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Shakeel Butt dd156e3fca mm/rmap: always do TTU_IGNORE_ACCESS 
[ Upstream commit 013339df116c2ee0d796dd8bfb8f293a2030c063 ]

Since commit 369ea8242c ("mm/rmap: update to new mmu_notifier semantic
v2"), the code to check the secondary MMU's page table access bit is
broken for !(TTU_IGNORE_ACCESS) because the page is unmapped from the
secondary MMU's page table before the check.  More specifically for those
secondary MMUs which unmap the memory in
mmu_notifier_invalidate_range_start() like kvm.

However memory reclaim is the only user of !(TTU_IGNORE_ACCESS) or the
absence of TTU_IGNORE_ACCESS and it explicitly performs the page table
access check before trying to unmap the page.  So, at worst the reclaim
will miss accesses in a very short window if we remove page table access
check in unmapping code.

There is an unintented consequence of !(TTU_IGNORE_ACCESS) for the memcg
reclaim.  From memcg reclaim the page_referenced() only account the
accesses from the processes which are in the same memcg of the target page
but the unmapping code is considering accesses from all the processes, so,
decreasing the effectiveness of memcg reclaim.

The simplest solution is to always assume TTU_IGNORE_ACCESS in unmapping
code.

Link: https://lkml.kernel.org/r/20201104231928.1494083-1-shakeelb@google.com
Fixes: 369ea8242c ("mm/rmap: update to new mmu_notifier semantic v2")
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-12-30 11:53:55 +01:00
arch mm/gup: prevent gup_fast from racing with COW during fork 2020-12-30 11:53:54 +01:00
block block-5.10-2020-12-05 2020-12-05 14:45:30 -08:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto crypto: Kconfig - CRYPTO_MANAGER_EXTRA_TESTS requires the manager 2020-12-30 11:53:09 +01:00
Documentation USB: UAS: introduce a quirk to set no_write_same 2020-12-21 13:30:08 +01:00
drivers mm/gup: prevent gup_fast from racing with COW during fork 2020-12-30 11:53:54 +01:00
fs ubifs: Fix error return code in ubifs_init_authentication() 2020-12-30 11:53:52 +01:00
include mm/rmap: always do TTU_IGNORE_ACCESS 2020-12-30 11:53:55 +01:00
init initramfs: fix clang build failure 2020-12-11 14:02:14 -08:00
ipc ipc: adjust proc_ipc_sem_dointvec definition to match prototype 2020-09-05 12:14:29 -07:00
kernel mm/gup: prevent gup_fast from racing with COW during fork 2020-12-30 11:53:54 +01:00
lib selftest/fpu: avoid clang warning 2020-12-11 14:02:14 -08:00
LICENSES LICENSES/deprecated: add Zlib license text 2020-09-16 14:33:49 +02:00
mm mm/rmap: always do TTU_IGNORE_ACCESS 2020-12-30 11:53:55 +01:00
net sunrpc: fix xs_read_xdr_buf for partial pages receive 2020-12-30 11:53:53 +01:00
samples samples/bpf: Fix possible hang in xdpsock with multiple threads 2020-12-30 11:53:49 +01:00
scripts scripts: kernel-doc: fix parsing function-like typedefs 2020-12-30 11:53:33 +01:00
security selinux: fix inode_doinit_with_dentry() LABEL_INVALID error handling 2020-12-30 11:53:03 +01:00
sound ASoC: wm_adsp: remove "ctl" from list on error in wm_adsp_create_control() 2020-12-30 11:53:50 +01:00
tools perf test: Fix metric parsing test 2020-12-30 11:53:54 +01:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt kvm: x86/mmu: Support dirty logging for the TDP MMU 2020-10-23 03:42:13 -04:00
.clang-format RDMA 5.10 pull request 2020-10-17 11:18:18 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.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 .gitignore: docs: ignore sphinx_*/ directories 2020-09-10 10:44:31 -06:00
.mailmap mailmap: add two more addresses of Uwe Kleine-König 2020-12-06 10:19:07 -08:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Jason Cooper to CREDITS 2020-11-30 10:20:34 +01:00
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 Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-12-10 15:30:13 -08:00
Makefile Linux 5.10.3 2020-12-26 16:02:46 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

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.