Dump the contents of the relevant struct_mm when we hit the bug condition.
Signed-off-by: NSasha Levin <sasha.levin@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Very similar to VM_BUG_ON_PAGE and VM_BUG_ON_VMA, dump struct_mm when the
bug is hit.

[akpm@linux-foundation.org: coding-style fixes]
[mhocko@suse.cz: fix build]
[mhocko@suse.cz: fix build some more]
[akpm@linux-foundation.org: do strange things to avoid doing strange things for the comma separators]
Signed-off-by: NSasha Levin <sasha.levin@oracle.com>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: NMichal Hocko <mhocko@suse.cz>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

dump_page() and dump_vma() are not specific to page_alloc.c, move them out
so page_alloc.c won't turn into the unofficial debug repository.
Signed-off-by: NSasha Levin <sasha.levin@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If a /proc/pid/pagemap read spans a [VMA, an unmapped region, then a
VM_SOFTDIRTY VMA], the virtual pages in the unmapped region are reported
as softdirty.  Here's a program to demonstrate the bug:

int main() {
	const uint64_t PAGEMAP_SOFTDIRTY = 1ul << 55;
	uint64_t pme[3];
	int fd = open("/proc/self/pagemap", O_RDONLY);;
	char *m = mmap(NULL, 3 * getpagesize(), PROT_READ,
	               MAP_ANONYMOUS | MAP_SHARED, -1, 0);
	munmap(m + getpagesize(), getpagesize());
	pread(fd, pme, 24, (unsigned long) m / getpagesize() * 8);
	assert(pme[0] & PAGEMAP_SOFTDIRTY);    /* passes */
	assert(!(pme[1] & PAGEMAP_SOFTDIRTY)); /* fails */
	assert(pme[2] & PAGEMAP_SOFTDIRTY);    /* passes */
	return 0;
}

(Note that all pages in new VMAs are softdirty until cleared).

Tested:
	Used the program given above. I'm going to include this code in
	a selftest in the future.

[n-horiguchi@ah.jp.nec.com: prevent pagemap_pte_range() from overrunning]
Signed-off-by: NPeter Feiner <pfeiner@google.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Jamie Liu <jamieliu@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-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>

Zones are allocated by the page allocator in either node or zone order.
Node ordering is preferred in terms of locality and is applied
automatically in one of three cases:

  1. If a node has only low memory

  2. If DMA/DMA32 is a high percentage of memory

  3. If low memory on a single node is greater than 70% of the node size

Otherwise zone ordering is used to preserve low memory for devices that
require it.  Unfortunately a consequence of this is that applications
running on a machine with balanced NUMA nodes will experience different
performance characteristics depending on which node they happen to start
from.

The point of zone ordering is to protect lower zones for devices that
require DMA/DMA32 memory.  When NUMA was first introduced, this was
critical as 32-bit NUMA machines existed and exhausting low memory
triggered OOMs easily as so many allocations required low memory.  On
64-bit machines the primary concern is devices that are 32-bit only which
is less severe than the low memory exhaustion problem on 32-bit NUMA.  It
seems there are really few devices that depends on it.

AGP -- I assume this is getting more rare but even then I think the allocations
	happen early in boot time where lowmem pressure is less of a problem

DRM -- If the device is 32-bit only then there may be low pressure. I didn't
	evaluate these in detail but it looks like some of these are mobile
	graphics card. Not many NUMA laptops out there. DRM folk should know
	better though.

Some TV cards -- Much demand for 32-bit capable TV cards on NUMA machines?

B43 wireless card -- again not really a NUMA thing.

I cannot find a good reason to incur a performance penalty on all 64-bit NUMA
machines in case someone throws a brain damanged TV or graphics card in there.
This patch defaults to node-ordering on 64-bit NUMA machines. I was tempted
to make it default everywhere but I understand that some embedded arches may
be using 32-bit NUMA where I cannot predict the consequences.

The performance impact depends on the workload and the characteristics of the
machine and the machine I tested on had a large Normal zone on node 0 so the
impact is within the noise for the majority of tests. The allocation stats
show more allocation requests were from DMA32 and local node. Running SpecJBB
with multiple JVMs and automatic NUMA balancing disabled the results were

specjbb
                     3.17.0-rc2            3.17.0-rc2
                        vanilla        nodeorder-v1r1
Min    1      29534.00 (  0.00%)     30020.00 (  1.65%)
Min    10    115717.00 (  0.00%)    134038.00 ( 15.83%)
Min    19    109718.00 (  0.00%)    114186.00 (  4.07%)
Min    28    104459.00 (  0.00%)    103639.00 ( -0.78%)
Min    37     98245.00 (  0.00%)    103756.00 (  5.61%)
Min    46     97198.00 (  0.00%)     96197.00 ( -1.03%)
Mean   1      30953.25 (  0.00%)     31917.75 (  3.12%)
Mean   10    124432.50 (  0.00%)    140904.00 ( 13.24%)
Mean   19    116033.50 (  0.00%)    119294.75 (  2.81%)
Mean   28    108365.25 (  0.00%)    106879.50 ( -1.37%)
Mean   37    102984.75 (  0.00%)    106924.25 (  3.83%)
Mean   46    100783.25 (  0.00%)    105368.50 (  4.55%)
Stddev 1       1260.38 (  0.00%)      1109.66 ( 11.96%)
Stddev 10      7434.03 (  0.00%)      5171.91 ( 30.43%)
Stddev 19      8453.84 (  0.00%)      5309.59 ( 37.19%)
Stddev 28      4184.55 (  0.00%)      2906.63 ( 30.54%)
Stddev 37      5409.49 (  0.00%)      3192.12 ( 40.99%)
Stddev 46      4521.95 (  0.00%)      7392.52 (-63.48%)
Max    1      32738.00 (  0.00%)     32719.00 ( -0.06%)
Max    10    136039.00 (  0.00%)    148614.00 (  9.24%)
Max    19    130566.00 (  0.00%)    127418.00 ( -2.41%)
Max    28    115404.00 (  0.00%)    111254.00 ( -3.60%)
Max    37    112118.00 (  0.00%)    111732.00 ( -0.34%)
Max    46    108541.00 (  0.00%)    116849.00 (  7.65%)
TPut   1     123813.00 (  0.00%)    127671.00 (  3.12%)
TPut   10    497730.00 (  0.00%)    563616.00 ( 13.24%)
TPut   19    464134.00 (  0.00%)    477179.00 (  2.81%)
TPut   28    433461.00 (  0.00%)    427518.00 ( -1.37%)
TPut   37    411939.00 (  0.00%)    427697.00 (  3.83%)
TPut   46    403133.00 (  0.00%)    421474.00 (  4.55%)

                            3.17.0-rc2  3.17.0-rc2
                               vanillanodeorder-v1r1
DMA allocs                           0           0
DMA32 allocs                        57     1491992
Normal allocs                 32543566    30026383
Movable allocs                       0           0
Direct pages scanned                 0           0
Kswapd pages scanned                 0           0
Kswapd pages reclaimed               0           0
Direct pages reclaimed               0           0
Kswapd efficiency                 100%        100%
Kswapd velocity                  0.000       0.000
Direct efficiency                 100%        100%
Direct velocity                  0.000       0.000
Percentage direct scans             0%          0%
Zone normal velocity             0.000       0.000
Zone dma32 velocity              0.000       0.000
Zone dma velocity                0.000       0.000
THP fault alloc                  55164       52987
THP collapse alloc                 139         147
THP splits                          26          21
NUMA alloc hit                 4169066     4250692
NUMA alloc miss                      0           0

Note that there were more DMA32 allocations with the patch applied.  In this
particular case there was no difference in numa_hit and numa_miss. The
expectation is that DMA32 was being used at the low watermark instead of
falling into the slow path. kswapd was not woken but it's not worken for
THP allocations.

On 32-bit, this patch defaults to zone-ordering as low memory depletion
can be a serious problem on 32-bit large memory machines. If the default
ordering was node then processes on node 0 will deplete the Normal zone
due to normal activity.  The problem is worse if CONFIG_HIGHPTE is not
set. If combined with large amounts of dirty/writeback pages in Normal
zone then there is also a high risk of OOM. The heuristics are removed
as it's not clear they were ever important on 32-bit. They were only
relevant for setting node-ordering on 64-bit.
Signed-off-by: NMel Gorman <mgorman@suse.de>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Since 2.6.24 there has been a paranoid check in move_freepages that looks
up the zone of two pages.  This is a very slow path and the only time I've
seen this bug trigger recently is when memory initialisation was broken
during patch development.  Despite the fact it's a slow path, this patch
converts the check to a VM_BUG_ON anyway as it has served its purpose by
now.
Signed-off-by: NMel Gorman <mgorman@suse.de>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NRik van Riel <riel@redhat.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Fix a deadlock problem caused by direct memory reclaim in o2net_wq.  The
situation is as follows:

1) Receive a connect message from another node, node queues a
   work_struct o2net_listen_work.

2) o2net_wq processes this work and call the following functions:

o2net_wq
-> o2net_accept_one
  -> sock_create_lite
    -> sock_alloc()
      -> kmem_cache_alloc with GFP_KERNEL
        -> ____cache_alloc_node
          ->__alloc_pages_nodemask
            -> do_try_to_free_pages
              -> shrink_slab
                -> evict
                  -> ocfs2_evict_inode
                    -> ocfs2_drop_lock
                      -> dlmunlock
                        -> o2net_send_message_vec

   then o2net_wq wait for the unlock reply from master.

3) tcp layer received the reply, call o2net_data_ready() and queue
   sc_rx_work, waiting o2net_wq to process this work.

4) o2net_wq is a single thread workqueue, it process the work one by
   one.  Right now it is still doing o2net_listen_work and cannot handle
   sc_rx_work.  so we deadlock.

Junxiao Bi's patch "mm: clear __GFP_FS when PF_MEMALLOC_NOIO is set"
(http://ozlabs.org/~akpm/mmots/broken-out/mm-clear-__gfp_fs-when-pf_memalloc_noio-is-set.patch)
clears __GFP_FS in memalloc_noio_flags() besides __GFP_IO.  We use
memalloc_noio_save() to set process flag PF_MEMALLOC_NOIO so that all
allocations done by this process are done as if GFP_NOIO was specified.
We are not reentering filesystem while doing memory reclaim.
Signed-off-by: Njoyce.xue <xuejiufei@huawei.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

commit 21caf2fc ("mm: teach mm by current context info to not do I/O
during memory allocation") introduces PF_MEMALLOC_NOIO flag to avoid doing
I/O inside memory allocation, __GFP_IO is cleared when this flag is set,
but __GFP_FS implies __GFP_IO, it should also be cleared.  Or it may still
run into I/O, like in superblock shrinker.  And this will make the kernel
run into the deadlock case described in that commit.

See Dave Chinner's comment about io in superblock shrinker:

Filesystem shrinkers do indeed perform IO from the superblock shrinker and
have for years.  Even clean inodes can require IO before they can be freed
- e.g.  on an orphan list, need truncation of post-eof blocks, need to
wait for ordered operations to complete before it can be freed, etc.

IOWs, Ext4, btrfs and XFS all can issue and/or block on arbitrary amounts
of IO in the superblock shrinker context.  XFS, in particular, has been
doing transactions and IO from the VFS inode cache shrinker since it was
first introduced....

Fix this by clearing __GFP_FS in memalloc_noio_flags(), this function has
masked all the gfp_mask that will be passed into fs for the processes
setting PF_MEMALLOC_NOIO in the direct reclaim path.

v1 thread at: https://lkml.org/lkml/2014/9/3/32Signed-off-by: NJunxiao Bi <junxiao.bi@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: joyce.xue <xuejiufei@huawei.com>
Cc: Ming Lei <ming.lei@canonical.com>
Cc: Trond Myklebust <trond.myklebust@primarydata.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

C      mm/compaction.o
mm/compaction.c: In function isolate_freepages_block:
mm/compaction.c:364:37: warning: flags may be used uninitialized in this function [-Wmaybe-uninitialized]
       && compact_unlock_should_abort(&cc->zone->lock, flags,
                                     ^
Signed-off-by: NXiubo Li <Li.Xiubo@freescale.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: David Rientjes <rientjes@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

- be consistent in printing the test which failed

- one message was actually wrong (a<b != b>a)

- don't print second bogus warning if browse_rb() failed

Cc: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Page reclaim tests zone_is_reclaim_dirty(), but the site that actually
sets this state does zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY), sending the
reader through layers indirection just to track down a simple bit.

Remove all zone flag wrappers and just use bitops against zone->flags
directly.  It's just as readable and the lines are barely any longer.

Also rename ZONE_TAIL_LRU_DIRTY to ZONE_DIRTY to match ZONE_WRITEBACK, and
remove the zone_flags_t typedef.
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NMel Gorman <mgorman@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Nested calls to min/max functions result in shadow warnings in W=2 builds.
 Avoid the warning by using the min3 and max3 macros to get the min/max of
3 values instead of nested calls.
Signed-off-by: NMark Rustad <mark.d.rustad@intel.com>
Signed-off-by: NJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When entering the page_alloc slowpath, we wakeup kswapd on every pgdat
according to the zonelist and high_zoneidx.  However, this doesn't take
nodemask into account, and could prematurely wakeup kswapd on some
unintended nodes.

This patch uses for_each_zone_zonelist_nodemask() instead of
for_each_zone_zonelist() in wake_all_kswapds() to avoid the above
situation.
Signed-off-by: NWeijie Yang <weijie.yang@samsung.com>
Acked-by: NMel Gorman <mgorman@suse.de>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Trivially convert a few VM_BUG_ON calls to VM_BUG_ON_VMA to extract
more information when they trigger.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NSasha Levin <sasha.levin@oracle.com>
Reviewed-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michel Lespinasse <walken@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Very similar to VM_BUG_ON_PAGE but dumps VMA information instead.
Signed-off-by: NSasha Levin <sasha.levin@oracle.com>
Reviewed-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michel Lespinasse <walken@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Introduce a helper to dump information about a VMA, this also makes
dump_page_flags more generic and re-uses that so the output looks very
similar to dump_page:

[   61.903437] vma ffff88070f88be00 start 00007fff25970000 end 00007fff25992000
[   61.903437] next ffff88070facd600 prev ffff88070face400 mm ffff88070fade000
[   61.903437] prot 8000000000000025 anon_vma ffff88070fa1e200 vm_ops           (null)
[   61.903437] pgoff 7ffffffdd file           (null) private_data           (null)
[   61.909129] flags: 0x100173(read|write|mayread|maywrite|mayexec|growsdown|account)

[akpm@linux-foundation.org: make dump_vma() require CONFIG_DEBUG_VM]
[swarren@nvidia.com: fix dump_vma() compilation]
Signed-off-by: NSasha Levin <sasha.levin@oracle.com>
Reviewed-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michel Lespinasse <walken@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Using __seq_open_private() removes boilerplate code from slabstats_open()

The resultant code is shorter and easier to follow.

This patch does not change any functionality.
Signed-off-by: NRob Jones <rob.jones@codethink.co.uk>
Acked-by: NChristoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Using seq_open_private() removes boilerplate code from vmalloc_open().

The resultant code is shorter and easier to follow.

However, please note that seq_open_private() call kzalloc() rather than
kmalloc() which may affect timing due to the memory initialisation
overhead.
Signed-off-by: NRob Jones <rob.jones@codethink.co.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This is designed to avoid a few ifdefs in .c files but it's obnoxious
because it can cause unsuspecting "migrate_page" symbols to get turned into
"NULL".

Just nuke it and use the ifdefs.

Cc: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
Cc: Rafael Aquini <aquini@redhat.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

- get_vma_policy(task) is not safe if task != current, remove this
  argument.

- get_vma_policy() no longer has callers outside of mempolicy.c,
  make it static.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Naoya 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>

Remove down_write(&mm->mmap_sem) in do_set_mempolicy(). This logic
was never correct and it is no longer needed, see the previous patch.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Naoya 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>

9e781440 "hold task->mempolicy while numa_maps scans." fixed the
race with the exiting task but this is not enough.

The current code assumes that get_vma_policy(task) should either see
task->mempolicy == NULL or it should be equal to ->task_mempolicy saved
by hold_task_mempolicy(), so we can never race with __mpol_put(). But
this can only work if we can't race with do_set_mempolicy(), and thus
we can't race with another do_set_mempolicy() or do_exit() after that.

However, do_set_mempolicy()->down_write(mmap_sem) can not prevent this
race. This task can exec, change it's ->mm, and call do_set_mempolicy()
after that; in this case they take 2 different locks.

Change hold_task_mempolicy() to use get_task_policy(), it never returns
NULL, and change show_numa_map() to use __get_vma_policy() or fall back
to proc_priv->task_mempolicy.

Note: this is the minimal fix, we will cleanup this code later. I think
hold_task_mempolicy() and release_task_mempolicy() should die, we can
move this logic into show_numa_map(). Or we can move get_task_policy()
outside of ->mmap_sem and !CONFIG_NUMA code at least.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Naoya 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>

Extract the code which looks for vma's policy from get_vma_policy()
into the new helper, __get_vma_policy(). Export get_task_policy().
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Naoya 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>

1. vma_policy_mof(task) is simply not safe unless task == current,
   it can race with do_exit()->mpol_put(). Remove this arg and update
   its single caller.

2. vma can not be NULL, remove this check and simplify the code.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Naoya 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>

Cleanup + preparation. Every user of get_task_policy() calls it
unconditionally, even if it is not going to use the result.

get_task_policy() is cheap but still this does not look clean, plus
the code looks simpler if get_task_policy() is called only when this
is really needed.

Note: I hope this is correct, but it is not clear why vma_policy_mof()
doesn't fall back to get_task_policy() if ->get_policy() returns NULL.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Naoya 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>

Every caller of get_task_policy() falls back to default_policy if it
returns NULL. Change get_task_policy() to do this.
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Naoya 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>

Trivial cleanup. alloc_pages_vma() can use mpol_cond_put().
Signed-off-by: NOleg Nesterov <oleg@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Naoya 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>

The deprecation warnings for the scan_unevictable interface triggers by
scripts doing `sysctl -a | grep something else'.  This is annoying and not
helpful.

The interface has been defunct since 264e56d8 ("mm: disable user
interface to manually rescue unevictable pages"), which was in 2011, and
there haven't been any reports of usecases for it, only reports that the
deprecation warnings are annying.  It's unlikely that anybody is using
this interface specifically at this point, so remove it.
Signed-off-by: NJohannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

During development of c/r we've noticed that in case if we need to support
user namespaces we face a problem with capabilities in prctl(PR_SET_MM,
...) call, in particular once new user namespace is created
capable(CAP_SYS_RESOURCE) no longer passes.

A approach is to eliminate CAP_SYS_RESOURCE check but pass all new values
in one bundle, which would allow the kernel to make more intensive test
for sanity of values and same time allow us to support checkpoint/restore
of user namespaces.

Thus a new command PR_SET_MM_MAP introduced. It takes a pointer of
prctl_mm_map structure which carries all the members to be updated.

	prctl(PR_SET_MM, PR_SET_MM_MAP, struct prctl_mm_map *, size)

	struct prctl_mm_map {
		__u64	start_code;
		__u64	end_code;
		__u64	start_data;
		__u64	end_data;
		__u64	start_brk;
		__u64	brk;
		__u64	start_stack;
		__u64	arg_start;
		__u64	arg_end;
		__u64	env_start;
		__u64	env_end;
		__u64	*auxv;
		__u32	auxv_size;
		__u32	exe_fd;
	};

All members except @exe_fd correspond ones of struct mm_struct.  To figure
out which available values these members may take here are meanings of the
members.

 - start_code, end_code: represent bounds of executable code area
 - start_data, end_data: represent bounds of data area
 - start_brk, brk: used to calculate bounds for brk() syscall
 - start_stack: used when accounting space needed for command
   line arguments, environment and shmat() syscall
 - arg_start, arg_end, env_start, env_end: represent memory area
   supplied for command line arguments and environment variables
 - auxv, auxv_size: carries auxiliary vector, Elf format specifics
 - exe_fd: file descriptor number for executable link (/proc/self/exe)

Thus we apply the following requirements to the values

1) Any member except @auxv, @auxv_size, @exe_fd is rather an address
   in user space thus it must be laying inside [mmap_min_addr, mmap_max_addr)
   interval.

2) While @[start|end]_code and @[start|end]_data may point to an nonexisting
   VMAs (say a program maps own new .text and .data segments during execution)
   the rest of members should belong to VMA which must exist.

3) Addresses must be ordered, ie @start_ member must not be greater or
   equal to appropriate @end_ member.

4) As in regular Elf loading procedure we require that @start_brk and
   @brk be greater than @end_data.

5) If RLIMIT_DATA rlimit is set to non-infinity new values should not
   exceed existing limit. Same applies to RLIMIT_STACK.

6) Auxiliary vector size must not exceed existing one (which is
   predefined as AT_VECTOR_SIZE and depends on architecture).

7) File descriptor passed in @exe_file should be pointing
   to executable file (because we use existing prctl_set_mm_exe_file_locked
   helper it ensures that the file we are going to use as exe link has all
   required permission granted).

Now about where these members are involved inside kernel code:

 - @start_code and @end_code are used in /proc/$pid/[stat|statm] output;

 - @start_data and @end_data are used in /proc/$pid/[stat|statm] output,
   also they are considered if there enough space for brk() syscall
   result if RLIMIT_DATA is set;

 - @start_brk shown in /proc/$pid/stat output and accounted in brk()
   syscall if RLIMIT_DATA is set; also this member is tested to
   find a symbolic name of mmap event for perf system (we choose
   if event is generated for "heap" area); one more aplication is
   selinux -- we test if a process has PROCESS__EXECHEAP permission
   if trying to make heap area being executable with mprotect() syscall;

 - @brk is a current value for brk() syscall which lays inside heap
   area, it's shown in /proc/$pid/stat. When syscall brk() succesfully
   provides new memory area to a user space upon brk() completion the
   mm::brk is updated to carry new value;

   Both @start_brk and @brk are actively used in /proc/$pid/maps
   and /proc/$pid/smaps output to find a symbolic name "heap" for
   VMA being scanned;

 - @start_stack is printed out in /proc/$pid/stat and used to
   find a symbolic name "stack" for task and threads in
   /proc/$pid/maps and /proc/$pid/smaps output, and as the same
   as with @start_brk -- perf system uses it for event naming.
   Also kernel treat this member as a start address of where
   to map vDSO pages and to check if there is enough space
   for shmat() syscall;

 - @arg_start, @arg_end, @env_start and @env_end are printed out
   in /proc/$pid/stat. Another access to the data these members
   represent is to read /proc/$pid/environ or /proc/$pid/cmdline.
   Any attempt to read these areas kernel tests with access_process_vm
   helper so a user must have enough rights for this action;

 - @auxv and @auxv_size may be read from /proc/$pid/auxv. Strictly
   speaking kernel doesn't care much about which exactly data is
   sitting there because it is solely for userspace;

 - @exe_fd is referred from /proc/$pid/exe and when generating
   coredump. We uses prctl_set_mm_exe_file_locked helper to update
   this member, so exe-file link modification remains one-shot
   action.

Still note that updating exe-file link now doesn't require sys-resource
capability anymore, after all there is no much profit in preventing setup
own file link (there are a number of ways to execute own code -- ptrace,
ld-preload, so that the only reliable way to find which exactly code is
executed is to inspect running program memory).  Still we require the
caller to be at least user-namespace root user.

I believe the old interface should be deprecated and ripped off in a
couple of kernel releases if no one against.

To test if new interface is implemented in the kernel one can pass
PR_SET_MM_MAP_SIZE opcode and the kernel returns the size of currently
supported struct prctl_mm_map.

[akpm@linux-foundation.org: fix 80-col wordwrap in macro definitions]
Signed-off-by: NCyrill Gorcunov <gorcunov@openvz.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: NAndrew Vagin <avagin@openvz.org>
Tested-by: NAndrew Vagin <avagin@openvz.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Acked-by: NSerge Hallyn <serge.hallyn@canonical.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Julien Tinnes <jln@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Instead of taking mm->mmap_sem inside prctl_set_mm_exe_file() move it out
and rename the helper to prctl_set_mm_exe_file_locked().  This will allow
to reuse this function in a next patch.
Signed-off-by: NCyrill Gorcunov <gorcunov@openvz.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Acked-by: NSerge Hallyn <serge.hallyn@canonical.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Julien Tinnes <jln@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NCyrill Gorcunov <gorcunov@openvz.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Acked-by: NSerge Hallyn <serge.hallyn@canonical.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Julien Tinnes <jln@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

To eliminate code duplication lets introduce check_data_rlimit helper
which we will use in brk() and prctl() syscalls.
Signed-off-by: NCyrill Gorcunov <gorcunov@openvz.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Acked-by: NSerge Hallyn <serge.hallyn@canonical.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Vasiliy Kulikov <segoon@openwall.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Julien Tinnes <jln@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

struct compact_control currently converts the gfp mask to a migratetype,
but we need the entire gfp mask in a follow-up patch.

Pass the entire gfp mask as part of struct compact_control.
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Reviewed-by: NZhang Yanfei <zhangyanfei@cn.fujitsu.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Acked-by: NMel Gorman <mgorman@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Christoph Lameter <cl@linux.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 page allocator has gfp flags (like __GFP_WAIT) and alloc flags (like
ALLOC_CPUSET) that have separate semantics.

The function allocflags_to_migratetype() actually takes gfp flags, not
alloc flags, and returns a migratetype.  Rename it to
gfpflags_to_migratetype().
Signed-off-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Reviewed-by: NZhang Yanfei <zhangyanfei@cn.fujitsu.com>
Reviewed-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Acked-by: NMel Gorman <mgorman@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Christoph Lameter <cl@linux.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 migration scanner skips PageBuddy pages, but does not consider their
order as checking page_order() is generally unsafe without holding the
zone->lock, and acquiring the lock just for the check wouldn't be a good
tradeoff.

Still, this could avoid some iterations over the rest of the buddy page,
and if we are careful, the race window between PageBuddy() check and
page_order() is small, and the worst thing that can happen is that we skip
too much and miss some isolation candidates.  This is not that bad, as
compaction can already fail for many other reasons like parallel
allocations, and those have much larger race window.

This patch therefore makes the migration scanner obtain the buddy page
order and use it to skip the whole buddy page, if the order appears to be
in the valid range.

It's important that the page_order() is read only once, so that the value
used in the checks and in the pfn calculation is the same.  But in theory
the compiler can replace the local variable by multiple inlines of
page_order().  Therefore, the patch introduces page_order_unsafe() that
uses ACCESS_ONCE to prevent this.

Testing with stress-highalloc from mmtests shows a 15% reduction in number
of pages scanned by migration scanner.  The reduction is >60% with
__GFP_NO_KSWAPD allocations, along with success rates better by few
percent.
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Reviewed-by: NZhang Yanfei <zhangyanfei@cn.fujitsu.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Acked-by: NMel Gorman <mgorman@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Unlike the migration scanner, the free scanner remembers the beginning of
the last scanned pageblock in cc->free_pfn.  It might be therefore
rescanning pages uselessly when called several times during single
compaction.  This might have been useful when pages were returned to the
buddy allocator after a failed migration, but this is no longer the case.

This patch changes the meaning of cc->free_pfn so that if it points to a
middle of a pageblock, that pageblock is scanned only from cc->free_pfn to
the end.  isolate_freepages_block() will record the pfn of the last page
it looked at, which is then used to update cc->free_pfn.

In the mmtests stress-highalloc benchmark, this has resulted in lowering
the ratio between pages scanned by both scanners, from 2.5 free pages per
migrate page, to 2.25 free pages per migrate page, without affecting
success rates.

With __GFP_NO_KSWAPD allocations, this appears to result in a worse ratio
(2.1 instead of 1.8), but page migration successes increased by 10%, so
this could mean that more useful work can be done until need_resched()
aborts this kind of compaction.
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Reviewed-by: NZhang Yanfei <zhangyanfei@cn.fujitsu.com>
Reviewed-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Acked-by: NMel Gorman <mgorman@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Compaction scanners try to lock zone locks as late as possible by checking
many page or pageblock properties opportunistically without lock and
skipping them if not unsuitable.  For pages that pass the initial checks,
some properties have to be checked again safely under lock.  However, if
the lock was already held from a previous iteration in the initial checks,
the rechecks are unnecessary.

This patch therefore skips the rechecks when the lock was already held.
This is now possible to do, since we don't (potentially) drop and
reacquire the lock between the initial checks and the safe rechecks
anymore.
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Reviewed-by: NZhang Yanfei <zhangyanfei@cn.fujitsu.com>
Reviewed-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Acked-by: NMel Gorman <mgorman@suse.de>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Compaction scanners regularly check for lock contention and need_resched()
through the compact_checklock_irqsave() function.  However, if there is no
contention, the lock can be held and IRQ disabled for potentially long
time.

This has been addressed by commit b2eef8c0 ("mm: compaction: minimise
the time IRQs are disabled while isolating pages for migration") for the
migration scanner.  However, the refactoring done by commit 2a1402aa
("mm: compaction: acquire the zone->lru_lock as late as possible") has
changed the conditions so that the lock is dropped only when there's
contention on the lock or need_resched() is true.  Also, need_resched() is
checked only when the lock is already held.  The comment "give a chance to
irqs before checking need_resched" is therefore misleading, as IRQs remain
disabled when the check is done.

This patch restores the behavior intended by commit b2eef8c0 and also
tries to better balance and make more deterministic the time spent by
checking for contention vs the time the scanners might run between the
checks.  It also avoids situations where checking has not been done often
enough before.  The result should be avoiding both too frequent and too
infrequent contention checking, and especially the potentially
long-running scans with IRQs disabled and no checking of need_resched() or
for fatal signal pending, which can happen when many consecutive pages or
pageblocks fail the preliminary tests and do not reach the later call site
to compact_checklock_irqsave(), as explained below.

Before the patch:

In the migration scanner, compact_checklock_irqsave() was called each
loop, if reached.  If not reached, some lower-frequency checking could
still be done if the lock was already held, but this would not result in
aborting contended async compaction until reaching
compact_checklock_irqsave() or end of pageblock.  In the free scanner, it
was similar but completely without the periodical checking, so lock can be
potentially held until reaching the end of pageblock.

After the patch, in both scanners:

The periodical check is done as the first thing in the loop on each
SWAP_CLUSTER_MAX aligned pfn, using the new compact_unlock_should_abort()
function, which always unlocks the lock (if locked) and aborts async
compaction if scheduling is needed.  It also aborts any type of compaction
when a fatal signal is pending.

The compact_checklock_irqsave() function is replaced with a slightly
different compact_trylock_irqsave().  The biggest difference is that the
function is not called at all if the lock is already held.  The periodical
need_resched() checking is left solely to compact_unlock_should_abort().
The lock contention avoidance for async compaction is achieved by the
periodical unlock by compact_unlock_should_abort() and by using trylock in
compact_trylock_irqsave() and aborting when trylock fails.  Sync
compaction does not use trylock.
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Reviewed-by: NZhang Yanfei <zhangyanfei@cn.fujitsu.com>
Acked-by: NMinchan Kim <minchan@kernel.org>
Acked-by: NMel Gorman <mgorman@suse.de>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Async compaction aborts when it detects zone lock contention or
need_resched() is true.  David Rientjes has reported that in practice,
most direct async compactions for THP allocation abort due to
need_resched().  This means that a second direct compaction is never
attempted, which might be OK for a page fault, but khugepaged is intended
to attempt a sync compaction in such case and in these cases it won't.

This patch replaces "bool contended" in compact_control with an int that
distinguishes between aborting due to need_resched() and aborting due to
lock contention.  This allows propagating the abort through all compaction
functions as before, but passing the abort reason up to
__alloc_pages_slowpath() which decides when to continue with direct
reclaim and another compaction attempt.

Another problem is that try_to_compact_pages() did not act upon the
reported contention (both need_resched() or lock contention) immediately
and would proceed with another zone from the zonelist.  When
need_resched() is true, that means initializing another zone compaction,
only to check again need_resched() in isolate_migratepages() and aborting.
 For zone lock contention, the unintended consequence is that the lock
contended status reported back to the allocator is detrmined from the last
zone where compaction was attempted, which is rather arbitrary.

This patch fixes the problem in the following way:
- async compaction of a zone aborting due to need_resched() or fatal signal
  pending means that further zones should not be tried. We report
  COMPACT_CONTENDED_SCHED to the allocator.
- aborting zone compaction due to lock contention means we can still try
  another zone, since it has different set of locks. We report back
  COMPACT_CONTENDED_LOCK only if *all* zones where compaction was attempted,
  it was aborted due to lock contention.

As a result of these fixes, khugepaged will proceed with second sync
compaction as intended, when the preceding async compaction aborted due to
need_resched().  Page fault compactions aborting due to need_resched()
will spare some cycles previously wasted by initializing another zone
compaction only to abort again.  Lock contention will be reported only
when compaction in all zones aborted due to lock contention, and therefore
it's not a good idea to try again after reclaim.

In stress-highalloc from mmtests configured to use __GFP_NO_KSWAPD, this
has improved number of THP collapse allocations by 10%, which shows
positive effect on khugepaged.  The benchmark's success rates are
unchanged as it is not recognized as khugepaged.  Numbers of compact_stall
and compact_fail events have however decreased by 20%, with
compact_success still a bit improved, which is good.  With benchmark
configured not to use __GFP_NO_KSWAPD, there is 6% improvement in THP
collapse allocations, and only slight improvement in stalls and failures.

[akpm@linux-foundation.org: fix warnings]
Reported-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Acked-by: NMel Gorman <mgorman@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Christoph Lameter <cl@linux.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 unification of the migrate and free scanner families of function has
highlighted a difference in how the scanners ensure they only isolate
pages of the intended zone.  This is important for taking zone lock or lru
lock of the correct zone.  Due to nodes overlapping, it is however
possible to encounter a different zone within the range of the zone being
compacted.

The free scanner, since its inception by commit 748446bb ("mm:
compaction: memory compaction core"), has been checking the zone of the
first valid page in a pageblock, and skipping the whole pageblock if the
zone does not match.

This checking was completely missing from the migration scanner at first,
and later added by commit dc908600 ("mm: compaction: check for
overlapping nodes during isolation for migration") in a reaction to a bug
report.  But the zone comparison in migration scanner is done once per a
single scanned page, which is more defensive and thus more costly than a
check per pageblock.

This patch unifies the checking done in both scanners to once per
pageblock, through a new pageblock_pfn_to_page() function, which also
includes pfn_valid() checks.  It is more defensive than the current free
scanner checks, as it checks both the first and last page of the
pageblock, but less defensive by the migration scanner per-page checks.
It assumes that node overlapping may result (on some architecture) in a
boundary between two nodes falling into the middle of a pageblock, but
that there cannot be a node0 node1 node0 interleaving within a single
pageblock.

The result is more code being shared and a bit less per-page CPU cost in
the migration scanner.
Signed-off-by: NVlastimil Babka <vbabka@suse.cz>
Cc: Minchan Kim <minchan@kernel.org>
Acked-by: NMel Gorman <mgorman@suse.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: NDavid Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>