> On Feb 16, 2020, at 2:18 PM, Rafael Aquini <aquini@xxxxxxxxxx> wrote: > > From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> > A user reported a bug against a distribution kernel while running > a proprietary workload described as "memory intensive that is not > swapping" that is expected to apply to mainline kernels. The workload > is read/write/modifying ranges of memory and checking the contents. They > reported that within a few hours that a bad PMD would be reported followed > by a memory corruption where expected data was all zeros. A partial report > of the bad PMD looked like > > [ 5195.338482] ../mm/pgtable-generic.c:33: bad pmd ffff8888157ba008(000002e0396009e2) > [ 5195.341184] ------------[ cut here ]------------ > [ 5195.356880] kernel BUG at ../mm/pgtable-generic.c:35! > .... > [ 5195.410033] Call Trace: > [ 5195.410471] [<ffffffff811bc75d>] change_protection_range+0x7dd/0x930 > [ 5195.410716] [<ffffffff811d4be8>] change_prot_numa+0x18/0x30 > [ 5195.410918] [<ffffffff810adefe>] task_numa_work+0x1fe/0x310 > [ 5195.411200] [<ffffffff81098322>] task_work_run+0x72/0x90 > [ 5195.411246] [<ffffffff81077139>] exit_to_usermode_loop+0x91/0xc2 > [ 5195.411494] [<ffffffff81003a51>] prepare_exit_to_usermode+0x31/0x40 > [ 5195.411739] [<ffffffff815e56af>] retint_user+0x8/0x10 > > Decoding revealed that the PMD was a valid prot_numa PMD and the bad PMD > was a false detection. The bug does not trigger if automatic NUMA balancing > or transparent huge pages is disabled. > > The bug is due a race in change_pmd_range between a pmd_trans_huge and > pmd_nond_or_clear_bad check without any locks held. During the pmd_trans_huge > check, a parallel protection update under lock can have cleared the PMD > and filled it with a prot_numa entry between the transhuge check and the > pmd_none_or_clear_bad check. > > While this could be fixed with heavy locking, it's only necessary to > make a copy of the PMD on the stack during change_pmd_range and avoid > races. A new helper is created for this as the check if quite subtle and the > existing similar helpful is not suitable. This passed 154 hours of testing > (usually triggers between 20 minutes and 24 hours) without detecting bad > PMDs or corruption. A basic test of an autonuma-intensive workload showed > no significant change in behaviour. > > Although Mel withdrew the patch on the face of LKML comment https://lkml.org/lkml/2017/4/10/922 > the race window aforementioned is still open, and we have reports of Linpack test reporting bad > residuals after the bad PMD warning is observed. In addition to that, bad rss-counter and > non-zero pgtables assertions are triggered on mm teardown for the task hitting the bad PMD. > > host kernel: mm/pgtable-generic.c:40: bad pmd 00000000b3152f68(8000000d2d2008e7) > .... > host kernel: BUG: Bad rss-counter state mm:00000000b583043d idx:1 val:512 > host kernel: BUG: non-zero pgtables_bytes on freeing mm: 4096 > > The issue is observed on a v4.18-based distribution kernel, but the race window is > expected to be applicable to mainline kernels, as well. After reverted this patch, it is no longer possible to reproduce a bug under memory pressure with swapping on linux-next 20200306, The trace is a bit off for some reasons, but it is basically, kernel BUG at include/linux/page-flags.h:317! end_swap_bio_write() SetPageError(page) VM_BUG_ON_PAGE(1 && PageCompound(page)) The page was allocated in, do_huge_pmd_anonymous_page() [ 9598.551238][ T794] oom_reaper: reaped process 49120 (oom02), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB [ 9690.896638][ T814] smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0027 address=0xffffffffffcc0000 flags=0x0010] [ 9690.910129][ T814] smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0027 address=0xffffffffffcc1000 flags=0x0010] [ 9690.923933][ T814] smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0027 address=0xffffffffffcc1900 flags=0x0010] [ 9690.937669][ T814] smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0027 address=0xffffffffffcc1d00 flags=0x0010] [ 9690.951468][ T814] smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0027 address=0xffffffffffcc2000 flags=0x0010] [ 9690.964803][ T814] smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0027 address=0xffffffffffcc2400 flags=0x0010] [ 9690.978256][ T814] smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0027 address=0xffffffffffcc2800 flags=0x0010] [ 9690.991423][ T814] smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0027 address=0xffffffffffcc2c00 flags=0x0010] [ 9691.004294][ T814] smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0027 address=0xffffffffffcc3000 flags=0x0010] [ 9691.017228][ T814] smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0027 address=0xffffffffffcc3400 flags=0x0010] [ 9691.029804][ T814] AMD-Vi: Event logged [IO_PAGE_FAULT device=23:00.0 domain=0x0027 address=0xffffffffffcc3800 flags=0x0010] [ 9691.041623][ T814] AMD-Vi: Event logged [IO_PAGE_FAULT device=23:00.0 domain=0x0027 address=0xffffffffffcc3c00 flags=0x0010] [ 9692.767064][ C8] smartpqi 0000:23:00.0: controller is offline: status code 0x14803 [ 9692.775562][ C8] smartpqi 0000:23:00.0: controller offline [ 9692.841721][ C36] sd 0:1:0:0: [sda] tag#693 UNKNOWN(0x2003) Result: hostbyte=0x01 driverbyte=0x00 cmd_age=1s [ 9692.841970][ C87] blk_update_request: I/O error, dev sda, sector 59046400 op 0x1:(WRITE) flags 0x8004000 phys_seg 4 prio class 0 [ 9692.842718][ C31] blk_update_request: I/O error, dev sda, sector 36509696 op 0x1:(WRITE) flags 0x8004000 phys_seg 4 prio class 0 [ 9692.842748][ C18] sd 0:1:0:0: [sda] tag#616 UNKNOWN(0x2003) Result: hostbyte=0x01 driverbyte=0x00 cmd_age=1s [ 9692.842757][ C28] sd 0:1:0:0: [sda] tag#841 UNKNOWN(0x2003) Result: hostbyte=0x01 driverbyte=0x00 cmd_age=1s [ 9692.842766][ C109] sd 0:1:0:0: [sda] tag#393 UNKNOWN(0x2003) Result: hostbyte=0x01 driverbyte=0x00 cmd_age=1s [ 9692.842811][ C109] sd 0:1:0:0: [sda] tag#393 CDB: opcode=0x2a 2a 00 01 60 c8 00 00 02 00 00 [ 9692.842840][ C13] sd 0:1:0:0: [sda] tag#324 UNKNOWN(0x2003) Result: hostbyte=0x01 driverbyte=0x00 cmd_age=1s [ 9692.842924][ C18] sd 0:1:0:0: [sda] tag#616 CDB: opcode=0x2a 2a 00 01 c7 8c 00 00 02 00 00 [ 9692.842932][ C109] blk_update_request: I/O error, dev sda, sector 23119872 op 0x1:(WRITE) flags 0x8004000 phys_seg 4 prio class 0 [ 9692.842938][ C28] sd 0:1:0:0: [sda] tag#841 CDB: opcode=0x2a 2a 00 03 2f cc 00 00 02 00 00 [ 9692.842984][ T213] sd 0:1:0:0: [sda] tag#47 UNKNOWN(0x2003) Result: hostbyte=0x01 driverbyte=0x00 cmd_age=1s [ 9692.842995][ C28] blk_update_request: I/O error, dev sda, sector 53464064 op 0x1:(WRITE) flags 0x8004000 phys_seg 4 prio class 0 [ 9692.843000][ C81] sd 0:1:0:0: [sda] tag#10 UNKNOWN(0x2003) Result: hostbyte=0x01 driverbyte=0x00 cmd_age=1s [ 9692.843031][ C18] blk_update_request: I/O error, dev sda, sector 29854720 op 0x1:(WRITE) flags 0x8004000 phys_seg 4 prio class 0 [ 9692.843056][ C13] sd 0:1:0:0: [sda] tag#324 CDB: opcode=0x2a 2a 00 03 17 66 00 00 02 00 00 [ 9692.843101][ C81] sd 0:1:0:0: [sda] tag#10 CDB: opcode=0x2a 2a 00 00 52 a4 00 00 02 00 00 [ 9692.843129][ C13] blk_update_request: I/O error, dev sda, sector 51865088 op 0x1:(WRITE) flags 0x8004000 phys_seg 4 prio class 0 [ 9692.843192][ C81] blk_update_request: I/O error, dev sda, sector 5415936 op 0x1:(WRITE) flags 0x8004000 phys_seg 4 prio class 0 [ 9692.843338][ T213] sd 0:1:0:0: [sda] tag#47 CDB: opcode=0x2a 2a 00 02 be 5a 00 00 02 00 00 [ 9692.843358][ C13] sd 0:1:0:0: [sda] tag#325 UNKNOWN(0x2003) Result: hostbyte=0x01 driverbyte=0x00 cmd_age=1s [ 9692.843480][ T213] blk_update_request: I/O error, dev sda, sector 46029312 op 0x1:(WRITE) flags 0x8004000 phys_seg 4 prio class 0 [ 9692.843485][ C13] sd 0:1:0:0: [sda] tag#325 CDB: opcode=0x2a 2a 00 03 17 68 00 00 02 00 00 [ 9692.843510][ C13] blk_update_request: I/O error, dev sda, sector 51865600 op 0x1:(WRITE) flags 0x8004000 phys_seg 4 prio class 0 [ 9692.843685][ C103] blk_update_request: I/O error, dev sda, sector 34941952 op 0x1:(WRITE) flags 0x8004000 phys_seg 4 prio class 0 [ 9692.843725][ C96] sd 0:1:0:0: [sda] tag#877 UNKNOWN(0x2003) Result: hostbyte=0x01 driverbyte=0x00 cmd_age=1s [ 9692.843744][ C92] Write-error on swap-device (254:1:39256632) [ 9692.843791][ C118] sd 0:1:0:0: [sda] tag#230 UNKNOWN(0x2003) Result: hostbyte=0x01 driverbyte=0x00 cmd_age=1s [ 9692.843866][ C64] Write-error on swap-device (254:1:63030016) [ 9692.843891][ C96] sd 0:1:0:0: [sda] tag#877 CDB: opcode=0x2a 2a 00 03 1e 48 00 00 02 00 00 [ 9692.844013][ C118] sd 0:1:0:0: [sda] tag#230 CDB: opcode=0x2a 2a 00 03 c6 26 00 00 02 00 00 [ 9692.844615][ C92] Write-error on swap-device (254:1:39256640) [ 9692.844643][ C64] Write-error on swap-device (254:1:63030024) [ 9692.845109][ C61] Write-error on swap-device (254:1:17105384) [ 9692.845192][ C25] page:fffff3b2ec3a8000 refcount:512 mapcount:0 mapping:000000009eb0338c index:0x7f6e58200 head:fffff3b2ec3a8000 order:9 compound_mapcount:0 compound_pincount:0 [ 9692.845226][ C25] anon flags: 0x45fffe0000d8454(uptodate|lru|workingset|owner_priv_1|writeback|head|reclaim|swapbacked) [ 9692.845254][ C25] raw: 045fffe0000d8454 fffff3b2f9d48008 fffff3b2f3270008 ffff97c3090f8209 [ 9692.845283][ C25] raw: 00000007f6e58200 000000000053c800 00000200ffffffff ffff97c8d71e9000 [ 9692.845293][ C122] Write-error on swap-device (254:1:39080184) [ 9692.845316][ T213] page:fffff3b2f77d8000 refcount:512 mapcount:0 mapping:00000000a4517f4e index:0x7f69d2200 head:fffff3b2f77d8000 order:9 compound_mapcount:0 compound_pincount:0 [ 9692.845330][ C25] page dumped because: VM_BUG_ON_PAGE(1 && PageCompound(page)) [ 9692.845427][ T213] anon flags: 0x45fffe0000d8454(uptodate|lru|workingset|owner_priv_1|writeback|head|reclaim|swapbacked) [ 9692.845433][ C25] page->mem_cgroup:ffff97c8d71e9000 [ 9692.845443][ C25] page_owner tracks the page as allocated [ 9692.845520][ T213] raw: 045fffe0000d8454 fffff3b2f5ec2f08 fffff3b2f6b88008 ffff97c715cc0609 [ 9692.845535][ C25] page last allocated via order 9, migratetype Movable, gfp_mask 0x1c20ca(GFP_TRANSHUGE_LIGHT) [ 9692.845606][ C25] prep_new_page+0x1cd/0x1f0 [ 9692.845628][ C25] get_page_from_freelist+0x18ac/0x24d0 [ 9692.845639][ T213] raw: 00000007f69d2200 00000000000bf400 00000200ffffffff ffff97c8d71e9000 [ 9692.845654][ C25] __alloc_pages_nodemask+0x1b1/0x450 [ 9692.845733][ T213] page dumped because: VM_BUG_ON_PAGE(1 && PageCompound(page)) [ 9692.845757][ C25] alloc_pages_vma+0x8a/0x2c0 [ 9692.845762][ T213] page->mem_cgroup:ffff97c8d71e9000 [ 9692.845779][ C25] do_huge_pmd_anonymous_page+0x1d4/0xc30 [ 9692.845786][ T213] page_owner tracks the page as allocated [ 9692.845807][ C25] __handle_mm_fault+0xd27/0xd50 [ 9692.845819][ T213] page last allocated via order 9, migratetype Movable, gfp_mask 0x1c20ca(GFP_TRANSHUGE_LIGHT) [ 9692.845833][ C25] handle_mm_fault+0xfc/0x2f0 [ 9692.845856][ T213] prep_new_page+0x1cd/0x1f0 [ 9692.845876][ C25] do_page_fault+0x263/0x6f9 [ 9692.845892][ T213] get_page_from_free7219][ C25] clone_endio+0xe4/0x2c0 [dm_mod] [ 9692.847226][ T213] kernel BUG at include/linux/page-flags.h:317! [ 9692.847234][ C64] Write-error on swap-device (254:1:63030064) [ 9692.847250][ C25] bio_endio+0x297/0x560 [ 9692.847255][ C61] Write-error on swap-device (254:1:17105424) [ 9692.847263][ C25] ? bio_advance+0x92/0x190 [ 9692.847267][ C122] Write-error on swap-device (254:1:39080224) [ 9692.847276][ C25] blk_update_request+0x201/0x920 [ 9692.847287][ C25] ? ___ratelimit+0x138/0x1e0 [ 9692.847312][ C25] scsi_end_request+0x6b/0x4b0 [ 9692.847320][ C25] ? ___ratelimit+0x3e/0x1e0 [ 9692.847329][ C25] scsi_io_completion+0x509/0x7e0 [ 9692.847340][ C25] scsi_finish_command+0x1ed/0x2a0 [ 9692.847350][ C25] scsi_softirq_done+0x1c9/0x1d0 [ 9692.847354][ C64] Write-error on swap-device (254:1:63030072) [ 9692.847363][ C25] ? blk_mq_check_inflight+0xa0/0xa0 [ 9692.847383][ C61] Write-error on swap-device (254:1:17105432) [ 9692.847397][ C122] Write-erro692.848242][ C25] RSP: 0018:ffffb02006b68bb0 EFLAGS: 00010086 [ 9692.848333][ T213] Workqueue: events pqi_ctrl_offline_worker [smartpqi] [ 9692.848346][ C61] Write-error on swap-device (254:1:17105528) [ 9692.848351][ C122] Write-error on swap-device (254:1:39080328) [ 9692.848428][ C25] RAX: 0000000000000000 RBX: ffff97c76d8d4b80 RCX: ffffffff9d51e8f0 [ 9692.848433][ C61] Write-error on swap-device (254:1:17105536) [ 9692.848437][ C122] Write-error on swap-device (254:1:39080336) [ 9692.848445][ T213] RIP: 0010:end_swap_bio_write+0x90/0x280 [ 9692.848450][ C25] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff97c7e539f00a [ 9692.848461][ T213] Code: 80 7b 1a 00 0f 84 58 01 00 00 4c 89 e6 bf 10 00 00 00 e8 33 f8 ff ff 84 c0 74 1d 48 c7 c6 18 7e 3b 9a 4c 89 e7 e8 20 78 fa ff <0f> 0b 48 c7 c7 b0 0b 6e 9a e8 04 ee 2b 00 4d 8d 74 24 08 ba 08 00 [ 9692.848466][ C25] RBP: ffffb02006b68bf0 R08: 0000000000000000 R09: 000097c7e539f00a [ 9692.848471][ T213] RSP: 0018:ffffb02006dd3908 EFLAGS: 00010286 [ 9692.848485][ C25] R10: 0000b02006b689a0 R11: 000097c7e5ax_pmem_core efivars acpi_cpufreq efivarfs ip_tables x_tables xfs sd_mod smartpqi scsi_transport_sas tg3 mlx5_core [ 9692.849818][ C122] Write-error on swap-device (254:1:39080440) [ 9692.849884][ T213] libphy [ 9692.849889][ C122] Write-error on swap-device (254:1:39080448) [ 9692.849952][ T213] firmware_class [ 9692.849959][ C122] Write-error on swap-device (254:1:39080456) [ 9692.849963][ T213] dm_mirror dm_region_hash dm_log dm_mod [ 9692.849990][ C122] Write-error on swap-device (254:1:39080464) [ 9692.850069][ C122] Write-error on swap-device (254:1:39080472) [ 9692.850107][ C122] Write-error on swap-device (254:1:39080480) [ 9692.850156][ C122] Write-error on swap-device (254:1:39080488) [ 9692.850220][ C122] Write-error on swap-device (254:1:39080496) [ 9692.850264][ C122] Write-error on swap-device (254:1:39080504) [ 9692.850323][ C122] Write-error on swap-device (254:1:39080512) [ 9692.850361][ C122] Write-error on swap-device (254:1:39080520) [ 9692.850411][ C122] Write-error on swap-device (254:1:39080528) > > Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx > Signed-off-by: Rafael Aquini <aquini@xxxxxxxxxx> > --- > mm/mprotect.c | 38 ++++++++++++++++++++++++++++++++++++-- > 1 file changed, 36 insertions(+), 2 deletions(-) > > diff --git a/mm/mprotect.c b/mm/mprotect.c > index 7a8e84f86831..9ea8cc0ab2fd 100644 > --- a/mm/mprotect.c > +++ b/mm/mprotect.c > @@ -161,6 +161,31 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd, > return pages; > } > > +/* > + * Used when setting automatic NUMA hinting protection where it is > + * critical that a numa hinting PMD is not confused with a bad PMD. > + */ > +static inline int pmd_none_or_clear_bad_unless_trans_huge(pmd_t *pmd) > +{ > + pmd_t pmdval = pmd_read_atomic(pmd); > + > + /* See pmd_none_or_trans_huge_or_clear_bad for info on barrier */ > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > + barrier(); > +#endif > + > + if (pmd_none(pmdval)) > + return 1; > + if (pmd_trans_huge(pmdval)) > + return 0; > + if (unlikely(pmd_bad(pmdval))) { > + pmd_clear_bad(pmd); > + return 1; > + } > + > + return 0; > +} > + > static inline unsigned long change_pmd_range(struct vm_area_struct *vma, > pud_t *pud, unsigned long addr, unsigned long end, > pgprot_t newprot, int dirty_accountable, int prot_numa) > @@ -178,8 +203,17 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, > unsigned long this_pages; > > next = pmd_addr_end(addr, end); > - if (!is_swap_pmd(*pmd) && !pmd_trans_huge(*pmd) && !pmd_devmap(*pmd) > - && pmd_none_or_clear_bad(pmd)) > + > + /* > + * Automatic NUMA balancing walks the tables with mmap_sem > + * held for read. It's possible a parallel update to occur > + * between pmd_trans_huge() and a pmd_none_or_clear_bad() > + * check leading to a false positive and clearing. > + * Hence, it's ecessary to atomically read the PMD value > + * for all the checks. > + */ > + if (!is_swap_pmd(*pmd) && !pmd_devmap(*pmd) && > + pmd_none_or_clear_bad_unless_trans_huge(pmd)) > goto next; > > /* invoke the mmu notifier if the pmd is populated */ > -- > 2.24.1 > >
