Re: Kernel crash after "mm: initialize pages on demand during boot"

From: Michal Hocko
Date: Wed Jun 27 2018 - 03:19:35 EST

This smells like an issue Naoya was seeing I guess (Cced)

On Tue 26-06-18 17:41:52, Herton R. Krzesinski wrote:
> Hi,
>
> While running proc01 test from ltp, or as I later found out if you just read
> kpagecount ("cat /proc/kpagecount > /dev/null"), I started to get the following
> oops on latest kernels (4.17+) in a specific system:
>
> [ 112.926100] general protection fault: 0000 [#1] SMP PTI
> [ 112.926691] CPU: 1 PID: 1230 Comm: proc01 Not tainted 4.18.0-rc2+ #1
> [ 112.927780] Hardware name: Dell Inc. PowerEdge C5220/0KXND9, BIOS 1.0.10 08/12/2011
> [ 112.928680] RIP: 0010:kpagecount_read+0xdd/0x160
> [ 112.929273] Code: 04 48 01 d7 74 9b f6 07 02 74 96 4c 89 ff 48 c1 e7 06 48 03 3d 14 36 c1 00 74 86 48 8b 4f 08 48 8d 51 ff 83 e1 01 48 0f 44 d7 <48> 8b 12 80 e6 01 0f 85 6b ff ff ff 48 8b 07 f6 c4 80 74 0c e8 4a
> [ 112.931444] RSP: 0018:ffffa67980bd3e08 EFLAGS: 00010202
> [ 112.932079] RAX: 0000000000000000 RBX: 00007fffffffeff9 RCX: 0000000000000001
> [ 112.932871] RDX: 3480e5b7a7da5592 RSI: 000000000063e680 RDI: ffffe03441fcf940
> [ 112.933630] RBP: 0000000000000400 R08: 0000000000000000 R09: 0000000000000001
> [ 112.934470] R10: ffffa67980bd3ed8 R11: 0000000000000000 R12: 000000000063e680
> [ 112.935283] R13: ffffa67980bd3f08 R14: 000000000063e9a8 R15: 000000000007f3e5
> [ 112.936149] FS: 00007fb682eab580(0000) GS:ffff9af0bf080000(0000) knlGS:0000000000000000
> [ 112.937094] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 112.937791] CR2: 00007ffe550ccff8 CR3: 0000000071de0004 CR4: 00000000000606e0
> [ 112.938603] Call Trace:
> [ 112.938866] proc_reg_read+0x3c/0x60
> [ 112.939296] __vfs_read+0x36/0x180
> [ 112.939778] vfs_read+0x8a/0x140
> [ 112.940118] ksys_read+0x4f/0xb0
> [ 112.940535] do_syscall_64+0x5b/0x180
> [ 112.940965] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 112.941736] RIP: 0033:0x7fb6829dba49
> [ 112.942196] Code: 00 48 8b 35 79 f4 2a 00 31 c9 64 83 3e 0b 75 c6 eb b4 e8 ca fb ff ff 66 2e 0f 1f 84 00 00 00 00 00 48 39 ca 77 27 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 07 c3 66 0f 1f 44 00 00 48 8b 15 41 f4 2a 00
> [ 112.944237] RSP: 002b:00007ffe550d4018 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
> [ 112.945151] RAX: ffffffffffffffda RBX: 0000000000000400 RCX: 00007fb6829dba49
> [ 112.945978] RDX: 0000000000000400 RSI: 000000000063e680 RDI: 0000000000000004
> [ 112.946773] RBP: 00007ffe550d5190 R08: 000000000133a81b R09: 00007ffe550d4a60
> [ 112.947536] R10: 0000000000000000 R11: 0000000000000246 R12: 00000000003f9c00
> [ 112.948521] R13: 0000000000000004 R14: 0000000000437b22 R15: 0000000000000000
> [ 112.949341] Modules linked in: binfmt_misc sunrpc intel_rapl x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel iTCO_wdt intel_cstate ipmi_ssif intel_uncore gpio_ich iTCO_vendor_support ipmi_si intel_rapl_perf dcdbas joydev pcspkr ipmi_devintf ipmi_msghandler sg ie31200_edac mei_me i2c_i801 lpc_ich mei xfs libcrc32c sd_mod ast drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm igb ahci libahci libata ptp crc32c_intel pps_core dca i2c_algo_bit dm_mirror dm_region_hash dm_log dm_mod
> [ 112.954919] ---[ end trace 36aa5a2dececb838 ]---
>
> In last days, I have been investigating this issue. While looking at the crash
> itself, I noticed it crashes on what looked like a non-initialized struct page.
> In the oops above, we have R15 = 7f3e5, which is pfn number in the loop at
> kpagecount_read():
>
> /home/rpmbuild/BUILD/kernel-4.18.0_rc2+/fs/proc/page.c: 59
> 0xffffffffb7d16494 <kpagecount_read+100>: callq 0xffffffffb81f3fc0 <_cond_resched>
> 0xffffffffb7d16499 <kpagecount_read+105>: add $0x8,%r14
> 0xffffffffb7d1649d <kpagecount_read+109>: lea (%r12,%rbp,1),%rax
> 0xffffffffb7d164a1 <kpagecount_read+113>: add $0x1,%r15
>
> At the same time, I started bisecting, since this didn't happen with 4.16 kernel.
> I ended up isolating the following commit as the trigger to this issue:
>
> git bisect bad c9e97a1997fbf3a1d18d4065c2ca381f0704d7e5
> # first bad commit: [c9e97a1997fbf3a1d18d4065c2ca381f0704d7e5] mm: initialize pages on demand during boot
>
> While looking at the commit, I did not see any issue with it, other than
> on the system I see the crash, it started to do deferred page initialization
> while it didn't before. And that's the key here. If you look at dmesg of the
> system:
>
> ...
> [ 0.000000] BIOS-provided physical RAM map:
> [ 0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009a3ff] usable
> [ 0.000000] BIOS-e820: [mem 0x000000000009a400-0x000000000009ffff] reserved
> [ 0.000000] BIOS-e820: [mem 0x00000000000e0000-0x00000000000fffff] reserved
> [ 0.000000] BIOS-e820: [mem 0x0000000000100000-0x000000007f3e4fff] usable
> [ 0.000000] BIOS-e820: [mem 0x000000007f3e5000-0x000000007f42cfff] ACPI NVS
> [ 0.000000] BIOS-e820: [mem 0x000000007f42d000-0x000000007f433fff] ACPI data
> [ 0.000000] BIOS-e820: [mem 0x000000007f434000-0x000000007f504fff] reserved
> [ 0.000000] BIOS-e820: [mem 0x000000007f505000-0x000000007f50ffff] ACPI NVS
> [ 0.000000] BIOS-e820: [mem 0x000000007f510000-0x000000007f535fff] reserved
> [ 0.000000] BIOS-e820: [mem 0x000000007f536000-0x000000007f578fff] ACPI NVS
> [ 0.000000] BIOS-e820: [mem 0x000000007f579000-0x000000007f7fffff] usable
> [ 0.000000] BIOS-e820: [mem 0x00000000e0000000-0x00000000efffffff] reserved
> [ 0.000000] BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed3ffff] reserved
> [ 0.000000] BIOS-e820: [mem 0x00000000ff000000-0x00000000ffffffff] reserved
> [ 0.000000] NX (Execute Disable) protection: active
> [ 0.000000] SMBIOS 2.7 present.
> [ 0.000000] DMI: Dell Inc. PowerEdge C5220/0KXND9, BIOS 1.0.10 08/12/2011
> [ 0.000000] e820: update [mem 0x00000000-0x00000fff] usable ==> reserved
> [ 0.000000] e820: remove [mem 0x000a0000-0x000fffff] usable
> [ 0.000000] last_pfn = 0x7f800 max_arch_pfn = 0x400000000
> ...
> [ 0.000000] NODE_DATA(0) allocated [mem 0x7f7d6000-0x7f7fffff]
> [ 0.000000] MEMBLOCK configuration:
> [ 0.000000] memory size = 0x000000007f605400 reserved size = 0x0000000005fe2000
> [ 0.000000] memory.cnt = 0x3
> [ 0.000000] memory[0x0] [0x0000000000001000-0x0000000000099fff], 0x0000000000099000 bytes on node 0 flags: 0x0
> [ 0.000000] memory[0x1] [0x0000000000100000-0x000000007f3e4fff], 0x000000007f2e5000 bytes on node 0 flags: 0x0
> [ 0.000000] memory[0x2] [0x000000007f579000-0x000000007f7fffff], 0x0000000000287000 bytes on node 0 flags: 0x0
> [ 0.000000] reserved.cnt = 0x5
> [ 0.000000] reserved[0x0] [0x0000000000000000-0x000000000000ffff], 0x0000000000010000 bytes on node 0 flags: 0x0
> [ 0.000000] reserved[0x1] [0x0000000000094000-0x00000000000fffff], 0x000000000006c000 bytes on node 0 flags: 0x0
> [ 0.000000] reserved[0x2] [0x0000000025000000-0x0000000026aa1fff], 0x0000000001aa2000 bytes on node 0 flags: 0x0
> [ 0.000000] reserved[0x3] [0x000000002f6bc000-0x0000000033b55fff], 0x000000000449a000 bytes on node 0 flags: 0x0
> [ 0.000000] reserved[0x4] [0x000000007f7d6000-0x000000007f7fffff], 0x000000000002a000 bytes flags: 0x0
> ...
> [ 0.000000] Zone ranges:
> [ 0.000000] DMA [mem 0x0000000000001000-0x0000000000ffffff]
> [ 0.000000] DMA32 [mem 0x0000000001000000-0x000000007f7fffff]
> [ 0.000000] Normal empty
> [ 0.000000] Device empty
> [ 0.000000] Movable zone start for each node
> [ 0.000000] Early memory node ranges
> [ 0.000000] node 0: [mem 0x0000000000001000-0x0000000000099fff]
> [ 0.000000] node 0: [mem 0x0000000000100000-0x000000007f3e4fff]
> [ 0.000000] node 0: [mem 0x000000007f579000-0x000000007f7fffff]
> [ 0.000000] Initmem setup node 0 [mem 0x0000000000001000-0x000000007f7fffff]
> [ 0.000000] On node 0 totalpages: 521733
> [ 0.000000] DMA zone: 64 pages used for memmap
> [ 0.000000] DMA zone: 21 pages reserved
> [ 0.000000] DMA zone: 3993 pages, LIFO batch:0
> [ 0.000000] DMA32 zone: 8096 pages used for memmap
> [ 0.000000] DMA32 zone: 517740 pages, LIFO batch:31
> [ 0.000000] Reserved but unavailable: 103 pages
> ...
>
> You you notice something right away: there is a hole in the range
> 0x0000000000001000-0x000000007f7fffff, which is between
> 0x000000007f3e5000 to 0x000000007f578fff. It's not a coincidence
> that the pfn 0x7f3e5 is part of the crash.
>
> Without deferred init page, the mem section with struct pages were being
> initialized in the loop at memmap_init_zone(). That's not the case anymore
> if you lower the number of pages you initialized. Later the
> for_each_free_mem_range loop at deferred_init_memmap() will only touch
> the memory block, the hole above will be kept unitialized. On the system,
> there are some ACPI ranges in the hole as you can see on dmesg, and when
> something tries to touch pages there unitialized, you can get the oops.
>
> I played with some approaches to try to avoid this. One would be to somehow guess
> a big pgdat->static_init_pgcnt so that we don't use deferred init for this case.
>
> Other way would be to mark the ACPI areas as reserved, so the reserved pages are
> initialized by deferred init code, after this patch the crash did not happen
> anymore here:
>
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -736,8 +736,10 @@ void __init e820__register_nosave_regions(unsigned long limit_pfn)
>
> pfn = PFN_DOWN(entry->addr + entry->size);
>
> - if (entry->type != E820_TYPE_RAM && entry->type != E820_TYPE_RESERVED_KERN)
> + if (entry->type != E820_TYPE_RAM && entry->type != E820_TYPE_RESERVED_KERN) {
> register_nosave_region(PFN_UP(entry->addr), pfn);
> + memblock_reserve(entry->addr, entry->size);
> + }
>
> if (pfn >= limit_pfn)
> break;
>
> However, not sure if there isn't anything else we could miss. I tried another
> fix, which is to force initialization of the holes:
>
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index ca59883c8364..cad4703136d6 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -95,6 +95,8 @@ ulong choose_memblock_flags(void);
> int memblock_add_range(struct memblock_type *type,
> phys_addr_t base, phys_addr_t size,
> int nid, unsigned long flags);
> +int memblock_remove_range(struct memblock_type *type,
> + phys_addr_t base, phys_addr_t size);
>
> void __next_mem_range(u64 *idx, int nid, ulong flags,
> struct memblock_type *type_a,
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 03d48d8835ba..cc99e89d71f0 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -680,7 +680,7 @@ static int __init_memblock memblock_isolate_range(struct memblock_type *type,
> return 0;
> }
>
> -static int __init_memblock memblock_remove_range(struct memblock_type *type,
> +int __init_memblock memblock_remove_range(struct memblock_type *type,
> phys_addr_t base, phys_addr_t size)
> {
> int start_rgn, end_rgn;
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 1521100f1e63..93e8bb0da72d 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5468,6 +5468,17 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
> struct page *page;
> #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
> struct memblock_region *r = NULL, *tmp;
> + static struct memblock_region hole_regions[INIT_MEMBLOCK_REGIONS];
> + struct memblock_type holes = {
> + .regions = hole_regions,
> + .cnt = 1,
> + .max = INIT_MEMBLOCK_REGIONS,
> + .name = "holes",
> + };
> + unsigned long spfn, epfn;
> + phys_addr_t start, end;
> + int i;
> + u64 j;
> #endif
>
> if (highest_memmap_pfn < end_pfn - 1)
> @@ -5492,10 +5503,22 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
> continue;
> if (!early_pfn_in_nid(pfn, nid))
> continue;
> - if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised))
> - break;
>
> #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
> + /* Make sure we initialize pages outside of memory ranges */
> + if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised)) {
> + memblock_add_range(&holes, PFN_PHYS(pfn), PFN_PHYS(end_pfn - pfn), nid, MEMBLOCK_NONE);
> + for_each_mem_pfn_range(i, nid, &spfn, &epfn, NULL)
> + memblock_remove_range(&holes, PFN_PHYS(spfn), PFN_PHYS(epfn - spfn));
> + for_each_mem_range(j, &holes, NULL, nid, MEMBLOCK_NONE, &start, &end, NULL) {
> + for (pfn = PFN_UP(start); pfn < PFN_DOWN(end); pfn++) {
> + struct page *page = pfn_to_page(pfn);
> + __init_single_page(page, pfn, zone, nid);
> + }
> + }
> + break;
> + }
> +
> /*
> * Check given memblock attribute by firmware which can affect
> * kernel memory layout. If zone==ZONE_MOVABLE but memory is
> @@ -5515,6 +5538,9 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
> continue;
> }
> }
> +#else
> + if (!update_defer_init(pgdat, pfn, end_pfn, &nr_initialised))
> + break;
> #endif
>
> not_early:
>
>
>
> This second change fixed the issue for me as well. I just want to report the
> issue and can submit a patch if one of approaches above are acceptable, and I
> did not miss anything.
>
> Thanks,
> --
> []'s
> Herton

--
Michal Hocko
SUSE Labs