linux-toradex.git/mm/memory_hotplug.c, branch v4.11

mm: add private lock to serialize memory hotplug operations

2017-03-16T23:56:18+00:00

Commit bfc8c90139eb ("mem-hotplug: implement get/put_online_mems")
introduced new functions get/put_online_mems() and mem_hotplug_begin/end()
in order to allow similar semantics for memory hotplug like for cpu
hotplug.

The corresponding functions for cpu hotplug are get/put_online_cpus()
and cpu_hotplug_begin/done() for cpu hotplug.

The commit however missed to introduce functions that would serialize
memory hotplug operations like they are done for cpu hotplug with
cpu_maps_update_begin/done().

This basically leaves mem_hotplug.active_writer unprotected and allows
concurrent writers to modify it, which may lead to problems as outlined
by commit f931ab479dd2 ("mm: fix devm_memremap_pages crash, use
mem_hotplug_{begin, done}").

That commit was extended again with commit b5d24fda9c3d ("mm,
devm_memremap_pages: hold device_hotplug lock over mem_hotplug_{begin,
done}") which serializes memory hotplug operations for some call sites
by using the device_hotplug lock.

In addition with commit 3fc21924100b ("mm: validate device_hotplug is held
for memory hotplug") a sanity check was added to mem_hotplug_begin() to
verify that the device_hotplug lock is held.

This in turn triggers the following warning on s390:

WARNING: CPU: 6 PID: 1 at drivers/base/core.c:643 assert_held_device_hotplug+0x4a/0x58
 Call Trace:
  assert_held_device_hotplug+0x40/0x58)
  mem_hotplug_begin+0x34/0xc8
  add_memory_resource+0x7e/0x1f8
  add_memory+0xda/0x130
  add_memory_merged+0x15c/0x178
  sclp_detect_standby_memory+0x2ae/0x2f8
  do_one_initcall+0xa2/0x150
  kernel_init_freeable+0x228/0x2d8
  kernel_init+0x2a/0x140
  kernel_thread_starter+0x6/0xc

One possible fix would be to add more lock_device_hotplug() and
unlock_device_hotplug() calls around each call site of
mem_hotplug_begin/end().  But that would give the device_hotplug lock
additional semantics it better should not have (serialize memory hotplug
operations).

Instead add a new memory_add_remove_lock which has the similar semantics
like cpu_add_remove_lock for cpu hotplug.

To keep things hopefully a bit easier the lock will be locked and unlocked
within the mem_hotplug_begin/end() functions.

Link: http://lkml.kernel.org/r/20170314125226.16779-2-heiko.carstens@de.ibm.com
Signed-off-by: Heiko Carstens 
Reported-by: Sebastian Ott 
Acked-by: Dan Williams 
Acked-by: Rafael J. Wysocki 
Cc: Michal Hocko 
Cc: Vladimir Davydov 
Cc: Ben Hutchings 
Cc: Gerald Schaefer 
Cc: Martin Schwidefsky 
Cc: Greg Kroah-Hartman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sched/headers: Prepare to move signal wakeup & sigpending methods from into

2017-03-02T07:42:32+00:00

Fix up affected files that include this signal functionality via sched.h.

Acked-by: Linus Torvalds 
Cc: Mike Galbraith 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar

memory-hotplug: use dev_online for memhp_auto_online

2017-02-25T01:46:56+00:00

Commit 31bc3858ea3e ("add automatic onlining policy for the newly added
memory") provides the capability to have added memory automatically
onlined during add, but this appears to be slightly broken.

The current implementation uses walk_memory_range() to call
online_memory_block, which uses memory_block_change_state() to online
the memory.  Instead, we should be calling device_online() for the
memory block in online_memory_block().  This would online the memory
(the memory bus online routine memory_subsys_online() called from
device_online calls memory_block_change_state()) and properly update the
device struct offline flag.

As a result of the current implementation, attempting to remove a memory
block after adding it using auto online fails.  This is because doing a
remove, for instance

  echo offline > /sys/devices/system/memory/memoryXXX/state

uses device_offline() which checks the dev->offline flag.

Link: http://lkml.kernel.org/r/20170222220744.8119.19687.stgit@ltcalpine2-lp14.aus.stglabs.ibm.com
Signed-off-by: Nathan Fontenot 
Cc: Michael Ellerman 
Cc: Michael Roth 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory_hotplug.c: fix overflow in test_pages_in_a_zone()

2017-02-25T01:46:56+00:00

When mainline introduced commit a96dfddbcc04 ("base/memory, hotplug: fix
a kernel oops in show_valid_zones()"), it obtained the valid start and
end pfn from the given pfn range.  The valid start pfn can fix the
actual issue, but it introduced another issue.  The valid end pfn will
may exceed the given end_pfn.

Although the incorrect overflow will not result in actual problem at
present, but I think it need to be fixed.

[toshi.kani@hpe.com: remove assumption that end_pfn is aligned by MAX_ORDER_NR_PAGES]
Fixes: a96dfddbcc04 ("base/memory, hotplug: fix a kernel oops in show_valid_zones()")
Link: http://lkml.kernel.org/r/1486467299-22648-1-git-send-email-zhongjiang@huawei.com
Signed-off-by: zhong jiang 
Signed-off-by: Toshi Kani 
Cc: Vlastimil Babka 
Cc: Mel Gorman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/hotplug: enable memory hotplug for non-lru movable pages

2017-02-25T01:46:55+00:00

We had considered all of the non-lru pages as unmovable before commit
bda807d44454 ("mm: migrate: support non-lru movable page migration").
But now some of non-lru pages like zsmalloc, virtio-balloon pages also
become movable.  So we can offline such blocks by using non-lru page
migration.

This patch straightforwardly adds non-lru migration code, which means
adding non-lru related code to the functions which scan over pfn and
collect pages to be migrated and isolate them before migration.

Signed-off-by: Yisheng Xie 
Cc: Michal Hocko 
Cc: Minchan Kim 
Cc: Naoya Horiguchi 
Cc: Vlastimil Babka 
Cc: Andi Kleen 
Cc: Hanjun Guo 
Cc: Johannes Weiner 
Cc: Joonsoo Kim 
Cc: Mel Gorman 
Cc: Reza Arbab 
Cc: Taku Izumi 
Cc: Vitaly Kuznetsov 
Cc: Xishi Qiu 
Cc: Yisheng Xie 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory_hotplug.c: unexport __remove_pages()

2017-02-25T01:46:53+00:00

It has no modular callers.

Cc: Dan Williams 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: validate device_hotplug is held for memory hotplug

2017-02-25T01:46:53+00:00

mem_hotplug_begin() assumes that it can set mem_hotplug.active_writer
and run the hotplug process without racing another thread.  Validate
this assumption with a lockdep assertion.

Link: http://lkml.kernel.org/r/148693886229.16345.1770484669403334689.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams 
Reported-by: Ben Hutchings 
Cc: Michal Hocko 
Cc: Toshi Kani 
Cc: Vlastimil Babka 
Cc: Logan Gunthorpe 
Cc: Greg Kroah-Hartman 
Cc: Masayoshi Mizuma 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory_hotplug: set magic number to page->freelist instead of page->lru.next

2017-02-23T00:41:29+00:00

To identify that pages of page table are allocated from bootmem
allocator, magic number sets to page->lru.next.

But page->lru list is initialized in reserve_bootmem_region().  So when
calling free_pagetable(), the function cannot find the magic number of
pages.  And free_pagetable() frees the pages by free_reserved_page() not
put_page_bootmem().

But if the pages are allocated from bootmem allocator and used as page
table, the pages have private flag.  So before freeing the pages, we
should clear the private flag by put_page_bootmem().

Before applying the commit 7bfec6f47bb0 ("mm, page_alloc: check multiple
page fields with a single branch"), we could find the following visible
issue:

  BUG: Bad page state in process kworker/u1024:1
  page:ffffea103cfd8040 count:0 mapcount:0 mappi
  flags: 0x6fffff80000800(private)
  page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
  bad because of flags: 0x800(private)
  
  Call Trace:
  [...] dump_stack+0x63/0x87
  [...] bad_page+0x114/0x130
  [...] free_pages_prepare+0x299/0x2d0
  [...] free_hot_cold_page+0x31/0x150
  [...] __free_pages+0x25/0x30
  [...] free_pagetable+0x6f/0xb4
  [...] remove_pagetable+0x379/0x7ff
  [...] vmemmap_free+0x10/0x20
  [...] sparse_remove_one_section+0x149/0x180
  [...] __remove_pages+0x2e9/0x4f0
  [...] arch_remove_memory+0x63/0xc0
  [...] remove_memory+0x8c/0xc0
  [...] acpi_memory_device_remove+0x79/0xa5
  [...] acpi_bus_trim+0x5a/0x8d
  [...] acpi_bus_trim+0x38/0x8d
  [...] acpi_device_hotplug+0x1b7/0x418
  [...] acpi_hotplug_work_fn+0x1e/0x29
  [...] process_one_work+0x152/0x400
  [...] worker_thread+0x125/0x4b0
  [...] kthread+0xd8/0xf0
  [...] ret_from_fork+0x22/0x40

And the issue still silently occurs.

Until freeing the pages of page table allocated from bootmem allocator,
the page->freelist is never used.  So the patch sets magic number to
page->freelist instead of page->lru.next.

[isimatu.yasuaki@jp.fujitsu.com: fix merge issue]
  Link: http://lkml.kernel.org/r/722b1cc4-93ac-dd8b-2be2-7a7e313b3b0b@gmail.com
Link: http://lkml.kernel.org/r/2c29bd9f-5b67-02d0-18a3-8828e78bbb6f@gmail.com
Signed-off-by: Yasuaki Ishimatsu 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: H. Peter Anvin 
Cc: Dave Hansen 
Cc: Vlastimil Babka 
Cc: Mel Gorman 
Cc: Xishi Qiu 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

base/memory, hotplug: fix a kernel oops in show_valid_zones()

2017-02-03T22:13:19+00:00

Reading a sysfs "memoryN/valid_zones" file leads to the following oops
when the first page of a range is not backed by struct page.
show_valid_zones() assumes that 'start_pfn' is always valid for
page_zone().

 BUG: unable to handle kernel paging request at ffffea017a000000
 IP: show_valid_zones+0x6f/0x160

This issue may happen on x86-64 systems with 64GiB or more memory since
their memory block size is bumped up to 2GiB.  [1] An example of such
systems is desribed below.  0x3240000000 is only aligned by 1GiB and
this memory block starts from 0x3200000000, which is not backed by
struct page.

 BIOS-e820: [mem 0x0000003240000000-0x000000603fffffff] usable

Since test_pages_in_a_zone() already checks holes, fix this issue by
extending this function to return 'valid_start' and 'valid_end' for a
given range.  show_valid_zones() then proceeds with the valid range.

[1] 'Commit bdee237c0343 ("x86: mm: Use 2GB memory block size on
    large-memory x86-64 systems")'

Link: http://lkml.kernel.org/r/20170127222149.30893-3-toshi.kani@hpe.com
Signed-off-by: Toshi Kani 
Cc: Greg Kroah-Hartman 
Cc: Zhang Zhen 
Cc: Reza Arbab 
Cc: David Rientjes 
Cc: Dan Williams 
Cc: 	[4.4+]

Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory_hotplug.c: check start_pfn in test_pages_in_a_zone()

2017-02-03T22:13:19+00:00

Patch series "fix a kernel oops when reading sysfs valid_zones", v2.

A sysfs memory file is created for each 2GiB memory block on x86-64 when
the system has 64GiB or more memory.  [1] When the start address of a
memory block is not backed by struct page, i.e.  a memory range is not
aligned by 2GiB, reading its 'valid_zones' attribute file leads to a
kernel oops.  This issue was observed on multiple x86-64 systems with
more than 64GiB of memory.  This patch-set fixes this issue.

Patch 1 first fixes an issue in test_pages_in_a_zone(), which does not
test the start section.

Patch 2 then fixes the kernel oops by extending test_pages_in_a_zone()
to return valid [start, end).

Note for stable kernels: The memory block size change was made by commit
bdee237c0343 ("x86: mm: Use 2GB memory block size on large-memory x86-64
systems"), which was accepted to 3.9.  However, this patch-set depends
on (and fixes) the change to test_pages_in_a_zone() made by commit
5f0f2887f4de ("mm/memory_hotplug.c: check for missing sections in
test_pages_in_a_zone()"), which was accepted to 4.4.

So, I recommend that we backport it up to 4.4.

[1] 'Commit bdee237c0343 ("x86: mm: Use 2GB memory block size on
    large-memory x86-64 systems")'

This patch (of 2):

test_pages_in_a_zone() does not check 'start_pfn' when it is aligned by
section since 'sec_end_pfn' is set equal to 'pfn'.  Since this function
is called for testing the range of a sysfs memory file, 'start_pfn' is
always aligned by section.

Fix it by properly setting 'sec_end_pfn' to the next section pfn.

Also make sure that this function returns 1 only when the range belongs
to a zone.

Link: http://lkml.kernel.org/r/20170127222149.30893-2-toshi.kani@hpe.com
Signed-off-by: Toshi Kani 
Cc: Andrew Banman 
Cc: Reza Arbab 
Cc: Greg KH 
Cc: 	[4.4+]
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds