We get 1 warning when building kernel with W=1:

  drivers/char/mem.c:220:12: warning: no previous prototype for 'phys_mem_access_prot_allowed' [-Wmissing-prototypes]
   int __weak phys_mem_access_prot_allowed(struct file *file,

In fact, its declaration is spreading to several header files in
different architecture, but need to be declare in common header file.

So this patch moves phys_mem_access_prot_allowed() to pgtable.h.

Link: http://lkml.kernel.org/r/1473751597-12139-1-git-send-email-baoyou.xie@linaro.orgSigned-off-by: NBaoyou Xie <baoyou.xie@linaro.org>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NRalf Baechle <ralf@linux-mips.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

So they are CONFIG_DEBUG_VM-only and more informative.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: David S. Miller <davem@davemloft.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jens Axboe <axboe@fb.com>
Cc: Joe Perches <joe@perches.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rik van Riel <riel@redhat.com>
Cc: Santosh Shilimkar <santosh.shilimkar@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit c32b3cbe ("oom, PM: make OOM detection in the freezer path
raceless") inserted a WARN_ON() into pagefault_out_of_memory() in order
to warn when we raced with disabling the OOM killer.

Now, patch "oom, suspend: fix oom_killer_disable vs.  pm suspend
properly" introduced a timeout for oom_killer_disable().  Even if we
raced with disabling the OOM killer and the system is OOM livelocked,
the OOM killer will be enabled eventually (in 20 seconds by default) and
the OOM livelock will be solved.  Therefore, we no longer need to warn
when we raced with disabling the OOM killer.

Link: http://lkml.kernel.org/r/1473442120-7246-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jpSigned-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: NMichal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fragmentation index and the vm.extfrag_threshold sysctl is meant as a
heuristic to prevent excessive compaction for costly orders (i.e.  THP).
It's unlikely to make any difference for non-costly orders, especially
with the default threshold.  But we cannot afford any uncertainty for
the non-costly orders where the only alternative to successful
reclaim/compaction is OOM.  After the recent patches we are guaranteed
maximum effort without heuristics from compaction before deciding OOM,
and fragindex is the last remaining heuristic.  Therefore skip fragindex
altogether for non-costly orders.
Suggested-by: NMichal Hocko <mhocko@suse.com>
Link: http://lkml.kernel.org/r/20160926162025.21555-5-vbabka@suse.czSigned-off-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The compaction_zonelist_suitable() function tries to determine if
compaction will be able to proceed after sufficient reclaim, i.e.
whether there are enough reclaimable pages to provide enough order-0
freepages for compaction.

This addition of reclaimable pages to the free pages works well for the
order-0 watermark check, but in the fragmentation index check we only
consider truly free pages.  Thus we can get fragindex value close to 0
which indicates failure do to lack of memory, and wrongly decide that
compaction won't be suitable even after reclaim.

Instead of trying to somehow adjust fragindex for reclaimable pages,
let's just skip it from compaction_zonelist_suitable().

Link: http://lkml.kernel.org/r/20160926162025.21555-4-vbabka@suse.czSigned-off-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The should_reclaim_retry() makes decisions based on no_progress_loops,
so it makes sense to also update the counter there.  It will be also
consistent with should_compact_retry() and compaction_retries.  No
functional change.

[hillf.zj@alibaba-inc.com: fix missing pointer dereferences]
Link: http://lkml.kernel.org/r/20160926162025.21555-3-vbabka@suse.czSigned-off-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NHillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Several people have reported premature OOMs for order-2 allocations
(stack) due to OOM rework in 4.7.  In the scenario (parallel kernel
build and dd writing to two drives) many pageblocks get marked as
Unmovable and compaction free scanner struggles to isolate free pages.
Joonsoo Kim pointed out that the free scanner skips pageblocks that are
not movable to prevent filling them and forcing non-movable allocations
to fallback to other pageblocks.  Such heuristic makes sense to help
prevent long-term fragmentation, but premature OOMs are relatively more
urgent problem.  As a compromise, this patch disables the heuristic only
for the ultimate compaction priority.

Link: http://lkml.kernel.org/r/20160906135258.18335-5-vbabka@suse.czReported-by: NRalf-Peter Rohbeck <Ralf-Peter.Rohbeck@quantum.com>
Reported-by: NArkadiusz Miskiewicz <a.miskiewicz@gmail.com>
Reported-by: NOlaf Hering <olaf@aepfle.de>
Suggested-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The new ultimate compaction priority disables some heuristics, which may
result in excessive cost.  This is fine for non-costly orders where we
want to try hard before resulting for OOM, but might be disruptive for
costly orders which do not trigger OOM and should generally have some
fallback.  Thus, we disable the full priority for costly orders.
Suggested-by: NMichal Hocko <mhocko@kernel.org>
Link: http://lkml.kernel.org/r/20160906135258.18335-4-vbabka@suse.czSigned-off-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

During reclaim/compaction loop, compaction priority can be increased by
the should_compact_retry() function, but the current code is not
optimal.  Priority is only increased when compaction_failed() is true,
which means that compaction has scanned the whole zone.  This may not
happen even after multiple attempts with a lower priority due to
parallel activity, so we might needlessly struggle on the lower
priorities and possibly run out of compaction retry attempts in the
process.

After this patch we are guaranteed at least one attempt at the highest
compaction priority even if we exhaust all retries at the lower
priorities.

Link: http://lkml.kernel.org/r/20160906135258.18335-3-vbabka@suse.czSigned-off-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "reintroduce compaction feedback for OOM decisions".

After several people reported OOM's for order-2 allocations in 4.7 due
to Michal Hocko's OOM rework, he reverted the part that considered
compaction feedback [1] in the decisions to retry reclaim/compaction.
This was to provide a fix quickly for 4.8 rc and 4.7 stable series,
while mmotm had an almost complete solution that instead improved
compaction reliability.

This series completes the mmotm solution and reintroduces the compaction
feedback into OOM decisions.  The first two patches restore the state of
mmotm before the temporary solution was merged, the last patch should be
the missing piece for reliability.  The third patch restricts the
hardened compaction to non-costly orders, since costly orders don't
result in OOMs in the first place.

[1] http://marc.info/?i=20160822093249.GA14916%40dhcp22.suse.cz%3E

This patch (of 4):

Commit 6b4e3181 ("mm, oom: prevent premature OOM killer invocation
for high order request") was intended as a quick fix of OOM regressions
for 4.8 and stable 4.7.x kernels.  For a better long-term solution, we
still want to consider compaction feedback, which should be possible
after some more improvements in the following patches.

This reverts commit 6b4e3181.

Link: http://lkml.kernel.org/r/20160906135258.18335-2-vbabka@suse.czSigned-off-by: NVlastimil Babka <vbabka@suse.cz>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

After using the offset of the swap entry as the key of the swap cache,
the page_index() becomes exactly same as page_file_index().  So the
page_file_index() is removed and the callers are changed to use
page_index() instead.

Link: http://lkml.kernel.org/r/1473270649-27229-2-git-send-email-ying.huang@intel.comSigned-off-by: N"Huang, Ying" <ying.huang@intel.com>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: Anna Schumaker <anna.schumaker@netapp.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch is to improve the performance of swap cache operations when
the type of the swap device is not 0.  Originally, the whole swap entry
value is used as the key of the swap cache, even though there is one
radix tree for each swap device.  If the type of the swap device is not
0, the height of the radix tree of the swap cache will be increased
unnecessary, especially on 64bit architecture.  For example, for a 1GB
swap device on the x86_64 architecture, the height of the radix tree of
the swap cache is 11.  But if the offset of the swap entry is used as
the key of the swap cache, the height of the radix tree of the swap
cache is 4.  The increased height causes unnecessary radix tree
descending and increased cache footprint.

This patch reduces the height of the radix tree of the swap cache via
using the offset of the swap entry instead of the whole swap entry value
as the key of the swap cache.  In 32 processes sequential swap out test
case on a Xeon E5 v3 system with RAM disk as swap, the lock contention
for the spinlock of the swap cache is reduced from 20.15% to 12.19%,
when the type of the swap device is 1.

Use the whole swap entry as key,

  perf-profile.calltrace.cycles-pp._raw_spin_lock_irq.__add_to_swap_cache.add_to_swap_cache.add_to_swap.shrink_page_list: 10.37,
  perf-profile.calltrace.cycles-pp._raw_spin_lock_irqsave.__remove_mapping.shrink_page_list.shrink_inactive_list.shrink_node_memcg: 9.78,

Use the swap offset as key,

  perf-profile.calltrace.cycles-pp._raw_spin_lock_irq.__add_to_swap_cache.add_to_swap_cache.add_to_swap.shrink_page_list: 6.25,
  perf-profile.calltrace.cycles-pp._raw_spin_lock_irqsave.__remove_mapping.shrink_page_list.shrink_inactive_list.shrink_node_memcg: 5.94,

Link: http://lkml.kernel.org/r/1473270649-27229-1-git-send-email-ying.huang@intel.comSigned-off-by: N"Huang, Ying" <ying.huang@intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

vm_insert_mixed() unlike vm_insert_pfn_prot() and vmf_insert_pfn_pmd(),
fails to check the pgprot_t it uses for the mapping against the one
recorded in the memtype tracking tree.  Add the missing call to
track_pfn_insert() to preclude cases where incompatible aliased mappings
are established for a given physical address range.

Link: http://lkml.kernel.org/r/147328717909.35069.14256589123570653697.stgit@dwillia2-desk3.amr.corp.intel.comSigned-off-by: NDan Williams <dan.j.williams@intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If store_mem_state() is called to online memory which is already online,
it will return 1, the value it got from device_online().

This is wrong because store_mem_state() is a device_attribute .store
function.  Thus a non-negative return value represents input bytes read.

Set the return value to -EINVAL in this case.

Link: http://lkml.kernel.org/r/1472743777-24266-1-git-send-email-arbab@linux.vnet.ibm.comSigned-off-by: NReza Arbab <arbab@linux.vnet.ibm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Xishi Qiu <qiuxishi@huawei.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Cc: Chen Yucong <slaoub@gmail.com>
Cc: Andrew Banman <abanman@sgi.com>
Cc: Seth Jennings <sjenning@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mem_cgroup_count_precharge() and mem_cgroup_move_charge() both call
walk_page_range() on the range 0 to ~0UL, neither provide a pte_hole
callback, which causes the current implementation to skip non-vma
regions.  This is all fine but follow up changes would like to make
walk_page_range more generic so it is better to be explicit about which
range to traverse so let's use highest_vm_end to explicitly traverse
only user mmaped memory.

[mhocko@kernel.org: rewrote changelog]
Link: http://lkml.kernel.org/r/1472655897-22532-1-git-send-email-james.morse@arm.comSigned-off-by: NJames Morse <james.morse@arm.com>
Acked-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The global zero page is used to satisfy an anonymous read fault.  If
THP(Transparent HugePage) is enabled then the global huge zero page is
used.  The global huge zero page uses an atomic counter for reference
counting and is allocated/freed dynamically according to its counter
value.

CPU time spent on that counter will greatly increase if there are a lot
of processes doing anonymous read faults.  This patch proposes a way to
reduce the access to the global counter so that the CPU load can be
reduced accordingly.

To do this, a new flag of the mm_struct is introduced:
MMF_USED_HUGE_ZERO_PAGE.  With this flag, the process only need to touch
the global counter in two cases:

 1 The first time it uses the global huge zero page;
 2 The time when mm_user of its mm_struct reaches zero.

Note that right now, the huge zero page is eligible to be freed as soon
as its last use goes away.  With this patch, the page will not be
eligible to be freed until the exit of the last process from which it
was ever used.

And with the use of mm_user, the kthread is not eligible to use huge
zero page either.  Since no kthread is using huge zero page today, there
is no difference after applying this patch.  But if that is not desired,
I can change it to when mm_count reaches zero.

Case used for test on Haswell EP:

  usemem -n 72 --readonly -j 0x200000 100G

Which spawns 72 processes and each will mmap 100G anonymous space and
then do read only access to that space sequentially with a step of 2MB.

  CPU cycles from perf report for base commit:
      54.03%  usemem   [kernel.kallsyms]   [k] get_huge_zero_page
  CPU cycles from perf report for this commit:
       0.11%  usemem   [kernel.kallsyms]   [k] mm_get_huge_zero_page

Performance(throughput) of the workload for base commit: 1784430792
Performance(throughput) of the workload for this commit: 4726928591
164% increase.

Runtime of the workload for base commit: 707592 us
Runtime of the workload for this commit: 303970 us
50% drop.

Link: http://lkml.kernel.org/r/fe51a88f-446a-4622-1363-ad1282d71385@intel.comSigned-off-by: NAaron Lu <aaron.lu@intel.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Trying to walk all of virtual memory requires architecture specific
knowledge.  On x86_64, addresses must be sign extended from bit 48,
whereas on arm64 the top VA_BITS of address space have their own set of
page tables.

clear_refs_write() calls walk_page_range() on the range 0 to ~0UL, it
provides a test_walk() callback that only expects to be walking over
VMAs.  Currently walk_pmd_range() will skip memory regions that don't
have a VMA, reporting them as a hole.

As this call only expects to walk user address space, make it walk 0 to
'highest_vm_end'.

Link: http://lkml.kernel.org/r/1472655792-22439-1-git-send-email-james.morse@arm.comSigned-off-by: NJames Morse <james.morse@arm.com>
Acked-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In current kernel code, we only call node_set_state(cpu_to_node(cpu),
N_CPU) when a cpu is hot plugged.  But we do not set the node state for
N_CPU when the cpus are brought online during boot.

So this could lead to failure when we check to see if a node contains
cpu with node_state(node_id, N_CPU).

One use case is in the node_reclaime function:

        /*
         * Only run node reclaim on the local node or on nodes that do
         * not
         * have associated processors. This will favor the local
         * processor
         * over remote processors and spread off node memory allocations
         * as wide as possible.
         */
        if (node_state(pgdat->node_id, N_CPU) && pgdat->node_id !=
                numa_node_id())
                return NODE_RECLAIM_NOSCAN;

I instrumented the kernel to call this function after boot and it always
returns 0 on a x86 desktop machine until I apply the attached patch.

   int num_cpu_node(void)
   {
       int i, nr_cpu_nodes = 0;

       for_each_node(i) {
               if (node_state(i, N_CPU))
                       ++ nr_cpu_nodes;
       }

       return nr_cpu_nodes;
   }

Fix this by checking each node for online CPU when we initialize
vmstat that's responsible for maintaining node state.

Link: http://lkml.kernel.org/r/20160829175922.GA21775@linux.intel.comSigned-off-by: NTim Chen <tim.c.chen@linux.intel.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: <Huang@linux.intel.com>
Cc: Ying <ying.huang@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

To support DAX pmd mappings with unmodified applications, filesystems
need to align an mmap address by the pmd size.

Call thp_get_unmapped_area() from f_op->get_unmapped_area.

Note, there is no change in behavior for a non-DAX file.

Link: http://lkml.kernel.org/r/1472497881-9323-3-git-send-email-toshi.kani@hpe.comSigned-off-by: NToshi Kani <toshi.kani@hpe.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When CONFIG_FS_DAX_PMD is set, DAX supports mmap() using pmd page size.
This feature relies on both mmap virtual address and FS block (i.e.
physical address) to be aligned by the pmd page size.  Users can use
mkfs options to specify FS to align block allocations.  However,
aligning mmap address requires code changes to existing applications for
providing a pmd-aligned address to mmap().

For instance, fio with "ioengine=mmap" performs I/Os with mmap() [1].
It calls mmap() with a NULL address, which needs to be changed to
provide a pmd-aligned address for testing with DAX pmd mappings.
Changing all applications that call mmap() with NULL is undesirable.

Add thp_get_unmapped_area(), which can be called by filesystem's
get_unmapped_area to align an mmap address by the pmd size for a DAX
file.  It calls the default handler, mm->get_unmapped_area(), to find a
range and then aligns it for a DAX file.

The patch is based on Matthew Wilcox's change that allows adding support
of the pud page size easily.

[1]: https://github.com/axboe/fio/blob/master/engines/mmap.c
Link: http://lkml.kernel.org/r/1472497881-9323-2-git-send-email-toshi.kani@hpe.comSigned-off-by: NToshi Kani <toshi.kani@hpe.com>
Reviewed-by: NDan Williams <dan.j.williams@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch will randomly perform mlock/mlock2 on a given memory region,
and verify the RLIMIT_MEMLOCK limitation works properly.
Suggested-by: NDavid Rientjes <rientjes@google.com>
Link: http://lkml.kernel.org/r/1473325970-11393-4-git-send-email-wei.guo.simon@gmail.comSigned-off-by: NSimon Guo <wei.guo.simon@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Eric B Munson <emunson@akamai.com>
Cc: Simon Guo <wei.guo.simon@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Alexey Klimov <klimov.linux@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Function seek_to_smaps_entry() can be useful for other selftest
functionalities, so move it out to header file.

Link: http://lkml.kernel.org/r/1473325970-11393-3-git-send-email-wei.guo.simon@gmail.comSigned-off-by: NSimon Guo <wei.guo.simon@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Eric B Munson <emunson@akamai.com>
Cc: Simon Guo <wei.guo.simon@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Alexey Klimov <klimov.linux@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch adds mlock() test for multiple invocation on the same address
area, and verify it doesn't mess the rlimit mlock limitation.

Link: http://lkml.kernel.org/r/1472554781-9835-5-git-send-email-wei.guo.simon@gmail.comSigned-off-by: NSimon Guo <wei.guo.simon@gmail.com>
Cc: Alexey Klimov <klimov.linux@gmail.com>
Cc: Eric B Munson <emunson@akamai.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Simon Guo <wei.guo.simon@gmail.com>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

To prepare mlock2.h whose functionality will be reused.

Link: http://lkml.kernel.org/r/1472554781-9835-4-git-send-email-wei.guo.simon@gmail.comSigned-off-by: NSimon Guo <wei.guo.simon@gmail.com>
Cc: Alexey Klimov <klimov.linux@gmail.com>
Cc: Eric B Munson <emunson@akamai.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Simon Guo <wei.guo.simon@gmail.com>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When one vma was with flag VM_LOCKED|VM_LOCKONFAULT (by invoking
mlock2(,MLOCK_ONFAULT)), it can again be populated with mlock() with
VM_LOCKED flag only.

There is a hole in mlock_fixup() which increase mm->locked_vm twice even
the two operations are on the same vma and both with VM_LOCKED flags.

The issue can be reproduced by following code:

  mlock2(p, 1024 * 64, MLOCK_ONFAULT); //VM_LOCKED|VM_LOCKONFAULT
  mlock(p, 1024 * 64);  //VM_LOCKED

Then check the increase VmLck field in /proc/pid/status(to 128k).

When vma is set with different vm_flags, and the new vm_flags is with
VM_LOCKED, it is not necessarily be a "new locked" vma.  This patch
corrects this bug by prevent mm->locked_vm from increment when old
vm_flags is already VM_LOCKED.

Link: http://lkml.kernel.org/r/1472554781-9835-3-git-send-email-wei.guo.simon@gmail.comSigned-off-by: NSimon Guo <wei.guo.simon@gmail.com>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Alexey Klimov <klimov.linux@gmail.com>
Cc: Eric B Munson <emunson@akamai.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Simon Guo <wei.guo.simon@gmail.com>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In do_mlock(), the check against locked memory limitation has a hole
which will fail following cases at step 3):

 1) User has a memory chunk from addressA with 50k, and user mem lock
    rlimit is 64k.
 2) mlock(addressA, 30k)
 3) mlock(addressA, 40k)

The 3rd step should have been allowed since the 40k request is
intersected with the previous 30k at step 2), and the 3rd step is
actually for mlock on the extra 10k memory.

This patch checks vma to caculate the actual "new" mlock size, if
necessary, and ajust the logic to fix this issue.

[akpm@linux-foundation.org: clean up comment layout]
[wei.guo.simon@gmail.com: correct a typo in count_mm_mlocked_page_nr()]
 Link: http://lkml.kernel.org/r/1473325970-11393-2-git-send-email-wei.guo.simon@gmail.com
Link: http://lkml.kernel.org/r/1472554781-9835-2-git-send-email-wei.guo.simon@gmail.comSigned-off-by: NSimon Guo <wei.guo.simon@gmail.com>
Cc: Alexey Klimov <klimov.linux@gmail.com>
Cc: Eric B Munson <emunson@akamai.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Simon Guo <wei.guo.simon@gmail.com>
Cc: Thierry Reding <treding@nvidia.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Since the lumpy reclaim is gone there is no source of higher order pages
if CONFIG_COMPACTION=n except for the order-0 pages reclaim which is
unreliable for that purpose to say the least.  Hitting an OOM for
!costly higher order requests is therefore all not that hard to imagine.
We are trying hard to not invoke OOM killer as much as possible but
there is simply no reliable way to detect whether more reclaim retries
make sense.

Disabling COMPACTION is not widespread but it seems that some users
might have disable the feature without realizing full consequences
(mostly along with disabling THP because compaction used to be THP
mainly thing).  This patch just adds a note if the OOM killer was
triggered by higher order request with compaction disabled.  This will
help us identifying possible misconfiguration right from the oom report
which is easier than to always keep in mind that somebody might have
disabled COMPACTION without a good reason.

Link: http://lkml.kernel.org/r/20160830111632.GD23963@dhcp22.suse.czSigned-off-by: NMichal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

File pages use a set of radix tree tags (DIRTY, TOWRITE, WRITEBACK,
etc.) to accelerate finding the pages with a specific tag in the radix
tree during inode writeback.  But for anonymous pages in the swap cache,
there is no inode writeback.  So there is no need to find the pages with
some writeback tags in the radix tree.  It is not necessary to touch
radix tree writeback tags for pages in the swap cache.

Per Rik van Riel's suggestion, a new flag AS_NO_WRITEBACK_TAGS is
introduced for address spaces which don't need to update the writeback
tags.  The flag is set for swap caches.  It may be used for DAX file
systems, etc.

With this patch, the swap out bandwidth improved 22.3% (from ~1.2GB/s to
~1.48GBps) in the vm-scalability swap-w-seq test case with 8 processes.
The test is done on a Xeon E5 v3 system.  The swap device used is a RAM
simulated PMEM (persistent memory) device.  The improvement comes from
the reduced contention on the swap cache radix tree lock.  To test
sequential swapping out, the test case uses 8 processes, which
sequentially allocate and write to the anonymous pages until RAM and
part of the swap device is used up.

Details of comparison is as follow,

base             base+patch
---------------- --------------------------
         %stddev     %change         %stddev
             \          |                \
   2506952 ±  2%     +28.1%    3212076 ±  7%  vm-scalability.throughput
   1207402 ±  7%     +22.3%    1476578 ±  6%  vmstat.swap.so
     10.86 ± 12%     -23.4%       8.31 ± 16%  perf-profile.cycles-pp._raw_spin_lock_irq.__add_to_swap_cache.add_to_swap_cache.add_to_swap.shrink_page_list
     10.82 ± 13%     -33.1%       7.24 ± 14%  perf-profile.cycles-pp._raw_spin_lock_irqsave.__remove_mapping.shrink_page_list.shrink_inactive_list.shrink_zone_memcg
     10.36 ± 11%    -100.0%       0.00 ± -1%  perf-profile.cycles-pp._raw_spin_lock_irqsave.__test_set_page_writeback.bdev_write_page.__swap_writepage.swap_writepage
     10.52 ± 12%    -100.0%       0.00 ± -1%  perf-profile.cycles-pp._raw_spin_lock_irqsave.test_clear_page_writeback.end_page_writeback.page_endio.pmem_rw_page

Link: http://lkml.kernel.org/r/1472578089-5560-1-git-send-email-ying.huang@intel.comSigned-off-by: N"Huang, Ying" <ying.huang@intel.com>
Acked-by: NRik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Tejun Heo <tj@kernel.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In ___alloc_bootmem_node_nopanic(), replace kzalloc() by kzalloc_node()
in order to allocate memory within given node preferentially when slab
is available

Link: http://lkml.kernel.org/r/1f487f12-6af4-5e4f-a28c-1de2361cdcd8@zoho.comSigned-off-by: Nzijun_hu <zijun_hu@htc.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix the following bugs:

 - the same ARCH_LOW_ADDRESS_LIMIT statements are duplicated between
   header and relevant source

 - don't ensure ARCH_LOW_ADDRESS_LIMIT perhaps defined by ARCH in
   asm/processor.h is preferred over default in linux/bootmem.h
   completely since the former header isn't included by the latter

Link: http://lkml.kernel.org/r/e046aeaa-e160-6d9e-dc1b-e084c2fd999f@zoho.comSigned-off-by: Nzijun_hu <zijun_hu@htc.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently significant amount of memory is reserved only in kernel booted
to capture kernel dump using the fa_dump method.

Kernels compiled with CONFIG_DEFERRED_STRUCT_PAGE_INIT will initialize
only certain size memory per node.  The certain size takes into account
the dentry and inode cache sizes.  Currently the cache sizes are
calculated based on the total system memory including the reserved
memory.  However such a kernel when booting the same kernel as fadump
kernel will not be able to allocate the required amount of memory to
suffice for the dentry and inode caches.  This results in crashes like

Hence only implement arch_reserved_kernel_pages() for CONFIG_FA_DUMP
configurations.  The amount reserved will be reduced while calculating
the large caches and will avoid crashes like the below on large systems
such as 32 TB systems.

  Dentry cache hash table entries: 536870912 (order: 16, 4294967296 bytes)
  vmalloc: allocation failure, allocated 4097114112 of 17179934720 bytes
  swapper/0: page allocation failure: order:0, mode:0x2080020(GFP_ATOMIC)
  CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.6-master+ #3
  Call Trace:
     dump_stack+0xb0/0xf0 (unreliable)
     warn_alloc_failed+0x114/0x160
     __vmalloc_node_range+0x304/0x340
     __vmalloc+0x6c/0x90
     alloc_large_system_hash+0x1b8/0x2c0
     inode_init+0x94/0xe4
     vfs_caches_init+0x8c/0x13c
     start_kernel+0x50c/0x578
     start_here_common+0x20/0xa8

Link: http://lkml.kernel.org/r/1472476010-4709-4-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Suggested-by: NMel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The total reserved memory in a system is accounted but not available for
use use outside mm/memblock.c.  By exposing the total reserved memory,
systems can better calculate the size of large hashes.

Link: http://lkml.kernel.org/r/1472476010-4709-3-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Suggested-by: NMel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Currently arch specific code can reserve memory blocks but
alloc_large_system_hash() may not take it into consideration when sizing
the hashes.  This can lead to bigger hash than required and lead to no
available memory for other purposes.  This is specifically true for
systems with CONFIG_DEFERRED_STRUCT_PAGE_INIT enabled.

One approach to solve this problem would be to walk through the memblock
regions and calculate the available memory and base the size of hash
system on the available memory.

The other approach would be to depend on the architecture to provide the
number of pages that are reserved.  This change provides hooks to allow
the architecture to provide the required info.

Link: http://lkml.kernel.org/r/1472476010-4709-2-git-send-email-srikar@linux.vnet.ibm.comSigned-off-by: NSrikar Dronamraju <srikar@linux.vnet.ibm.com>
Suggested-by: NMel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use the existing enums instead of hardcoded index when looking at the
zonelist.  This makes it more readable.  No functionality change by this
patch.

Link: http://lkml.kernel.org/r/1472227078-24852-1-git-send-email-aneesh.kumar@linux.vnet.ibm.comSigned-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: NAnshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

oom reaper was skipped for an mm which is shared with the kernel thread
(aka use_mm()).  The primary concern was that such a kthread might want
to read from the userspace memory and see zero page as a result of the
oom reaper action.  This is no longer a problem after "mm: make sure
that kthreads will not refault oom reaped memory" because any attempt to
fault in when the MMF_UNSTABLE is set will result in SIGBUS and so the
target user should see an error.  This means that we can finally allow
oom reaper also to tasks which share their mm with kthreads.

Link: http://lkml.kernel.org/r/1472119394-11342-10-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There are only few use_mm() users in the kernel right now.  Most of them
write to the target memory but vhost driver relies on
copy_from_user/get_user from a kernel thread context.  This makes it
impossible to reap the memory of an oom victim which shares the mm with
the vhost kernel thread because it could see a zero page unexpectedly
and theoretically make an incorrect decision visible outside of the
killed task context.

To quote Michael S. Tsirkin:
: Getting an error from __get_user and friends is handled gracefully.
: Getting zero instead of a real value will cause userspace
: memory corruption.

The vhost kernel thread is bound to an open fd of the vhost device which
is not tight to the mm owner life cycle in general.  The device fd can
be inherited or passed over to another process which means that we
really have to be careful about unexpected memory corruption because
unlike for normal oom victims the result will be visible outside of the
oom victim context.

Make sure that no kthread context (users of use_mm) can ever see
corrupted data because of the oom reaper and hook into the page fault
path by checking MMF_UNSTABLE mm flag.  __oom_reap_task_mm will set the
flag before it starts unmapping the address space while the flag is
checked after the page fault has been handled.  If the flag is set then
SIGBUS is triggered so any g-u-p user will get a error code.

Regular tasks do not need this protection because all which share the mm
are killed when the mm is reaped and so the corruption will not outlive
them.

This patch shouldn't have any visible effect at this moment because the
OOM killer doesn't invoke oom reaper for tasks with mm shared with
kthreads yet.

Link: http://lkml.kernel.org/r/1472119394-11342-9-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Acked-by: N"Michael S. Tsirkin" <mst@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There are no users of exit_oom_victim on !current task anymore so enforce
the API to always work on the current.

Link: http://lkml.kernel.org/r/1472119394-11342-8-git-send-email-mhocko@kernel.orgSigned-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit 74070542 ("oom, suspend: fix oom_reaper vs.
oom_killer_disable race") has workaround an existing race between
oom_killer_disable and oom_reaper by adding another round of
try_to_freeze_tasks after the oom killer was disabled.  This was the
easiest thing to do for a late 4.7 fix.  Let's fix it properly now.

After "oom: keep mm of the killed task available" we no longer have to
call exit_oom_victim from the oom reaper because we have stable mm
available and hide the oom_reaped mm by MMF_OOM_SKIP flag.  So let's
remove exit_oom_victim and the race described in the above commit
doesn't exist anymore if.

Unfortunately this alone is not sufficient for the oom_killer_disable
usecase because now we do not have any reliable way to reach
exit_oom_victim (the victim might get stuck on a way to exit for an
unbounded amount of time).  OOM killer can cope with that by checking mm
flags and move on to another victim but we cannot do the same for
oom_killer_disable as we would lose the guarantee of no further
interference of the victim with the rest of the system.  What we can do
instead is to cap the maximum time the oom_killer_disable waits for
victims.  The only current user of this function (pm suspend) already
has a concept of timeout for back off so we can reuse the same value
there.

Let's drop set_freezable for the oom_reaper kthread because it is no
longer needed as the reaper doesn't wake or thaw any processes.

Link: http://lkml.kernel.org/r/1472119394-11342-7-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

After "oom: keep mm of the killed task available" we can safely detect
an oom victim by checking task->signal->oom_mm so we do not need the
signal_struct counter anymore so let's get rid of it.

This alone wouldn't be sufficient for nommu archs because
exit_oom_victim doesn't hide the process from the oom killer anymore.
We can, however, mark the mm with a MMF flag in __mmput.  We can reuse
MMF_OOM_REAPED and rename it to a more generic MMF_OOM_SKIP.

Link: http://lkml.kernel.org/r/1472119394-11342-6-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Lockdep complains that __mmdrop is not safe from the softirq context:

  =================================
  [ INFO: inconsistent lock state ]
  4.6.0-oomfortification2-00011-geeb3eadeab96-dirty #949 Tainted: G        W
  ---------------------------------
  inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
  swapper/1/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
   (pgd_lock){+.?...}, at: pgd_free+0x19/0x6b
  {SOFTIRQ-ON-W} state was registered at:
     __lock_acquire+0xa06/0x196e
     lock_acquire+0x139/0x1e1
     _raw_spin_lock+0x32/0x41
     __change_page_attr_set_clr+0x2a5/0xacd
     change_page_attr_set_clr+0x16f/0x32c
     set_memory_nx+0x37/0x3a
     free_init_pages+0x9e/0xc7
     alternative_instructions+0xa2/0xb3
     check_bugs+0xe/0x2d
     start_kernel+0x3ce/0x3ea
     x86_64_start_reservations+0x2a/0x2c
     x86_64_start_kernel+0x17a/0x18d
  irq event stamp: 105916
  hardirqs last  enabled at (105916): free_hot_cold_page+0x37e/0x390
  hardirqs last disabled at (105915): free_hot_cold_page+0x2c1/0x390
  softirqs last  enabled at (105878): _local_bh_enable+0x42/0x44
  softirqs last disabled at (105879): irq_exit+0x6f/0xd1

  other info that might help us debug this:
   Possible unsafe locking scenario:

         CPU0
         ----
    lock(pgd_lock);
    <Interrupt>
      lock(pgd_lock);

   *** DEADLOCK ***

  1 lock held by swapper/1/0:
   #0:  (rcu_callback){......}, at: rcu_process_callbacks+0x390/0x800

  stack backtrace:
  CPU: 1 PID: 0 Comm: swapper/1 Tainted: G        W       4.6.0-oomfortification2-00011-geeb3eadeab96-dirty #949
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
  Call Trace:
   <IRQ>
    print_usage_bug.part.25+0x259/0x268
    mark_lock+0x381/0x567
    __lock_acquire+0x993/0x196e
    lock_acquire+0x139/0x1e1
    _raw_spin_lock+0x32/0x41
    pgd_free+0x19/0x6b
    __mmdrop+0x25/0xb9
    __put_task_struct+0x103/0x11e
    delayed_put_task_struct+0x157/0x15e
    rcu_process_callbacks+0x660/0x800
    __do_softirq+0x1ec/0x4d5
    irq_exit+0x6f/0xd1
    smp_apic_timer_interrupt+0x42/0x4d
    apic_timer_interrupt+0x8e/0xa0
   <EOI>
    arch_cpu_idle+0xf/0x11
    default_idle_call+0x32/0x34
    cpu_startup_entry+0x20c/0x399
    start_secondary+0xfe/0x101

More over commit a79e53d8 ("x86/mm: Fix pgd_lock deadlock") was
explicit about pgd_lock not to be called from the irq context.  This
means that __mmdrop called from free_signal_struct has to be postponed
to a user context.  We already have a similar mechanism for mmput_async
so we can use it here as well.  This is safe because mm_count is pinned
by mm_users.

This fixes bug introduced by "oom: keep mm of the killed task available"

Link: http://lkml.kernel.org/r/1472119394-11342-5-git-send-email-mhocko@kernel.orgSigned-off-by: NMichal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>