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Shakeel Butt 013339df11 mm/rmap: always do TTU_IGNORE_ACCESS 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>		2020-12-15 12:13:39 -08:00
Documentation	mm: memcontrol: add file_thp, shmem_thp to memory.stat	2020-12-15 12:13:39 -08:00
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arch	mm/gup: prevent gup_fast from racing with COW during fork	2020-12-15 12:13:39 -08:00
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drivers	mm/gup: prevent gup_fast from racing with COW during fork	2020-12-15 12:13:39 -08:00
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include	mm/rmap: always do TTU_IGNORE_ACCESS	2020-12-15 12:13:39 -08:00
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kernel	mm/gup: prevent gup_fast from racing with COW during fork	2020-12-15 12:13:39 -08:00
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mm	mm/rmap: always do TTU_IGNORE_ACCESS	2020-12-15 12:13:39 -08:00
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tools	selftests/vm: 2x speedup for run_vmtests.sh	2020-12-15 12:13:38 -08:00
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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.