In isolate_single_pageblock() called by start_isolate_page_range(), there
are some pageblock isolation issues causing a potential infinite loop when
isolating a page range.  This is reported by Qian Cai.

1. the pageblock was isolated by just changing pageblock migratetype
   without checking unmovable pages. Calling set_migratetype_isolate() to
   isolate pageblock properly.
2. an off-by-one error caused migrating pages unnecessarily, since the page
   is not crossing pageblock boundary.
3. migrating a compound page across pageblock boundary then splitting the
   free page later has a small race window that the free page might be
   allocated again, so that the code will try again, causing an potential
   infinite loop. Temporarily set the to-be-migrated page's pageblock to
   MIGRATE_ISOLATE to prevent that and bail out early if no free page is
   found after page migration.

An additional fix to split_free_page() aims to avoid crashing in
__free_one_page().  When the free page is split at the specified
split_pfn_offset, free_page_order should check both the first bit of
free_page_pfn and the last bit of split_pfn_offset and use the smaller
one.  For example, if free_page_pfn=0x10000, split_pfn_offset=0xc000,
free_page_order should first be 0x8000 then 0x4000, instead of 0x4000 then
0x8000, which the original algorithm did.

[akpm@linux-foundation.org: suppress min() warning]
Link: https://lkml.kernel.org/r/20220524194756.1698351-1-zi.yan@sent.com
Fixes: b2c9e2fb ("mm: make alloc_contig_range work at pageblock granularity")
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand <david@redhat.com>
Cc: Eric Ren <renzhengeek@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

I have been focusing on mm for the past two years.  e.g.  developing,
fixing bugs, reviewing related to HugeTLB system.  I would like to help
Mike and other people working on HugeTLB by reviewing their work.

When I first introduced the vmemmmap reduction, I forgot to update
MAINTAINERS file.  Let's update it as well.  And rename "HUGETLB
FILESYSTEM" to "HUGETLB SUBSYSTEM" since some files are not only related
to filesystem but also memory management (the name of FILESYSTEM cannot
cover this area).

Link: https://lkml.kernel.org/r/20220521074103.79468-1-songmuchun@bytedance.comSigned-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

ZSMALLOC depends on MMU so ZRAM should also depend on MMU since 'select'
does not follow any dependency chains.

Fixes this Kconfig warning:

WARNING: unmet direct dependencies detected for ZSMALLOC
  Depends on [n]: MMU [=n]
  Selected by [y]:
  - ZRAM [=y] && BLK_DEV [=y] && BLOCK [=y] && SYSFS [=y] && (CRYPTO_LZO [=y] || CRYPTO_ZSTD [=m] || CRYPTO_LZ4 [=m] || CRYPTO_LZ4HC [=n] || CRYPTO_842 [=n])

Link: https://lkml.kernel.org/r/20220522204027.22964-1-rdunlap@infradead.org
Fixes: b3fbd58f ("mm: Kconfig: simplify zswap configuration")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Shmem swapoff makes no progress: the index to indices is not incremented. 
But "ret" is no longer a return value, so use folio_batch_count() instead.

Link: https://lkml.kernel.org/r/c32bee8a-f0aa-245-f94e-24dd271924fa@google.com
Fixes: da08e9b7 ("mm/shmem: convert shmem_swapin_page() to shmem_swapin_folio()")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Tested-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

If the first goto is taken, 'fd' is not opened yet (and is un-initialized).
So a direct return is safer.

Link: https://lkml.kernel.org/r/628312312eb40e0e39463a2c06415fde5295c716.1653229120.git.christophe.jaillet@wanadoo.fr
Fixes: c1a31a2f ("cgroup: fix racy check in alloc_pagecache_max_30M() helper function")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: David Vernet <void@manifault.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Use HPAGE_PMD_SIZE instead of open coding.

Link: https://lkml.kernel.org/r/20220517145120.118523-1-wangkefeng.wang@huawei.comSigned-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Fixes following sparse warnings:

  CHECK   mm/vmscan.c
mm/vmscan.c: note: in included file (through
include/trace/trace_events.h, include/trace/define_trace.h,
include/trace/events/vmscan.h):
./include/trace/events/vmscan.h:281:1: sparse: warning:
 cast to restricted isolate_mode_t
./include/trace/events/vmscan.h:281:1: sparse: warning:
 restricted isolate_mode_t degrades to integer

Link: https://lkml.kernel.org/r/e85d7ff2-fd10-53f8-c24e-ba0458439c1b@openvz.orgSigned-off-by: Vasily Averin <vvs@openvz.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

With gcc version 12.0.1 20220401 (Red Hat 12.0.1-0), building with
defconfig results in the following compilation error:

|   CC      mm/swapfile.o
| mm/swapfile.c: In function `setup_swap_info':
| mm/swapfile.c:2291:47: error: array subscript -1 is below array bounds
|  of `struct plist_node[]' [-Werror=array-bounds]
|  2291 |                                 p->avail_lists[i].prio = 1;
|       |                                 ~~~~~~~~~~~~~~^~~
| In file included from mm/swapfile.c:16:
| ./include/linux/swap.h:292:27: note: while referencing `avail_lists'
|   292 |         struct plist_node avail_lists[]; /*
|       |                           ^~~~~~~~~~~

This is due to the compiler detecting that the mask in
node_states[__state] could theoretically be zero, which would lead to
first_node() returning -1 through find_first_bit.

I believe that the warning/error is legitimate.  I first tried adding a
test to check that the node mask is not emtpy, since a similar test exists
in the case where MAX_NUMNODES == 1.

However, adding the if statement causes other warnings to appear in
for_each_cpu_node_but, because it introduces a dangling else ambiguity. 
And unfortunately, GCC is not smart enough to detect that the added test
makes the case where (node) == -1 impossible, so it still complains with
the same message.

This is why I settled on replacing that with a harmless, but relatively
useless (node) >= 0 test.  Based on the warning for the dangling else, I
also decided to fix the case where MAX_NUMNODES == 1 by moving the
condition inside the for loop.  It will still only be tested once.  This
ensures that the meaning of an else following for_each_node_mask or
derivatives would not silently have a different meaning depending on the
configuration.

Link: https://lkml.kernel.org/r/20220414150855.2407137-3-dinechin@redhat.comSigned-off-by: Christophe de Dinechin <christophe@dinechin.org>
Signed-off-by: Christophe de Dinechin <dinechin@redhat.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ben Segall <bsegall@google.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Zhen Lei <thunder.leizhen@huawei.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

We expect no warnings to be issued when we specify __GFP_NOWARN, but
currently in paths like alloc_pages() and kmalloc(), there are still some
warnings printed, fix it.

But for some warnings that report usage problems, we don't deal with them.
If such warnings are printed, then we should fix the usage problems. 
Such as the following case:

	WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));

[zhengqi.arch@bytedance.com: v2]
 Link: https://lkml.kernel.org/r/20220511061951.1114-1-zhengqi.arch@bytedance.com
Link: https://lkml.kernel.org/r/20220510113809.80626-1-zhengqi.arch@bytedance.comSigned-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Currently, trace point mm_page_alloc_zone_locked() doesn't show correct
information.

First, when alloc_flag has ALLOC_HARDER/ALLOC_CMA, page can be allocated
from MIGRATE_HIGHATOMIC/MIGRATE_CMA.  Nevertheless, tracepoint use
requested migration type not MIGRATE_HIGHATOMIC and MIGRATE_CMA.

Second, after commit 44042b44 ("mm/page_alloc: allow high-order pages
to be stored on the per-cpu lists") percpu-list can store high order
pages.  But trace point determine whether it is a refiil of percpu-list by
comparing requested order and 0.

To handle these problems, make mm_page_alloc_zone_locked() only be called
by __rmqueue_smallest with correct migration type.  With a new argument
called percpu_refill, it can show roughly whether it is a refill of
percpu-list.

Link: https://lkml.kernel.org/r/20220512025307.57924-1-vvghjk1234@gmail.comSigned-off-by: Wonhyuk Yang <vvghjk1234@gmail.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Baik Song An <bsahn@etri.re.kr>
Cc: Hong Yeon Kim <kimhy@etri.re.kr>
Cc: Taeung Song <taeung@reallinux.co.kr>
Cc: <linuxgeek@linuxgeek.io>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

This patch fixes two issues:
1. Add __initdata attribute according to include/linux/init.h:
	For initialized data:
	You should insert __initdata between the variable name and equal
	sign followed by value

2. Fix below error reported by checkpatch.pl:
	ERROR: do not initialise statics to false

Special thanks to Muchun Song :)

Link: https://lkml.kernel.org/r/20220516030039.1487005-1-bh1scw@gmail.comSigned-off-by: Fanjun Kong <bh1scw@gmail.com>
Suggested-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

When shmem_reconfigure() calls __percpu_counter_compare(), the second
parameter is unsigned long long.  But in the definition of
__percpu_counter_compare(), the second parameter is s64.  So when
__percpu_counter_compare() executes abs(count - rhs), UBSAN shows the
following warning:

================================================================================
UBSAN: Undefined behaviour in lib/percpu_counter.c:209:6
signed integer overflow:
0 - -9223372036854775808 cannot be represented in type 'long long int'
CPU: 1 PID: 9636 Comm: syz-executor.2 Tainted: G                 ---------r-  - 4.18.0 #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
Call Trace:
 __dump_stack home/install/linux-rh-3-10/lib/dump_stack.c:77 [inline]
 dump_stack+0x125/0x1ae home/install/linux-rh-3-10/lib/dump_stack.c:117
 ubsan_epilogue+0xe/0x81 home/install/linux-rh-3-10/lib/ubsan.c:159
 handle_overflow+0x19d/0x1ec home/install/linux-rh-3-10/lib/ubsan.c:190
 __percpu_counter_compare+0x124/0x140 home/install/linux-rh-3-10/lib/percpu_counter.c:209
 percpu_counter_compare home/install/linux-rh-3-10/./include/linux/percpu_counter.h:50 [inline]
 shmem_remount_fs+0x1ce/0x6b0 home/install/linux-rh-3-10/mm/shmem.c:3530
 do_remount_sb+0x11b/0x530 home/install/linux-rh-3-10/fs/super.c:888
 do_remount home/install/linux-rh-3-10/fs/namespace.c:2344 [inline]
 do_mount+0xf8d/0x26b0 home/install/linux-rh-3-10/fs/namespace.c:2844
 ksys_mount+0xad/0x120 home/install/linux-rh-3-10/fs/namespace.c:3075
 __do_sys_mount home/install/linux-rh-3-10/fs/namespace.c:3089 [inline]
 __se_sys_mount home/install/linux-rh-3-10/fs/namespace.c:3086 [inline]
 __x64_sys_mount+0xbf/0x160 home/install/linux-rh-3-10/fs/namespace.c:3086
 do_syscall_64+0xca/0x5c0 home/install/linux-rh-3-10/arch/x86/entry/common.c:298
 entry_SYSCALL_64_after_hwframe+0x6a/0xdf
RIP: 0033:0x46b5e9
Code: 5d db fa ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 2b db fa ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f54d5f22c68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 000000000077bf60 RCX: 000000000046b5e9
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000000
RBP: 000000000077bf60 R08: 0000000020000140 R09: 0000000000000000
R10: 00000000026740a4 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd1fb1592f R14: 00007f54d5f239c0 R15: 000000000077bf6c
================================================================================

[akpm@linux-foundation.org: tweak error message text]
Link: https://lkml.kernel.org/r/20220513025225.2678727-1-luomeng12@huawei.comSigned-off-by: Luo Meng <luomeng12@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mpol_set_nodemask()(mm/mempolicy.c) does not set up nodemask when
pol->mode is MPOL_LOCAL.  Check pol->mode before access
pol->w.cpuset_mems_allowed in mpol_rebind_policy()(mm/mempolicy.c).

BUG: KMSAN: uninit-value in mpol_rebind_policy mm/mempolicy.c:352 [inline]
BUG: KMSAN: uninit-value in mpol_rebind_task+0x2ac/0x2c0 mm/mempolicy.c:368
 mpol_rebind_policy mm/mempolicy.c:352 [inline]
 mpol_rebind_task+0x2ac/0x2c0 mm/mempolicy.c:368
 cpuset_change_task_nodemask kernel/cgroup/cpuset.c:1711 [inline]
 cpuset_attach+0x787/0x15e0 kernel/cgroup/cpuset.c:2278
 cgroup_migrate_execute+0x1023/0x1d20 kernel/cgroup/cgroup.c:2515
 cgroup_migrate kernel/cgroup/cgroup.c:2771 [inline]
 cgroup_attach_task+0x540/0x8b0 kernel/cgroup/cgroup.c:2804
 __cgroup1_procs_write+0x5cc/0x7a0 kernel/cgroup/cgroup-v1.c:520
 cgroup1_tasks_write+0x94/0xb0 kernel/cgroup/cgroup-v1.c:539
 cgroup_file_write+0x4c2/0x9e0 kernel/cgroup/cgroup.c:3852
 kernfs_fop_write_iter+0x66a/0x9f0 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:2162 [inline]
 new_sync_write fs/read_write.c:503 [inline]
 vfs_write+0x1318/0x2030 fs/read_write.c:590
 ksys_write+0x28b/0x510 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0xdb/0x120 fs/read_write.c:652
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Uninit was created at:
 slab_post_alloc_hook mm/slab.h:524 [inline]
 slab_alloc_node mm/slub.c:3251 [inline]
 slab_alloc mm/slub.c:3259 [inline]
 kmem_cache_alloc+0x902/0x11c0 mm/slub.c:3264
 mpol_new mm/mempolicy.c:293 [inline]
 do_set_mempolicy+0x421/0xb70 mm/mempolicy.c:853
 kernel_set_mempolicy mm/mempolicy.c:1504 [inline]
 __do_sys_set_mempolicy mm/mempolicy.c:1510 [inline]
 __se_sys_set_mempolicy+0x44c/0xb60 mm/mempolicy.c:1507
 __x64_sys_set_mempolicy+0xd8/0x110 mm/mempolicy.c:1507
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

KMSAN: uninit-value in mpol_rebind_task (2)
https://syzkaller.appspot.com/bug?id=d6eb90f952c2a5de9ea718a1b873c55cb13b59dc

This patch seems to fix below bug too.
KMSAN: uninit-value in mpol_rebind_mm (2)
https://syzkaller.appspot.com/bug?id=f2fecd0d7013f54ec4162f60743a2b28df40926b

The uninit-value is pol->w.cpuset_mems_allowed in mpol_rebind_policy().
When syzkaller reproducer runs to the beginning of mpol_new(),

	    mpol_new() mm/mempolicy.c
	  do_mbind() mm/mempolicy.c
	kernel_mbind() mm/mempolicy.c

`mode` is 1(MPOL_PREFERRED), nodes_empty(*nodes) is `true` and `flags`
is 0. Then

	mode = MPOL_LOCAL;
	...
	policy->mode = mode;
	policy->flags = flags;

will be executed. So in mpol_set_nodemask(),

	    mpol_set_nodemask() mm/mempolicy.c
	  do_mbind()
	kernel_mbind()

pol->mode is 4 (MPOL_LOCAL), that `nodemask` in `pol` is not initialized,
which will be accessed in mpol_rebind_policy().

Link: https://lkml.kernel.org/r/20220512123428.fq3wofedp6oiotd4@ppc.localdomainSigned-off-by: Wang Cheng <wanngchenng@gmail.com>
Reported-by: <syzbot+217f792c92599518a2ab@syzkaller.appspotmail.com>
Tested-by: <syzbot+217f792c92599518a2ab@syzkaller.appspotmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The rmap locks(i_mmap_rwsem and anon_vma->root->rwsem) could be contended
under memory pressure if processes keep working on their vmas(e.g., fork,
mmap, munmap).  It makes reclaim path stuck.  In our real workload traces,
we see kswapd is waiting the lock for 300ms+(worst case, a sec) and it
makes other processes entering direct reclaim, which were also stuck on
the lock.

This patch makes lru aging path try_lock mode like shink_page_list so the
reclaim context will keep working with next lru pages without being stuck.
if it found the rmap lock contended, it rotates the page back to head of
lru in both active/inactive lrus to make them consistent behavior, which
is basic starting point rather than adding more heristic.

Since this patch introduces a new "contended" field as out-param along
with try_lock in-param in rmap_walk_control, it's not immutable any longer
if the try_lock is set so remove const keywords on rmap related functions.
Since rmap walking is already expensive operation, I doubt the const
would help sizable benefit( And we didn't have it until 5.17).

In a heavy app workload in Android, trace shows following statistics.  It
almost removes rmap lock contention from reclaim path.

Martin Liu reported:

Before:

   max_dur(ms)  min_dur(ms)  max-min(dur)ms  avg_dur(ms)  sum_dur(ms)  count blocked_function
         1632            0            1631   151.542173        31672    209  page_lock_anon_vma_read
          601            0             601   145.544681        28817    198  rmap_walk_file

After:

   max_dur(ms)  min_dur(ms)  max-min(dur)ms  avg_dur(ms)  sum_dur(ms)  count blocked_function
          NaN          NaN              NaN          NaN          NaN    0.0             NaN
            0            0                0     0.127645            1     12  rmap_walk_file

[minchan@kernel.org: add comment, per Matthew]
  Link: https://lkml.kernel.org/r/YnNqeB5tUf6LZ57b@google.com
Link: https://lkml.kernel.org/r/20220510215423.164547-1-minchan@kernel.orgSigned-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: John Dias <joaodias@google.com>
Cc: Tim Murray <timmurray@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Martin Liu <liumartin@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Applications can currently escape their cgroup memory containment when
zswap is enabled.  This patch adds per-cgroup tracking and limiting of
zswap backend memory to rectify this.

The existing cgroup2 memory.stat file is extended to show zswap statistics
analogous to what's in meminfo and vmstat.  Furthermore, two new control
files, memory.zswap.current and memory.zswap.max, are added to allow
tuning zswap usage on a per-workload basis.  This is important since not
all workloads benefit from zswap equally; some even suffer compared to
disk swap when memory contents don't compress well.  The optimal size of
the zswap pool, and the threshold for writeback, also depends on the size
of the workload's warm set.

The implementation doesn't use a traditional page_counter transaction. 
zswap is unconventional as a memory consumer in that we only know the
amount of memory to charge once expensive compression has occurred.  If
zwap is disabled or the limit is already exceeded we obviously don't want
to compress page upon page only to reject them all.  Instead, the limit is
checked against current usage, then we compress and charge.  This allows
some limit overrun, but not enough to matter in practice.

[hannes@cmpxchg.org: fix for CONFIG_SLOB builds]
  Link: https://lkml.kernel.org/r/YnwD14zxYjUJPc2w@cmpxchg.org
[hannes@cmpxchg.org: opt out of cgroups v1]
  Link: https://lkml.kernel.org/r/Yn6it9mBYFA+/lTb@cmpxchg.org
Link: https://lkml.kernel.org/r/20220510152847.230957-7-hannes@cmpxchg.orgSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Currently it requires poking at debugfs to figure out the size and
population of the zswap cache on a host.  There are no counters for reads
and writes against the cache.  As a result, it's difficult to understand
zswap behavior on production systems.

Print zswap memory consumption and how many pages are zswapped out in
/proc/meminfo.  Count zswapouts and zswapins in /proc/vmstat.

Link: https://lkml.kernel.org/r/20220510152847.230957-6-hannes@cmpxchg.orgSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

- CONFIG_ZRAM: Zram is a user-facing feature, whereas zsmalloc is
  not. Don't make the user chase down a technical dependency like
  that, just select it in automatically when zram is requested. The
  CONFIG_CRYPTO dependency is redundant due to more specific deps.

- CONFIG_ZPOOL: This is not a user-facing feature. Hide the symbol and
  have it selected in as needed.

- CONFIG_ZSWAP: Select CRYPTO instead of depend. Common pattern.

- Make the ZSWAP suboptions and their descriptions (compression,
  allocation backend) a bit more straight-forward for the user.

Link: https://lkml.kernel.org/r/20220510152847.230957-5-hannes@cmpxchg.orgSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

There are several clusters of related config options spread throughout the
mostly flat MM submenu.  Group them together and put specialization
options into further subdirectories to make the MM submenu a bit more
organized and easier to navigate.

[hannes@cmpxchg.org: fix kbuild warnings]
  Link: https://lkml.kernel.org/r/YnvkSVivfnT57Vwh@cmpxchg.org
[hannes@cmpxchg.org: fix more kbuild warnings]
  Link: https://lkml.kernel.org/r/Ynz8NusTdEGcCnJN@cmpxchg.org
Link: https://lkml.kernel.org/r/20220510152847.230957-4-hannes@cmpxchg.orgSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

These are currently under General Setup. MM seems like a better fit.

Link: https://lkml.kernel.org/r/20220510152847.230957-3-hannes@cmpxchg.orgSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "zswap: accounting & cgroup control", v2.

Zswap can consume nearly a quarter of RAM in the default configuration,
yet it's neither listed in /proc/meminfo, nor is it accounted and
manageable on a per-cgroup basis.

This makes reasoning about the memory situation on a host in general
rather difficult.  On shared/cgrouped hosts, the consequences are worse. 
First, workloads can escape memory containment and cause resource priority
inversions: a lo-pri group can fill the global zswap pool and force a
hi-pri group out to disk.  Second, not all workloads benefit from zswap
equally.  Some even suffer when memory contents compress poorly, and are
better off going to disk swap directly.  On a host with mixed workloads,
it's currently not possible to enable zswap for one workload but not for
the other.

This series implements the missing global accounting as well as cgroup
tracking & control for zswap backing memory:

- Patch 1 refreshes the very out-of-date meminfo documentation in
  Documentation/filesystems/proc.rst.

- Patches 2-4 clean up related and adjacent options in Kconfig. Not
  actual dependencies, just things I noticed during development.

- Patch 5 adds meminfo and vmstat coverage for zswap consumption and
  activity.

- Patch 6 implements per-cgroup tracking & control of zswap memory.


This patch (of 6):

Add new entries.  Minor corrections and cleanups.

[hannes@cmpxchg.org: fix htmldocs warnings]
  Link: https://lkml.kernel.org/r/Ynve8dg4zJyhH2gW@cmpxchg.org
[hannes@cmpxchg.org: change `Unevictable' wording, per David]
  Link: https://lkml.kernel.org/r/YnwFraZlVWQoCjz3@cmpxchg.org
Link: https://lkml.kernel.org/r/20220510152847.230957-1-hannes@cmpxchg.org
Link: https://lkml.kernel.org/r/20220510152847.230957-2-hannes@cmpxchg.orgSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Since commit 4efaceb1 ("mm, swap: use rbtree for swap_extent"), rbtree
is used for swap extent.  Also curr_swap_extent is removed at that time. 
Update the corresponding comment.

Link: https://lkml.kernel.org/r/20220509131416.17553-16-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

If no pages were pinned, 0 is returned in fact.  Fix the corresponding
comment.

[akpm@linux-foundation.org: s/nr_pages/nr_segs/ also, per David, reflow comment]
Link: https://lkml.kernel.org/r/20220509131416.17553-15-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Since commit 10a9c496 ("mm: simplify try_to_unuse"), frontswap
parameter is removed.  Update the corresponding comment.

Link: https://lkml.kernel.org/r/20220509131416.17553-14-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Since commit 3159f943 ("xarray: Replace exceptional entries"), there
is only one bit of 'type' can be shifted up.  Update the corresponding
comment.

Link: https://lkml.kernel.org/r/20220509131416.17553-13-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Add helper swap_offset_available() to remove some duplicated codes.  Minor
readability improvement.

[akpm@linux-foundation.org: s/swap_offset_available/swap_offset_available_and_locked/, per Neil]
Link: https://lkml.kernel.org/r/20220509131416.17553-12-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Use flags of si directly to check SWP_STABLE_WRITES to avoid possible
READ_ONCE and thus save some cpu cycles.

[akpm@linux-foundation.org: use data_race() on si->flags, per Neil]
Link: https://lkml.kernel.org/r/20220509131416.17553-10-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Make page_swapcount and __lru_add_drain_all static.  They are only used
within the file now.

Link: https://lkml.kernel.org/r/20220509131416.17553-9-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

If p is NULL, __swap_duplicate will already return -EINVAL.  So if we
reach here, p must be non-NULL.

Link: https://lkml.kernel.org/r/20220509131416.17553-8-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

refill_swap_slots_cache is always called when cache->nr is 0.  So remove
such buggy and confusing check.

Link: https://lkml.kernel.org/r/20220509131416.17553-7-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

If offset exceeds the si->max, print bad swap offset entry to help debug
the unexpected case.

Link: https://lkml.kernel.org/r/20220509131416.17553-6-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The return value of free_swap_slot is always 0 and also ignored now. 
Remove it to clean up the code.

Link: https://lkml.kernel.org/r/20220509131416.17553-5-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Fold __swap_info_get() into its sole caller to make code more clear. 
Minor readability improvement.

Link: https://lkml.kernel.org/r/20220509131416.17553-4-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Use helper macro __ATTR_RW to define vma_ra_enabled_attr to make code more
clear.  Minor readability improvement.

Link: https://lkml.kernel.org/r/20220509131416.17553-3-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Peter Xu <peterx@redhat.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "A few cleanup patches for swap".

This series contains a few patches to fix the comment, remove unneeded
return value, use some helpers and so on.  More details can be found in
the respective changelogs.


This patch (of 14):

Use helper is_swap_pte() to check whether pte is swap entry to make code
more clear.  Minor readability improvement.

Link: https://lkml.kernel.org/r/20220509131416.17553-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220509131416.17553-2-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Howells <dhowells@redhat.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The readonly FS THP relies on khugepaged to collapse THP for suitable
vmas.  But the behavior is inconsistent for "always" mode
(https://lore.kernel.org/linux-mm/00f195d4-d039-3cf2-d3a1-a2c88de397a0@suse.cz/).

The "always" mode means THP allocation should be tried all the time and
khugepaged should try to collapse THP all the time.  Of course the
allocation and collapse may fail due to other factors and conditions.

Currently file THP may not be collapsed by khugepaged even though all the
conditions are met.  That does break the semantics of "always" mode.

So make sure readonly FS vmas are registered to khugepaged to fix the
break.

Register suitable vmas in common mmap path, that could cover both readonly
FS vmas and shmem vmas, so remove the khugepaged calls in shmem.c.

Still need to keep the khugepaged call in vma_merge() since vma_merge() is
called in a lot of places, for example, madvise, mprotect, etc.

Link: https://lkml.kernel.org/r/20220510203222.24246-9-shy828301@gmail.comSigned-off-by: Yang Shi <shy828301@gmail.com>
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Vlastmil Babka <vbabka@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Song Liu <song@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The khugepaged_enter_vma_merge() actually does as the same thing as the
khugepaged_enter() section called by shmem_mmap(), so consolidate them
into one helper and rename it to khugepaged_enter_vma().

Link: https://lkml.kernel.org/r/20220510203222.24246-8-shy828301@gmail.comSigned-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Vlastmil Babka <vbabka@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Song Liu <song@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The hugepage_vma_check() could be reused by khugepaged_enter() and
khugepaged_enter_vma_merge(), but it is static in khugepaged.c.  Make it
non-static and declare it in khugepaged.h.

Link: https://lkml.kernel.org/r/20220510203222.24246-7-shy828301@gmail.comSigned-off-by: Yang Shi <shy828301@gmail.com>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Song Liu <song@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The most callers of khugepaged_enter() don't care about the return value. 
Only dup_mmap(), anonymous THP page fault and MADV_HUGEPAGE handle the
error by returning -ENOMEM.  Actually it is not harmful for them to ignore
the error case either.  It also sounds overkilling to fail fork() and page
fault early due to khugepaged_enter() error, and MADV_HUGEPAGE does set
VM_HUGEPAGE flag regardless of the error.

Link: https://lkml.kernel.org/r/20220510203222.24246-6-shy828301@gmail.comSigned-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Vlastmil Babka <vbabka@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Since commit a4aeaa06 ("mm: khugepaged: skip huge page collapse for
special files"), khugepaged just collapses THP for regular file which is
the intended usecase for readonly fs THP.  Only show regular file as THP
eligible accordingly.

And make file_thp_enabled() available for khugepaged too in order to
remove duplicate code.

Link: https://lkml.kernel.org/r/20220510203222.24246-5-shy828301@gmail.comSigned-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Vlastmil Babka <vbabka@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The DAX vma may be seen by khugepaged when the mm has other khugepaged
suitable vmas.  So khugepaged may try to collapse THP for DAX vma, but it
will fail due to page sanity check, for example, page is not on LRU.

So it is not harmful, but it is definitely pointless to run khugepaged
against DAX vma, so skip it in early check.

Link: https://lkml.kernel.org/r/20220510203222.24246-4-shy828301@gmail.comSigned-off-by: Yang Shi <shy828301@gmail.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Vlastmil Babka <vbabka@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>