[PATCH v6 05/10] mm/memory_hotplug: Shrink zones when offlining memory

Mon Oct 14 20:39:13 AEDT 2019

On 06.10.19 10:56, David Hildenbrand wrote:
> We currently try to shrink a single zone when removing memory. We use the
> zone of the first page of the memory we are removing. If that memmap was
> never initialized (e.g., memory was never onlined), we will read garbage
> and can trigger kernel BUGs (due to a stale pointer):
> 
> :/# [   23.912993] BUG: unable to handle page fault for address: 000000000000353d
> [   23.914219] #PF: supervisor write access in kernel mode
> [   23.915199] #PF: error_code(0x0002) - not-present page
> [   23.916160] PGD 0 P4D 0
> [   23.916627] Oops: 0002 [#1] SMP PTI
> [   23.917256] CPU: 1 PID: 7 Comm: kworker/u8:0 Not tainted 5.3.0-rc5-next-20190820+ #317
> [   23.918900] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.4
> [   23.921194] Workqueue: kacpi_hotplug acpi_hotplug_work_fn
> [   23.922249] RIP: 0010:clear_zone_contiguous+0x5/0x10
> [   23.923173] Code: 48 89 c6 48 89 c3 e8 2a fe ff ff 48 85 c0 75 cf 5b 5d c3 c6 85 fd 05 00 00 01 5b 5d c3 0f 1f 840
> [   23.926876] RSP: 0018:ffffad2400043c98 EFLAGS: 00010246
> [   23.927928] RAX: 0000000000000000 RBX: 0000000200000000 RCX: 0000000000000000
> [   23.929458] RDX: 0000000000200000 RSI: 0000000000140000 RDI: 0000000000002f40
> [   23.930899] RBP: 0000000140000000 R08: 0000000000000000 R09: 0000000000000001
> [   23.932362] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000140000
> [   23.933603] R13: 0000000000140000 R14: 0000000000002f40 R15: ffff9e3e7aff3680
> [   23.934913] FS:  0000000000000000(0000) GS:ffff9e3e7bb00000(0000) knlGS:0000000000000000
> [   23.936294] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   23.937481] CR2: 000000000000353d CR3: 0000000058610000 CR4: 00000000000006e0
> [   23.938687] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [   23.939889] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [   23.941168] Call Trace:
> [   23.941580]  __remove_pages+0x4b/0x640
> [   23.942303]  ? mark_held_locks+0x49/0x70
> [   23.943149]  arch_remove_memory+0x63/0x8d
> [   23.943921]  try_remove_memory+0xdb/0x130
> [   23.944766]  ? walk_memory_blocks+0x7f/0x9e
> [   23.945616]  __remove_memory+0xa/0x11
> [   23.946274]  acpi_memory_device_remove+0x70/0x100
> [   23.947308]  acpi_bus_trim+0x55/0x90
> [   23.947914]  acpi_device_hotplug+0x227/0x3a0
> [   23.948714]  acpi_hotplug_work_fn+0x1a/0x30
> [   23.949433]  process_one_work+0x221/0x550
> [   23.950190]  worker_thread+0x50/0x3b0
> [   23.950993]  kthread+0x105/0x140
> [   23.951644]  ? process_one_work+0x550/0x550
> [   23.952508]  ? kthread_park+0x80/0x80
> [   23.953367]  ret_from_fork+0x3a/0x50
> [   23.954025] Modules linked in:
> [   23.954613] CR2: 000000000000353d
> [   23.955248] ---[ end trace 93d982b1fb3e1a69 ]---
> 
> Instead, shrink the zones when offlining memory or when onlining failed.
> Introduce and use remove_pfn_range_from_zone(() for that. We now properly
> shrink the zones, even if we have DIMMs whereby
> - Some memory blocks fall into no zone (never onlined)
> - Some memory blocks fall into multiple zones (offlined+re-onlined)
> - Multiple memory blocks that fall into different zones
> 
> Drop the zone parameter (with a potential dubious value) from
> __remove_pages() and __remove_section().
> 
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Will Deacon <will at kernel.org>
> Cc: Tony Luck <tony.luck at intel.com>
> Cc: Fenghua Yu <fenghua.yu at intel.com>
> Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> Cc: Paul Mackerras <paulus at samba.org>
> Cc: Michael Ellerman <mpe at ellerman.id.au>
> Cc: Heiko Carstens <heiko.carstens at de.ibm.com>
> Cc: Vasily Gorbik <gor at linux.ibm.com>
> Cc: Christian Borntraeger <borntraeger at de.ibm.com>
> Cc: Yoshinori Sato <ysato at users.sourceforge.jp>
> Cc: Rich Felker <dalias at libc.org>
> Cc: Dave Hansen <dave.hansen at linux.intel.com>
> Cc: Andy Lutomirski <luto at kernel.org>
> Cc: Peter Zijlstra <peterz at infradead.org>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: Ingo Molnar <mingo at redhat.com>
> Cc: Borislav Petkov <bp at alien8.de>
> Cc: "H. Peter Anvin" <hpa at zytor.com>
> Cc: x86 at kernel.org
> Cc: Andrew Morton <akpm at linux-foundation.org>
> Cc: Mark Rutland <mark.rutland at arm.com>
> Cc: Steve Capper <steve.capper at arm.com>
> Cc: Mike Rapoport <rppt at linux.ibm.com>
> Cc: Anshuman Khandual <anshuman.khandual at arm.com>
> Cc: Yu Zhao <yuzhao at google.com>
> Cc: Jun Yao <yaojun8558363 at gmail.com>
> Cc: Robin Murphy <robin.murphy at arm.com>
> Cc: Michal Hocko <mhocko at suse.com>
> Cc: Oscar Salvador <osalvador at suse.de>
> Cc: "Matthew Wilcox (Oracle)" <willy at infradead.org>
> Cc: Christophe Leroy <christophe.leroy at c-s.fr>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar at linux.ibm.com>
> Cc: Pavel Tatashin <pasha.tatashin at soleen.com>
> Cc: Gerald Schaefer <gerald.schaefer at de.ibm.com>
> Cc: Halil Pasic <pasic at linux.ibm.com>
> Cc: Tom Lendacky <thomas.lendacky at amd.com>
> Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> Cc: Masahiro Yamada <yamada.masahiro at socionext.com>
> Cc: Dan Williams <dan.j.williams at intel.com>
> Cc: Wei Yang <richard.weiyang at gmail.com>
> Cc: Qian Cai <cai at lca.pw>
> Cc: Jason Gunthorpe <jgg at ziepe.ca>
> Cc: Logan Gunthorpe <logang at deltatee.com>
> Cc: Ira Weiny <ira.weiny at intel.com>
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: linux-ia64 at vger.kernel.org
> Cc: linuxppc-dev at lists.ozlabs.org
> Cc: linux-s390 at vger.kernel.org
> Cc: linux-sh at vger.kernel.org
> Fixes: d0dc12e86b31 ("mm/memory_hotplug: optimize memory hotplug")

@Andrew, can you convert that to

Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") # visible after d0dc12e86b319

While adding cc'ing stable at vger.kernel.org # v4.13+ would be nice,
I doubt it will be easily possible to backport, as we are missing
some prereq patches (e.g., from Oscar like 2c2a5af6fed2 ("mm,
memory_hotplug: add nid parameter to arch_remove_memory")). But, it could
be done with some work.

I think "Cc: stable at vger.kernel.org # v5.0+" could be done more
easily. Maybe it's okay to not cc:stable this one. We usually
online all memory (except s390x), however, s390x does not remove that
memory ever. Devmem with driver reserved memory would be, however,
worth backporting this.

Thoughts?

-- 

Thanks,

David / dhildenb