DAMON GitHub repos have moved from awslabs GitHub org to damonitor org[1].
Following the change, URLs on documents are also updated[2].  However,
commit 2e9b3d6e ("Docs/damon/maintainer-profile: add links in place"),
which was added just after the update, was using the deprecated GitHub
URLs.  Update those to use damonitor GitHub URLs instead.

[1] https://lore.kernel.org/20240813232158.83903-1-sj@kernel.org
[2] https://lore.kernel.org/20240826015741.80707-2-sj@kernel.org

Link: https://lkml.kernel.org/r/20241011170154.70651-3-sj@kernel.org


Fixes: 2e9b3d6e ("Docs/damon/maintainer-profile: add links in place")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "Docs/damon/maintainer-profile: a couple of minor hotfixes".

DAMON maintainer-profile.rst file patches[1] that were merged into the
v6.12-rc1 have a couple of minor mistakes.  Fix those.

[1] https://lore.kernel.org/20240826015741.80707-1-sj@kernel.org


This patch (of 2):

Links to external web pages on DAMON's maintainer-profile.rst are missing
'_' suffixes.  As a result, rendered document is having only verbose URLs
that cannot be clicked.  Fix those.

Also, update the link texts for git trees to contain the names of the
trees, for better readability and avoiding below Sphinx warning.

    maintainer-profile.rst:4: WARNING: Duplicate explicit target name: "tree".

Link: https://lkml.kernel.org/r/20241011170154.70651-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20241011170154.70651-2-sj@kernel.org


Fixes: 2e9b3d6e ("Docs/damon/maintainer-profile: add links in place")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Signed-off-by: Dennis Lam <dennis.lamerice@gmail.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20240906204914.42698-2-dennis.lamerice@gmail.com>

Signed-off-by: Dennis Lam <dennis.lamerice@gmail.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20240908161928.3700-1-dennis.lamerice@gmail.com>

We added a public Google calendar for easy sharing of DAMON bi-weekly
meetups[1].  Add it to the official document for a better visibility.

[1] https://lore.kernel.org/all/20240717235812.53087-1-sj@kernel.org/

Link: https://lkml.kernel.org/r/20240826015741.80707-4-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Alex Shi <alexs@kernel.org>
Cc: Hu Haowen <2023002089@link.tyut.edu.cn>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

maintainer-profile.rst for DAMON separates the links and target
definitions.  It is not really necessary, and only makes the readability
worse.  At least the definitions need the section title (say,
"References").  Just add the links in place on the doc.

Link: https://lkml.kernel.org/r/20240826015741.80707-3-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Alex Shi <alexs@kernel.org>
Cc: Hu Haowen <2023002089@link.tyut.edu.cn>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "Docs/damon: update GitHub repo URLs and maintainer-profile".

Replace GitHub URLS on DAMON documents for none-kernel parts DAMON repos
with new ones[1] via the first patch.  With following two patches,
wordsmith maitnainer-profile for better readability, and document the
Google clendsar for bi-weekly meetups, respectively.

[1] https://lore.kernel.org/20240813232158.83903-1-sj@kernel.org


This patch (of 3):

GitHub repos for non-kernel parts of DAMON project including 'damo',
'damon-tests' and 'damoos' will be moved[1] from 'awslabs' org to
'damonitor', by 2024-09-05.  Update related URLs in kernel tree.

[1] https://lore.kernel.org/20240813232158.83903-1-sj@kernel.org

Link: https://lkml.kernel.org/r/20240826015741.80707-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20240826015741.80707-2-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Alex Shi <alexs@kernel.org>
Cc: Hu Haowen <2023002089@link.tyut.edu.cn>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Yanteng Si <siyanteng@loongson.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

There are no more callers of isolate_lru_page(), remove it.

[wangkefeng.wang@huawei.com: convert page to folio in comment and document, per Matthew]
  Link: https://lkml.kernel.org/r/20240826144114.1928071-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20240826065814.1336616-6-wangkefeng.wang@huawei.com


Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This flag is now only used on folios, so we can remove all the page
accessors.

Link: https://lkml.kernel.org/r/20240821193445.2294269-7-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

All users are gone, let's remove it and any leftovers in comments.  We'll
leave any FOLL/follow_page_() naming cleanups as future work.

Link: https://lkml.kernel.org/r/20240802155524.517137-11-david@redhat.com


Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Readers of DAMON subsystem documents index would want to further learn how
they can use DAMON from the user-space.  Add the link to the admin guide.

Link: https://lkml.kernel.org/r/20240701192706.51415-10-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

DAMON subsystem documents index page provides a short intro of DAMON core
concepts.  Add links to sections of the design document to let users
easily browse to the details.

Link: https://lkml.kernel.org/r/20240701192706.51415-9-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Readers of the design document would wonder how they can configure and use
specific DAMON features.  Add links to sections of DAMON sysfs interface
usage document that provides the answers for easier browsing.

Link: https://lkml.kernel.org/r/20240701192706.51415-8-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

'Programmable Modules' section provides high level descriptions of the
DAMON API-based kernel modules layer.  But 'Modules' section, which is at
the end of the document, provides every detail about the layer including
that of 'Programmable Modules' section.

Since the brief summary of the layers at the beginning of the document has
a link to the 'Modules' section, browsing to the section is not that
difficult.  Remove 'Programmable Modules' section in favor of 'Modules'
section and reducing duplicates.

Link: https://lkml.kernel.org/r/20240701192706.51415-7-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Docs/mm/damon/design: move 'Configurable Operations Set' section into 'Operations Set Layer' section

'Configurable Operations Set' section is for providing a description of
the pluggability of the operations set layer.  Just after that,
'Operations Set Layer' section, which is dedicated for the entire things
of the layer, follows.  The layout is odd, and some descriptions are
duplicated.  Move 'Configurable Operations Set' section into 'Operations
Set Layer' and re-write some of the detailed descriptions.

Link: https://lkml.kernel.org/r/20240701192706.51415-6-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

DAMON design document briefly explains the overall layers architecture
first, and then provides detailed explanations of each layer with
dedicated sections.  Letting readers go directly to the detailed sections
for specific layers could help easy browsing of the not-very-short
document.  Add links from the overall summary to the sections of details.

Link: https://lkml.kernel.org/r/20240701192706.51415-5-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

DAMON design document is not explaining how min_nr_regions limit is kept,
and what happens if the number of regions exceeds max_nr_regions.  Add
more clarification for those.

Link: https://lkml.kernel.org/r/20240701192706.51415-3-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "Docs/damon: minor fixups and improvements".

Fixup typos, clarify regions merging operation design with recent change,
add access pattern snapshot example use case, and improve readability of
the design document and subsystem documents index by
reorganizing/wordsmithing and adding links to other sections and/or
documents for easy browsing.


This patch (of 9):

Fix two typos.  The first one is just a simple typo: s/accurach/accuracy/

The second one is made by the author being out of their mind.  'Region
Based Sampling' section of the doc is mistakenly calling the access
frequency counter of region as 'nr_regions'.  Fix it with the correct
name, 'nr_accesses'.

Link: https://lkml.kernel.org/r/20240701192706.51415-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20240701192706.51415-2-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

DAMON bi-weekly community meetup series has continued since 2022-08-15 for
community members who prefer synchronous chat over asynchronous mails. 
Recently I got some feedbacks about the series from a few people.  They
told me the series is helpful for understanding of the project and
particiapting to the development, but it could be further better in terms
of the visibility.  Based on that, I started sending meeting reminder for
every occurrence.  For people who don't subscribe the mailing list,
however, adding an announcement on the official document could be helpful.
Document the series on DAMON maintainer's profile for the purpose.

Link: https://lkml.kernel.org/r/20240621163626.74815-3-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "Docs/mm/damon/maintaier-profile: document a mailing tool and
community meetup series", v2.

There is a mailing tool that developed and maintained by DAMON
maintainer aiming to support DAMON community.  Also there are DAMON
community meetup series.  Both are known to have rooms of improvements
in terms of their visibility.  Document those on the maintainer's
profile document.


This patch (of 2):

Since DAMON was merged into mainline, I periodically received some
questions around DAMON's mailing lists based workflow.  The workflow is
not different from the normal ones that well documented, but it is also
true that it is not always easy and familiar for everyone.

I personally overcame it by developing and using a simple tool, named
HacKerMaiL (hkml)[1].  Based on my experience, I believe it is matured
enough to be used for simple workflows like that of DAMON.  Actually some
DAMON contributors and Linux kernel developers other than myself told me
they are using the tool.

As DAMON maintainer, I also believe helping new DAMON community members
onboarding to the worklow is one of the most important parts of my
responsibilities.  For the reason, the tool is announced[2] to support
DAMON community.  To further increasing the visibility of the fact,
document the tool and the support plan on DAMON maintainer's profile.

[1] https://github.com/damonitor/hackermail
[2] https://github.com/damonitor/hackermail/commit/3909dad91301

Link: https://lkml.kernel.org/r/20240621163626.74815-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20240621163626.74815-2-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This patch adds damon description for "migrate_hot" and "migrate_cold"
actions for both usage and design documents as long as a new
"target_nid" knob to set the migration target node.

[sj@kernel.org: trivial fixups for DAMOS_MIGRATE_{HOT,COLD} documentation]
  Link: https://lkml.kernel.org/r/20240618213630.84846-2-sj@kernel.org
Link: https://lkml.kernel.org/r/20240614030010.751-8-honggyu.kim@sk.com


Signed-off-by: Honggyu Kim <honggyu.kim@sk.com>
Signed-off-by: SeongJae Park &lt;sj@kernel.org&gt;Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Gregory Price <gregory.price@memverge.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Hyeongtak Ji <hyeongtak.ji@sk.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

pxx_huge() has been removed in recent commit 9636f055 ("mm/treewide:
remove pXd_huge()"), however there are still three comments referencing
the API that got overlooked.  Remove them.

Link: https://lkml.kernel.org/r/20240527154855.528816-1-peterx@redhat.com


Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Commit 49fd9b6d ("mm/vmscan: fix a lot of comments") renamed
shrink_page_list() to shrink_folio_list().  Fix up the remaining
references to the old name in comments and documentation.

Link: https://lkml.kernel.org/r/20240517091348.1185566-1-illia@yshyn.com


Signed-off-by: Illia Ostapyshyn <illia@yshyn.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The memory allocation profiling document was added to the bottom of the
new outline.  Apparently it was not decided by well-defined guidelines
or a thorough discussions.  Rather than that, it was added there just
because there was no place for such unsorted documents.  Now there is
the chapter.  Move the document to the new place.

Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240701190512.49379-5-sj@kernel.org

The intention of 'Legacy Documentation' chapter is to keep the old
documents that not yet sorted into the new outline, and encourage new
documents to be integrated in the new outline from the beginning.

However, the new outline will take some more time to be completed.  It
has started about two years ago, and still many parts are not yet
written.  Also, there is no clear guidline for placing each document for
all cases, for not only the 'legacy' documents, but also for new
documents.  For example, memory allocation profiling document has been
added to the bottom of the new outline.  Apparently it was not following
some well-defined guideliens or a result of a discussion.

Furthermore, the title ("legacy") makes people feel the documents on the
chapter might be outdated or not actively maintained.

Rename 'Legacy Documentation' to 'Unsorted Documentation' and remove the
description saying it is for 'older' documents.  After this change, new
documents that not clear enough where it should be placed on the new
outline can be added on the chapter while well-defined guidelines or
discussion for the new outline is made.

Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240701190512.49379-4-sj@kernel.org

'Memory Management Guide' chapter aims to be not an additional chapter
of the document, but the ultimate single outline of the document.  In
the sense, marking it as a chapter under the document makes no sense,
and the rendered document looks odd.  Remove the chapter marker.

Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240701190512.49379-3-sj@kernel.org

'Theory of operation' part of allocation-profiling document is
apparently a chapter.  However, it is mistakenly marked as a document
title.  As a result, rendered mm document index page shows two items for
the document.  Fix it to be marked as a chapter.

Signed-off-by: SeongJae Park <sj@kernel.org>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240701190512.49379-2-sj@kernel.org

Minor grammar fixes in vmalloced-kernel-stacks

Signed-off-by: Nir Lichtman <nir@lichtman.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240619215944.GA3571421@lichtman.org

The document mentions any patches for review should based on mm-unstable
instead of damon/next.  It should be the recommended process, but
sometimes patches based on damon/next could be posted for some reasons. 
Actually, the DAMON-based tiered memory management patchset[1] was written
on top of 'young page' DAMOS filter patchset, which was in damon/next tree
as of the writing.

Allow such case and just ask such things to be clearly specified.

[1] https://lore.kernel.org/20240405060858.2818-1-honggyu.kim@sk.com

Link: https://lkml.kernel.org/r/20240503180318.72798-11-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The document says the maintainer is working on only PST.  The maintainer
respects daylight saving system, though.  Update the time zone to PT.

Link: https://lkml.kernel.org/r/20240503180318.72798-10-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Filters section is listing currently supported filter types in a normal
paragraph.  Since the number of types are higher than four, it is not easy
to read for only specific types.  Use a list for easier finding of
specific types.

[sj@kernel.org: fix build warning]
  Link: https://lkml.kernel.org/r/20240507161747.52430-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20240503180318.72798-9-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

__split_huge_pmd_locked() can be called for a present THP, devmap or
(non-present) migration entry.  It calls pmdp_invalidate() unconditionally
on the pmdp and only determines if it is present or not based on the
returned old pmd.  This is a problem for the migration entry case because
pmd_mkinvalid(), called by pmdp_invalidate() must only be called for a
present pmd.

On arm64 at least, pmd_mkinvalid() will mark the pmd such that any future
call to pmd_present() will return true.  And therefore any lockless
pgtable walker could see the migration entry pmd in this state and start
interpretting the fields as if it were present, leading to BadThings (TM).
GUP-fast appears to be one such lockless pgtable walker.

x86 does not suffer the above problem, but instead pmd_mkinvalid() will
corrupt the offset field of the swap entry within the swap pte.  See link
below for discussion of that problem.

Fix all of this by only calling pmdp_invalidate() for a present pmd.  And
for good measure let's add a warning to all implementations of
pmdp_invalidate[_ad]().  I've manually reviewed all other
pmdp_invalidate[_ad]() call sites and believe all others to be conformant.

This is a theoretical bug found during code review.  I don't have any test
case to trigger it in practice.

Link: https://lkml.kernel.org/r/20240501143310.1381675-1-ryan.roberts@arm.com
Link: https://lore.kernel.org/all/0dd7827a-6334-439a-8fd0-43c98e6af22b@arm.com/


Fixes: 84c3fc4e ("mm: thp: check pmd migration entry in common path")
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Update DAMON design document for the newly added DAMOS filter type, 'young
page'.

Link: https://lkml.kernel.org/r/20240426195247.100306-6-sj@kernel.org


Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Honggyu Kim <honggyu.kim@sk.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Allow page_table_check hooks to check over userfaultfd wr-protect criteria
upon pgtable updates.  The rule is no co-existance allowed for any
writable flag against userfault wr-protect flag.

This should be better than c2da319c, where we used to only sanitize such
issues during a pgtable walk, but when hitting such issue we don't have a
good chance to know where does that writable bit came from [1], so that
even the pgtable walk exposes a kernel bug (which is still helpful on
triaging) but not easy to track and debug.

Now we switch to track the source.  It's much easier too with the recent
introduction of page table check.

There are some limitations with using the page table check here for
userfaultfd wr-protect purpose:

  - It is only enabled with explicit enablement of page table check configs
  and/or boot parameters, but should be good enough to track at least
  syzbot issues, as syzbot should enable PAGE_TABLE_CHECK[_ENFORCED] for
  x86 [1].  We used to have DEBUG_VM but it's now off for most distros,
  while distros also normally not enable PAGE_TABLE_CHECK[_ENFORCED], which
  is similar.

  - It conditionally works with the ptep_modify_prot API.  It will be
  bypassed when e.g. XEN PV is enabled, however still work for most of the
  rest scenarios, which should be the common cases so should be good
  enough.

  - Hugetlb check is a bit hairy, as the page table check cannot identify
  hugetlb pte or normal pte via trapping at set_pte_at(), because of the
  current design where hugetlb maps every layers to pte_t... For example,
  the default set_huge_pte_at() can invoke set_pte_at() directly and lose
  the hugetlb context, treating it the same as a normal pte_t. So far it's
  fine because we have huge_pte_uffd_wp() always equals to pte_uffd_wp() as
  long as supported (x86 only).  It'll be a bigger problem when we'll
  define _PAGE_UFFD_WP differently at various pgtable levels, because then
  one huge_pte_uffd_wp() per-arch will stop making sense first.. as of now
  we can leave this for later too.

This patch also removes commit c2da319c altogether, as we have something
better now.

[1] https://lore.kernel.org/all/000000000000dce0530615c89210@google.com/

Link: https://lkml.kernel.org/r/20240417212549.2766883-1-peterx@redhat.com


Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Let's track the mapcount of large folios in a single value.  The mapcount
of a large folio currently corresponds to the sum of the entire mapcount
and all page mapcounts.

This sum is what we actually want to know in folio_mapcount() and it is
also sufficient for implementing folio_mapped().

With PTE-mapped THP becoming more important and more widely used, we want
to avoid looping over all pages of a folio just to obtain the mapcount of
large folios.  The comment "In the common case, avoid the loop when no
pages mapped by PTE" in folio_total_mapcount() does no longer hold for
mTHP that are always mapped by PTE.

Further, we are planning on using folio_mapcount() more frequently, and
might even want to remove page mapcounts for large folios in some kernel
configs.  Therefore, allow for reading the mapcount of large folios
efficiently and atomically without looping over any pages.

Maintain the mapcount also for hugetlb pages for simplicity.  Use the new
mapcount to implement folio_mapcount() and folio_mapped().  Make
page_mapped() simply call folio_mapped().  We can now get rid of
folio_large_is_mapped().

_nr_pages_mapped is now only used in rmap code and for debugging purposes.
Keep folio_nr_pages_mapped() around, but document that its use should be
limited to rmap internals and debugging purposes.

This change implies one additional atomic add/sub whenever
mapping/unmapping (parts of) a large folio.

As we now batch RMAP operations for PTE-mapped THP during fork(), during
unmap/zap, and when PTE-remapping a PMD-mapped THP, and we adjust the
large mapcount for a PTE batch only once, the added overhead in the common
case is small.  Only when unmapping individual pages of a large folio
(e.g., during COW), the overhead might be bigger in comparison, but it's
essentially one additional atomic operation.

Note that before the new mapcount would overflow, already our refcount
would overflow: each mapping requires a folio reference.  Extend the
focumentation of folio_mapcount().

Link: https://lkml.kernel.org/r/20240409192301.907377-5-david@redhat.com


Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Richard Chang <richardycc@google.com>
Cc: Rich Felker <dalias@libc.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Fix spelling and grammar in Docs descriptions

Signed-off-by: Remington Brasga <rbrasga@uci.edu>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240429225527.2329-1-rbrasga@uci.edu

Mostly rewording, but remove entirely the copy of page_fixed_fake_head()
in the documentation; we can refer people to the actual source if
necessary.

Link: https://lkml.kernel.org/r/20240326171045.410737-10-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Provide documentation for memory allocation profiling.

Link: https://lkml.kernel.org/r/20240321163705.3067592-38-surenb@google.com


Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Tested-by: Kees Cook <keescook@chromium.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alex Gaynor <alex.gaynor@gmail.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Andreas Hindborg <a.hindborg@samsung.com>
Cc: Benno Lossin <benno.lossin@proton.me>
Cc: "Björn Roy Baron" <bjorn3_gh@protonmail.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Gary Guo <gary@garyguo.net>
Cc: Miguel Ojeda <ojeda@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Current code does not contemplate scenarios were an allocation and free
operation on the same pages do not handle it in the same amount at once. 
To give an example, page_alloc_exact(), where we will allocate a page of
enough order to stafisfy the size request, but we will free the remainings
right away.

In the above example, we will increment the stack_record refcount only
once, but we will decrease it the same number of times as number of unused
pages we have to free.  This will lead to a warning because of refcount
imbalance.

Fix this by recording the number of base pages in the refcount field.

Link: https://lkml.kernel.org/r/20240404070702.2744-3-osalvador@suse.de


Reported-by:  <syzbot+41bbfdb8d41003d12c0f@syzkaller.appspotmail.com>
Closes: https://lore.kernel.org/linux-mm/00000000000090e8ff0613eda0e5@google.com


Fixes: 217b2119 ("mm,page_owner: implement the tracking of the stacks count")
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

__napi_alloc_skb() is napi_alloc_skb() with the added flexibility
of choosing gfp_mask. This is a NAPI function, so GFP_ATOMIC is
implied. The only practical choice the caller has is whether to
set __GFP_NOWARN. But that's a false choice, too, allocation failures
in atomic context will happen, and printing warnings in logs,
effectively for a packet drop, is both too much and very likely
non-actionable.

This leads me to a conclusion that most uses of napi_alloc_skb()
are simply misguided, and should use __GFP_NOWARN in the first
place. We also have a "standard" way of reporting allocation
failures via the queue stat API (qstats::rx-alloc-fail).

The direct motivation for this patch is that one of the drivers
used at Meta calls napi_alloc_skb() (so prior to this patch without
__GFP_NOWARN), and the resulting OOM warning is the top networking
warning in our fleet.

Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20240327040213.3153864-1-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>