When I was investigating the swap code, I found the below possible race
window:

CPU 1                                   	CPU 2
-----                                   	-----
do_swap_page
  if (data_race(si->flags & SWP_SYNCHRONOUS_IO)
  swap_readpage
    if (data_race(sis->flags & SWP_FS_OPS)) {
                                        	swapoff
					  	  ..
					  	  p->swap_file = NULL;
					  	  ..
    struct file *swap_file = sis->swap_file;
    struct address_space *mapping = swap_file->f_mapping;[oops!]

Note that for the pages that are swapped in through swap cache, this isn't
an issue. Because the page is locked, and the swap entry will be marked
with SWAP_HAS_CACHE, so swapoff() can not proceed until the page has been
unlocked.

Fix this race by using get/put_swap_device() to guard against concurrent
swapoff.

Link: https://lkml.kernel.org/r/20210426123316.806267-3-linmiaohe@huawei.com
Fixes: 0bcac06f ("mm,swap: skip swapcache for swapin of synchronous device")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "close various race windows for swap", v6.

When I was investigating the swap code, I found some possible race
windows.  This series aims to fix all these races.  But using current
get/put_swap_device() to guard against concurrent swapoff for
swap_readpage() looks terrible because swap_readpage() may take really
long time.  And to reduce the performance overhead on the hot-path as much
as possible, it appears we can use the percpu_ref to close this race
window(as suggested by Huang, Ying).  The patch 1 adds percpu_ref support
for swap and most of the remaining patches try to use this to close
various race windows.  More details can be found in the respective
changelogs.

This patch (of 4):

Using current get/put_swap_device() to guard against concurrent swapoff
for some swap ops, e.g.  swap_readpage(), looks terrible because they
might take really long time.  This patch adds the percpu_ref support to
serialize against concurrent swapoff(as suggested by Huang, Ying).  Also
we remove the SWP_VALID flag because it's used together with RCU solution.

Link: https://lkml.kernel.org/r/20210426123316.806267-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20210426123316.806267-2-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pagewalk ignores hugepd entries and walk down the tables as if it was
traditionnal entries, leading to crazy result.

Add walk_hugepd_range() and use it to walk hugepage tables.

Link: https://lkml.kernel.org/r/38d04410700c8d02f28ba37e020b62c55d6f3d2c.1624597695.git.christophe.leroy@csgroup.euSigned-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Steven Price <steven.price@arm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Daniel Axtens <dja@axtens.net>
Cc: "Oliver O'Halloran" <oohall@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

has_pinned 32bit can be packed in the MMF_HAS_PINNED bit as a noop
cleanup.

Any atomic_inc/dec to the mm cacheline shared by all threads in pin-fast
would reintroduce a loss of SMP scalability to pin-fast, so there's no
future potential usefulness to keep an atomic in the mm for this.

set_bit(MMF_HAS_PINNED) will be theoretically a bit slower than WRITE_ONCE
(atomic_set is equivalent to WRITE_ONCE), but the set_bit (just like
atomic_set after this commit) has to be still issued only once per "mm",
so the difference between the two will be lost in the noise.

will-it-scale "mmap2" shows no change in performance with enterprise
config as expected.

will-it-scale "pin_fast" retains the > 4000% SMP scalability performance
improvement against upstream as expected.

This is a noop as far as overall performance and SMP scalability are
concerned.

[peterx@redhat.com: pack has_pinned in MMF_HAS_PINNED]
  Link: https://lkml.kernel.org/r/YJqWESqyxa8OZA+2@t490s
[akpm@linux-foundation.org: coding style fixes]
[peterx@redhat.com: fix build for task_mmu.c, introduce mm_set_has_pinned_flag, fix comments]

Link: https://lkml.kernel.org/r/20210507150553.208763-4-peterx@redhat.comSigned-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

has_pinned cannot be written by each pin-fast or it won't scale in SMP.
This isn't "false sharing" strictly speaking (it's more like "true
non-sharing"), but it creates the same SMP scalability bottleneck of
"false sharing".

To verify the improvement, below test is done on 40 cpus host with
Intel(R) Xeon(R) CPU E5-2630 v4 @ 2.20GHz (must be with
CONFIG_GUP_TEST=y):

  $ sudo chrt -f 1 ./gup_test -a  -m 512 -j 40

Where we can get (average value for 40 threads):

  Old kernel: 477729.97 (+- 3.79%)
  New kernel:  89144.65 (+-11.76%)

On a similar condition with 256 cpus, this commits increases the SMP
scalability of pin_user_pages_fast() executed by different threads of the
same process by more than 4000%.

[peterx@redhat.com: rewrite commit message, add parentheses against "(A & B)"]

Link: https://lkml.kernel.org/r/20210507150553.208763-3-peterx@redhat.comSigned-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "mm/gup: Fix pin page write cache bouncing on has_pinned", v2.

This series contains 3 patches, the 1st one enables threading for
gup_benchmark in the kselftest.  The latter two patches are collected from
Andrea's local branch which can fix write cache bouncing issue with
pinning fast-gup.

To be explicit on the latter two patches:

  - the 2nd patch fixes the perf degrade when introducing has_pinned, then

  - the last patch tries to remove the has_pinned with a bit in mm->flags

For patch 3: originally I think we had a plan to reuse has_pinned into a
counter very soon, however that's not happening at least until today, so
maybe it proves that we can remove it until we really want such a counter
for whatever reason.  As the commit message stated, it saves 4 bytes for
each mm without observable regressions.

Regarding testing: we can reference to the commit message of patch 2 for
some detailed testing with will-is-scale.  Meanwhile I did patch 1 just
because then we can even easily verify the patchset using the existing
kselftest facilities or even regress test it in the future with the repo
if we want.

Below numbers are extra verification tests that I did besides commit
message of patch 2 using the new gup_benchmark and 256 cpus.  Below test
is done on 40 cpus host with Intel(R) Xeon(R) CPU E5-2630 v4 @ 2.20GHz,
and I can get similar result (of course the write cache bouncing get
severe with even more cores).

After patch 1 applied (only test patch, so using old kernel):

  $ sudo chrt -f 1 ./gup_test -a  -m 512 -j 40
  PIN_FAST_BENCHMARK: Time: get:459632 put:5990 us
  PIN_FAST_BENCHMARK: Time: get:461967 put:5840 us
  PIN_FAST_BENCHMARK: Time: get:464521 put:6140 us
  PIN_FAST_BENCHMARK: Time: get:465176 put:7100 us
  PIN_FAST_BENCHMARK: Time: get:465960 put:6733 us
  PIN_FAST_BENCHMARK: Time: get:465324 put:6781 us
  PIN_FAST_BENCHMARK: Time: get:466018 put:7130 us
  PIN_FAST_BENCHMARK: Time: get:466362 put:7118 us
  PIN_FAST_BENCHMARK: Time: get:465118 put:6975 us
  PIN_FAST_BENCHMARK: Time: get:466422 put:6602 us
  PIN_FAST_BENCHMARK: Time: get:465791 put:6818 us
  PIN_FAST_BENCHMARK: Time: get:467091 put:6298 us
  PIN_FAST_BENCHMARK: Time: get:467694 put:5432 us
  PIN_FAST_BENCHMARK: Time: get:469575 put:5581 us
  PIN_FAST_BENCHMARK: Time: get:468124 put:6055 us
  PIN_FAST_BENCHMARK: Time: get:468877 put:6720 us
  PIN_FAST_BENCHMARK: Time: get:467212 put:4961 us
  PIN_FAST_BENCHMARK: Time: get:467834 put:6697 us
  PIN_FAST_BENCHMARK: Time: get:470778 put:6398 us
  PIN_FAST_BENCHMARK: Time: get:469788 put:6310 us
  PIN_FAST_BENCHMARK: Time: get:488277 put:7113 us
  PIN_FAST_BENCHMARK: Time: get:486613 put:7085 us
  PIN_FAST_BENCHMARK: Time: get:486940 put:7202 us
  PIN_FAST_BENCHMARK: Time: get:488728 put:7101 us
  PIN_FAST_BENCHMARK: Time: get:487570 put:7327 us
  PIN_FAST_BENCHMARK: Time: get:489260 put:7027 us
  PIN_FAST_BENCHMARK: Time: get:488846 put:6866 us
  PIN_FAST_BENCHMARK: Time: get:488521 put:6745 us
  PIN_FAST_BENCHMARK: Time: get:489950 put:6459 us
  PIN_FAST_BENCHMARK: Time: get:489777 put:6617 us
  PIN_FAST_BENCHMARK: Time: get:488224 put:6591 us
  PIN_FAST_BENCHMARK: Time: get:488644 put:6477 us
  PIN_FAST_BENCHMARK: Time: get:488754 put:6711 us
  PIN_FAST_BENCHMARK: Time: get:488875 put:6743 us
  PIN_FAST_BENCHMARK: Time: get:489290 put:6657 us
  PIN_FAST_BENCHMARK: Time: get:490264 put:6684 us
  PIN_FAST_BENCHMARK: Time: get:489631 put:6737 us
  PIN_FAST_BENCHMARK: Time: get:488434 put:6655 us
  PIN_FAST_BENCHMARK: Time: get:492213 put:6297 us
  PIN_FAST_BENCHMARK: Time: get:491124 put:6173 us

After the whole series applied (new fixed kernel):

  $ sudo chrt -f 1 ./gup_test -a  -m 512 -j 40
  PIN_FAST_BENCHMARK: Time: get:82038 put:7041 us
  PIN_FAST_BENCHMARK: Time: get:82144 put:6817 us
  PIN_FAST_BENCHMARK: Time: get:83417 put:6674 us
  PIN_FAST_BENCHMARK: Time: get:82540 put:6594 us
  PIN_FAST_BENCHMARK: Time: get:83214 put:6681 us
  PIN_FAST_BENCHMARK: Time: get:83444 put:6889 us
  PIN_FAST_BENCHMARK: Time: get:83194 put:7499 us
  PIN_FAST_BENCHMARK: Time: get:84876 put:7369 us
  PIN_FAST_BENCHMARK: Time: get:86092 put:10289 us
  PIN_FAST_BENCHMARK: Time: get:86153 put:10415 us
  PIN_FAST_BENCHMARK: Time: get:85026 put:7751 us
  PIN_FAST_BENCHMARK: Time: get:85458 put:7944 us
  PIN_FAST_BENCHMARK: Time: get:85735 put:8154 us
  PIN_FAST_BENCHMARK: Time: get:85851 put:8299 us
  PIN_FAST_BENCHMARK: Time: get:86323 put:9617 us
  PIN_FAST_BENCHMARK: Time: get:86288 put:10496 us
  PIN_FAST_BENCHMARK: Time: get:87697 put:9346 us
  PIN_FAST_BENCHMARK: Time: get:87980 put:8382 us
  PIN_FAST_BENCHMARK: Time: get:88719 put:8400 us
  PIN_FAST_BENCHMARK: Time: get:87616 put:8588 us
  PIN_FAST_BENCHMARK: Time: get:86730 put:9563 us
  PIN_FAST_BENCHMARK: Time: get:88167 put:8673 us
  PIN_FAST_BENCHMARK: Time: get:86844 put:9777 us
  PIN_FAST_BENCHMARK: Time: get:88068 put:11774 us
  PIN_FAST_BENCHMARK: Time: get:86170 put:15676 us
  PIN_FAST_BENCHMARK: Time: get:87967 put:12827 us
  PIN_FAST_BENCHMARK: Time: get:95773 put:7652 us
  PIN_FAST_BENCHMARK: Time: get:87734 put:13650 us
  PIN_FAST_BENCHMARK: Time: get:89833 put:14237 us
  PIN_FAST_BENCHMARK: Time: get:96186 put:8029 us
  PIN_FAST_BENCHMARK: Time: get:95532 put:8886 us
  PIN_FAST_BENCHMARK: Time: get:95351 put:5826 us
  PIN_FAST_BENCHMARK: Time: get:96401 put:8407 us
  PIN_FAST_BENCHMARK: Time: get:96473 put:8287 us
  PIN_FAST_BENCHMARK: Time: get:97177 put:8430 us
  PIN_FAST_BENCHMARK: Time: get:98120 put:5263 us
  PIN_FAST_BENCHMARK: Time: get:96271 put:7757 us
  PIN_FAST_BENCHMARK: Time: get:99628 put:10467 us
  PIN_FAST_BENCHMARK: Time: get:99344 put:10045 us
  PIN_FAST_BENCHMARK: Time: get:94212 put:15485 us

Summary:

  Old kernel: 477729.97 (+-3.79%)
  New kernel:  89144.65 (+-11.76%)

This patch (of 3):

Add a new parameter "-j N" to support concurrent gup test.

Link: https://lkml.kernel.org/r/20210507150553.208763-1-peterx@redhat.com
Link: https://lkml.kernel.org/r/20210507150553.208763-2-peterx@redhat.comSigned-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

These functions implement the address_space ->set_page_dirty operation and
should live in pagemap.h, not mm.h so that the rest of the kernel doesn't
get funny ideas about calling them directly.

Link: https://lkml.kernel.org/r/20210615162342.1669332-7-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Use __set_page_dirty_no_writeback() instead.  This will set the dirty bit
on the page, which will be used to avoid calling set_page_dirty() in the
future.  It will have no effect on actually writing the page back, as the
pages are not on any LRU lists.

[akpm@linux-foundation.org: export __set_page_dirty_no_writeback() to modules]

Link: https://lkml.kernel.org/r/20210615162342.1669332-6-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Use __set_page_dirty_no_writeback() instead.  This will set the dirty bit
on the page, which will be used to avoid calling set_page_dirty() in the
future.  It will have no effect on actually writing the page back, as the
pages are not on any LRU lists.

Link: https://lkml.kernel.org/r/20210615162342.1669332-5-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The only difference between iomap_set_page_dirty() and
__set_page_dirty_nobuffers() is that the latter includes a debugging check
that a !Uptodate page has private data.

Link: https://lkml.kernel.org/r/20210615162342.1669332-4-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This is fundamentally the same code, so just call it instead of
duplicating it.

Link: https://lkml.kernel.org/r/20210615162342.1669332-3-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "Further set_page_dirty cleanups".

Prompted by Christoph's recent patches, here are some more patches to
improve the state of set_page_dirty().  They're all from the folio tree,
so they've been tested to a certain extent.

This patch (of 6):

Nothing in __set_page_dirty() is specific to buffer_head, so move it to
mm/page-writeback.c.  That removes the only caller of
account_page_dirtied() outside of page-writeback.c, so make it static.

Link: https://lkml.kernel.org/r/20210615162342.1669332-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20210615162342.1669332-2-willy@infradead.orgSigned-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
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>

Remove the CONFIG_BLOCK default to __set_page_dirty_buffers and just wire
that method up for the missing instances.

[hch@lst.de: ecryptfs: add a ->set_page_dirty cludge]
  Link: https://lkml.kernel.org/r/20210624125250.536369-1-hch@lst.de

Link: https://lkml.kernel.org/r/20210614061512.3966143-4-hch@lst.deSigned-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Tyler Hicks <code@tyhicks.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Move the ramfs aops to libfs and reuse them for kernfs and configfs.
Thosw two did not wire up ->set_page_dirty before and now get
__set_page_dirty_no_writeback, which is the right one for no-writeback
address_space usage.

Drop the now unused exports of the libfs helpers only used for ramfs-style
pagecache usage.

Link: https://lkml.kernel.org/r/20210614061512.3966143-3-hch@lst.deSigned-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "remove the implicit .set_page_dirty default".

This series cleans up a few lose ends around ->set_page_dirty, most
importantly removes the default to the buffer head based on if no method
is wired up.

This patch (of 3):

__set_page_dirty is only used by built-in code.

Link: https://lkml.kernel.org/r/20210614061512.3966143-1-hch@lst.de
Link: https://lkml.kernel.org/r/20210614061512.3966143-2-hch@lst.deSigned-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Asynchronously try to release dying cgwbs by switching attached inodes to
the nearest living ancestor wb.  It helps to get rid of per-cgroup
writeback structures themselves and of pinned memory and block cgroups,
which are significantly larger structures (mostly due to large per-cpu
statistics data).  This prevents memory waste and helps to avoid different
scalability problems caused by large piles of dying cgroups.

Reuse the existing mechanism of inode switching used for foreign inode
detection.  To speed things up batch up to 115 inode switching in a single
operation (the maximum number is selected so that the resulting struct
inode_switch_wbs_context can fit into 1024 bytes).  Because every
switching consists of two steps divided by an RCU grace period, it would
be too slow without batching.  Please note that the whole batch counts as
a single operation (when increasing/decreasing isw_nr_in_flight).  This
allows to keep umounting working (flush the switching queue), however
prevents cleanups from consuming the whole switching quota and effectively
blocking the frn switching.

A cgwb cleanup operation can fail due to different reasons (e.g.  not
enough memory, the cgwb has an in-flight/pending io, an attached inode in
a wrong state, etc).  In this case the next scheduled cleanup will make a
new attempt.  An attempt is made each time a new cgwb is offlined (in
other words a memcg and/or a blkcg is deleted by a user).  In the future
an additional attempt scheduled by a timer can be implemented.

[guro@fb.com: replace open-coded "115" with arithmetic]
  Link: https://lkml.kernel.org/r/YMEcSBcq/VXMiPPO@carbon.dhcp.thefacebook.com
[guro@fb.com: add smp_mb() to inode_prepare_wbs_switch()]
  Link: https://lkml.kernel.org/r/YMFa+guFw7OFjf3X@carbon.dhcp.thefacebook.com
[willy@infradead.org: fix documentation]
  Link: https://lkml.kernel.org/r/20210615200242.1716568-2-willy@infradead.org

Link: https://lkml.kernel.org/r/20210608230225.2078447-9-guro@fb.comSigned-off-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Currently only a single inode can be switched to another writeback
structure at once.  That means to switch an inode a separate
inode_switch_wbs_context structure must be allocated, and a separate rcu
callback and work must be scheduled.

It's fine for the existing ad-hoc switching, which is not happening that
often, but sub-optimal for massive switching required in order to release
a writeback structure.  To prepare for it, let's add a support for
switching multiple inodes at once.

Instead of containing a single inode pointer, inode_switch_wbs_context
will contain a NULL-terminated array of inode pointers.
inode_do_switch_wbs() will be called for each inode.

To optimize the locking bdi->wb_switch_rwsem, old_wb's and new_wb's
list_locks will be acquired and released only once altogether for all
inodes.  wb_wakeup() will be also be called only once.  Instead of calling
wb_put(old_wb) after each successful switch, wb_put_many() is introduced
and used.

Link: https://lkml.kernel.org/r/20210608230225.2078447-8-guro@fb.comSigned-off-by: Roman Gushchin <guro@fb.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Split out the functional part of the inode_switch_wbs_work_fn() function
as inode_do switch_wbs() to reuse it later for switching inodes attached
to dying cgwbs.

This commit doesn't bring any functional changes.

Link: https://lkml.kernel.org/r/20210608230225.2078447-7-guro@fb.comSigned-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Currently there is no way to iterate over inodes attached to a specific
cgwb structure.  It limits the ability to efficiently reclaim the
writeback structure itself and associated memory and block cgroup
structures without scanning all inodes belonging to a sb, which can be
prohibitively expensive.

While dirty/in-active-writeback an inode belongs to one of the
bdi_writeback's io lists: b_dirty, b_io, b_more_io and b_dirty_time.  Once
cleaned up, it's removed from all io lists.  So the inode->i_io_list can
be reused to maintain the list of inodes, attached to a bdi_writeback
structure.

This patch introduces a new wb->b_attached list, which contains all inodes
which were dirty at least once and are attached to the given cgwb.  Inodes
attached to the root bdi_writeback structures are never placed on such
list.  The following patch will use this list to try to release cgwbs
structures more efficiently.

Link: https://lkml.kernel.org/r/20210608230225.2078447-6-guro@fb.comSigned-off-by: Roman Gushchin <guro@fb.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Inode's wb switching requires two steps divided by an RCU grace period.
It's currently implemented as an RCU callback inode_switch_wbs_rcu_fn(),
which schedules inode_switch_wbs_work_fn() as a work.

Switching to the rcu_work API allows to do the same in a cleaner and
slightly shorter form.

Link: https://lkml.kernel.org/r/20210608230225.2078447-5-guro@fb.comSigned-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

isw_nr_in_flight is used to determine whether the inode switch queue
should be flushed from the umount path.  Currently it's increased after
grabbing an inode and even scheduling the switch work.  It means the
umount path can walk past cleanup_offline_cgwb() with active inode
references, which can result in a "Busy inodes after unmount." message and
use-after-free issues (with inode->i_sb which gets freed).

Fix it by incrementing isw_nr_in_flight before doing anything with the
inode and decrementing in the case when switching wasn't scheduled.

The problem hasn't yet been seen in the real life and was discovered by
Jan Kara by looking into the code.

Link: https://lkml.kernel.org/r/20210608230225.2078447-4-guro@fb.comSigned-off-by: Roman Gushchin <guro@fb.com>
Suggested-by: Jan Kara <jack@suse.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

A full memory barrier is required between clearing SB_ACTIVE flag in
generic_shutdown_super() and checking isw_nr_in_flight in
cgroup_writeback_umount(), otherwise a new switch operation might be
scheduled after atomic_read(&isw_nr_in_flight) returned 0.  This would
result in a non-flushed isw_wq, and a potential crash.

The problem hasn't yet been seen in the real life and was discovered by
Jan Kara by looking into the code.

Link: https://lkml.kernel.org/r/20210608230225.2078447-3-guro@fb.comSigned-off-by: Roman Gushchin <guro@fb.com>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Jan Kara <jack@suse.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "cgroup, blkcg: prevent dirty inodes to pin dying memory cgroups", v9.

When an inode is getting dirty for the first time it's associated with a
wb structure (see __inode_attach_wb()).  It can later be switched to
another wb (if e.g.  some other cgroup is writing a lot of data to the
same inode), but otherwise stays attached to the original wb until being
reclaimed.

The problem is that the wb structure holds a reference to the original
memory and blkcg cgroups.  So if an inode has been dirty once and later is
actively used in read-only mode, it has a good chance to pin down the
original memory and blkcg cgroups forever.  This is often the case with
services bringing data for other services, e.g.  updating some rpm
packages.

In the real life it becomes a problem due to a large size of the memcg
structure, which can easily be 1000x larger than an inode.  Also a really
large number of dying cgroups can raise different scalability issues, e.g.
making the memory reclaim costly and less effective.

To solve the problem inodes should be eventually detached from the
corresponding writeback structure.  It's inefficient to do it after every
writeback completion.  Instead it can be done whenever the original memory
cgroup is offlined and writeback structure is getting killed.  Scanning
over a (potentially long) list of inodes and detach them from the
writeback structure can take quite some time.  To avoid scanning all
inodes, attached inodes are kept on a new list (b_attached).  To make it
less noticeable to a user, the scanning and switching is performed from a
work context.

Big thanks to Jan Kara, Dennis Zhou, Hillf Danton and Tejun Heo for their
ideas and contribution to this patchset.

This patch (of 8):

If an inode's state has I_WILL_FREE flag set, the inode will be freed
soon, so there is no point in trying to switch the inode to a different
cgwb.

I_WILL_FREE was ignored since the introduction of the inode switching, so
it looks like it doesn't lead to any noticeable issues for a user.  This
is why the patch is not intended for a stable backport.

Link: https://lkml.kernel.org/r/20210608230225.2078447-1-guro@fb.com
Link: https://lkml.kernel.org/r/20210608230225.2078447-2-guro@fb.comSigned-off-by: Roman Gushchin <guro@fb.com>
Suggested-by: Jan Kara <jack@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dennis Zhou <dennis@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

As account_page_dirtied() was always protected by xa_lock_irqsave(), so
using __this_cpu_inc() is better.

Link: https://lkml.kernel.org/r/20210512144742.4764-1-wuchi.zero@gmail.comSigned-off-by: Chi Wu <wuchi.zero@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Howard Cochran <hcochran@kernelspring.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

As the value of pos_ratio_polynom() clamp between 0 and 2LL <<
RATELIMIT_CALC_SHIFT, the global control line should be consistent with
it.

Link: https://lkml.kernel.org/r/20210511103606.3732-1-wuchi.zero@gmail.comSigned-off-by: Chi Wu <wuchi.zero@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@fb.com>
Cc: Howard Cochran <hcochran@kernelspring.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Fix performance when BDI's share of ratio is 0.

The issue is similar to commit 74d36944 ("writeback: Fix
performance regression in wb_over_bg_thresh()").

Balance_dirty_pages and the writeback worker will also disagree on
whether writeback when a BDI uses BDI_CAP_STRICTLIMIT and BDI's share
of the thresh ratio is zero.

For example, A thread on cpu0 writes 32 pages and then
balance_dirty_pages, it will wake up background writeback and pauses
because wb_dirty > wb->wb_thresh = 0 (share of thresh ratio is zero).
A thread may runs on cpu0 again because scheduler prefers pre_cpu.
Then writeback worker may runs on other cpus(1,2..) which causes the
value of wb_stat(wb, WB_RECLAIMABLE) in wb_over_bg_thresh is 0 and does
not writeback and returns.

Thus, balance_dirty_pages keeps looping, sleeping and then waking up the
worker who will do nothing. It remains stuck in this state until the
writeback worker hit the right dirty cpu or the dirty pages expire.

The fix that we should get the wb_stat_sum radically when thresh is low.

Link: https://lkml.kernel.org/r/20210428225046.16301-1-wuchi.zero@gmail.comSigned-off-by: Chi Wu <wuchi.zero@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The get_writeback_state() has gone since 2006, kill related comments.

Link: https://lkml.kernel.org/r/20210508125026.56600-1-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The page reporting won't be triggered if the freeing page can't come up
with a free area, whose size is equal or bigger than the threshold (page
reporting order).  The default page reporting order, equal to
@pageblock_order, is too huge on some architectures to trigger page
reporting.  One example is ARM64 when 64KB base page size is used.

      PAGE_SIZE:          64KB
      pageblock_order:    13       (512MB)
      MAX_ORDER:          14

This specifies the page reporting order to 5 (2MB) for this specific case
so that page reporting can be triggered.

Link: https://lkml.kernel.org/r/20210625014710.42954-5-gshan@redhat.comSigned-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The page reporting order (threshold) is sticky to @pageblock_order by
default.  The page reporting can never be triggered because the freeing
page can't come up with a free area like that huge.  The situation becomes
worse when the system memory becomes heavily fragmented.

For example, the following configurations are used on ARM64 when 64KB base
page size is enabled.  In this specific case, the page reporting won't be
triggered until the freeing page comes up with a 512MB free area.  That's
hard to be met, especially when the system memory becomes heavily
fragmented.

   PAGE_SIZE:          64KB
   HPAGE_SIZE:         512MB
   pageblock_order:    13       (512MB)
   MAX_ORDER:          14

This allows the drivers to specify the page reporting order when the page
reporting device is registered.  It falls back to @pageblock_order if it's
not specified by the driver.  The existing users (hv_balloon and
virtio_balloon) don't specify it and @pageblock_order is still taken as
their page reporting order.  So this shouldn't introduce any functional
changes.

Link: https://lkml.kernel.org/r/20210625014710.42954-4-gshan@redhat.comSigned-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The macro PAGE_REPORTING_MIN_ORDER is defined as the page reporting
threshold.  It can't be adjusted at runtime.

This introduces a variable (@page_reporting_order) to replace the marcro
(PAGE_REPORTING_MIN_ORDER).  MAX_ORDER is assigned to it initially,
meaning the page reporting is disabled.  It will be specified by driver if
valid one is provided.  Otherwise, it will fall back to @pageblock_order.
It's also exported so that the page reporting order can be adjusted at
runtime.

Link: https://lkml.kernel.org/r/20210625014710.42954-3-gshan@redhat.comSigned-off-by: Gavin Shan <gshan@redhat.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "mm/page_reporting: Make page reporting work on arm64 with 64KB page size", v4.

The page reporting threshold is currently equal to @pageblock_order, which
is 13 and 512MB on arm64 with 64KB base page size selected.  The page
reporting won't be triggered if the freeing page can't come up with a free
area like that huge.  The condition is hard to be met, especially when the
system memory becomes fragmented.

This series intends to solve the issue by having page reporting threshold
as 5 (2MB) on arm64 with 64KB base page size.  The patches are organized
as:

   PATCH[1/4] Fix some coding style in __page_reporting_request().
   PATCH[2/4] Represents page reporting order with variable so that it can
              be exported as module parameter.
   PATCH[3/4] Allows the device driver (e.g. virtio_balloon) to specify
              the page reporting order when the device info is registered.
   PATCH[4/4] Specifies the page reporting order to 5, corresponding to
              2MB in size on ARM64 when 64KB base page size is used.

This patch (of 4):

The lines of comments would be starting with one, instead two space.  This
corrects the style.

Link: https://lkml.kernel.org/r/20210625014710.42954-1-gshan@redhat.com
Link: https://lkml.kernel.org/r/20210625014710.42954-2-gshan@redhat.comSigned-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Alexander Duyck <alexanderduyck@fb.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mmap_lock will explicitly disable/enable preemption upon manipulating its
local CPU variables.  This is to be expected, but in this case, it doesn't
play well with PREEMPT_RT.  The preemption disabled code section also
takes a spin-lock.  Spin-locks in RT systems will try to schedule, which
is exactly what we're trying to avoid.

To mitigate this, convert the explicit preemption handling to local_locks.
Which are RT aware, and will disable migration instead of preemption when
PREEMPT_RT=y.

The faulty call trace looks like the following:
    __mmap_lock_do_trace_*()
      preempt_disable()
      get_mm_memcg_path()
        cgroup_path()
          kernfs_path_from_node()
            spin_lock_irqsave() /* Scheduling while atomic! */

Link: https://lkml.kernel.org/r/20210604163506.2103900-1-nsaenzju@redhat.com
Fixes: 2b5067a8 ("mm: mmap_lock: add tracepoints around lock acquisition ")
Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Tested-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

On certain platforms, THP support could not just be validated via the
build option CONFIG_TRANSPARENT_HUGEPAGE.  Instead
has_transparent_hugepage() also needs to be called upon to verify THP
runtime support.  Otherwise the debug test will just run into unusable THP
helpers like in the case of a 4K hash config on powerpc platform [1].
This just moves all pfn_pmd() and pfn_pud() after THP runtime validation
with has_transparent_hugepage() which prevents the mentioned problem.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=213069

Link: https://lkml.kernel.org/r/1621397588-19211-1-git-send-email-anshuman.khandual@arm.com
Fixes: 787d563b ("mm/debug_vm_pgtable: fix kernel crash by checking for THP support")
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Link: https://lkml.kernel.org/r/20210506131402.10416-1-tangbin@cmss.chinamobile.comSigned-off-by: Zhang Shengju <zhangshengju@cmss.chinamobile.com>
Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

grab_mapping_entry() has a bug in handling of ENOMEM condition.  Suppose
we have a PMD entry at index i which we are downgrading to a PTE entry.
grab_mapping_entry() will set pmd_downgrade to true, lock the entry, clear
the entry in xarray, and decrement mapping->nrpages.  The it will call:

	entry = dax_make_entry(pfn_to_pfn_t(0), flags);
	dax_lock_entry(xas, entry);

which inserts new PTE entry into xarray.  However this may fail allocating
the new node.  We handle this by:

	if (xas_nomem(xas, mapping_gfp_mask(mapping) & ~__GFP_HIGHMEM))
		goto retry;

however pmd_downgrade stays set to true even though 'entry' returned from
get_unlocked_entry() will be NULL now.  And we will go again through the
downgrade branch.  This is mostly harmless except that mapping->nrpages is
decremented again and we temporarily have an invalid entry stored in
xarray.  Fix the problem by setting pmd_downgrade to false each time we
lookup the entry we work with so that it matches the entry we found.

Link: https://lkml.kernel.org/r/20210622160015.18004-1-jack@suse.cz
Fixes: b15cd800 ("dax: Convert page fault handlers to XArray")
Signed-off-by: Jan Kara <jack@suse.cz>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This commit contains 3 modifications:

1. Convert the type of jiffies_scan_wait to "unsigned long".

2. Use READ/WRITE_ONCE() for accessing "jiffies_scan_wait".

3. Fix the possible wrong memory scanning period.  If you set a large
   memory scanning period like blow, then the "secs" variable will be
   non-zero, however the value of "jiffies_scan_wait" will be zero.

    echo "scan=0x10000000" > /sys/kernel/debug/kmemleak

It is because the type of the msecs_to_jiffies()'s parameter is "unsigned
int", and the "secs * 1000" is larger than its max value.  This in turn
leads a unexpected jiffies_scan_wait, maybe zero.  We corret it by
replacing kstrtoul() with kstrtouint(), and check the msecs to prevent it
larger than UINT_MAX.

Link: https://lkml.kernel.org/r/20210613174022.23044-1-yanfei.xu@windriver.comSigned-off-by: Yanfei Xu <yanfei.xu@windriver.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

When running the kernel with panic_on_taint, the usual slub debug error
messages are not being printed when object corruption happens.  That's
because we panic in add_taint(), which is called before printing the
additional information.  This is a bit unfortunate as the error messages
are actually very useful, especially before a panic.  Let's fix this by
moving add_taint() after the errors are printed on the console.

Link: https://lkml.kernel.org/r/1623860738-146761-1-git-send-email-quic_c_gdjako@quicinc.comSigned-off-by: Georgi Djakov <quic_c_gdjako@quicinc.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

alloc_calls and free_calls implementation in sysfs have two issues, one is
PAGE_SIZE limitation of sysfs and other is it does not adhere to "one
value per file" rule.

To overcome this issues, move the alloc_calls and free_calls
implementation to debugfs.

Debugfs cache will be created if SLAB_STORE_USER flag is set.

Rename the alloc_calls/free_calls to alloc_traces/free_traces, to be
inline with what it does.

[faiyazm@codeaurora.org: fix the leak of alloc/free traces debugfs interface]
  Link: https://lkml.kernel.org/r/1624248060-30286-1-git-send-email-faiyazm@codeaurora.org

Link: https://lkml.kernel.org/r/1623438200-19361-1-git-send-email-faiyazm@codeaurora.orgSigned-off-by: Faiyaz Mohammed <faiyazm@codeaurora.org>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Obscuring the pointers that slub shows when debugging makes for some
confusing slub debug messages:

 Padding overwritten. 0x0000000079f0674a-0x000000000d4dce17

Those addresses are hashed for kernel security reasons.  If we're trying
to be secure with slub_debug on the commandline we have some big problems
given that we dump whole chunks of kernel memory to the kernel logs.
Let's force on the no_hash_pointers commandline flag when slub_debug is on
the commandline.  This makes slub debug messages more meaningful and if by
chance a kernel address is in some slub debug object dump we will have a
better chance of figuring out what went wrong.

Note that we don't use %px in the slub code because we want to reduce the
number of places that %px is used in the kernel.  This also nicely prints
a big fat warning at kernel boot if slub_debug is on the commandline so
that we know that this kernel shouldn't be used on production systems.

[akpm@linux-foundation.org: fix build with CONFIG_SLUB_DEBUG=n]

Link: https://lkml.kernel.org/r/20210601182202.3011020-5-swboyd@chromium.orgSigned-off-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Petr Mladek <pmladek@suse.com>
Cc: Joe Perches <joe@perches.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Ideally, slab_fix() would be marked with __printf and the format here
would not use \n as that's emitted by the slab_fix().  Make these changes.

Link: https://lkml.kernel.org/r/20210601182202.3011020-4-swboyd@chromium.orgSigned-off-by: Joe Perches <joe@perches.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>