linux-stable.git/mm/memory_hotplug.c, branch v4.14.151

mm, memory_hotplug: test_pages_in_a_zone do not pass the end of zone

2019-03-13T21:03:18+00:00

[ Upstream commit 24feb47c5fa5b825efb0151f28906dfdad027e61 ]

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 pages access from
test_pages_in_a_zone() function triggered by memory_hotplug sysfs
handlers.

Here are the the panic examples:
 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

Fix this by checking whether the pfn to check is within the zone.

[mhocko@suse.com: separated this change from http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com]
Link: http://lkml.kernel.org/r/20190128144506.15603-3-mhocko@kernel.org

[mhocko@suse.com: separated this change from
http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com]
Signed-off-by: Michal Hocko 
Signed-off-by: Mikhail Zaslonko 
Tested-by: Mikhail Gavrilov 
Reviewed-by: Oscar Salvador 
Tested-by: Gerald Schaefer 
Cc: Heiko Carstens 
Cc: Martin Schwidefsky 
Cc: Mikhail Gavrilov 
Cc: Pavel Tatashin 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

mm, memory_hotplug: is_mem_section_removable do not pass the end of a zone

2019-03-13T21:03:17+00:00

[ Upstream commit efad4e475c312456edb3c789d0996d12ed744c13 ]

Patch series "mm, memory_hotplug: fix uninitialized pages fallouts", v2.

Mikhail Zaslonko has posted fixes for the two bugs quite some time ago
[1].  I have pushed back on those fixes because I believed that it is
much better to plug the problem at the initialization time rather than
play whack-a-mole all over the hotplug code and find all the places
which expect the full memory section to be initialized.

We have ended up with commit 2830bf6f05fb ("mm, memory_hotplug:
initialize struct pages for the full memory section") merged and cause a
regression [2][3].  The reason is that there might be memory layouts
when two NUMA nodes share the same memory section so the merged fix is
simply incorrect.

In order to plug this hole we really have to be zone range aware in
those handlers.  I have split up the original patch into two.  One is
unchanged (patch 2) and I took a different approach for `removable'
crash.

[1] http://lkml.kernel.org/r/20181105150401.97287-2-zaslonko@linux.ibm.com
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1666948
[3] http://lkml.kernel.org/r/20190125163938.GA20411@dhcp22.suse.cz

This patch (of 2):

Mikhail has reported the following VM_BUG_ON triggered when reading sysfs
removable state of a memory block:

 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

The reason is that the memory block spans the zone boundary and we are
stumbling over an unitialized struct page.  Fix this by enforcing zone
range in is_mem_section_removable so that we never run away from a zone.

Link: http://lkml.kernel.org/r/20190128144506.15603-2-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Reported-by: Mikhail Zaslonko 
Debugged-by: Mikhail Zaslonko 
Tested-by: Gerald Schaefer 
Tested-by: Mikhail Gavrilov 
Reviewed-by: Oscar Salvador 
Cc: Pavel Tatashin 
Cc: Heiko Carstens 
Cc: Martin Schwidefsky 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Sasha Levin

hwpoison, memory_hotplug: allow hwpoisoned pages to be offlined

2019-01-13T09:01:02+00:00

commit b15c87263a69272423771118c653e9a1d0672caa upstream.

We have received a bug report that an injected MCE about faulty memory
prevents memory offline to succeed on 4.4 base kernel.  The underlying
reason was that the HWPoison page has an elevated reference count and the
migration keeps failing.  There are two problems with that.  First of all
it is dubious to migrate the poisoned page because we know that accessing
that memory is possible to fail.  Secondly it doesn't make any sense to
migrate a potentially broken content and preserve the memory corruption
over to a new location.

Oscar has found out that 4.4 and the current upstream kernels behave
slightly differently with his simply testcase

===

int main(void)
{
        int ret;
        int i;
        int fd;
        char *array = malloc(4096);
        char *array_locked = malloc(4096);

        fd = open("/tmp/data", O_RDONLY);
        read(fd, array, 4095);

        for (i = 0; i < 4096; i++)
                array_locked[i] = 'd';

        ret = mlock((void *)PAGE_ALIGN((unsigned long)array_locked), sizeof(array_locked));
        if (ret)
                perror("mlock");

        sleep (20);

        ret = madvise((void *)PAGE_ALIGN((unsigned long)array_locked), 4096, MADV_HWPOISON);
        if (ret)
                perror("madvise");

        for (i = 0; i < 4096; i++)
                array_locked[i] = 'd';

        return 0;
}
===

+ offline this memory.

In 4.4 kernels he saw the hwpoisoned page to be returned back to the LRU
list
kernel:  [] dump_trace+0x59/0x340
kernel:  [] show_stack_log_lvl+0xea/0x170
kernel:  [] show_stack+0x21/0x40
kernel:  [] dump_stack+0x5c/0x7c
kernel:  [] warn_slowpath_common+0x81/0xb0
kernel:  [] __pagevec_lru_add_fn+0x14c/0x160
kernel:  [] pagevec_lru_move_fn+0xad/0x100
kernel:  [] __lru_cache_add+0x6c/0xb0
kernel:  [] add_to_page_cache_lru+0x46/0x70
kernel:  [] extent_readpages+0xc3/0x1a0 [btrfs]
kernel:  [] __do_page_cache_readahead+0x177/0x200
kernel:  [] ondemand_readahead+0x168/0x2a0
kernel:  [] generic_file_read_iter+0x41f/0x660
kernel:  [] __vfs_read+0xcd/0x140
kernel:  [] vfs_read+0x7a/0x120
kernel:  [] kernel_read+0x3b/0x50
kernel:  [] do_execveat_common.isra.29+0x490/0x6f0
kernel:  [] do_execve+0x28/0x30
kernel:  [] call_usermodehelper_exec_async+0xfb/0x130
kernel:  [] ret_from_fork+0x55/0x80

And that latter confuses the hotremove path because an LRU page is
attempted to be migrated and that fails due to an elevated reference
count.  It is quite possible that the reuse of the HWPoisoned page is some
kind of fixed race condition but I am not really sure about that.

With the upstream kernel the failure is slightly different.  The page
doesn't seem to have LRU bit set but isolate_movable_page simply fails and
do_migrate_range simply puts all the isolated pages back to LRU and
therefore no progress is made and scan_movable_pages finds same set of
pages over and over again.

Fix both cases by explicitly checking HWPoisoned pages before we even try
to get reference on the page, try to unmap it if it is still mapped.  As
explained by Naoya:

: Hwpoison code never unmapped those for no big reason because
: Ksm pages never dominate memory, so we simply didn't have strong
: motivation to save the pages.

Also put WARN_ON(PageLRU) in case there is a race and we can hit LRU
HWPoison pages which shouldn't happen but I couldn't convince myself about
that.  Naoya has noted the following:

: Theoretically no such gurantee, because try_to_unmap() doesn't have a
: guarantee of success and then memory_failure() returns immediately
: when hwpoison_user_mappings fails.
: Or the following code (comes after hwpoison_user_mappings block) also impli=
: es
: that the target page can still have PageLRU flag.
:
:         /*
:          * Torn down by someone else?
:          */
:         if (PageLRU(p) && !PageSwapCache(p) && p->mapping =3D=3D NULL) {
:                 action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED);
:                 res =3D -EBUSY;
:                 goto out;
:         }
:
: So I think it's OK to keep "if (WARN_ON(PageLRU(page)))" block in
: current version of your patch.

Link: http://lkml.kernel.org/r/20181206120135.14079-1-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Reviewed-by: Oscar Salvador 
Debugged-by: Oscar Salvador 
Tested-by: Oscar Salvador 
Acked-by: David Hildenbrand 
Acked-by: Naoya Horiguchi 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

mm/memory_hotplug: define find_{smallest|biggest}_section_pfn as unsigned long

2017-10-04T00:54:26+00:00

find_{smallest|biggest}_section_pfn()s find the smallest/biggest section
and return the pfn of the section.  But the functions are defined as int.
So the functions always return 0x00000000 - 0xffffffff.  It means if
memory address is over 16TB, the functions does not work correctly.

To handle 64 bit value, the patch defines
find_{smallest|biggest}_section_pfn() as unsigned long.

Fixes: 815121d2b5cd ("memory_hotplug: clear zone when removing the memory")
Link: http://lkml.kernel.org/r/d9d5593a-d0a4-c4be-ab08-493df59a85c6@gmail.com
Signed-off-by: Yasuaki Ishimatsu 
Acked-by: Michal Hocko 
Cc: Xishi Qiu 
Cc: Reza Arbab 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/memory_hotplug: change pfn_to_section_nr/section_nr_to_pfn macro to inline function

2017-10-04T00:54:25+00:00

pfn_to_section_nr() and section_nr_to_pfn() are defined as macro.
pfn_to_section_nr() has no issue even if it is defined as macro.  But
section_nr_to_pfn() has overflow issue if sec is defined as int.

section_nr_to_pfn() just shifts sec by PFN_SECTION_SHIFT.  If sec is
defined as unsigned long, section_nr_to_pfn() returns pfn as 64 bit value.
But if sec is defined as int, section_nr_to_pfn() returns pfn as 32 bit
value.

__remove_section() calculates start_pfn using section_nr_to_pfn() and
scn_nr defined as int.  So if hot-removed memory address is over 16TB,
overflow issue occurs and section_nr_to_pfn() does not calculate correct
pfn.

To make callers use proper arg, the patch changes the macros to inline
functions.

Fixes: 815121d2b5cd ("memory_hotplug: clear zone when removing the memory")
Link: http://lkml.kernel.org/r/e643a387-e573-6bbf-d418-c60c8ee3d15e@gmail.com
Signed-off-by: Yasuaki Ishimatsu 
Acked-by: Michal Hocko 
Cc: Xishi Qiu 
Cc: Reza Arbab 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, memory_hotplug: add scheduling point to __add_pages

2017-10-04T00:54:25+00:00

Patch series "mm, memory_hotplug: fix few soft lockups in memory
hotadd".

Johannes has noticed few soft lockups when adding a large nvdimm device.
All of them were caused by a long loop without any explicit cond_resched
which is a problem for !PREEMPT kernels.

The fix is quite straightforward.  Just make sure that cond_resched gets
called from time to time.

This patch (of 3):

__add_pages gets a pfn range to add and there is no upper bound for a
single call.  This is usually a memory block aligned size for the
regular memory hotplug - smaller sizes are usual for memory balloning
drivers, or the whole NUMA node for physical memory online.  There is no
explicit scheduling point in that code path though.

This can lead to long latencies while __add_pages is executed and we
have even seen a soft lockup report during nvdimm initialization with
!PREEMPT kernel

  NMI watchdog: BUG: soft lockup - CPU#11 stuck for 23s! [kworker/u641:3:832]
  [...]
  Workqueue: events_unbound async_run_entry_fn
  task: ffff881809270f40 ti: ffff881809274000 task.ti: ffff881809274000
  RIP: _raw_spin_unlock_irqrestore+0x11/0x20
  RSP: 0018:ffff881809277b10  EFLAGS: 00000286
  [...]
  Call Trace:
    sparse_add_one_section+0x13d/0x18e
    __add_pages+0x10a/0x1d0
    arch_add_memory+0x4a/0xc0
    devm_memremap_pages+0x29d/0x430
    pmem_attach_disk+0x2fd/0x3f0 [nd_pmem]
    nvdimm_bus_probe+0x64/0x110 [libnvdimm]
    driver_probe_device+0x1f7/0x420
    bus_for_each_drv+0x52/0x80
    __device_attach+0xb0/0x130
    bus_probe_device+0x87/0xa0
    device_add+0x3fc/0x5f0
    nd_async_device_register+0xe/0x40 [libnvdimm]
    async_run_entry_fn+0x43/0x150
    process_one_work+0x14e/0x410
    worker_thread+0x116/0x490
    kthread+0xc7/0xe0
    ret_from_fork+0x3f/0x70
  DWARF2 unwinder stuck at ret_from_fork+0x3f/0x70

Fix this by adding cond_resched once per each memory section in the
given pfn range.  Each section is constant amount of work which itself
is not too expensive but many of them will just add up.

Link: http://lkml.kernel.org/r/20170918121410.24466-2-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Reported-by: Johannes Thumshirn 
Tested-by: Johannes Thumshirn 
Cc: Dan Williams 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/ZONE_DEVICE: new type of ZONE_DEVICE for unaddressable memory

2017-09-09T01:26:46+00:00

HMM (heterogeneous memory management) need struct page to support
migration from system main memory to device memory.  Reasons for HMM and
migration to device memory is explained with HMM core patch.

This patch deals with device memory that is un-addressable memory (ie CPU
can not access it).  Hence we do not want those struct page to be manage
like regular memory.  That is why we extend ZONE_DEVICE to support
different types of memory.

A persistent memory type is define for existing user of ZONE_DEVICE and a
new device un-addressable type is added for the un-addressable memory
type.  There is a clear separation between what is expected from each
memory type and existing user of ZONE_DEVICE are un-affected by new
requirement and new use of the un-addressable type.  All specific code
path are protect with test against the memory type.

Because memory is un-addressable we use a new special swap type for when a
page is migrated to device memory (this reduces the number of maximum swap
file).

The main two additions beside memory type to ZONE_DEVICE is two callbacks.
First one, page_free() is call whenever page refcount reach 1 (which
means the page is free as ZONE_DEVICE page never reach a refcount of 0).
This allow device driver to manage its memory and associated struct page.

The second callback page_fault() happens when there is a CPU access to an
address that is back by a device page (which are un-addressable by the
CPU).  This callback is responsible to migrate the page back to system
main memory.  Device driver can not block migration back to system memory,
HMM make sure that such page can not be pin into device memory.

If device is in some error condition and can not migrate memory back then
a CPU page fault to device memory should end with SIGBUS.

[arnd@arndb.de: fix warning]
  Link: http://lkml.kernel.org/r/20170823133213.712917-1-arnd@arndb.de
Link: http://lkml.kernel.org/r/20170817000548.32038-8-jglisse@redhat.com
Signed-off-by: Jérôme Glisse 
Signed-off-by: Arnd Bergmann 
Acked-by: Dan Williams 
Cc: Ross Zwisler 
Cc: Aneesh Kumar 
Cc: Balbir Singh 
Cc: Benjamin Herrenschmidt 
Cc: David Nellans 
Cc: Evgeny Baskakov 
Cc: Johannes Weiner 
Cc: John Hubbard 
Cc: Kirill A. Shutemov 
Cc: Mark Hairgrove 
Cc: Michal Hocko 
Cc: Paul E. McKenney 
Cc: Sherry Cheung 
Cc: Subhash Gutti 
Cc: Vladimir Davydov 
Cc: Bob Liu 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: memory_hotplug: memory hotremove supports thp migration

2017-09-09T01:26:45+00:00

This patch enables thp migration for memory hotremove.

Link: http://lkml.kernel.org/r/20170717193955.20207-11-zi.yan@sent.com
Signed-off-by: Naoya Horiguchi 
Signed-off-by: Zi Yan 
Cc: "H. Peter Anvin" 
Cc: Anshuman Khandual 
Cc: Dave Hansen 
Cc: David Nellans 
Cc: Ingo Molnar 
Cc: Kirill A. Shutemov 
Cc: Mel Gorman 
Cc: Minchan Kim 
Cc: Thomas Gleixner 
Cc: Vlastimil Babka 
Cc: Andrea Arcangeli 
Cc: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, memory_hotplug: get rid of zonelists_mutex

2017-09-07T00:27:26+00:00

zonelists_mutex was introduced by commit 4eaf3f64397c ("mem-hotplug: fix
potential race while building zonelist for new populated zone") to
protect zonelist building from races.  This is no longer needed though
because both memory online and offline are fully serialized.  New users
have grown since then.

Notably setup_per_zone_wmarks wants to prevent from races between memory
hotplug, khugepaged setup and manual min_free_kbytes update via sysctl
(see cfd3da1e49bb ("mm: Serialize access to min_free_kbytes").  Let's
add a private lock for that purpose.  This will not prevent from seeing
halfway through memory hotplug operation but that shouldn't be a big
deal becuse memory hotplug will update watermarks explicitly so we will
eventually get a full picture.  The lock just makes sure we won't race
when updating watermarks leading to weird results.

Also __build_all_zonelists manipulates global data so add a private lock
for it as well.  This doesn't seem to be necessary today but it is more
robust to have a lock there.

While we are at it make sure we document that memory online/offline
depends on a full serialization either via mem_hotplug_begin() or
device_lock.

Link: http://lkml.kernel.org/r/20170721143915.14161-9-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Cc: Johannes Weiner 
Cc: Joonsoo Kim 
Cc: Mel Gorman 
Cc: Shaohua Li 
Cc: Toshi Kani 
Cc: Vlastimil Babka 
Cc: Haicheng Li 
Cc: Wu Fengguang 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm, memory_hotplug: remove explicit build_all_zonelists from try_online_node

2017-09-07T00:27:26+00:00

try_online_node calls hotadd_new_pgdat which already calls
build_all_zonelists.  So the additional call is redundant.  Even though
hotadd_new_pgdat will only initialize zonelists of the new node this is
the right thing to do because such a node doesn't have any memory so
other zonelists would ignore all the zones from this node anyway.

Link: http://lkml.kernel.org/r/20170721143915.14161-6-mhocko@kernel.org
Signed-off-by: Michal Hocko 
Acked-by: Vlastimil Babka 
Cc: Toshi Kani 
Cc: Johannes Weiner 
Cc: Joonsoo Kim 
Cc: Mel Gorman 
Cc: Shaohua Li 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds