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Johannes Weiner 9317d0fffe mm: page_counter: mitigate consequences of a page_counter underflow
When the unsigned page_counter underflows, even just by a few pages, a
cgroup will not be able to run anything afterwards and trigger the OOM
killer in a loop.

Underflows shouldn't happen, but when they do in practice, we may just be
off by a small amount that doesn't interfere with the normal operation -
consequences don't need to be that dire.

Reset the page_counter to 0 upon underflow.  We'll issue a warning that
the accounting will be off and then try to keep limping along.

[ We used to do this with the original res_counter, where it was a
  more straight-forward correction inside the spinlock section. I
  didn't carry it forward into the lockless page counters for
  simplicity, but it turns out this is quite useful in practice. ]

Link: https://lkml.kernel.org/r/20210408143155.2679744-1-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Chris Down <chris@chrisdown.name>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Roman Gushchin <guro@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2021-04-30 11:20:38 -07:00
arch mm: move page_mapping_file to pagemap.h 2021-04-30 11:20:37 -07:00
block cgroup: rstat: punt root-level optimization to individual controllers 2021-04-30 11:20:37 -07:00
certs certs: add 'x509_revocation_list' to gitignore 2021-04-26 10:48:07 -07:00
crypto for-5.13/drivers-2021-04-27 2021-04-28 14:39:37 -07:00
Documentation mm: gup: remove FOLL_SPLIT 2021-04-30 11:20:37 -07:00
drivers RDMA/umem: batch page unpin in __ib_umem_release() 2021-04-30 11:20:37 -07:00
fs iomap: use filemap_range_needs_writeback() for O_DIRECT reads 2021-04-30 11:20:36 -07:00
include linux/memcontrol.h: remove duplicate struct declaration 2021-04-30 11:20:38 -07:00
init Kconfig updates for v5.13 2021-04-29 14:32:00 -07:00
ipc fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
kernel cgroup: rstat: punt root-level optimization to individual controllers 2021-04-30 11:20:37 -07:00
lib mm/memtest: add ARCH_USE_MEMTEST 2021-04-30 11:20:36 -07:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm mm: page_counter: mitigate consequences of a page_counter underflow 2021-04-30 11:20:38 -07:00
net Networking changes for 5.13. 2021-04-29 11:57:23 -07:00
samples kfifo: fix ternary sign extension bugs 2021-04-30 11:20:35 -07:00
scripts scripts: a new script for checking duplicate struct declaration 2021-04-30 11:20:35 -07:00
security Networking changes for 5.13. 2021-04-29 11:57:23 -07:00
sound - Core Frameworks 2021-04-28 15:59:13 -07:00
tools kselftests: cgroup: update kmem test for new vmstat implementation 2021-04-30 11:20:38 -07:00
usr Kbuild updates for v5.12 2021-02-25 10:17:31 -08:00
virt KVM: x86/mmu: Consider the hva in mmu_notifier retry 2021-02-22 13:16:53 -05:00
.clang-format cxl for 5.12 2021-02-24 09:38:36 -08:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: generate Module.symvers only when vmlinux exists 2021-04-25 05:17:02 +09:00
.mailmap It's been a relatively busy cycle in docsland, though more than usually 2021-04-26 13:22:43 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS - Core Frameworks 2021-04-28 15:59:13 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Kbuild updates for v5.13 2021-04-29 14:24:39 -07:00
Makefile Kconfig updates for v5.13 2021-04-29 14:32:00 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.