables(E) iptable_filter(E) ip_tables(E) x_tables(E) kvm_intel(E) kvm(E) irqbypass(E) crct10dif_pclmul(E) crc32_pclmul(E) ghash_clmulni_intel(E) bochs_drm(E) ttm(E) aesni_intel(E) drm_kms_helper(E) aes_x86_64(E) crypto_simd(E) cryptd(E) glue_helper(E) drm(E) virtio_net(E) syscopyarea(E) sysfillrect(E) net_failover(E) sysimgblt(E) pcspkr(E) failover(E) i2c_piix4(E) fb_sys_fops(E) parport_pc(E) parport(E) button(E) btrfs(E) libcrc32c(E) xor(E) zstd_decompress(E) zstd_compress(E) xxhash(E) raid6_pq(E) sd_mod(E) ata_generic(E) ata_piix(E) ahci(E) libahci(E) libata(E) crc32c_intel(E) serio_raw(E) virtio_pci(E) virtio_ring(E) virtio(E) sg(E) scsi_mod(E) autofs4(E) > kernel: CR2: 0000000000000008 > kernel: ---[ end trace bdb71590872849fb ]--- > kernel: RIP: 0010:__offline_pages+0x6ae/0x900 > kernel: Code: 48 c7 c6 d0 3e a4 81 e8 44 c8 ad ff 49 8b 04 24 bf 00 10 00 00 a9 00 00 01 00 74 09 41 0f b6 4c 24 51 48 d3 e7 e8 42 2a c1 ff <8b> 40 08 83 f8 09 0f 84 b0 fc ff ff 83 f8 12 0f 84 a7 fc ff ff 83 > kernel: RSP: 0018:ffffc900008e3d20 EFLAGS: 00010246 > kernel: RAX: 0000000000000000 RBX: ffffea0000000000 RCX: 0000000000000009 > kernel: RDX: ffffffff825c64f0 RSI: 0000000000001000 RDI: 0000000000001000 > kernel: RBP: ffffc900008e3d68 R08: 0000000000200000 R09: 00000000000001e4 > kernel: R10: 0000000000000058 R11: ffffffff8254a854 R12: ffffea0004200000 > kernel: R13: 0000000000108000 R14: 0000000000110000 R15: 0000000000000000 > kernel: FS: 00007ff172339b80(0000) GS:ffff88803eb00000(0000) knlGS:0000000000000000 > kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > kernel: CR2: 0000000000000008 CR3: 0000000038d78006 CR4: 00000000003606a0 > kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Fix this by getting the head page and testing against it. > > [1] https://patchwork.kernel.org/patch/10739963/ So this should be probably folded into the above patch as it is incomplete unless I am missing something. > Signed-off-by: Oscar Salvador <osalvador@xxxxxxx> Other than that the change looks good to me. Acked-by: Michal Hocko <mhocko@xxxxxxxx> > --- > mm/memory_hotplug.c | 15 ++++++++++----- > 1 file changed, 10 insertions(+), 5 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index ec22c86d9f89..25aee4f04a72 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1335,12 +1335,17 @@ static unsigned long scan_movable_pages(unsigned long start, unsigned long end) > if (__PageMovable(page)) > return pfn; > if (PageHuge(page)) { > - if (hugepage_migration_supported(page_hstate(page)) && > - page_huge_active(page)) > + struct page *head = compound_head(page); > + > + if (hugepage_migration_supported(page_hstate(head)) && > + page_huge_active(head)) > return pfn; > - else > - pfn = round_up(pfn + 1, > - 1 << compound_order(page)) - 1; > + else { > + unsigned long skip; > + > + skip = (1 << compound_order(head)) - (page - head); > + pfn += skip - 1; > + } > } > } > } > -- > 2.13.7 -- Michal Hocko SUSE Labs
