linux_dsm_epyc7002/include
Vlastimil Babka ea57485af8 mm, page_alloc: fix check for NULL preferred_zone
Patch series "fix premature OOM regression in 4.7+ due to cpuset races".

This is v2 of my attempt to fix the recent report based on LTP cpuset
stress test [1].  The intention is to go to stable 4.9 LTSS with this,
as triggering repeated OOMs is not nice.  That's why the patches try to
be not too intrusive.

Unfortunately why investigating I found that modifying the testcase to
use per-VMA policies instead of per-task policies will bring the OOM's
back, but that seems to be much older and harder to fix problem.  I have
posted a RFC [2] but I believe that fixing the recent regressions has a
higher priority.

Longer-term we might try to think how to fix the cpuset mess in a better
and less error prone way.  I was for example very surprised to learn,
that cpuset updates change not only task->mems_allowed, but also
nodemask of mempolicies.  Until now I expected the parameter to
alloc_pages_nodemask() to be stable.  I wonder why do we then treat
cpusets specially in get_page_from_freelist() and distinguish HARDWALL
etc, when there's unconditional intersection between mempolicy and
cpuset.  I would expect the nodemask adjustment for saving overhead in
g_p_f(), but that clearly doesn't happen in the current form.  So we
have both crazy complexity and overhead, AFAICS.

[1] https://lkml.kernel.org/r/CAFpQJXUq-JuEP=QPidy4p_=FN0rkH5Z-kfB4qBvsf6jMS87Edg@mail.gmail.com
[2] https://lkml.kernel.org/r/7c459f26-13a6-a817-e508-b65b903a8378@suse.cz

This patch (of 4):

Since commit c33d6c06f6 ("mm, page_alloc: avoid looking up the first
zone in a zonelist twice") we have a wrong check for NULL preferred_zone,
which can theoretically happen due to concurrent cpuset modification.  We
check the zoneref pointer which is never NULL and we should check the zone
pointer.  Also document this in first_zones_zonelist() comment per Michal
Hocko.

Fixes: c33d6c06f6 ("mm, page_alloc: avoid looking up the first zone in a zonelist twice")
Link: http://lkml.kernel.org/r/20170120103843.24587-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Ganapatrao Kulkarni <gpkulkarni@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-01-24 16:26:14 -08:00
..
acpi More ACPI updates for v4.10-rc1 2016-12-22 10:19:32 -08:00
asm-generic asm-prototypes: Clear any CPP defines before declaring the functions 2017-01-05 12:57:42 +01:00
clocksource
crypto This pull contains one set of changes: a conversion of the crypto DocBook 2016-12-17 16:00:34 -08:00
drm drm/probe-helpers: Drop locking from poll_enable 2017-01-12 20:31:17 +01:00
dt-bindings dt-bindings: mfd: Remove TPS65217 interrupts 2016-12-27 10:06:00 -08:00
keys
kvm KVM: arm64: Access CNTHCTL_EL2 bit fields correctly on VHE systems 2017-01-13 11:19:25 +00:00
linux mm, page_alloc: fix check for NULL preferred_zone 2017-01-24 16:26:14 -08:00
math-emu
media [media] cec: pass parent device in register(), not allocate() 2016-11-29 12:07:17 -02:00
memory
misc
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2016-12-27 16:04:37 -08:00
pcmcia
ras
rdma Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
rxrpc
scsi Merge remote-tracking branch 'mkp-scsi/fixes' into fixes 2017-01-17 17:32:54 -05:00
soc powerpc updates for 4.10 2016-12-16 09:26:42 -08:00
sound Merge remote-tracking branches 'asoc/fix/arizona', 'asoc/fix/dpcm', 'asoc/fix/dwc', 'asoc/fix/fsl-ssi' and 'asoc/fix/hdmi-codec' into asoc-linus 2017-01-10 10:47:50 +00:00
target target: add XCOPY target/segment desc sense codes 2017-01-10 08:40:32 -08:00
trace Merge branch 'for-linus-4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 2017-01-13 17:40:22 -08:00
uapi bpf: rework prog_digest into prog_tag 2017-01-16 14:03:31 -05:00
video
xen xen: features and fixes for 4.10 rc0 2016-12-13 16:07:55 -08:00
Kbuild