Patch series "mm/zsmalloc: change back to per-size_class lock, v2".

Commit c0547d0b ("zsmalloc: consolidate zs_pool's migrate_lock and
size_class's locks") changed per-size_class lock to pool spinlock to
prepare reclaim support in zsmalloc.  Then reclaim support in zsmalloc had
been dropped in favor of LRU reclaim in zswap, but this locking change had
been left there.

Obviously, the scalability of pool spinlock is worse than per-size_class. 
And we have a workaround that using 32 pools in zswap to avoid this
scalability problem, which brings its own problems like memory waste and
more memory fragmentation.

So this series changes back to use per-size_class lock and using testing
data in much stressed situation to verify that we can use only one pool in
zswap.  Note we only test and care about the zsmalloc backend, which makes
sense now since zsmalloc became a lot more popular than other backends.

Testing kernel build (make bzImage -j32) on tmpfs with memory.max=1GB, and
zswap shrinker enabled with 10GB swapfile on ext4.

				real	user    sys
6.10.0-rc3			138.18	1241.38 1452.73
6.10.0-rc3-onepool		149.45	1240.45 1844.69
6.10.0-rc3-onepool-perclass	138.23	1242.37 1469.71

We can see from "sys" column that per-size_class locking with only one
pool in zswap can have near performance with the current 32 pools.


This patch (of 2):

This patch is almost the revert of the commit c0547d0b ("zsmalloc:
consolidate zs_pool's migrate_lock and size_class's locks"), which changed
to use a global pool->lock instead of per-size_class lock and
pool->migrate_lock, was preparation for suppporting reclaim in zsmalloc. 
Then reclaim in zsmalloc had been dropped in favor of LRU reclaim in
zswap.

In theory, per-size_class is more fine-grained than the pool->lock, since
a pool can have many size_classes.  As for the additional
pool->migrate_lock, only free() and map() need to grab it to access stable
handle to get zspage, and only in read lock mode.

Link: https://lkml.kernel.org/r/20240625-zsmalloc-lock-mm-everything-v3-0-ad941699cb61@linux.dev
Link: https://lkml.kernel.org/r/20240621-zsmalloc-lock-mm-everything-v2-0-d30e9cd2b793@linux.dev
Link: https://lkml.kernel.org/r/20240617-zsmalloc-lock-mm-everything-v1-0-5e5081ea11b3@linux.dev
Link: https://lkml.kernel.org/r/20240617-zsmalloc-lock-mm-everything-v1-1-5e5081ea11b3@linux.devSigned-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

During conflict resolution a line was unintentionally removed by a ksm.c
patch.

Link: https://lkml.kernel.org/r/85b0d694-d1ac-8e7a-2e50-1edc03eee21a@google.com
Fixes: ac90c56b ("mm/ksm: refactor out try_to_merge_with_zero_page()")
Reported-by: Hugh Dickins <hughd@google.com>
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

If CONFIG_ZSWAP is set to N, it means zswap cannot be enabled. 
zswap_never_enabled() should return true.

The only effect of this issue is that with Barry's latest large folio
swapin patches for zram ("mm: support mTHP swap-in for zRAM-like
swapfile"), we will always fallback to order-0 swapin, even mistakenly
when !CONFIG_ZSWAP.

Basically this bug makes Barry's in progress patches not work at all.

The API was created to inform the mm core that zswap has never been
enabled, allowing the mm core to perform mTHP swap-in.  This is a
transitional solution until zswap supports mTHP.  If zswap has been
enabled, performing mTHP swap-in will result in corrupted data.  You
may find the answer in the mTHP swap-in series:

https://lore.kernel.org/linux-mm/CAJD7tkZ4FQr6HZpduOdvmqgg_-whuZYE-Bz5O2t6yzw6Yg+v1A@mail.gmail.com/

Link: https://lkml.kernel.org/r/20240629232231.42394-1-21cnbao@gmail.com
Fixes: 0300e17d67c3 ("mm: zswap: add zswap_never_enabled()")
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: Chengming Zhou <chengming.zhou@linux.dev>
Acked-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Chris Li <chrisl@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Nhat Pham <nphamcs@gmail.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The optimization of list_empty(&folio->_deferred_list) aimed to prevent
increasing the PTL duration when a large folio is partially unmapped, for
example, from subpage 0 to subpage (nr - 2).

But Ryan's commit 5ed890ce ("mm: vmscan: avoid split during
shrink_folio_list()") actually splits this kind of large folios.  This
makes the "optimization" useless.

Additionally, the list_empty() technically required a data_race()
annotation.

Link: https://lkml.kernel.org/r/20240629234155.53524-1-21cnbao@gmail.comSigned-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The prefetchw() is introduced from an ancient patch[1].

The change log says:

    The basic idea is to free higher order pages instead of going
    through every single one.  Also, some unnecessary atomic operations
    are done away with and replaced with non-atomic equivalents, and
    prefetching is done where it helps the most.  For a more in-depth
    discusion of this patch, please see the linux-ia64 archives (topic
    is "free bootmem feedback patch").

So there are several changes improve the bootmem freeing, in which the
most basic idea is freeing higher order pages.  And as Matthew says,
"Itanium CPUs of this era had no prefetchers."

I did 10 round bootup tests before and after this change, the data doesn't
prove prefetchw() help speeding up bootmem freeing.  The sum of the 10
round bootmem freeing time after prefetchw() removal even 5.2% faster than
before.

[1]: https://lore.kernel.org/linux-ia64/40F46962.4090604@sgi.com/

Link: https://lkml.kernel.org/r/20240702020931.7061-1-richard.weiyang@gmail.comSigned-off-by: Wei Yang <richard.weiyang@gmail.com>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The functions set_max_threads() and task_struct_whitelist() are only used
by fork_init() during bootup.

Let's add __init tag to them.

Link: https://lkml.kernel.org/r/20240701013410.17260-2-richard.weiyang@gmail.comSigned-off-by: Wei Yang <richard.weiyang@gmail.com>
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Since we plan to move the accounting into __free_pages_core(),
totalram_pages may not represent the total usable pages on system at this
point when defer_init is enabled.

Instead we can get the total usable pages from memblock directly.

Link: https://lkml.kernel.org/r/20240701013410.17260-1-richard.weiyang@gmail.comSigned-off-by: Wei Yang <richard.weiyang@gmail.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

CONFIG_MEMCG_KMEM used to be a user-visible option for whether slab
tracking is enabled.  It has been default-enabled and equivalent to
CONFIG_MEMCG for almost a decade.  We've only grown more kernel memory
accounting sites since, and there is no imaginable cgroup usecase going
forward that wants to track user pages but not the multitude of
user-drivable kernel allocations.

Link: https://lkml.kernel.org/r/20240701153148.452230-1-hannes@cmpxchg.orgSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Memcg v1-specific fields serve a buffer function between read-mostly and
update often parts of the mem_cgroup_per_node structure.  If
CONFIG_MEMCG_V1 is not set and these fields are not present, an explicit
cacheline padding is needed.

Link: https://lkml.kernel.org/r/20240701185932.704807-2-roman.gushchin@linux.devSigned-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Suggested-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

After the grouping of the cgroup v1-related fields and the corresponding
reorganization of the struct mem_cgroup, the existing cache line padding
doesn't make much sense anymore.  Let's drop it for now and put back to
new places, if necessary.

Link: https://lkml.kernel.org/r/20240701185932.704807-1-roman.gushchin@linux.devSigned-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Suggested-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
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.orgSigned-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.orgSigned-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.orgSigned-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.orgSigned-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.orgSigned-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.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

DAMON user-space tool (damo) provides access pattern snapshot feature,
which is expected to be frequently used for real time access pattern
analysis.  The snapshot output is also showing what DAMON provides on its
own, including the 'age' information.

In contrast, the recorded access patterns, which is shown as an example
usage on the quick start section, shows what users can make from what
DAMON provided.  It includes information that generated outside of DAMON
and makes the 'age' concept bit unclear.  Hence snapshot output is easier
at understanding the raw realtime output of DAMON.  Add the snapshot usage
example on the quick start section.

Link: https://lkml.kernel.org/r/20240701192706.51415-4-sj@kernel.orgSigned-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.orgSigned-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.orgSigned-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Commit 19eaf449 ("mm: thp: support allocation of anonymous multi-size
THP") added mTHP support for anonymous shmem.  We can configure different
policies through the multi-size THP sysfs interface for anonymous shmem.

But when we configure the "advise" policy of
/sys/kernel/mm/transparent_hugepage/hugepages-xxxkB/shmem_enabled, we
cannot write the "advise", but write the "madvise", which is unreasonable.
We should keep the output and input values consistent, which is more
convenient for users.

Link: https://lkml.kernel.org/r/20240628032327.16987-1-libang.li@antgroup.com
Fixes: 61a57f1b1da9 ("mm: shmem: add multi-size THP sysfs interface for anonymous shmem")
Signed-off-by: Bang Li <libang.li@antgroup.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Bang Li <libang.li@antgroup.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Centralize the _GNU_SOURCE definition to CFLAGS in lib.mk.  Remove
redundant defines from Makefiles that import lib.mk.  Convert any usage of
"#define _GNU_SOURCE 1" to "#define _GNU_SOURCE".

This uses the form "-D_GNU_SOURCE=", which is equivalent to
"#define _GNU_SOURCE".

Otherwise using "-D_GNU_SOURCE" is equivalent to "-D_GNU_SOURCE=1" and
"#define _GNU_SOURCE 1", which is less commonly seen in source code and
would require many changes in selftests to avoid redefinition warnings.

Link: https://lkml.kernel.org/r/20240625223454.1586259-2-edliaw@google.comSigned-off-by: Edward Liaw <edliaw@google.com>
Suggested-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: André Almeida <andrealmeid@igalia.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kees Cook <kees@kernel.org>
Cc: Kevin Tian <kevin.tian@intel.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Reinette Chatre <reinette.chatre@intel.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Both Ryan and Chris have been utilizing the small test program to aid in
debugging and identifying issues with swap entry allocation.  While a real
or intricate workload might be more suitable for assessing the correctness
and effectiveness of the swap allocation policy, a small test program
presents a simpler means of understanding the problem and initially
verifying the improvements being made.

Let's endeavor to integrate it into tools/mm.  Although it presently only
accommodates 64KB and 4KB, I'm optimistic that we can expand its
capabilities to support multiple sizes and simulate more complex systems
in the future as required.

Basically, we have

1. Use MADV_PAGEPUT for rapid swap-out, putting the swap allocation
   code under high exercise in a short time.

2. Use MADV_DONTNEED to simulate the behavior of libc and Java heap in
   freeing memory, as well as for munmap, app exits, or OOM killer
   scenarios.  This ensures new mTHP is always generated, released or
   swapped out, similar to the behavior on a PC or Android phone where
   many applications are frequently started and terminated.

3. Swap in with or without the "-a" option to observe how fragments
   due to swap-in and the incoming swap-in of large folios will impact
   swap-out fallback.

Due to 2, we ensure a certain proportion of mTHP.  Similarly, because of
3, we maintain a certain proportion of small folios, as we don't support
large folios swap-in, meaning any swap-in will immediately result in small
folios.  Therefore, with both 2 and 3, we automatically achieve a system
containing both mTHP and small folios.  Additionally, 1 provides the
ability to continuously swap them out.

We can also use "-s" to add a dedicated small folios memory area.

[akpm@linux-foundation.org: thp_swap_allocator_test.c needs mman.h, per Kairui Song]
Link: https://lkml.kernel.org/r/20240622071231.576056-2-21cnbao@gmail.comSigned-off-by: Barry Song <v-songbaohua@oppo.com>
Acked-by: Chris Li <chrisl@kernel.org>
Tested-by: Chris Li <chrisl@kernel.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Tested-by: Ryan Roberts <ryan.roberts@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The folio_migrate_copy() is just a wrapper of folio_copy() and
folio_migrate_flags(), it is simple and only aio use it for now, unfold it
and remove folio_migrate_copy().

Link: https://lkml.kernel.org/r/20240626085328.608006-7-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Jane Chu <jane.chu@oracle.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This is similar to __migrate_folio(), use folio_mc_copy() in HugeTLB folio
migration to avoid panic when copy from poisoned folio.

Link: https://lkml.kernel.org/r/20240626085328.608006-6-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The folio migration is widely used in kernel, memory compaction, memory
hotplug, soft offline page, numa balance, memory demote/promotion, etc,
but once access a poisoned source folio when migrating, the kerenl will
panic.

There is a mechanism in the kernel to recover from uncorrectable memory
errors, ARCH_HAS_COPY_MC, which is already used in other core-mm paths,
eg, CoW, khugepaged, coredump, ksm copy, see copy_mc_to_{user,kernel},
copy_mc_{user_}highpage callers.

In order to support poisoned folio copy recover from migrate folio, we
chose to make folio migration tolerant of memory failures and return error
for folio migration, because folio migration is no guarantee of success,
this could avoid the similar panic shown below.

  CPU: 1 PID: 88343 Comm: test_softofflin Kdump: loaded Not tainted 6.6.0
  pc : copy_page+0x10/0xc0
  lr : copy_highpage+0x38/0x50
  ...
  Call trace:
   copy_page+0x10/0xc0
   folio_copy+0x78/0x90
   migrate_folio_extra+0x54/0xa0
   move_to_new_folio+0xd8/0x1f0
   migrate_folio_move+0xb8/0x300
   migrate_pages_batch+0x528/0x788
   migrate_pages_sync+0x8c/0x258
   migrate_pages+0x440/0x528
   soft_offline_in_use_page+0x2ec/0x3c0
   soft_offline_page+0x238/0x310
   soft_offline_page_store+0x6c/0xc0
   dev_attr_store+0x20/0x40
   sysfs_kf_write+0x4c/0x68
   kernfs_fop_write_iter+0x130/0x1c8
   new_sync_write+0xa4/0x138
   vfs_write+0x238/0x2d8
   ksys_write+0x74/0x110

Note, folio copy is moved in the begin of the __migrate_folio(), which
could simplify the error handling since there is no turning back if
folio_migrate_mapping() return success, the downside is the folio copied
even though folio_migrate_mapping() return fail, an optimization is to
check whether source folio does not have extra refs before we do folio
copy.

Link: https://lkml.kernel.org/r/20240626085328.608006-5-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The folio refcount check is moved out for both !mapping and mapping folio,
also update comment from page to folio for folio_migrate_mapping().

No functional change intended.

Link: https://lkml.kernel.org/r/20240626085328.608006-4-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Add a #MC variant of folio_copy() which uses copy_mc_highpage() to support
#MC handled during folio copy, it will be used in folio migration soon.

Link: https://lkml.kernel.org/r/20240626085328.608006-3-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "mm: migrate: support poison recover from migrate folio", v5.

The folio migration is widely used in kernel, memory compaction, memory
hotplug, soft offline page, numa balance, memory demote/promotion, etc,
but once access a poisoned source folio when migrating, the kernel will
panic.

There is a mechanism in the kernel to recover from uncorrectable memory
errors, ARCH_HAS_COPY_MC(eg, Machine Check Safe Memory Copy on x86), which
is already used in NVDIMM or core-mm paths(eg, CoW, khugepaged, coredump,
ksm copy), see copy_mc_to_{user,kernel}, copy_mc_{user_}highpage callers.

This series of patches provide the recovery mechanism from folio copy for
the widely used folio migration.  Please note, because folio migration is
no guarantee of success, so we could chose to make folio migration
tolerant of memory failures, adding folio_mc_copy() which is a #MC
versions of folio_copy(), once accessing a poisoned source folio, we could
return error and make the folio migration fail, and this could avoid the
similar panic shown below.

  CPU: 1 PID: 88343 Comm: test_softofflin Kdump: loaded Not tainted 6.6.0
  pc : copy_page+0x10/0xc0
  lr : copy_highpage+0x38/0x50
  ...
  Call trace:
   copy_page+0x10/0xc0
   folio_copy+0x78/0x90
   migrate_folio_extra+0x54/0xa0
   move_to_new_folio+0xd8/0x1f0
   migrate_folio_move+0xb8/0x300
   migrate_pages_batch+0x528/0x788
   migrate_pages_sync+0x8c/0x258
   migrate_pages+0x440/0x528
   soft_offline_in_use_page+0x2ec/0x3c0
   soft_offline_page+0x238/0x310
   soft_offline_page_store+0x6c/0xc0
   dev_attr_store+0x20/0x40
   sysfs_kf_write+0x4c/0x68
   kernfs_fop_write_iter+0x130/0x1c8
   new_sync_write+0xa4/0x138
   vfs_write+0x238/0x2d8
   ksys_write+0x74/0x110


This patch (of 5):

There is a memory_failure_queue() call after copy_mc_[user]_highpage(),
see callers, eg, CoW/KSM page copy, it is used to mark the source page as
h/w poisoned and unmap it from other tasks, and the upcomming poison
recover from migrate folio will do the similar thing, so let's move the
memory_failure_queue() into the copy_mc_[user]_highpage() instead of
adding it into each user, this should also enhance the handling of
poisoned page in khugepaged.

Link: https://lkml.kernel.org/r/20240626085328.608006-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20240626085328.608006-2-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

crashes from deferred split racing folio migration", needed by "mm:
migrate: split folio_migrate_mapping()".

Now working at Oracle.

Link: https://lkml.kernel.org/r/20240703092704.11571-1-lorenzo.stoakes@oracle.comSigned-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Even on 6.10-rc6, I've been seeing elusive "Bad page state"s (often on
flags when freeing, yet the flags shown are not bad: PG_locked had been
set and cleared??), and VM_BUG_ON_PAGE(page_ref_count(page) == 0)s from
deferred_split_scan()'s folio_put(), and a variety of other BUG and WARN
symptoms implying double free by deferred split and large folio migration.

6.7 commit 9bcef597 ("mm: memcg: fix split queue list crash when large
folio migration") was right to fix the memcg-dependent locking broken in
85ce2c51 ("memcontrol: only transfer the memcg data for migration"),
but missed a subtlety of deferred_split_scan(): it moves folios to its own
local list to work on them without split_queue_lock, during which time
folio->_deferred_list is not empty, but even the "right" lock does nothing
to secure the folio and the list it is on.

Fortunately, deferred_split_scan() is careful to use folio_try_get(): so
folio_migrate_mapping() can avoid the race by folio_undo_large_rmappable()
while the old folio's reference count is temporarily frozen to 0 - adding
such a freeze in the !mapping case too (originally, folio lock and
unmapping and no swap cache left an anon folio unreachable, so no freezing
was needed there: but the deferred split queue offers a way to reach it).

Link: https://lkml.kernel.org/r/29c83d1a-11ca-b6c9-f92e-6ccb322af510@google.com
Fixes: 9bcef597 ("mm: memcg: fix split queue list crash when large folio migration")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

On a system with Perl 5.12.1, commit 5ef6dc08
("lib/build_OID_registry: don't mention the full path of the script in
output") causes the build to fail with the error below.

     Bareword found where operator expected at ./lib/build_OID_registry line 41, near "s#^\Q$abs_srctree/\E##r"
     syntax error at ./lib/build_OID_registry line 41, near "s#^\Q$abs_srctree/\E##r"
     Execution of ./lib/build_OID_registry aborted due to compilation errors.
     make[3]: *** [lib/Makefile:352: lib/oid_registry_data.c] Error 255

Ahmad Fatoum analyzed that non-destructive substitution is only supported since
Perl 5.13.2. Instead of dropping `r` and having the side effect of modifying
`$0`, introduce a dedicated variable to support older Perl versions.

Link: https://lkml.kernel.org/r/20240702223512.8329-2-pmenzel@molgen.mpg.de
Link: https://lkml.kernel.org/r/20240701155802.75152-1-pmenzel@molgen.mpg.de
Fixes: 5ef6dc08 ("lib/build_OID_registry: don't mention the full path of the script in output")
Link: https://lore.kernel.org/all/259f7a87-2692-480e-9073-1c1c35b52f67@molgen.mpg.de/Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Suggested-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Nicolas Schier <nicolas@fjasle.eu>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

A kernel warning was reported when pinning folio in CMA memory when
launching SEV virtual machine.  The splat looks like:

[  464.325306] WARNING: CPU: 13 PID: 6734 at mm/gup.c:1313 __get_user_pages+0x423/0x520
[  464.325464] CPU: 13 PID: 6734 Comm: qemu-kvm Kdump: loaded Not tainted 6.6.33+ #6
[  464.325477] RIP: 0010:__get_user_pages+0x423/0x520
[  464.325515] Call Trace:
[  464.325520]  <TASK>
[  464.325523]  ? __get_user_pages+0x423/0x520
[  464.325528]  ? __warn+0x81/0x130
[  464.325536]  ? __get_user_pages+0x423/0x520
[  464.325541]  ? report_bug+0x171/0x1a0
[  464.325549]  ? handle_bug+0x3c/0x70
[  464.325554]  ? exc_invalid_op+0x17/0x70
[  464.325558]  ? asm_exc_invalid_op+0x1a/0x20
[  464.325567]  ? __get_user_pages+0x423/0x520
[  464.325575]  __gup_longterm_locked+0x212/0x7a0
[  464.325583]  internal_get_user_pages_fast+0xfb/0x190
[  464.325590]  pin_user_pages_fast+0x47/0x60
[  464.325598]  sev_pin_memory+0xca/0x170 [kvm_amd]
[  464.325616]  sev_mem_enc_register_region+0x81/0x130 [kvm_amd]

Per the analysis done by yangge, when starting the SEV virtual machine, it
will call pin_user_pages_fast(..., FOLL_LONGTERM, ...) to pin the memory. 
But the page is in CMA area, so fast GUP will fail then fallback to the
slow path due to the longterm pinnalbe check in try_grab_folio().

The slow path will try to pin the pages then migrate them out of CMA area.
But the slow path also uses try_grab_folio() to pin the page, it will
also fail due to the same check then the above warning is triggered.

In addition, the try_grab_folio() is supposed to be used in fast path and
it elevates folio refcount by using add ref unless zero.  We are guaranteed
to have at least one stable reference in slow path, so the simple atomic add
could be used.  The performance difference should be trivial, but the
misuse may be confusing and misleading.

Redefined try_grab_folio() to try_grab_folio_fast(), and try_grab_page()
to try_grab_folio(), and use them in the proper paths.  This solves both
the abuse and the kernel warning.

The proper naming makes their usecase more clear and should prevent from
abusing in the future.

peterx said:

: The user will see the pin fails, for gpu-slow it further triggers the WARN
: right below that failure (as in the original report):
: 
:         folio = try_grab_folio(page, page_increm - 1,
:                                 foll_flags);
:         if (WARN_ON_ONCE(!folio)) { <------------------------ here
:                 /*
:                         * Release the 1st page ref if the
:                         * folio is problematic, fail hard.
:                         */
:                 gup_put_folio(page_folio(page), 1,
:                                 foll_flags);
:                 ret = -EFAULT;
:                 goto out;
:         }

[1] https://lore.kernel.org/linux-mm/1719478388-31917-1-git-send-email-yangge1116@126.com/

[shy828301@gmail.com: fix implicit declaration of function try_grab_folio_fast]
  Link: https://lkml.kernel.org/r/CAHbLzkowMSso-4Nufc9hcMehQsK9PNz3OSu-+eniU-2Mm-xjhA@mail.gmail.com
Link: https://lkml.kernel.org/r/20240628191458.2605553-1-yang@os.amperecomputing.com
Fixes: 57edfcfd ("mm/gup: accelerate thp gup even for "pages != NULL"")
Signed-off-by: Yang Shi <yang@os.amperecomputing.com>
Reported-by: yangge <yangge1116@126.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>	[6.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Add the documentation for soft offline behaviors / costs, and what the new
enable_soft_offline sysctl is for.

[jiaqiyan@google.com: fix kerneldoc warnings]
  Link: https://lkml.kernel.org/r/CACw3F52=GxTCDw-PqFh3-GDM-fo3GbhGdu0hedxYXOTT4TQSTg@mail.gmail.com
[jiaqiyan@google.com: there are more blank lines needed]
  Link: https://lkml.kernel.org/r/CACw3F52_obAB742XeDRNun4BHBYtrxtbvp5NkUincXdaob0j1g@mail.gmail.com
Link: https://lkml.kernel.org/r/20240626050818.2277273-5-jiaqiyan@google.comSigned-off-by: Jiaqi Yan <jiaqiyan@google.com>
Acked-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Frank van der Linden <fvdl@google.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Add regression and new tests when hugepage has correctable memory errors,
and how userspace wants to deal with it:

* if enable_soft_offline=1, mapped hugepage is soft offlined
* if enable_soft_offline=0, mapped hugepage is intact

Free hugepages case is not explicitly covered by the tests.

Hugepage having corrected memory errors is emulated with
MADV_SOFT_OFFLINE.

[jiaqiyan@google.com: v7]
  Link: https://lkml.kernel.org/r/20240628205958.2845610-4-jiaqiyan@google.com
Link: https://lkml.kernel.org/r/20240626050818.2277273-4-jiaqiyan@google.comSigned-off-by: Jiaqi Yan <jiaqiyan@google.com>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Frank van der Linden <fvdl@google.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Correctable memory errors are very common on servers with large amount of
memory, and are corrected by ECC.  Soft offline is kernel's additional
recovery handling for memory pages having (excessive) corrected memory
errors.  Impacted page is migrated to a healthy page if inuse; the
original page is discarded for any future use.

The actual policy on whether (and when) to soft offline should be
maintained by userspace, especially in case of an 1G HugeTLB page. 
Soft-offline dissolves the HugeTLB page, either in-use or free, into
chunks of 4K pages, reducing HugeTLB pool capacity by 1 hugepage.  If
userspace has not acknowledged such behavior, it may be surprised when
later failed to mmap hugepages due to lack of hugepages.  In case of a
transparent hugepage, it will be split into 4K pages as well; userspace
will stop enjoying the transparent performance.

In addition, discarding the entire 1G HugeTLB page only because of
corrected memory errors sounds very costly and kernel better not doing
under the hood.  But today there are at least 2 such cases doing so:
1. when GHES driver sees both GHES_SEV_CORRECTED and
   CPER_SEC_ERROR_THRESHOLD_EXCEEDED after parsing CPER.
2. RAS Correctable Errors Collector counts correctable errors per
   PFN and when the counter for a PFN reaches threshold
In both cases, userspace has no control of the soft offline performed
by kernel's memory failure recovery.

This commit gives userspace the control of softofflining any page: kernel
only soft offlines raw page / transparent hugepage / HugeTLB hugepage if
userspace has agreed to.  The interface to userspace is a new sysctl at
/proc/sys/vm/enable_soft_offline.  By default its value is set to 1 to
preserve existing behavior in kernel.  When set to 0, soft-offline (e.g. 
MADV_SOFT_OFFLINE) will fail with EOPNOTSUPP.

[jiaqiyan@google.com: v7]
  Link: https://lkml.kernel.org/r/20240628205958.2845610-3-jiaqiyan@google.com
Link: https://lkml.kernel.org/r/20240626050818.2277273-3-jiaqiyan@google.comSigned-off-by: Jiaqi Yan <jiaqiyan@google.com>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Frank van der Linden <fvdl@google.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "Userspace controls soft-offline pages", v6.

Correctable memory errors are very common on servers with large amount of
memory, and are corrected by ECC, but with two pain points to users:

1. Correction usually happens on the fly and adds latency overhead
2. Not-fully-proved theory states excessive correctable memory
   errors can develop into uncorrectable memory error.

Soft offline is kernel's additional solution for memory pages having
(excessive) corrected memory errors.  Impacted page is migrated to healthy
page if it is in use, then the original page is discarded for any future
use.

The actual policy on whether (and when) to soft offline should be
maintained by userspace, especially in case of an 1G HugeTLB page. 
Soft-offline dissolves the HugeTLB page, either in-use or free, into
chunks of 4K pages, reducing HugeTLB pool capacity by 1 hugepage.  If
userspace has not acknowledged such behavior, it may be surprised when
later mmap hugepages MAP_FAILED due to lack of hugepages.  In case of a
transparent hugepage, it will be split into 4K pages as well; userspace
will stop enjoying the transparent performance.

In addition, discarding the entire 1G HugeTLB page only because of
corrected memory errors sounds very costly and kernel better not doing
under the hood.  But today there are at least 2 such cases:

1. GHES driver sees both GHES_SEV_CORRECTED and
   CPER_SEC_ERROR_THRESHOLD_EXCEEDED after parsing CPER.
2. RAS Correctable Errors Collector counts correctable errors per
   PFN and when the counter for a PFN reaches threshold

In both cases, userspace has no control of the soft offline performed by
kernel's memory failure recovery.

This patch series give userspace the control of softofflining any page:
kernel only soft offlines raw page / transparent hugepage / HugeTLB
hugepage if userspace has agreed to.  The interface to userspace is a new
sysctl called enable_soft_offline under /proc/sys/vm.  By default
enable_soft_line is 1 to preserve existing behavior in kernel.


This patch (of 4):

Logs from soft_offline_page and soft_offline_in_use_page have different
formats than majority of the memory failure code:

  "Memory failure: 0x${pfn}: ${lower_case_message}"

Convert them to the following format:

  "Soft offline: 0x${pfn}: ${lower_case_message}"

No functional change in this commit.

Link: https://lkml.kernel.org/r/20240626050818.2277273-1-jiaqiyan@google.com
Link: https://lkml.kernel.org/r/20240626050818.2277273-2-jiaqiyan@google.comSigned-off-by: Jiaqi Yan <jiaqiyan@google.com>
Acked-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Lance Yang <ioworker0@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Frank van der Linden <fvdl@google.com>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Currently it uses WARN_ON_ONCE() if seq_buf overflows when user reads
memory.stat, the only advantage of WARN_ON_ONCE is that the splat is so
verbose that it gets noticed.  And also it panics the system if
panic_on_warn is enabled.  It seems like the warning is just an over
reaction and a simple pr_warn should just achieve the similar effect.

Link: https://lkml.kernel.org/r/20240628072333.2496527-1-xiujianfeng@huawei.comSigned-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Both the end of memory_stat_format() and memcg_stat_format() will call
WARN_ON_ONCE(seq_buf_has_overflowed()).  However, memory_stat_format() is
the only caller of memcg_stat_format(), when memcg is on the default
hierarchy, seq_buf_has_overflowed() will be executed twice, so remove the
redundant one.

Link: https://lkml.kernel.org/r/20240626094232.2432891-1-xiujianfeng@huawei.comSigned-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

If CONFIG_PTE_MARKER_UFFD_WP is disabled, then we turn off three features
in userfaultfd_api (UFFD_FEATURE_WP_HUGETLBFS_SHMEM,
UFFD_FEATURE_WP_UNPOPULATED, and UFFD_FEATURE_WP_ASYNC).

Currently this test always will call uffdio_regsiter with the flag
UFFDIO_REGISTER_MODE_WP.  However, the kernel ensures in vma_can_userfault
that if the feature UFFD_FEATURE_WP_HUGETLBFS_SHMEM is disabled, only
allow the VM_UFFD_WP on anonymous vmas, meaning our call to
uffdio_regsiter will fail.

We still want to be able to run the test even if we have
CONFIG_PTE_MARKER_UFFD_WP disabled, so check to see if the feature
UFFD_FEATURE_WP_HUGETLBFS_SHMEM has been turned off in the test and if so,
disable us from calling uffdio_regsiter with the flag
UFFDIO_REGISTER_MODE_WP.

Link: https://lkml.kernel.org/r/20240626130513.120193-3-audra@redhat.comSigned-off-by: Audra Mitchell <audra@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Rafael Aquini <raquini@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>