mm/compaction: reverse the change that forbade sync migraton with __GFP_NO_KSWAPD

It's uncertain this has been beneficial, so it's safer to undo it.  All
other compaction users would still go in synchronous mode if a first
attempt at async compaction failed.  Hopefully we don't need to force
special behavior for THP (which is the only __GFP_NO_KSWAPD user so far
and it's the easier to exercise and to be noticeable).  This also make
__GFP_NO_KSWAPD return to its original strict semantics specific to bypass
kswapd, as THP allocations have khugepaged for the async THP
allocations/compactions.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Alex Villacis Lasso <avillaci@fiec.espol.edu.ec>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm: break out page allocation warning code

This originally started as a simple patch to give vmalloc() some more
verbose output on failure on top of the plain page allocator messages.
Johannes suggested that it might be nicer to lead with the vmalloc() info
_before_ the page allocator messages.

But, I do think there's a lot of value in what __alloc_pages_slowpath()
does with its filtering and so forth.

This patch creates a new function which other allocators can call instead
of relying on the internal page allocator warnings.  It also gives this
function private rate-limiting which separates it from other
printk_ratelimit() users.

Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm: fail GFP_DMA allocations when ZONE_DMA is not configured

The page allocator will improperly return a page from ZONE_NORMAL even
when __GFP_DMA is passed if CONFIG_ZONE_DMA is disabled.  The caller
expects DMA memory, perhaps for ISA devices with 16-bit address registers,
and may get higher memory resulting in undefined behavior.

This patch causes the page allocator to return NULL in such circumstances
with a warning emitted to the kernel log on the first occurrence.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
memcg: fix get_scan_count() for small targets

During memory reclaim we determine the number of pages to be scanned per
zone as

	(anon + file) >> priority.
Assume
	scan = (anon + file) >> priority.

If scan < SWAP_CLUSTER_MAX, the scan will be skipped for this time and
priority gets higher.  This has some problems.

  1. This increases priority as 1 without any scan.
     To do scan in this priority, amount of pages should be larger than 512M.
     If pages>>priority < SWAP_CLUSTER_MAX, it's recorded and scan will be
     batched, later. (But we lose 1 priority.)
     If memory size is below 16M, pages >> priority is 0 and no scan in
     DEF_PRIORITY forever.

  2. If zone->all_unreclaimabe==true, it's scanned only when priority==0.
     So, x86's ZONE_DMA will never be recoverred until the user of pages
     frees memory by itself.

  3. With memcg, the limit of memory can be small. When using small memcg,
     it gets priority < DEF_PRIORITY-2 very easily and need to call
     wait_iff_congested().
     For doing scan before priorty=9, 64MB of memory should be used.

Then, this patch tries to scan SWAP_CLUSTER_MAX of pages in force...when

  1. the target is enough small.
  2. it's kswapd or memcg reclaim.

Then we can avoid rapid priority drop and may be able to recover
all_unreclaimable in a small zones.  And this patch removes nr_saved_scan.
 This will allow scanning in this priority even when pages >> priority is
very small.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Ying Han <yinghan@google.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Revert "mm: fail GFP_DMA allocations when ZONE_DMA is not configured"

This reverts commit a197b59ae6e8bee56fcef37ea2482dc08414e2ac.

As rmk says:
 "Commit a197b59ae6e8 (mm: fail GFP_DMA allocations when ZONE_DMA is not
  configured) is causing regressions on ARM with various drivers which
  use GFP_DMA.

  The behaviour up until now has been to silently ignore that flag when
  CONFIG_ZONE_DMA is not enabled, and to allocate from the normal zone.
  However, as a result of the above commit, such allocations now fail
  which causes drivers to fail.  These are regressions compared to the
  previous kernel version."

so just revert it.

Requested-by: Russell King <linux@arm.linux.org.uk>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm: page allocator: initialise ZLC for first zone eligible for zone_reclaim

commit cd38b115d5ad79b0100ac6daa103c4fe2c50a913 upstream.

There have been a small number of complaints about significant stalls
while copying large amounts of data on NUMA machines reported on a
distribution bugzilla.  In these cases, zone_reclaim was enabled by
default due to large NUMA distances.  In general, the complaints have not
been about the workload itself unless it was a file server (in which case
the recommendation was disable zone_reclaim).

The stalls are mostly due to significant amounts of time spent scanning
the preferred zone for pages to free.  After a failure, it might fallback
to another node (as zonelists are often node-ordered rather than
zone-ordered) but stall quickly again when the next allocation attempt
occurs.  In bad cases, each page allocated results in a full scan of the
preferred zone.

Patch 1 checks the preferred zone for recent allocation failure
        which is particularly important if zone_reclaim has failed
        recently.  This avoids rescanning the zone in the near future and
        instead falling back to another node.  This may hurt node locality
        in some cases but a failure to zone_reclaim is more expensive than
        a remote access.

Patch 2 clears the zlc information after direct reclaim.
        Otherwise, zone_reclaim can mark zones full, direct reclaim can
        reclaim enough pages but the zone is still not considered for
        allocation.

This was tested on a 24-thread 2-node x86_64 machine.  The tests were
focused on large amounts of IO.  All tests were bound to the CPUs on
node-0 to avoid disturbances due to processes being scheduled on different
nodes.  The kernels tested are

3.0-rc6-vanilla		Vanilla 3.0-rc6
zlcfirst		Patch 1 applied
zlcreconsider		Patches 1+2 applied

FS-Mark
./fs_mark  -d  /tmp/fsmark-10813  -D  100  -N  5000  -n  208  -L  35  -t  24  -S0  -s  524288
                fsmark-3.0-rc6       3.0-rc6       		3.0-rc6
                   vanilla			 zlcfirs 	zlcreconsider
Files/s  min          54.90 ( 0.00%)       49.80 (-10.24%)       49.10 (-11.81%)
Files/s  mean        100.11 ( 0.00%)      135.17 (25.94%)      146.93 (31.87%)
Files/s  stddev       57.51 ( 0.00%)      138.97 (58.62%)      158.69 (63.76%)
Files/s  max         361.10 ( 0.00%)      834.40 (56.72%)      802.40 (55.00%)
Overhead min       76704.00 ( 0.00%)    76501.00 ( 0.27%)    77784.00 (-1.39%)
Overhead mean    1485356.51 ( 0.00%)  1035797.83 (43.40%)  1594680.26 (-6.86%)
Overhead stddev  1848122.53 ( 0.00%)   881489.88 (109.66%)  1772354.90 ( 4.27%)
Overhead max     7989060.00 ( 0.00%)  3369118.00 (137.13%) 10135324.00 (-21.18%)
MMTests Statistics: duration
User/Sys Time Running Test (seconds)        501.49    493.91    499.93
Total Elapsed Time (seconds)               2451.57   2257.48   2215.92

MMTests Statistics: vmstat
Page Ins                                       46268       63840       66008
Page Outs                                   90821596    90671128    88043732
Swap Ins                                           0           0           0
Swap Outs                                          0           0           0
Direct pages scanned                        13091697     8966863     8971790
Kswapd pages scanned                               0     1830011     1831116
Kswapd pages reclaimed                             0     1829068     1829930
Direct pages reclaimed                      13037777     8956828     8648314
Kswapd efficiency                               100%         99%         99%
Kswapd velocity                                0.000     810.643     826.346
Direct efficiency                                99%         99%         96%
Direct velocity                             5340.128    3972.068    4048.788
Percentage direct scans                         100%         83%         83%
Page writes by reclaim                             0           3           0
Slabs scanned                                 796672      720640      720256
Direct inode steals                          7422667     7160012     7088638
Kswapd inode steals                                0     1736840     2021238

Test completes far faster with a large increase in the number of files
created per second.  Standard deviation is high as a small number of
iterations were much higher than the mean.  The number of pages scanned by
zone_reclaim is reduced and kswapd is used for more work.

LARGE DD
               		3.0-rc6       3.0-rc6       3.0-rc6
                   	vanilla     zlcfirst     zlcreconsider
download tar           59 ( 0.00%)   59 ( 0.00%)   55 ( 7.27%)
dd source files       527 ( 0.00%)  296 (78.04%)  320 (64.69%)
delete source          36 ( 0.00%)   19 (89.47%)   20 (80.00%)
MMTests Statistics: duration
User/Sys Time Running Test (seconds)        125.03    118.98    122.01
Total Elapsed Time (seconds)                624.56    375.02    398.06

MMTests Statistics: vmstat
Page Ins                                     3594216      439368      407032
Page Outs                                   23380832    23380488    23377444
Swap Ins                                           0           0           0
Swap Outs                                          0         436         287
Direct pages scanned                        17482342    69315973    82864918
Kswapd pages scanned                               0      519123      575425
Kswapd pages reclaimed                             0      466501      522487
Direct pages reclaimed                       5858054     2732949     2712547
Kswapd efficiency                               100%         89%         90%
Kswapd velocity                                0.000    1384.254    1445.574
Direct efficiency                                33%          3%          3%
Direct velocity                            27991.453  184832.737  208171.929
Percentage direct scans                         100%         99%         99%
Page writes by reclaim                             0        5082       13917
Slabs scanned                                  17280       29952       35328
Direct inode steals                           115257     1431122      332201
Kswapd inode steals                                0           0      979532

This test downloads a large tarfile and copies it with dd a number of
times - similar to the most recent bug report I've dealt with.  Time to
completion is reduced.  The number of pages scanned directly is still
disturbingly high with a low efficiency but this is likely due to the
number of dirty pages encountered.  The figures could probably be improved
with more work around how kswapd is used and how dirty pages are handled
but that is separate work and this result is significant on its own.

Streaming Mapped Writer
MMTests Statistics: duration
User/Sys Time Running Test (seconds)        124.47    111.67    112.64
Total Elapsed Time (seconds)               2138.14   1816.30   1867.56

MMTests Statistics: vmstat
Page Ins                                       90760       89124       89516
Page Outs                                  121028340   120199524   120736696
Swap Ins                                           0          86          55
Swap Outs                                          0           0           0
Direct pages scanned                       114989363    96461439    96330619
Kswapd pages scanned                        56430948    56965763    57075875
Kswapd pages reclaimed                      27743219    27752044    27766606
Direct pages reclaimed                         49777       46884       36655
Kswapd efficiency                                49%         48%         48%
Kswapd velocity                            26392.541   31363.631   30561.736
Direct efficiency                                 0%          0%          0%
Direct velocity                            53780.091   53108.759   51581.004
Percentage direct scans                          67%         62%         62%
Page writes by reclaim                           385         122        1513
Slabs scanned                                  43008       39040       42112
Direct inode steals                                0          10           8
Kswapd inode steals                              733         534         477

This test just creates a large file mapping and writes to it linearly.
Time to completion is again reduced.

The gains are mostly down to two things.  In many cases, there is less
scanning as zone_reclaim simply gives up faster due to recent failures.
The second reason is that memory is used more efficiently.  Instead of
scanning the preferred zone every time, the allocator falls back to
another zone and uses it instead improving overall memory utilisation.

This patch: initialise ZLC for first zone eligible for zone_reclaim.

The zonelist cache (ZLC) is used among other things to record if
zone_reclaim() failed for a particular zone recently.  The intention is to
avoid a high cost scanning extremely long zonelists or scanning within the
zone uselessly.

Currently the zonelist cache is setup only after the first zone has been
considered and zone_reclaim() has been called.  The objective was to avoid
a costly setup but zone_reclaim is itself quite expensive.  If it is
failing regularly such as the first eligible zone having mostly mapped
pages, the cost in scanning and allocation stalls is far higher than the
ZLC initialisation step.

This patch initialises ZLC before the first eligible zone calls
zone_reclaim().  Once initialised, it is checked whether the zone failed
zone_reclaim recently.  If it has, the zone is skipped.  As the first zone
is now being checked, additional care has to be taken about zones marked
full.  A zone can be marked "full" because it should not have enough
unmapped pages for zone_reclaim but this is excessive as direct reclaim or
kswapd may succeed where zone_reclaim fails.  Only mark zones "full" after
zone_reclaim fails if it failed to reclaim enough pages after scanning.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Stefan Priebe <s.priebe@profihost.ag>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
mm: page allocator: reconsider zones for allocation after direct reclaim

commit 76d3fbf8fbf6cc78ceb63549e0e0c5bc8a88f838 upstream.

With zone_reclaim_mode enabled, it's possible for zones to be considered
full in the zonelist_cache so they are skipped in the future.  If the
process enters direct reclaim, the ZLC may still consider zones to be full
even after reclaiming pages.  Reconsider all zones for allocation if
direct reclaim returns successfully.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Stefan Priebe <s.priebe@profihost.ag>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
mm: avoid livelock on !__GFP_FS allocations

Under the following conditions, __alloc_pages_slowpath can loop
forever:
gfp_mask & __GFP_WAIT is true
gfp_mask & __GFP_FS is false
reclaim and compaction make no progress
order <= PAGE_ALLOC_COSTLY_ORDER

The gfp conditions are normally invalid, because !__GFP_FS
disables most of the reclaim methods that __GFP_WAIT would
wait for.  However, these conditions happen very often during
suspend and resume, when pm_restrict_gfp_mask() effectively
converts all GFP_KERNEL allocations into __GFP_WAIT.

The oom killer is not run because gfp_mask & __GFP_FS is false,
but should_alloc_retry will always return true when order is less
than PAGE_ALLOC_COSTLY_ORDER.  __alloc_pages_slowpath will
loop forever between the rebalance label and should_alloc_retry,
unless another thread happens to release enough pages to satisfy
the allocation.

Add a check to detect when PM has disabled __GFP_FS, and do not
retry if reclaim is not making any progress.

[taken from patch on lkml by Mel Gorman, commit message by ccross]
Change-Id: I864a24e9d9fd98bd0e3d6e9c1e85b6c1b766850e
Signed-off-by: Colin Cross <ccross@android.com>
mm: use required fixed size of movable zone if FIX_MOVABLE_ZONE

If FIX_MOVABLE_ZONE is enabled, we want a specific size and
location of ZONE_MOVABLE.

Change-Id: I0b858c7310cd328e1118abc9d5fe6f364bb4ffad
Signed-off-by: Larry Bassel <lbassel@codeaurora.org>
mm: Cast lowmem_reserve to long

z->lowmem_reserve[classzone_idx] is an unsigned long but
free_pages and min are longs. If free_pages is
negative, the function will incorrectly return true
because it will treat the negative long as a large,
positive unsigned long.

This change casts z->lowmem_reserve to a long and
fixes a typo in the comment.

Change-Id: Icada1fa5ca650fbcdb0656f637adbb98f223eec5
Signed-off-by: Jack Cheung <jackc@codeaurora.org>
thp: set compound tail page _count to zero

commit 58a84aa92723d1ac3e1cc4e3b0ff49291663f7e1 upstream.

Commit 70b50f94f1644 ("mm: thp: tail page refcounting fix") keeps all
page_tail->_count zero at all times.  But the current kernel does not
set page_tail->_count to zero if a 1GB page is utilized.  So when an
IOMMU 1GB page is used by KVM, it wil result in a kernel oops because a
tail page's _count does not equal zero.

  kernel BUG at include/linux/mm.h:386!
  invalid opcode: 0000 [#1] SMP
  Call Trace:
    gup_pud_range+0xb8/0x19d
    get_user_pages_fast+0xcb/0x192
    ? trace_hardirqs_off+0xd/0xf
    hva_to_pfn+0x119/0x2f2
    gfn_to_pfn_memslot+0x2c/0x2e
    kvm_iommu_map_pages+0xfd/0x1c1
    kvm_iommu_map_memslots+0x7c/0xbd
    kvm_iommu_map_guest+0xaa/0xbf
    kvm_vm_ioctl_assigned_device+0x2ef/0xa47
    kvm_vm_ioctl+0x36c/0x3a2
    do_vfs_ioctl+0x49e/0x4e4
    sys_ioctl+0x5a/0x7c
    system_call_fastpath+0x16/0x1b
  RIP  gup_huge_pud+0xf2/0x159

Signed-off-by: Youquan Song <youquan.song@intel.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
mm: Ensure that pfn_valid() is called once per pageblock when reserving pageblocks

commit d021563888312018ca65681096f62e36c20e63cc upstream.

setup_zone_migrate_reserve() expects that zone->start_pfn starts at
pageblock_nr_pages aligned pfn otherwise we could access beyond an
existing memblock resulting in the following panic if
CONFIG_HOLES_IN_ZONE is not configured and we do not check pfn_valid:

  IP: [<c02d331d>] setup_zone_migrate_reserve+0xcd/0x180
  *pdpt = 0000000000000000 *pde = f000ff53f000ff53
  Oops: 0000 [#1] SMP
  Pid: 1, comm: swapper Not tainted 3.0.7-0.7-pae #1 VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform
  EIP: 0060:[<c02d331d>] EFLAGS: 00010006 CPU: 0
  EIP is at setup_zone_migrate_reserve+0xcd/0x180
  EAX: 000c0000 EBX: f5801fc0 ECX: 000c0000 EDX: 00000000
  ESI: 000c01fe EDI: 000c01fe EBP: 00140000 ESP: f2475f58
  DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
  Process swapper (pid: 1, ti=f2474000 task=f2472cd0 task.ti=f2474000)
  Call Trace:
  [<c02d389c>] __setup_per_zone_wmarks+0xec/0x160
  [<c02d3a1f>] setup_per_zone_wmarks+0xf/0x20
  [<c08a771c>] init_per_zone_wmark_min+0x27/0x86
  [<c020111b>] do_one_initcall+0x2b/0x160
  [<c086639d>] kernel_init+0xbe/0x157
  [<c05cae26>] kernel_thread_helper+0x6/0xd
  Code: a5 39 f5 89 f7 0f 46 fd 39 cf 76 40 8b 03 f6 c4 08 74 32 eb 91 90 89 c8 c1 e8 0e 0f be 80 80 2f 86 c0 8b 14 85 60 2f 86 c0 89 c8 <2b> 82 b4 12 00 00 c1 e0 05 03 82 ac 12 00 00 8b 00 f6 c4 08 0f
  EIP: [<c02d331d>] setup_zone_migrate_reserve+0xcd/0x180 SS:ESP 0068:f2475f58
  CR2: 00000000000012b4

We crashed in pageblock_is_reserved() when accessing pfn 0xc0000 because
highstart_pfn = 0x36ffe.

The issue was introduced in 3.0-rc1 by 6d3163ce ("mm: check if any page
in a pageblock is reserved before marking it MIGRATE_RESERVE").

Make sure that start_pfn is always aligned to pageblock_nr_pages to
ensure that pfn_valid s always called at the start of each pageblock.
Architectures with holes in pageblocks will be correctly handled by
pfn_valid_within in pageblock_is_reserved.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Tested-by: Dang Bo <bdang@vmware.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Arve Hjnnevg <arve@android.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
mm: fix NULL ptr dereference in __count_immobile_pages

commit 687875fb7de4a95223af20ee024282fa9099f860 upstream.

Fix the following NULL ptr dereference caused by

  cat /sys/devices/system/memory/memory0/removable

Pid: 13979, comm: sed Not tainted 3.0.13-0.5-default #1 IBM BladeCenter LS21 -[7971PAM]-/Server Blade
RIP: __count_immobile_pages+0x4/0x100
Process sed (pid: 13979, threadinfo ffff880221c36000, task ffff88022e788480)
Call Trace:
  is_pageblock_removable_nolock+0x34/0x40
  is_mem_section_removable+0x74/0xf0
  show_mem_removable+0x41/0x70
  sysfs_read_file+0xfe/0x1c0
  vfs_read+0xc7/0x130
  sys_read+0x53/0xa0
  system_call_fastpath+0x16/0x1b

We are crashing because we are trying to dereference NULL zone which
came from pfn=0 (struct page ffffea0000000000). According to the boot
log this page is marked reserved:
e820 update range: 0000000000000000 - 0000000000010000 (usable) ==> (reserved)

and early_node_map confirms that:
early_node_map[3] active PFN ranges
    1: 0x00000010 -> 0x0000009c
    1: 0x00000100 -> 0x000bffa3
    1: 0x00100000 -> 0x00240000

The problem is that memory_present works in PAGE_SECTION_MASK aligned
blocks so the reserved range sneaks into the the section as well.  This
also means that free_area_init_node will not take care of those reserved
pages and they stay uninitialized.

When we try to read the removable status we walk through all available
sections and hope that the zone is valid for all pages in the section.
But this is not true in this case as the zone and nid are not initialized.

We have only one node in this particular case and it is marked as node=1
(rather than 0) and that made the problem visible because page_to_nid will
return 0 and there are no zones on the node.

Let's check that the zone is valid and that the given pfn falls into its
boundaries and mark the section not removable.  This might cause some
false positives, probably, but we do not have any sane way to find out
whether the page is reserved by the platform or it is just not used for
whatever other reasons.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>