| Message ID | 20181221062809.31771-1-osalvador@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] mm, page_alloc: Fix has_unmovable_pages for HugePages | expand |
On 21.12.18 07:28, Oscar Salvador wrote: > v3 -> v2: Get rid of the round_up() > v2 -> v1: Adjust skip pages logic per Michal > > From 8c057ff497a078f28e293af8c0bd089893a57753 Mon Sep 17 00:00:00 2001 > From: Oscar Salvador <osalvador@suse.de> > Date: Wed, 19 Dec 2018 00:04:18 +0000 > Subject: [PATCH] mm, page_alloc: fix has_unmovable_pages for HugePages > > While playing with gigantic hugepages and memory_hotplug, I triggered the > following #PF when "cat memoryX/removable": > > <--- > 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: 1481 Comm: cat Tainted: G E 4.20.0-rc6-mm1-1-default+ #18 > kernel: Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014 > kernel: RIP: 0010:has_unmovable_pages+0x154/0x210 > kernel: Code: 1b ff ff ff eb 32 48 8b 45 00 bf 00 10 00 00 a9 00 00 01 00 74 07 0f b6 4d 51 48 d3 e7 e8 c4 81 05 00 48 85 c0 49 89 c1 75 7e <41> 8b 41 08 83 f8 09 74 41 83 f8 1b 74 3c 4d 2b 64 24 58 49 81 ec > kernel: RSP: 0018:ffffc90000a1fd30 EFLAGS: 00010246 > kernel: RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000009 > kernel: RDX: ffffffff82aed4f0 RSI: 0000000000001000 RDI: 0000000000001000 > kernel: RBP: ffffea0001800000 R08: 0000000000200000 R09: 0000000000000000 > kernel: R10: 0000000000001000 R11: 0000000000000003 R12: ffff88813ffd45c0 > kernel: R13: 0000000000060000 R14: 0000000000000001 R15: ffffea0000000000 > kernel: FS: 00007fd71d9b3500(0000) GS:ffff88813bb00000(0000) knlGS:0000000000000000 > kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > kernel: CR2: 0000000000000008 CR3: 00000001371c2002 CR4: 00000000003606e0 > kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > kernel: Call Trace: > kernel: is_mem_section_removable+0x7d/0x100 > kernel: removable_show+0x90/0xb0 > kernel: dev_attr_show+0x1c/0x50 > kernel: sysfs_kf_seq_show+0xca/0x1b0 > kernel: seq_read+0x133/0x380 > kernel: __vfs_read+0x26/0x180 > kernel: vfs_read+0x89/0x140 > kernel: ksys_read+0x42/0x90 > kernel: do_syscall_64+0x5b/0x180 > kernel: entry_SYSCALL_64_after_hwframe+0x44/0xa9 > kernel: RIP: 0033:0x7fd71d4c8b41 > kernel: Code: fe ff ff 48 8d 3d 27 9e 09 00 48 83 ec 08 e8 96 02 02 00 66 0f 1f 44 00 00 8b 05 ea fc 2c 00 48 63 ff 85 c0 75 13 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 57 f3 c3 0f 1f 44 00 00 55 53 48 89 d5 48 89 > kernel: RSP: 002b:00007ffeab5f6448 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 > kernel: RAX: ffffffffffffffda RBX: 0000000000020000 RCX: 00007fd71d4c8b41 > kernel: RDX: 0000000000020000 RSI: 00007fd71d809000 RDI: 0000000000000003 > kernel: RBP: 0000000000020000 R08: ffffffffffffffff R09: 0000000000000000 > kernel: R10: 000000000000038b R11: 0000000000000246 R12: 00007fd71d809000 > kernel: R13: 0000000000000003 R14: 00007fd71d80900f R15: 0000000000020000 > 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) drm_kms_helper(E) drm(E) aesni_intel(E) virtio_net(E) syscopyarea(E) net_failover(E) sysfillrect(E) failover(E) aes_x86_64(E) crypto_simd(E) sysimgblt(E) cryptd(E) pcspkr(E) glue_helper(E) parport_pc(E) fb_sys_fops(E) i2c_piix4(E) parport(E) button(E) btrfs(E) libcrc32c(E) xor(E) zstd_decompress(E) zstd_compress(E) raid6_pq(E) sd_mod(E) ata_generic(E) ata_piix(E) ahci(E) libahci(E) serio_raw(E) crc32c_intel(E) virtio_pci(E) virtio_ring(E) virtio(E) libata(E) sg(E) scsi_mod(E) autofs4(E) > kernel: CR2: 0000000000000008 > kernel: ---[ end trace 49cade81474e40e7 ]--- > kernel: RIP: 0010:has_unmovable_pages+0x154/0x210 > kernel: Code: 1b ff ff ff eb 32 48 8b 45 00 bf 00 10 00 00 a9 00 00 01 00 74 07 0f b6 4d 51 48 d3 e7 e8 c4 81 05 00 48 85 c0 49 89 c1 75 7e <41> 8b 41 08 83 f8 09 74 41 83 f8 1b 74 3c 4d 2b 64 24 58 49 81 ec > kernel: RSP: 0018:ffffc90000a1fd30 EFLAGS: 00010246 > kernel: RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000009 > kernel: RDX: ffffffff82aed4f0 RSI: 0000000000001000 RDI: 0000000000001000 > kernel: RBP: ffffea0001800000 R08: 0000000000200000 R09: 0000000000000000 > kernel: R10: 0000000000001000 R11: 0000000000000003 R12: ffff88813ffd45c0 > kernel: R13: 0000000000060000 R14: 0000000000000001 R15: ffffea0000000000 > kernel: FS: 00007fd71d9b3500(0000) GS:ffff88813bb00000(0000) knlGS:0000000000000000 > kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > kernel: CR2: 0000000000000008 CR3: 00000001371c2002 CR4: 00000000003606e0 > kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > ---> > > The reason is we do not pass the Head to page_hstate(), and so, the call > to compound_order() in page_hstate() returns 0, so we end up checking all > hstates's size to match PAGE_SIZE. > > Obviously, we do not find any hstate matching that size, and we return > NULL. Then, we dereference that NULL pointer in > hugepage_migration_supported() and we got the #PF from above. > > Fix that by getting the head page before calling page_hstate(). > > Also, since gigantic pages span several pageblocks, re-adjust the logic > for skipping pages. > While are it, we can also get rid of the round_up(). > > Signed-off-by: Oscar Salvador <osalvador@suse.de> > Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/page_alloc.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 2ec9cc407216..995d1079f958 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7802,11 +7802,14 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, > * handle each tail page individually in migration. > */ > if (PageHuge(page)) { > + struct page *head = compound_head(page); > + unsigned int skip_pages; > > - if (!hugepage_migration_supported(page_hstate(page))) > + if (!hugepage_migration_supported(page_hstate(head))) > goto unmovable; > > - iter = round_up(iter + 1, 1<<compound_order(page)) - 1; > + skip_pages = (1 << compound_order(head)) - (page - head); > + iter += skip_pages - 1; > continue; > } > > Makes sense to me Reviewed-by: David Hildenbrand <david@redhat.com>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 2ec9cc407216..995d1079f958 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7802,11 +7802,14 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, * handle each tail page individually in migration. */ if (PageHuge(page)) { + struct page *head = compound_head(page); + unsigned int skip_pages; - if (!hugepage_migration_supported(page_hstate(page))) + if (!hugepage_migration_supported(page_hstate(head))) goto unmovable; - iter = round_up(iter + 1, 1<<compound_order(page)) - 1; + skip_pages = (1 << compound_order(head)) - (page - head); + iter += skip_pages - 1; continue; }