Ignore my above comments. I bisected this again using a more reliable
reproducer and found the first bad commit to be:
f1dd2cd13c4bbbc9a7c4617b3b034fa643de98fe is the first bad commit
commit f1dd2cd13c4bbbc9a7c4617b3b034fa643de98fe
Author: Michal Hocko <[email protected]>
Date: Thu Jul 6 15:38:11 2017 -0700
mm, memory_hotplug: do not associate hotadded memory to zones until online
The current memory hotplug implementation relies on having all the
struct pages associate with a zone/node during the physical hotplug
phase (arch_add_memory->__add_pages->__add_section->__add_zone). In the
vast majority of cases this means that they are added to ZONE_NORMAL.
This has been so since 9d99aaa31f59 ("[PATCH] x86_64: Support memory
hotadd without sparsemem") and it wasn't a big deal back then because
movable onlining didn't exist yet.
Much later memory hotplug wanted to (ab)use ZONE_MOVABLE for movable
onlining 511c2aba8f07 ("mm, memory-hotplug: dynamic configure movable
memory and portion memory") and then things got more complicated.
Rather than reconsidering the zone association which was no longer
needed (because the memory hotplug already depended on SPARSEMEM) a
convoluted semantic of zone shifting has been developed. Only the
currently last memblock or the one adjacent to the zone_movable can be
onlined movable. This essentially means that the online type changes as
the new memblocks are added.
Let's simulate memory hot online manually
$ echo 0x100000000 > /sys/devices/system/memory/probe
$ grep . /sys/devices/system/memory/memory32/valid_zones
Normal Movable
$ echo $((0x100000000+(128<<20))) > /sys/devices/system/memory/probe
$ grep . /sys/devices/system/memory/memory3?/valid_zones
/sys/devices/system/memory/memory32/valid_zones:Normal
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
$ echo $((0x100000000+2*(128<<20))) > /sys/devices/system/memory/probe
$ grep . /sys/devices/system/memory/memory3?/valid_zones
/sys/devices/system/memory/memory32/valid_zones:Normal
/sys/devices/system/memory/memory33/valid_zones:Normal
/sys/devices/system/memory/memory34/valid_zones:Normal Movable
$ echo online_movable > /sys/devices/system/memory/memory34/state
$ grep . /sys/devices/system/memory/memory3?/valid_zones
/sys/devices/system/memory/memory32/valid_zones:Normal
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Movable Normal
This is an awkward semantic because an udev event is sent as soon as the
block is onlined and an udev handler might want to online it based on
some policy (e.g. association with a node) but it will inherently race
with new blocks showing up.
This patch changes the physical online phase to not associate pages with
any zone at all. All the pages are just marked reserved and wait for
the onlining phase to be associated with the zone as per the online
request. There are only two requirements
- existing ZONE_NORMAL and ZONE_MOVABLE cannot overlap
- ZONE_NORMAL precedes ZONE_MOVABLE in physical addresses
the latter one is not an inherent requirement and can be changed in the
future. It preserves the current behavior and made the code slightly
simpler. This is subject to change in future.
This means that the same physical online steps as above will lead to the
following state: Normal Movable
/sys/devices/system/memory/memory32/valid_zones:Normal Movable
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory32/valid_zones:Normal Movable
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Normal Movable
/sys/devices/system/memory/memory32/valid_zones:Normal Movable
/sys/devices/system/memory/memory33/valid_zones:Normal Movable
/sys/devices/system/memory/memory34/valid_zones:Movable
Implementation:
The current move_pfn_range is reimplemented to check the above
requirements (allow_online_pfn_range) and then updates the respective
zone (move_pfn_range_to_zone), the pgdat and links all the pages in the
pfn range with the zone/node. __add_pages is updated to not require the
zone and only initializes sections in the range. This allowed to
simplify the arch_add_memory code (s390 could get rid of quite some of
code).
devm_memremap_pages is the only user of arch_add_memory which relies on
the zone association because it only hooks into the memory hotplug only
half way. It uses it to associate the new memory with ZONE_DEVICE but
doesn't allow it to be {on,off}lined via sysfs. This means that this
particular code path has to call move_pfn_range_to_zone explicitly.
The original zone shifting code is kept in place and will be removed in
the follow up patch for an easier review.
Please note that this patch also changes the original behavior when
offlining a memory block adjacent to another zone (Normal vs. Movable)
used to allow to change its movable type. This will be handled later.
[[email protected]: simplify zone_intersects()]
Link:
http://lkml.kernel.org/r/[email protected]
[[email protected]: remove duplicate call for set_page_links]
Link:
http://lkml.kernel.org/r/[email protected]
[[email protected]: remove unused local `i']
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Michal Hocko <[email protected]>
Signed-off-by: Wei Yang <[email protected]>
Tested-by: Dan Williams <[email protected]>
Tested-by: Reza Arbab <[email protected]>
Acked-by: Heiko Carstens <[email protected]> # For s390 bits
Acked-by: Vlastimil Babka <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Daniel Kiper <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Igor Mammedov <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Tobias Regnery <[email protected]>
Cc: Toshi Kani <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Xishi Qiu <[email protected]>
Cc: Yasuaki Ishimatsu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
:040000 040000 dca0ef52236584b5c8c259bd24af9e941acd8f61
16dc4a7bdc0e5f9e5689484814a7532c2a2a658f M arch
:040000 040000 c778bd5d4f71bb7eedeeee5cd41205f3ee8988d6
3a3cbdc1bded174f94557e0df36fa3a969494614 M drivers
:040000 040000 26cd3e2e3b96b9ba52e88d874c3a694aa165432a
fffd98c095893c6d21be55c4b1b557622b247bcb M include
:040000 040000 c7b57745068ed37966fdb258f0e668963035d3da
b881b885d3329f4b4adcd5260c823a771c33629a M kernel
:040000 040000 7ace9d1295af184e06a45164a0e056173080fa33
08ba75397576db653a4f3bb6d3ff7780bc01d561 M mm
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https://bugs.launchpad.net/bugs/1747069
Title:
artful 4.13 i386 kernels crash after memory hotplug remove
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