linux-stable.git/mm/page_alloc.c, branch v4.19.26 Linux kernel stable tree mm/page_alloc.c: don't call kasan_free_pages() at deferred mem init 2019-02-12T18:47:18+00:00 Waiman Long longman@redhat.com 2018-12-28T08:38:51+00:00 f73c77535f67db55cd0aa83a47eeb16f925d063c [ Upstream commit 3c0c12cc8f00ca5f81acb010023b8eb13e9a7004 ] When CONFIG_KASAN is enabled on large memory SMP systems, the deferrred pages initialization can take a long time. Below were the reported init times on a 8-socket 96-core 4TB IvyBridge system. 1) Non-debug kernel without CONFIG_KASAN [ 8.764222] node 1 initialised, 132086516 pages in 7027ms 2) Debug kernel with CONFIG_KASAN [ 146.288115] node 1 initialised, 132075466 pages in 143052ms So the page init time in a debug kernel was 20X of the non-debug kernel. The long init time can be problematic as the page initialization is done with interrupt disabled. In this particular case, it caused the appearance of following warning messages as well as NMI backtraces of all the cores that were doing the initialization. [ 68.240049] rcu: INFO: rcu_sched detected stalls on CPUs/tasks: [ 68.241000] rcu: 25-...0: (100 ticks this GP) idle=b72/1/0x4000000000000000 softirq=915/915 fqs=16252 [ 68.241000] rcu: 44-...0: (95 ticks this GP) idle=49a/1/0x4000000000000000 softirq=788/788 fqs=16253 [ 68.241000] rcu: 54-...0: (104 ticks this GP) idle=03a/1/0x4000000000000000 softirq=721/825 fqs=16253 [ 68.241000] rcu: 60-...0: (103 ticks this GP) idle=cbe/1/0x4000000000000000 softirq=637/740 fqs=16253 [ 68.241000] rcu: 72-...0: (105 ticks this GP) idle=786/1/0x4000000000000000 softirq=536/641 fqs=16253 [ 68.241000] rcu: 84-...0: (99 ticks this GP) idle=292/1/0x4000000000000000 softirq=537/537 fqs=16253 [ 68.241000] rcu: 111-...0: (104 ticks this GP) idle=bde/1/0x4000000000000000 softirq=474/476 fqs=16253 [ 68.241000] rcu: (detected by 13, t=65018 jiffies, g=249, q=2) The long init time was mainly caused by the call to kasan_free_pages() to poison the newly initialized pages. On a 4TB system, we are talking about almost 500GB of memory probably on the same node. In reality, we may not need to poison the newly initialized pages before they are ever allocated. So KASAN poisoning of freed pages before the completion of deferred memory initialization is now disabled. Those pages will be properly poisoned when they are allocated or freed after deferred pages initialization is done. With this change, the new page initialization time became: [ 21.948010] node 1 initialised, 132075466 pages in 18702ms This was still about double the non-debug kernel time, but was much better than before. Link: http://lkml.kernel.org/r/1544459388-8736-1-git-send-email-longman@redhat.com Signed-off-by: Waiman Long <longman@redhat.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Alexander Potapenko <glider@google.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com> Cc: Oscar Salvador <osalvador@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 3c0c12cc8f00ca5f81acb010023b8eb13e9a7004 ]

When CONFIG_KASAN is enabled on large memory SMP systems, the deferrred
pages initialization can take a long time.  Below were the reported init
times on a 8-socket 96-core 4TB IvyBridge system.

  1) Non-debug kernel without CONFIG_KASAN
     [    8.764222] node 1 initialised, 132086516 pages in 7027ms

  2) Debug kernel with CONFIG_KASAN
     [  146.288115] node 1 initialised, 132075466 pages in 143052ms

So the page init time in a debug kernel was 20X of the non-debug kernel.
The long init time can be problematic as the page initialization is done
with interrupt disabled.  In this particular case, it caused the
appearance of following warning messages as well as NMI backtraces of all
the cores that were doing the initialization.

[   68.240049] rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
[   68.241000] rcu: 	25-...0: (100 ticks this GP) idle=b72/1/0x4000000000000000 softirq=915/915 fqs=16252
[   68.241000] rcu: 	44-...0: (95 ticks this GP) idle=49a/1/0x4000000000000000 softirq=788/788 fqs=16253
[   68.241000] rcu: 	54-...0: (104 ticks this GP) idle=03a/1/0x4000000000000000 softirq=721/825 fqs=16253
[   68.241000] rcu: 	60-...0: (103 ticks this GP) idle=cbe/1/0x4000000000000000 softirq=637/740 fqs=16253
[   68.241000] rcu: 	72-...0: (105 ticks this GP) idle=786/1/0x4000000000000000 softirq=536/641 fqs=16253
[   68.241000] rcu: 	84-...0: (99 ticks this GP) idle=292/1/0x4000000000000000 softirq=537/537 fqs=16253
[   68.241000] rcu: 	111-...0: (104 ticks this GP) idle=bde/1/0x4000000000000000 softirq=474/476 fqs=16253
[   68.241000] rcu: 	(detected by 13, t=65018 jiffies, g=249, q=2)

The long init time was mainly caused by the call to kasan_free_pages() to
poison the newly initialized pages.  On a 4TB system, we are talking about
almost 500GB of memory probably on the same node.

In reality, we may not need to poison the newly initialized pages before
they are ever allocated.  So KASAN poisoning of freed pages before the
completion of deferred memory initialization is now disabled.  Those pages
will be properly poisoned when they are allocated or freed after deferred
pages initialization is done.

With this change, the new page initialization time became:

[   21.948010] node 1 initialised, 132075466 pages in 18702ms

This was still about double the non-debug kernel time, but was much
better than before.

Link: http://lkml.kernel.org/r/1544459388-8736-1-git-send-email-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Revert "mm, memory_hotplug: initialize struct pages for the full memory section" 2019-01-31T07:14:41+00:00 Michal Hocko mhocko@suse.com 2019-01-25T18:08:58+00:00 6bab957396ce60d2c25d161657c7d3e744989fb5 commit 4aa9fc2a435abe95a1e8d7f8c7b3d6356514b37a upstream. This reverts commit 2830bf6f05fb3e05bc4743274b806c821807a684. The underlying assumption that one sparse section belongs into a single numa node doesn't hold really. Robert Shteynfeld has reported a boot failure. The boot log was not captured but his memory layout is as follows: Early memory node ranges node 1: [mem 0x0000000000001000-0x0000000000090fff] node 1: [mem 0x0000000000100000-0x00000000dbdf8fff] node 1: [mem 0x0000000100000000-0x0000001423ffffff] node 0: [mem 0x0000001424000000-0x0000002023ffffff] This means that node0 starts in the middle of a memory section which is also in node1. memmap_init_zone tries to initialize padding of a section even when it is outside of the given pfn range because there are code paths (e.g. memory hotplug) which assume that the full worth of memory section is always initialized. In this particular case, though, such a range is already intialized and most likely already managed by the page allocator. Scribbling over those pages corrupts the internal state and likely blows up when any of those pages gets used. Reported-by: Robert Shteynfeld <robert.shteynfeld@gmail.com> Fixes: 2830bf6f05fb ("mm, memory_hotplug: initialize struct pages for the full memory section") Cc: stable@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 4aa9fc2a435abe95a1e8d7f8c7b3d6356514b37a upstream.

This reverts commit 2830bf6f05fb3e05bc4743274b806c821807a684.

The underlying assumption that one sparse section belongs into a single
numa node doesn't hold really. Robert Shteynfeld has reported a boot
failure. The boot log was not captured but his memory layout is as
follows:

  Early memory node ranges
    node   1: [mem 0x0000000000001000-0x0000000000090fff]
    node   1: [mem 0x0000000000100000-0x00000000dbdf8fff]
    node   1: [mem 0x0000000100000000-0x0000001423ffffff]
    node   0: [mem 0x0000001424000000-0x0000002023ffffff]

This means that node0 starts in the middle of a memory section which is
also in node1.  memmap_init_zone tries to initialize padding of a
section even when it is outside of the given pfn range because there are
code paths (e.g.  memory hotplug) which assume that the full worth of
memory section is always initialized.

In this particular case, though, such a range is already intialized and
most likely already managed by the page allocator.  Scribbling over
those pages corrupts the internal state and likely blows up when any of
those pages gets used.

Reported-by: Robert Shteynfeld <robert.shteynfeld@gmail.com>
Fixes: 2830bf6f05fb ("mm, memory_hotplug: initialize struct pages for the full memory section")
Cc: stable@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
mm, page_alloc: fix has_unmovable_pages for HugePages 2018-12-29T12:37:59+00:00 Oscar Salvador osalvador@suse.de 2018-12-21T22:31:00+00:00 e27666dd8ffad78cd82a39624b1be66bdd50f31e commit 17e2e7d7e1b83fa324b3f099bfe426659aa3c2a4 upstream. While playing with gigantic hugepages and memory_hotplug, I triggered the following #PF when "cat memoryX/removable": BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 #PF error: [normal kernel read fault] PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI CPU: 1 PID: 1481 Comm: cat Tainted: G E 4.20.0-rc6-mm1-1-default+ #18 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014 RIP: 0010:has_unmovable_pages+0x154/0x210 Call Trace: is_mem_section_removable+0x7d/0x100 removable_show+0x90/0xb0 dev_attr_show+0x1c/0x50 sysfs_kf_seq_show+0xca/0x1b0 seq_read+0x133/0x380 __vfs_read+0x26/0x180 vfs_read+0x89/0x140 ksys_read+0x42/0x90 do_syscall_64+0x5b/0x180 entry_SYSCALL_64_after_hwframe+0x44/0xa9 The reason is we do not pass the Head to page_hstate(), and so, the call to compound_order() in page_hstate() returns 0, so we end up checking all hstates's size to match PAGE_SIZE. Obviously, we do not find any hstate matching that size, and we return NULL. Then, we dereference that NULL pointer in hugepage_migration_supported() and we got the #PF from above. Fix that by getting the head page before calling page_hstate(). Also, since gigantic pages span several pageblocks, re-adjust the logic for skipping pages. While are it, we can also get rid of the round_up(). [osalvador@suse.de: remove round_up(), adjust skip pages logic per Michal] Link: http://lkml.kernel.org/r/20181221062809.31771-1-osalvador@suse.de Link: http://lkml.kernel.org/r/20181217225113.17864-1-osalvador@suse.de Signed-off-by: Oscar Salvador <osalvador@suse.de> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Pavel Tatashin <pavel.tatashin@microsoft.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: <stable@vger.kernel.org> 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@linuxfoundation.org> 
commit 17e2e7d7e1b83fa324b3f099bfe426659aa3c2a4 upstream.

While playing with gigantic hugepages and memory_hotplug, I triggered
the following #PF when "cat memoryX/removable":

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
  #PF error: [normal kernel read fault]
  PGD 0 P4D 0
  Oops: 0000 [#1] SMP PTI
  CPU: 1 PID: 1481 Comm: cat Tainted: G            E     4.20.0-rc6-mm1-1-default+ #18
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014
  RIP: 0010:has_unmovable_pages+0x154/0x210
  Call Trace:
   is_mem_section_removable+0x7d/0x100
   removable_show+0x90/0xb0
   dev_attr_show+0x1c/0x50
   sysfs_kf_seq_show+0xca/0x1b0
   seq_read+0x133/0x380
   __vfs_read+0x26/0x180
   vfs_read+0x89/0x140
   ksys_read+0x42/0x90
   do_syscall_64+0x5b/0x180
   entry_SYSCALL_64_after_hwframe+0x44/0xa9

The reason is we do not pass the Head to page_hstate(), and so, the call
to compound_order() in page_hstate() returns 0, so we end up checking
all hstates's size to match PAGE_SIZE.

Obviously, we do not find any hstate matching that size, and we return
NULL.  Then, we dereference that NULL pointer in
hugepage_migration_supported() and we got the #PF from above.

Fix that by getting the head page before calling page_hstate().

Also, since gigantic pages span several pageblocks, re-adjust the logic
for skipping pages.  While are it, we can also get rid of the
round_up().

[osalvador@suse.de: remove round_up(), adjust skip pages logic per Michal]
  Link: http://lkml.kernel.org/r/20181221062809.31771-1-osalvador@suse.de
Link: http://lkml.kernel.org/r/20181217225113.17864-1-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Pavel Tatashin <pavel.tatashin@microsoft.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org>
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@linuxfoundation.org>
mm, memory_hotplug: initialize struct pages for the full memory section 2018-12-29T12:37:58+00:00 Mikhail Zaslonko zaslonko@linux.ibm.com 2018-12-21T22:30:46+00:00 7592dbfaf3efcfa36d5652e5713298776c793d40 commit 2830bf6f05fb3e05bc4743274b806c821807a684 upstream. If memory end is not aligned with the sparse memory section boundary, the mapping of such a section is only partly initialized. This may lead to VM_BUG_ON due to uninitialized struct page access from is_mem_section_removable() or test_pages_in_a_zone() function triggered by memory_hotplug sysfs handlers: Here are the the panic examples: CONFIG_DEBUG_VM=y CONFIG_DEBUG_VM_PGFLAGS=y kernel parameter mem=2050M -------------------------- page:000003d082008000 is uninitialized and poisoned page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) Call Trace: ( test_pages_in_a_zone+0xde/0x160) show_valid_zones+0x5c/0x190 dev_attr_show+0x34/0x70 sysfs_kf_seq_show+0xc8/0x148 seq_read+0x204/0x480 __vfs_read+0x32/0x178 vfs_read+0x82/0x138 ksys_read+0x5a/0xb0 system_call+0xdc/0x2d8 Last Breaking-Event-Address: test_pages_in_a_zone+0xde/0x160 Kernel panic - not syncing: Fatal exception: panic_on_oops kernel parameter mem=3075M -------------------------- page:000003d08300c000 is uninitialized and poisoned page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) Call Trace: ( is_mem_section_removable+0xb4/0x190) show_mem_removable+0x9a/0xd8 dev_attr_show+0x34/0x70 sysfs_kf_seq_show+0xc8/0x148 seq_read+0x204/0x480 __vfs_read+0x32/0x178 vfs_read+0x82/0x138 ksys_read+0x5a/0xb0 system_call+0xdc/0x2d8 Last Breaking-Event-Address: is_mem_section_removable+0xb4/0x190 Kernel panic - not syncing: Fatal exception: panic_on_oops Fix the problem by initializing the last memory section of each zone in memmap_init_zone() till the very end, even if it goes beyond the zone end. Michal said: : This has alwways been problem AFAIU. It just went unnoticed because we : have zeroed memmaps during allocation before f7f99100d8d9 ("mm: stop : zeroing memory during allocation in vmemmap") and so the above test : would simply skip these ranges as belonging to zone 0 or provided a : garbage. : : So I guess we do care for post f7f99100d8d9 kernels mostly and : therefore Fixes: f7f99100d8d9 ("mm: stop zeroing memory during : allocation in vmemmap") Link: http://lkml.kernel.org/r/20181212172712.34019-2-zaslonko@linux.ibm.com Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap") Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com> Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> Suggested-by: Michal Hocko <mhocko@kernel.org> Acked-by: Michal Hocko <mhocko@suse.com> Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com> Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: <stable@vger.kernel.org> 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@linuxfoundation.org> 
commit 2830bf6f05fb3e05bc4743274b806c821807a684 upstream.

If memory end is not aligned with the sparse memory section boundary,
the mapping of such a section is only partly initialized.  This may lead
to VM_BUG_ON due to uninitialized struct page access from
is_mem_section_removable() or test_pages_in_a_zone() function triggered
by memory_hotplug sysfs handlers:

Here are the the panic examples:
 CONFIG_DEBUG_VM=y
 CONFIG_DEBUG_VM_PGFLAGS=y

 kernel parameter mem=2050M
 --------------------------
 page:000003d082008000 is uninitialized and poisoned
 page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
 Call Trace:
 ( test_pages_in_a_zone+0xde/0x160)
   show_valid_zones+0x5c/0x190
   dev_attr_show+0x34/0x70
   sysfs_kf_seq_show+0xc8/0x148
   seq_read+0x204/0x480
   __vfs_read+0x32/0x178
   vfs_read+0x82/0x138
   ksys_read+0x5a/0xb0
   system_call+0xdc/0x2d8
 Last Breaking-Event-Address:
   test_pages_in_a_zone+0xde/0x160
 Kernel panic - not syncing: Fatal exception: panic_on_oops

 kernel parameter mem=3075M
 --------------------------
 page:000003d08300c000 is uninitialized and poisoned
 page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
 Call Trace:
 ( is_mem_section_removable+0xb4/0x190)
   show_mem_removable+0x9a/0xd8
   dev_attr_show+0x34/0x70
   sysfs_kf_seq_show+0xc8/0x148
   seq_read+0x204/0x480
   __vfs_read+0x32/0x178
   vfs_read+0x82/0x138
   ksys_read+0x5a/0xb0
   system_call+0xdc/0x2d8
 Last Breaking-Event-Address:
   is_mem_section_removable+0xb4/0x190
 Kernel panic - not syncing: Fatal exception: panic_on_oops

Fix the problem by initializing the last memory section of each zone in
memmap_init_zone() till the very end, even if it goes beyond the zone end.

Michal said:

: This has alwways been problem AFAIU.  It just went unnoticed because we
: have zeroed memmaps during allocation before f7f99100d8d9 ("mm: stop
: zeroing memory during allocation in vmemmap") and so the above test
: would simply skip these ranges as belonging to zone 0 or provided a
: garbage.
:
: So I guess we do care for post f7f99100d8d9 kernels mostly and
: therefore Fixes: f7f99100d8d9 ("mm: stop zeroing memory during
: allocation in vmemmap")

Link: http://lkml.kernel.org/r/20181212172712.34019-2-zaslonko@linux.ibm.com
Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap")
Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Suggested-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: <stable@vger.kernel.org>
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@linuxfoundation.org>
mm/page_alloc.c: fix calculation of pgdat->nr_zones 2018-12-17T08:24:40+00:00 Wei Yang richard.weiyang@gmail.com 2018-11-30T22:09:07+00:00 505bc9f3899699114d32782c0ad494d3b15ae29a [ Upstream commit 8f416836c0d50b198cad1225132e5abebf8980dc ] init_currently_empty_zone() will adjust pgdat->nr_zones and set it to 'zone_idx(zone) + 1' unconditionally. This is correct in the normal case, while not exact in hot-plug situation. This function is used in two places: * free_area_init_core() * move_pfn_range_to_zone() In the first case, we are sure zone index increase monotonically. While in the second one, this is under users control. One way to reproduce this is: ---------------------------- 1. create a virtual machine with empty node1 -m 4G,slots=32,maxmem=32G \ -smp 4,maxcpus=8 \ -numa node,nodeid=0,mem=4G,cpus=0-3 \ -numa node,nodeid=1,mem=0G,cpus=4-7 2. hot-add cpu 3-7 cpu-add [3-7] 2. hot-add memory to nod1 object_add memory-backend-ram,id=ram0,size=1G device_add pc-dimm,id=dimm0,memdev=ram0,node=1 3. online memory with following order echo online_movable > memory47/state echo online > memory40/state After this, node1 will have its nr_zones equals to (ZONE_NORMAL + 1) instead of (ZONE_MOVABLE + 1). Michal said: "Having an incorrect nr_zones might result in all sorts of problems which would be quite hard to debug (e.g. reclaim not considering the movable zone). I do not expect many users would suffer from this it but still this is trivial and obviously right thing to do so backporting to the stable tree shouldn't be harmful (last famous words)" Link: http://lkml.kernel.org/r/20181117022022.9956-1-richard.weiyang@gmail.com Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online") Signed-off-by: Wei Yang <richard.weiyang@gmail.com> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Cc: Anshuman Khandual <anshuman.khandual@arm.com> Cc: Dave Hansen <dave.hansen@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 8f416836c0d50b198cad1225132e5abebf8980dc ]

init_currently_empty_zone() will adjust pgdat->nr_zones and set it to
'zone_idx(zone) + 1' unconditionally.  This is correct in the normal
case, while not exact in hot-plug situation.

This function is used in two places:

  * free_area_init_core()
  * move_pfn_range_to_zone()

In the first case, we are sure zone index increase monotonically.  While
in the second one, this is under users control.

One way to reproduce this is:
----------------------------

1. create a virtual machine with empty node1

   -m 4G,slots=32,maxmem=32G \
   -smp 4,maxcpus=8          \
   -numa node,nodeid=0,mem=4G,cpus=0-3 \
   -numa node,nodeid=1,mem=0G,cpus=4-7

2. hot-add cpu 3-7

   cpu-add [3-7]

2. hot-add memory to nod1

   object_add memory-backend-ram,id=ram0,size=1G
   device_add pc-dimm,id=dimm0,memdev=ram0,node=1

3. online memory with following order

   echo online_movable > memory47/state
   echo online > memory40/state

After this, node1 will have its nr_zones equals to (ZONE_NORMAL + 1)
instead of (ZONE_MOVABLE + 1).

Michal said:
 "Having an incorrect nr_zones might result in all sorts of problems
  which would be quite hard to debug (e.g. reclaim not considering the
  movable zone). I do not expect many users would suffer from this it
  but still this is trivial and obviously right thing to do so
  backporting to the stable tree shouldn't be harmful (last famous
  words)"

Link: http://lkml.kernel.org/r/20181117022022.9956-1-richard.weiyang@gmail.com
Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online")
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: Sasha Levin <sashal@kernel.org>
mm, page_alloc: check for max order in hot path 2018-12-01T08:37:34+00:00 Michal Hocko mhocko@suse.com 2018-11-16T23:08:53+00:00 9dec38554aa876700acb851b35ee0c5e28841e03 [ Upstream commit c63ae43ba53bc432b414fd73dd5f4b01fcb1ab43 ] Konstantin has noticed that kvmalloc might trigger the following warning: WARNING: CPU: 0 PID: 6676 at mm/vmstat.c:986 __fragmentation_index+0x54/0x60 [...] Call Trace: fragmentation_index+0x76/0x90 compaction_suitable+0x4f/0xf0 shrink_node+0x295/0x310 node_reclaim+0x205/0x250 get_page_from_freelist+0x649/0xad0 __alloc_pages_nodemask+0x12a/0x2a0 kmalloc_large_node+0x47/0x90 __kmalloc_node+0x22b/0x2e0 kvmalloc_node+0x3e/0x70 xt_alloc_table_info+0x3a/0x80 [x_tables] do_ip6t_set_ctl+0xcd/0x1c0 [ip6_tables] nf_setsockopt+0x44/0x60 SyS_setsockopt+0x6f/0xc0 do_syscall_64+0x67/0x120 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 the problem is that we only check for an out of bound order in the slow path and the node reclaim might happen from the fast path already. This is fixable by making sure that kvmalloc doesn't ever use kmalloc for requests that are larger than KMALLOC_MAX_SIZE but this also shows that the code is rather fragile. A recent UBSAN report just underlines that by the following report UBSAN: Undefined behaviour in mm/page_alloc.c:3117:19 shift exponent 51 is too large for 32-bit type 'int' CPU: 0 PID: 6520 Comm: syz-executor1 Not tainted 4.19.0-rc2 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0xd2/0x148 lib/dump_stack.c:113 ubsan_epilogue+0x12/0x94 lib/ubsan.c:159 __ubsan_handle_shift_out_of_bounds+0x2b6/0x30b lib/ubsan.c:425 __zone_watermark_ok+0x2c7/0x400 mm/page_alloc.c:3117 zone_watermark_fast mm/page_alloc.c:3216 [inline] get_page_from_freelist+0xc49/0x44c0 mm/page_alloc.c:3300 __alloc_pages_nodemask+0x21e/0x640 mm/page_alloc.c:4370 alloc_pages_current+0xcc/0x210 mm/mempolicy.c:2093 alloc_pages include/linux/gfp.h:509 [inline] __get_free_pages+0x12/0x60 mm/page_alloc.c:4414 dma_mem_alloc+0x36/0x50 arch/x86/include/asm/floppy.h:156 raw_cmd_copyin drivers/block/floppy.c:3159 [inline] raw_cmd_ioctl drivers/block/floppy.c:3206 [inline] fd_locked_ioctl+0xa00/0x2c10 drivers/block/floppy.c:3544 fd_ioctl+0x40/0x60 drivers/block/floppy.c:3571 __blkdev_driver_ioctl block/ioctl.c:303 [inline] blkdev_ioctl+0xb3c/0x1a30 block/ioctl.c:601 block_ioctl+0x105/0x150 fs/block_dev.c:1883 vfs_ioctl fs/ioctl.c:46 [inline] do_vfs_ioctl+0x1c0/0x1150 fs/ioctl.c:687 ksys_ioctl+0x9e/0xb0 fs/ioctl.c:702 __do_sys_ioctl fs/ioctl.c:709 [inline] __se_sys_ioctl fs/ioctl.c:707 [inline] __x64_sys_ioctl+0x7e/0xc0 fs/ioctl.c:707 do_syscall_64+0xc4/0x510 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe Note that this is not a kvmalloc path. It is just that the fast path really depends on having sanitzed order as well. Therefore move the order check to the fast path. Link: http://lkml.kernel.org/r/20181113094305.GM15120@dhcp22.suse.cz Signed-off-by: Michal Hocko <mhocko@suse.com> Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Reported-by: Kyungtae Kim <kt0755@gmail.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Balbir Singh <bsingharora@gmail.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Pavel Tatashin <pavel.tatashin@microsoft.com> Cc: Oscar Salvador <osalvador@suse.de> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Aaron Lu <aaron.lu@intel.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Byoungyoung Lee <lifeasageek@gmail.com> Cc: "Dae R. Jeong" <threeearcat@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit c63ae43ba53bc432b414fd73dd5f4b01fcb1ab43 ]

Konstantin has noticed that kvmalloc might trigger the following
warning:

  WARNING: CPU: 0 PID: 6676 at mm/vmstat.c:986 __fragmentation_index+0x54/0x60
  [...]
  Call Trace:
   fragmentation_index+0x76/0x90
   compaction_suitable+0x4f/0xf0
   shrink_node+0x295/0x310
   node_reclaim+0x205/0x250
   get_page_from_freelist+0x649/0xad0
   __alloc_pages_nodemask+0x12a/0x2a0
   kmalloc_large_node+0x47/0x90
   __kmalloc_node+0x22b/0x2e0
   kvmalloc_node+0x3e/0x70
   xt_alloc_table_info+0x3a/0x80 [x_tables]
   do_ip6t_set_ctl+0xcd/0x1c0 [ip6_tables]
   nf_setsockopt+0x44/0x60
   SyS_setsockopt+0x6f/0xc0
   do_syscall_64+0x67/0x120
   entry_SYSCALL_64_after_hwframe+0x3d/0xa2

the problem is that we only check for an out of bound order in the slow
path and the node reclaim might happen from the fast path already.  This
is fixable by making sure that kvmalloc doesn't ever use kmalloc for
requests that are larger than KMALLOC_MAX_SIZE but this also shows that
the code is rather fragile.  A recent UBSAN report just underlines that
by the following report

  UBSAN: Undefined behaviour in mm/page_alloc.c:3117:19
  shift exponent 51 is too large for 32-bit type 'int'
  CPU: 0 PID: 6520 Comm: syz-executor1 Not tainted 4.19.0-rc2 #1
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
  Call Trace:
   __dump_stack lib/dump_stack.c:77 [inline]
   dump_stack+0xd2/0x148 lib/dump_stack.c:113
   ubsan_epilogue+0x12/0x94 lib/ubsan.c:159
   __ubsan_handle_shift_out_of_bounds+0x2b6/0x30b lib/ubsan.c:425
   __zone_watermark_ok+0x2c7/0x400 mm/page_alloc.c:3117
   zone_watermark_fast mm/page_alloc.c:3216 [inline]
   get_page_from_freelist+0xc49/0x44c0 mm/page_alloc.c:3300
   __alloc_pages_nodemask+0x21e/0x640 mm/page_alloc.c:4370
   alloc_pages_current+0xcc/0x210 mm/mempolicy.c:2093
   alloc_pages include/linux/gfp.h:509 [inline]
   __get_free_pages+0x12/0x60 mm/page_alloc.c:4414
   dma_mem_alloc+0x36/0x50 arch/x86/include/asm/floppy.h:156
   raw_cmd_copyin drivers/block/floppy.c:3159 [inline]
   raw_cmd_ioctl drivers/block/floppy.c:3206 [inline]
   fd_locked_ioctl+0xa00/0x2c10 drivers/block/floppy.c:3544
   fd_ioctl+0x40/0x60 drivers/block/floppy.c:3571
   __blkdev_driver_ioctl block/ioctl.c:303 [inline]
   blkdev_ioctl+0xb3c/0x1a30 block/ioctl.c:601
   block_ioctl+0x105/0x150 fs/block_dev.c:1883
   vfs_ioctl fs/ioctl.c:46 [inline]
   do_vfs_ioctl+0x1c0/0x1150 fs/ioctl.c:687
   ksys_ioctl+0x9e/0xb0 fs/ioctl.c:702
   __do_sys_ioctl fs/ioctl.c:709 [inline]
   __se_sys_ioctl fs/ioctl.c:707 [inline]
   __x64_sys_ioctl+0x7e/0xc0 fs/ioctl.c:707
   do_syscall_64+0xc4/0x510 arch/x86/entry/common.c:290
   entry_SYSCALL_64_after_hwframe+0x49/0xbe

Note that this is not a kvmalloc path.  It is just that the fast path
really depends on having sanitzed order as well.  Therefore move the
order check to the fast path.

Link: http://lkml.kernel.org/r/20181113094305.GM15120@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Reported-by: Kyungtae Kim <kt0755@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Pavel Tatashin <pavel.tatashin@microsoft.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Byoungyoung Lee <lifeasageek@gmail.com>
Cc: "Dae R. Jeong" <threeearcat@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
mm, memory_hotplug: check zone_movable in has_unmovable_pages 2018-12-01T08:37:33+00:00 Michal Hocko mhocko@suse.com 2018-11-16T23:08:15+00:00 b44fd1268bd2ffa0ae72b647c96fea44eac9cd98 [ Upstream commit 9d7899999c62c1a81129b76d2a6ecbc4655e1597 ] Page state checks are racy. Under a heavy memory workload (e.g. stress -m 200 -t 2h) it is quite easy to hit a race window when the page is allocated but its state is not fully populated yet. A debugging patch to dump the struct page state shows has_unmovable_pages: pfn:0x10dfec00, found:0x1, count:0x0 page:ffffea0437fb0000 count:1 mapcount:1 mapping:ffff880e05239841 index:0x7f26e5000 compound_mapcount: 1 flags: 0x5fffffc0090034(uptodate|lru|active|head|swapbacked) Note that the state has been checked for both PageLRU and PageSwapBacked already. Closing this race completely would require some sort of retry logic. This can be tricky and error prone (think of potential endless or long taking loops). Workaround this problem for movable zones at least. Such a zone should only contain movable pages. Commit 15c30bc09085 ("mm, memory_hotplug: make has_unmovable_pages more robust") has told us that this is not strictly true though. Bootmem pages should be marked reserved though so we can move the original check after the PageReserved check. Pages from other zones are still prone to races but we even do not pretend that memory hotremove works for those so pre-mature failure doesn't hurt that much. Link: http://lkml.kernel.org/r/20181106095524.14629-1-mhocko@kernel.org Fixes: 15c30bc09085 ("mm, memory_hotplug: make has_unmovable_pages more robust") Signed-off-by: Michal Hocko <mhocko@suse.com> Reported-by: Baoquan He <bhe@redhat.com> Tested-by: Baoquan He <bhe@redhat.com> Acked-by: Baoquan He <bhe@redhat.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Acked-by: Balbir Singh <bsingharora@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 9d7899999c62c1a81129b76d2a6ecbc4655e1597 ]

Page state checks are racy.  Under a heavy memory workload (e.g.  stress
-m 200 -t 2h) it is quite easy to hit a race window when the page is
allocated but its state is not fully populated yet.  A debugging patch to
dump the struct page state shows

  has_unmovable_pages: pfn:0x10dfec00, found:0x1, count:0x0
  page:ffffea0437fb0000 count:1 mapcount:1 mapping:ffff880e05239841 index:0x7f26e5000 compound_mapcount: 1
  flags: 0x5fffffc0090034(uptodate|lru|active|head|swapbacked)

Note that the state has been checked for both PageLRU and PageSwapBacked
already.  Closing this race completely would require some sort of retry
logic.  This can be tricky and error prone (think of potential endless
or long taking loops).

Workaround this problem for movable zones at least.  Such a zone should
only contain movable pages.  Commit 15c30bc09085 ("mm, memory_hotplug:
make has_unmovable_pages more robust") has told us that this is not
strictly true though.  Bootmem pages should be marked reserved though so
we can move the original check after the PageReserved check.  Pages from
other zones are still prone to races but we even do not pretend that
memory hotremove works for those so pre-mature failure doesn't hurt that
much.

Link: http://lkml.kernel.org/r/20181106095524.14629-1-mhocko@kernel.org
Fixes: 15c30bc09085 ("mm, memory_hotplug: make has_unmovable_pages more robust")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Baoquan He <bhe@redhat.com>
Tested-by: Baoquan He <bhe@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
mm, sched/numa: Remove remaining traces of NUMA rate-limiting 2018-10-09T06:30:51+00:00 Srikar Dronamraju srikar@linux.vnet.ibm.com 2018-10-06T11:23:19+00:00 e054637597ba36d3729ba6a3a3dd7aad8e2a3003 Remove the leftover pglist_data::numabalancing_migrate_lock and its initialization, we stopped using this lock with: efaffc5e40ae ("mm, sched/numa: Remove rate-limiting of automatic NUMA balancing migration") [ mingo: Rewrote the changelog. ] Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Acked-by: Mel Gorman <mgorman@techsingularity.net> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Linux-MM <linux-mm@kvack.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@surriel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1538824999-31230-1-git-send-email-srikar@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org> 
Remove the leftover pglist_data::numabalancing_migrate_lock and its
initialization, we stopped using this lock with:

  efaffc5e40ae ("mm, sched/numa: Remove rate-limiting of automatic NUMA balancing migration")

[ mingo: Rewrote the changelog. ]

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux-MM <linux-mm@kvack.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1538824999-31230-1-git-send-email-srikar@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
mm, sched/numa: Remove rate-limiting of automatic NUMA balancing migration 2018-10-02T09:31:14+00:00 Mel Gorman mgorman@techsingularity.net 2018-10-01T10:05:24+00:00 efaffc5e40aeced0bcb497ed7a0a5b8c14abfcdf Rate limiting of page migrations due to automatic NUMA balancing was introduced to mitigate the worst-case scenario of migrating at high frequency due to false sharing or slowly ping-ponging between nodes. Since then, a lot of effort was spent on correctly identifying these pages and avoiding unnecessary migrations and the safety net may no longer be required. Jirka Hladky reported a regression in 4.17 due to a scheduler patch that avoids spreading STREAM tasks wide prematurely. However, once the task was properly placed, it delayed migrating the memory due to rate limiting. Increasing the limit fixed the problem for him. Currently, the limit is hard-coded and does not account for the real capabilities of the hardware. Even if an estimate was attempted, it would not properly account for the number of memory controllers and it could not account for the amount of bandwidth used for normal accesses. Rather than fudging, this patch simply eliminates the rate limiting. However, Jirka reports that a STREAM configuration using multiple processes achieved similar performance to 4.16. In local tests, this patch improved performance of STREAM relative to the baseline but it is somewhat machine-dependent. Most workloads show little or not performance difference implying that there is not a heavily reliance on the throttling mechanism and it is safe to remove. STREAM on 2-socket machine 4.19.0-rc5 4.19.0-rc5 numab-v1r1 noratelimit-v1r1 MB/sec copy 43298.52 ( 0.00%) 44673.38 ( 3.18%) MB/sec scale 30115.06 ( 0.00%) 31293.06 ( 3.91%) MB/sec add 32825.12 ( 0.00%) 34883.62 ( 6.27%) MB/sec triad 32549.52 ( 0.00%) 34906.60 ( 7.24% Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Reviewed-by: Rik van Riel <riel@surriel.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Jirka Hladky <jhladky@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Linux-MM <linux-mm@kvack.org> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/20181001100525.29789-2-mgorman@techsingularity.net Signed-off-by: Ingo Molnar <mingo@kernel.org> 
Rate limiting of page migrations due to automatic NUMA balancing was
introduced to mitigate the worst-case scenario of migrating at high
frequency due to false sharing or slowly ping-ponging between nodes.
Since then, a lot of effort was spent on correctly identifying these
pages and avoiding unnecessary migrations and the safety net may no longer
be required.

Jirka Hladky reported a regression in 4.17 due to a scheduler patch that
avoids spreading STREAM tasks wide prematurely. However, once the task
was properly placed, it delayed migrating the memory due to rate limiting.
Increasing the limit fixed the problem for him.

Currently, the limit is hard-coded and does not account for the real
capabilities of the hardware. Even if an estimate was attempted, it would
not properly account for the number of memory controllers and it could
not account for the amount of bandwidth used for normal accesses. Rather
than fudging, this patch simply eliminates the rate limiting.

However, Jirka reports that a STREAM configuration using multiple
processes achieved similar performance to 4.16. In local tests, this patch
improved performance of STREAM relative to the baseline but it is somewhat
machine-dependent. Most workloads show little or not performance difference
implying that there is not a heavily reliance on the throttling mechanism
and it is safe to remove.

STREAM on 2-socket machine
                         4.19.0-rc5             4.19.0-rc5
                         numab-v1r1       noratelimit-v1r1
MB/sec copy     43298.52 (   0.00%)    44673.38 (   3.18%)
MB/sec scale    30115.06 (   0.00%)    31293.06 (   3.91%)
MB/sec add      32825.12 (   0.00%)    34883.62 (   6.27%)
MB/sec triad    32549.52 (   0.00%)    34906.60 (   7.24%

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Reviewed-by: Rik van Riel <riel@surriel.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jirka Hladky <jhladky@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux-MM <linux-mm@kvack.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20181001100525.29789-2-mgorman@techsingularity.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
mm/hugetlb: filter out hugetlb pages if HUGEPAGE migration is not supported. 2018-09-04T23:45:02+00:00 Aneesh Kumar K.V aneesh.kumar@linux.ibm.com 2018-09-04T22:45:59+00:00 464c7ffbcb164b2e5cebfa406b7fc6cdb7945344 When scanning for movable pages, filter out Hugetlb pages if hugepage migration is not supported. Without this we hit infinte loop in __offline_pages() where we do pfn = scan_movable_pages(start_pfn, end_pfn); if (pfn) { /* We have movable pages */ ret = do_migrate_range(pfn, end_pfn); goto repeat; } Fix this by checking hugepage_migration_supported both in has_unmovable_pages which is the primary backoff mechanism for page offlining and for consistency reasons also into scan_movable_pages because it doesn't make any sense to return a pfn to non-migrateable huge page. This issue was revealed by, but not caused by 72b39cfc4d75 ("mm, memory_hotplug: do not fail offlining too early"). Link: http://lkml.kernel.org/r/20180824063314.21981-1-aneesh.kumar@linux.ibm.com Fixes: 72b39cfc4d75 ("mm, memory_hotplug: do not fail offlining too early") Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Reported-by: Haren Myneni <haren@linux.vnet.ibm.com> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
When scanning for movable pages, filter out Hugetlb pages if hugepage
migration is not supported.  Without this we hit infinte loop in
__offline_pages() where we do

	pfn = scan_movable_pages(start_pfn, end_pfn);
	if (pfn) { /* We have movable pages */
		ret = do_migrate_range(pfn, end_pfn);
		goto repeat;
	}

Fix this by checking hugepage_migration_supported both in
has_unmovable_pages which is the primary backoff mechanism for page
offlining and for consistency reasons also into scan_movable_pages
because it doesn't make any sense to return a pfn to non-migrateable
huge page.

This issue was revealed by, but not caused by 72b39cfc4d75 ("mm,
memory_hotplug: do not fail offlining too early").

Link: http://lkml.kernel.org/r/20180824063314.21981-1-aneesh.kumar@linux.ibm.com
Fixes: 72b39cfc4d75 ("mm, memory_hotplug: do not fail offlining too early")
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reported-by: Haren Myneni <haren@linux.vnet.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>