linux.git/tools/vm/page-types.c, branch v6.2

mm/page-flags: reuse PG_mappedtodisk as PG_anon_exclusive for PageAnon() pages

2022-05-10T01:20:44+00:00

The basic question we would like to have a reliable and efficient answer
to is: is this anonymous page exclusive to a single process or might it be
shared?  We need that information for ordinary/single pages, hugetlb
pages, and possibly each subpage of a THP.

Introduce a way to mark an anonymous page as exclusive, with the ultimate
goal of teaching our COW logic to not do "wrong COWs", whereby GUP pins
lose consistency with the pages mapped into the page table, resulting in
reported memory corruptions.

Most pageflags already have semantics for anonymous pages, however,
PG_mappedtodisk should never apply to pages in the swapcache, so let's
reuse that flag.

As PG_has_hwpoisoned also uses that flag on the second tail page of a
compound page, convert it to PG_error instead, which is marked as
PF_NO_TAIL, so never used for tail pages.

Use custom page flag modification functions such that we can do additional
sanity checks.  The semantics we'll put into some kernel doc in the future
are:

"
  PG_anon_exclusive is *usually* only expressive in combination with a
  page table entry. Depending on the page table entry type it might
  store the following information:

       Is what's mapped via this page table entry exclusive to the
       single process and can be mapped writable without further
       checks? If not, it might be shared and we might have to COW.

  For now, we only expect PTE-mapped THPs to make use of
  PG_anon_exclusive in subpages. For other anonymous compound
  folios (i.e., hugetlb), only the head page is logically mapped and
  holds this information.

  For example, an exclusive, PMD-mapped THP only has PG_anon_exclusive
  set on the head page. When replacing the PMD by a page table full
  of PTEs, PG_anon_exclusive, if set on the head page, will be set on
  all tail pages accordingly. Note that converting from a PTE-mapping
  to a PMD mapping using the same compound page is currently not
  possible and consequently doesn't require care.

  If GUP wants to take a reliable pin (FOLL_PIN) on an anonymous page,
  it should only pin if the relevant PG_anon_exclusive is set. In that
  case, the pin will be fully reliable and stay consistent with the pages
  mapped into the page table, as the bit cannot get cleared (e.g., by
  fork(), KSM) while the page is pinned. For anonymous pages that
  are mapped R/W, PG_anon_exclusive can be assumed to always be set
  because such pages cannot possibly be shared.

  The page table lock protecting the page table entry is the primary
  synchronization mechanism for PG_anon_exclusive; GUP-fast that does
  not take the PT lock needs special care when trying to clear the
  flag.

  Page table entry types and PG_anon_exclusive:
  * Present: PG_anon_exclusive applies.
  * Swap: the information is lost. PG_anon_exclusive was cleared.
  * Migration: the entry holds this information instead.
               PG_anon_exclusive was cleared.
  * Device private: PG_anon_exclusive applies.
  * Device exclusive: PG_anon_exclusive applies.
  * HW Poison: PG_anon_exclusive is stale and not changed.

  If the page may be pinned (FOLL_PIN), clearing PG_anon_exclusive is
  not allowed and the flag will stick around until the page is freed
  and folio->mapping is cleared.
"

We won't be clearing PG_anon_exclusive on destructive unmapping (i.e.,
zapping) of page table entries, page freeing code will handle that when
also invalidate page->mapping to not indicate PageAnon() anymore.  Letting
information about exclusivity stick around will be an important property
when adding sanity checks to unpinning code.

Note that we properly clear the flag in free_pages_prepare() via
PAGE_FLAGS_CHECK_AT_PREP for each individual subpage of a compound page,
so there is no need to manually clear the flag.

Link: https://lkml.kernel.org/r/20220428083441.37290-12-david@redhat.com
Signed-off-by: David Hildenbrand 
Acked-by: Vlastimil Babka 
Cc: Andrea Arcangeli 
Cc: Christoph Hellwig 
Cc: David Rientjes 
Cc: Don Dutile 
Cc: Hugh Dickins 
Cc: Jan Kara 
Cc: Jann Horn 
Cc: Jason Gunthorpe 
Cc: John Hubbard 
Cc: Khalid Aziz 
Cc: "Kirill A. Shutemov" 
Cc: Liang Zhang 
Cc: "Matthew Wilcox (Oracle)" 
Cc: Michal Hocko 
Cc: Mike Kravetz 
Cc: Mike Rapoport 
Cc: Nadav Amit 
Cc: Oded Gabbay 
Cc: Oleg Nesterov 
Cc: Pedro Demarchi Gomes 
Cc: Peter Xu 
Cc: Rik van Riel 
Cc: Roman Gushchin 
Cc: Shakeel Butt 
Cc: Yang Shi 
Signed-off-by: Andrew Morton

tools/vm/page-types.c: print file offset in hexadecimal

2021-11-06T20:30:40+00:00

In page list mode (with -l and -L option), virtual address and physical
address are printed in hexadecimal, but file offset is not, which is
confusing, so let's align it.

Link: https://lkml.kernel.org/r/20211004061325.1525902-4-naoya.horiguchi@linux.dev
Signed-off-by: Naoya Horiguchi 
Cc: Bin Wang 
Cc: Changbin Du 
Cc: Christian Hansen 
Cc: Konstantin Khlebnikov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tools/vm/page-types.c: move show_file() to summary output

2021-11-06T20:30:40+00:00

Currently file info from show_file() is printed out within page list
like below, but this is inconvenient a little to utilize the page list
from other scripts (maybe needs additional filtering).

    $ ./page-types -f page-types.c -l
    foffset offset  len     flags
    page-types.c Inode: 15108680 Size: 30953 (8 pages)
    Modify: Sat Oct  2 23:11:20 2021 (2399 seconds ago)
    Access: Sat Oct  2 23:11:28 2021 (2391 seconds ago)
    0       d9f59e  1       ___U_lA____________________________________
    1       1031eb5 1       __RU_l_____________________________________
    2       13bf717 1       __RU_l_____________________________________
    3       13ac333 1       ___U_lA____________________________________
    4       d9f59f  1       __RU_l_____________________________________
    5       183fd49 1       ___U_lA____________________________________
    6       13cbf69 1       ___U_lA____________________________________
    7       d9ef05  1       ___U_lA____________________________________

                 flags      page-count       MB  symbolic-flags                     long-symbolic-flags
    0x000000000000002c               3        0  __RU_l_____________________________________        referenced,uptodate,lru
    0x0000000000000068               5        0  ___U_lA____________________________________        uptodate,lru,active
                 total               8        0

With this patch file info is printed out in summary part like below:

    $ ./page-types -f page-types.c -l
    foffset offset  len     flags
    0       d9f59e  1       ___U_lA_____________________________________
    1       1031eb5 1       __RU_l______________________________________
    2       13bf717 1       __RU_l______________________________________
    3       13ac333 1       ___U_lA_____________________________________
    4       d9f59f  1       __RU_l______________________________________
    5       183fd49 1       ___U_lA_____________________________________
    6       13cbf69 1       ___U_lA_____________________________________

    page-types.c Inode: 15108680 Size: 30953 (8 pages)
    Modify: Sat Oct  2 23:11:20 2021 (2435 seconds ago)
    Access: Sat Oct  2 23:11:28 2021 (2427 seconds ago)

                 flags      page-count       MB  symbolic-flags                     long-symbolic-flags
    0x000000000000002c               3        0  __RU_l______________________________________       referenced,uptodate,lru
    0x0000000000000068               4        0  ___U_lA_____________________________________       uptodate,lru,active
                 total               7        0

Link: https://lkml.kernel.org/r/20211004061325.1525902-3-naoya.horiguchi@linux.dev
Signed-off-by: Naoya Horiguchi 
Cc: Bin Wang 
Cc: Changbin Du 
Cc: Christian Hansen 
Cc: Konstantin Khlebnikov 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tools/vm/page-types.c: make walk_file() aware of address range option

2021-11-06T20:30:40+00:00

Patch series "tools/vm/page-types.c: a few improvements".

This patchset adds some improvements on tools/vm/page-types.c.  Patch
1/3 makes -a option (specify address range) work with -f (file cache
mode).  Patch 2/3 and 3/3 are to fix minor formatting issues of this
tool.  These would make life a little easier for the users of this tool.

Please see individual patches for more details about specific issues.

This patch (of 3):

-a|--addr option is used to limit the range of address to be scanned for
page status.  It works now for physical address space (dafult mode) or for
virtual address space (with -p option), but not for file address space
(with -f option).  So make walk_file() aware of -a option.

Link: https://lkml.kernel.org/r/20211004061325.1525902-1-naoya.horiguchi@linux.dev
Link: https://lkml.kernel.org/r/20211004061325.1525902-2-naoya.horiguchi@linux.dev
Signed-off-by: Naoya Horiguchi 
Cc: Konstantin Khlebnikov 
Cc: Christian Hansen 
Cc: Changbin Du 
Cc: Bin Wang 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tools/vm/page-types: remove dependency on opt_file for idle page tracking

2021-09-24T23:13:35+00:00

Idle page tracking can also be used for process address space, not only
file mappings.

Without this change, using with '-i' option for process address space
encounters below errors reported.

  $ sudo ./page-types -p $(pidof bash) -i
  mark page idle: Bad file descriptor
  mark page idle: Bad file descriptor
  mark page idle: Bad file descriptor
  mark page idle: Bad file descriptor
  ...

Link: https://lkml.kernel.org/r/20210917032826.10669-1-changbin.du@gmail.com
Signed-off-by: Changbin Du 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: Add PG_arch_2 page flag

2020-09-04T11:46:06+00:00

For arm64 MTE support it is necessary to be able to mark pages that
contain user space visible tags that will need to be saved/restored e.g.
when swapped out.

To support this add a new arch specific flag (PG_arch_2). This flag is
only available on 64-bit architectures due to the limited number of
spare page flags on the 32-bit ones.

Signed-off-by: Steven Price 
[catalin.marinas@arm.com: use CONFIG_64BIT for guarding this new flag]
Signed-off-by: Catalin Marinas 
Cc: Andrew Morton

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 276

2019-06-05T15:36:36+00:00

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation version 2 this program is distributed
  in the hope that it will be useful but without any warranty without
  even the implied warranty of merchantability or fitness for a
  particular purpose see the gnu general public license for more
  details you should find a copy of v2 of the gnu general public
  license somewhere on your linux system if not write to the free
  software foundation inc 59 temple place suite 330 boston ma 02111
  1307 usa

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 1 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Allison Randal 
Reviewed-by: Alexios Zavras 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190529141900.073926682@linutronix.de
Signed-off-by: Greg Kroah-Hartman

mm: convert PG_balloon to PG_offline

2019-03-06T05:07:14+00:00

PG_balloon was introduced to implement page migration/compaction for
pages inflated in virtio-balloon.  Nowadays, it is only a marker that a
page is part of virtio-balloon and therefore logically offline.

We also want to make use of this flag in other balloon drivers - for
inflated pages or when onlining a section but keeping some pages offline
(e.g.  used right now by XEN and Hyper-V via set_online_page_callback()).

We are going to expose this flag to dump tools like makedumpfile.  But
instead of exposing PG_balloon, let's generalize the concept of marking
pages as logically offline, so it can be reused for other purposes later
on.

Rename PG_balloon to PG_offline.  This is an indicator that the page is
logically offline, the content stale and that it should not be touched
(e.g.  a hypervisor would have to allocate backing storage in order for
the guest to dump an unused page).  We can then e.g.  exclude such pages
from dumps.

We replace and reuse KPF_BALLOON (23), as this shouldn't really harm
(and for now the semantics stay the same).  In following patches, we
will make use of this bit also in other balloon drivers.  While at it,
document PGTABLE.

[akpm@linux-foundation.org: fix comment text, per David]
Link: http://lkml.kernel.org/r/20181119101616.8901-3-david@redhat.com
Signed-off-by: David Hildenbrand 
Acked-by: Konstantin Khlebnikov 
Acked-by: Michael S. Tsirkin 
Acked-by: Pankaj gupta 
Cc: Jonathan Corbet 
Cc: Alexey Dobriyan 
Cc: Mike Rapoport 
Cc: Christian Hansen 
Cc: Vlastimil Babka 
Cc: "Kirill A. Shutemov" 
Cc: Stephen Rothwell 
Cc: Matthew Wilcox 
Cc: Michal Hocko 
Cc: Pavel Tatashin 
Cc: Alexander Duyck 
Cc: Naoya Horiguchi 
Cc: Miles Chen 
Cc: David Rientjes 
Cc: Kazuhito Hagio 
Cc: Arnd Bergmann 
Cc: Baoquan He 
Cc: Borislav Petkov 
Cc: Boris Ostrovsky 
Cc: Dave Young 
Cc: Greg Kroah-Hartman 
Cc: Haiyang Zhang 
Cc: Juergen Gross 
Cc: Julien Freche 
Cc: Kairui Song 
Cc: "K. Y. Srinivasan" 
Cc: Len Brown 
Cc: Lianbo Jiang 
Cc: Michal Hocko 
Cc: Nadav Amit 
Cc: Omar Sandoval 
Cc: Pavel Machek 
Cc: Rafael J. Wysocki 
Cc: "Rafael J. Wysocki" 
Cc: Stefano Stabellini 
Cc: Stephen Hemminger 
Cc: Vitaly Kuznetsov 
Cc: Xavier Deguillard 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tools/vm/page-types.c: fix "kpagecount returned fewer pages than expected" failures

2018-12-28T20:11:50+00:00

Because kpagecount_read() fakes success if map counts are not being
collected, clamp the page count passed to it by walk_pfn() to the pages
value returned by the preceding call to kpageflags_read().

Link: http://lkml.kernel.org/r/1543962269-26116-1-git-send-email-anthony.yznaga@oracle.com
Fixes: 7f1d23e60718 ("tools/vm/page-types.c: include shared map counts")
Signed-off-by: Anthony Yznaga 
Reviewed-by: Naoya Horiguchi 
Cc: Vlastimil Babka 
Cc: Matthew Wilcox 
Cc: David Rientjes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tools/vm/page-types.c: fix "defined but not used" warning

2018-09-04T23:45:02+00:00

debugfs_known_mountpoints[] is not used any more, so let's remove it.

Link: http://lkml.kernel.org/r/1535102651-19418-1-git-send-email-n-horiguchi@ah.jp.nec.com
Signed-off-by: Naoya Horiguchi 
Reviewed-by: Andrew Morton 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds