I found the following pattern that leads in to interesting findings:

  grep -r "ret.*|=.*__put_user" *
  grep -r "ret.*|=.*__get_user" *
  grep -r "ret.*|=.*__copy" *

The __put_user() calls in compat_ioctl.c, ptrace compat, signal compat,
since those appear in compat code, we could probably expect the kernel
addresses not to be reachable in the lower 32-bit range, so I think they
might not be exploitable.

For the "__get_user" cases, I don't think those are exploitable: the worse
that can happen is that the kernel will copy kernel memory into in-kernel
buffers, and will fail immediately afterward.

The alpha csum_partial_copy_from_user() seems to be missing the
access_ok() check entirely.  The fix is inspired from x86.  This could
lead to information leak on alpha.  I also noticed that many architectures
map csum_partial_copy_from_user() to csum_partial_copy_generic(), but I
wonder if the latter is performing the access checks on every
architectures.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The use of strict_strtoul() is not preferred, because strict_strtoul() is
obsolete.  Thus, kstrtoul() should be used.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: Tom Gundersen <teg@jklm.no>
Cc: Mike Waychison <mikew@google.com>
Acked-by: Mike Waychison <mikew@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Convert drivers/platform/x86/apple-gmux to use dev_pm_ops instead of
legacy pm_ops.  This patch depends on pnp driver bus ops change to invoke
pnp_driver dev_pm_ops.

Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Cc: Matthew Garrett <matthew.garrett@nebula.com>
Cc: Leonidas Da Silva Barbosa <leosilva@linux.vnet.ibm.com>
Cc: Ashley Lai <ashley@ashleylai.com>
Cc: Rajiv Andrade <mail@srajiv.net>
Cc: Marcel Selhorst <tpmdd@selhorst.net>
Cc: Sirrix AG <tpmdd@sirrix.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Peter Hüwe <PeterHuewe@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Convert drivers/char/tpm/tpm_tis.c to use dev_pm_ops instead of legacy
pm_ops.  This patch depends on pnp driver bus ops change to invoke
pnp_driver dev_pm_ops.

Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Cc: Matthew Garrett <matthew.garrett@nebula.com>
Cc: Leonidas Da Silva Barbosa <leosilva@linux.vnet.ibm.com>
Cc: Ashley Lai <ashley@ashleylai.com>
Cc: Rajiv Andrade <mail@srajiv.net>
Cc: Marcel Selhorst <tpmdd@selhorst.net>
Cc: Sirrix AG <tpmdd@sirrix.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Peter Hüwe <PeterHuewe@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Convert drivers/rtc/rtc-cmos to use dev_pm_ops instead of legacy pm_ops.
This patch depends on pnp driver bus ops change to invoke pnp_driver
dev_pm_ops.

Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Cc: Matthew Garrett <matthew.garrett@nebula.com>
Cc: Leonidas Da Silva Barbosa <leosilva@linux.vnet.ibm.com>
Cc: Ashley Lai <ashley@ashleylai.com>
Cc: Rajiv Andrade <mail@srajiv.net>
Cc: Marcel Selhorst <tpmdd@selhorst.net>
Cc: Sirrix AG <tpmdd@sirrix.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Peter Hüwe <PeterHuewe@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

pnp_bus_suspend() and pnp_bus_resume() invoke legacy pm_ops from
pnp_driver.  Changed pnp_bus_suspend() and pnp_bus_resume() to check if
pnp driver has dev_pm_ops and call.  If dev_pm_ops don't exist, then call
use legacy pm_ops.  Without this change, pnp_driver dev_pm_ops will not
get called.

In addition to the pnp driver bus pm_ops change to invoke driver
dev_pm_ops, this patch set contains changes to rtc-cmos, tpm_tis, and
apple-gmux pnp drivers to convert from legacy pm_ops to dev_pm_ops.

This patch (of 4):

pnp_bus_suspend() and pnp_bus_resume() invoke legacy pm_ops from
pnp_driver.  Changed pnp_bus_suspend() and pnp_bus_resume() to check if
pnp driver has dev_pm_ops and call.  If dev_pm_ops don't exist, then call
use legacy pm_ops.  Without this change, pnp_driver dev_pm_ops will not
get called.

Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Cc: Matthew Garrett <matthew.garrett@nebula.com>
Cc: Leonidas Da Silva Barbosa <leosilva@linux.vnet.ibm.com>
Cc: Ashley Lai <ashley@ashleylai.com>
Cc: Rajiv Andrade <mail@srajiv.net>
Cc: Marcel Selhorst <tpmdd@selhorst.net>
Cc: Sirrix AG <tpmdd@sirrix.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Peter Hüwe <PeterHuewe@gmx.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

A memory cgroup with (1) multiple threshold notifications and (2) at least
one threshold >=2G was not reliable.  Specifically the notifications would
either not fire or would not fire in the proper order.

The __mem_cgroup_threshold() signaling logic depends on keeping 64 bit
thresholds in sorted order.  mem_cgroup_usage_register_event() sorts them
with compare_thresholds(), which returns the difference of two 64 bit
thresholds as an int.  If the difference is positive but has bit[31] set,
then sort() treats the difference as negative and breaks sort order.

This fix compares the two arbitrary 64 bit thresholds returning the
classic -1, 0, 1 result.

The test below sets two notifications (at 0x1000 and 0x81001000):
  cd /sys/fs/cgroup/memory
  mkdir x
  for x in 4096 2164264960; do
    cgroup_event_listener x/memory.usage_in_bytes $x | sed "s/^/$x listener:/" &
  done
  echo $$ > x/cgroup.procs
  anon_leaker 500M

v3.11-rc7 fails to signal the 4096 event listener:
  Leaking...
  Done leaking pages.

Patched v3.11-rc7 properly notifies:
  Leaking...
  4096 listener:2013:8:31:14:13:36
  Done leaking pages.

The fixed bug is old.  It appears to date back to the introduction of
memcg threshold notifications in v2.6.34-rc1-116-g2e72b6347c94 "memcg:
implement memory thresholds"

Signed-off-by: Greg Thelen <gthelen@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Use the helper function instead of __GFP_ZERO.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Use the helper function instead of __GFP_ZERO.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

pgoff is not used after the statement "pgoff = vma->vm_pgoff;", so the
assignment is redundant.

Signed-off-by: Yanchuan Nian <ycnian@gmail.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

There is a race between mark inode dirty and writeback thread, see the
following scenario.  In this case, writeback thread will not run though
there is dirty_io.

__mark_inode_dirty()                                          bdi_writeback_workfn()
	...                                                       	...
	spin_lock(&inode->i_lock);
	...
	if (bdi_cap_writeback_dirty(bdi)) {
	    <<< assume wb has dirty_io, so wakeup_bdi is false.
	    <<< the following inode_dirty also have wakeup_bdi false.
	    if (!wb_has_dirty_io(&bdi->wb))
		    wakeup_bdi = true;
	}
	spin_unlock(&inode->i_lock);
	                                                            <<< assume last dirty_io is removed here.
	                                                            pages_written = wb_do_writeback(wb);
	                                                            ...
	                                                            <<< work_list empty and wb has no dirty_io,
	                                                            <<< delayed_work will not be queued.
	                                                            if (!list_empty(&bdi->work_list) ||
	                                                                (wb_has_dirty_io(wb) && dirty_writeback_interval))
	                                                                queue_delayed_work(bdi_wq, &wb->dwork,
	                                                                    msecs_to_jiffies(dirty_writeback_interval * 10));
	spin_lock(&bdi->wb.list_lock);
	inode->dirtied_when = jiffies;
	<<< new dirty_io is added.
	list_move(&inode->i_wb_list, &bdi->wb.b_dirty);
	spin_unlock(&bdi->wb.list_lock);

	<<< though there is dirty_io, but wakeup_bdi is false,
	<<< so writeback thread will not be waked up and
	<<< the new dirty_io will not be flushed.
	if (wakeup_bdi)
	    bdi_wakeup_thread_delayed(bdi);

Writeback will run until there is a new flush work queued.  This may cause
a lot of dirty pages stay in memory for a long time.

Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

madvise_hwpoison() has two locals called "ret".  Fix it all up.

Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The return value outside for loop is always zero which means
madvise_hwpoison return success, however, this is not truth for
soft_offline_page w/ failure return value.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

  Injecting memory failure for page 0x19d0 at 0xb77d2000
  MCE 0x19d0: non LRU page recovery: Ignored
  MCE: Software-unpoisoned page 0x19d0
  BUG: Bad page state in process bash  pfn:019d0
  page:f3461a00 count:0 mapcount:0 mapping:  (null) index:0x0
  page flags: 0x40000404(referenced|reserved)
  Modules linked in: nfsd auth_rpcgss i915 nfs_acl nfs lockd video drm_kms_helper drm bnep rfcomm sunrpc bluetooth psmouse parport_pc ppdev lp serio_raw fscache parport gpio_ich lpc_ich mac_hid i2c_algo_bit tpm_tis wmi usb_storage hid_generic usbhid hid e1000e firewire_ohci firewire_core ahci ptp libahci pps_core crc_itu_t
  CPU: 3 PID: 2123 Comm: bash Not tainted 3.11.0-rc6+ #12
  Hardware name: LENOVO 7034DD7/        , BIOS 9HKT47AUS 01//2012
   00000000 00000000 e9625ea0 c15ec49b f3461a00 e9625eb8 c15ea119 c17cbf18
   ef084314 000019d0 f3461a00 e9625ed8 c110dc8a f3461a00 00000001 00000000
   f3461a00 40000404 00000000 e9625ef8 c110dcc1 f3461a00 f3461a00 000019d0
  Call Trace:
    dump_stack+0x41/0x52
    bad_page+0xcf/0xeb
    free_pages_prepare+0x12a/0x140
    free_hot_cold_page+0x21/0x110
    __put_single_page+0x21/0x30
    put_page+0x25/0x40
    unpoison_memory+0x107/0x200
    hwpoison_unpoison+0x20/0x30
    simple_attr_write+0xb6/0xd0
    vfs_write+0xa0/0x1b0
    SyS_write+0x4f/0x90
    sysenter_do_call+0x12/0x22
  Disabling lock debugging due to kernel taint

Testcase:

#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <sys/mman.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <errno.h>

#define PAGES_TO_TEST 1
#define PAGE_SIZE	4096

int main(void)
{
	char *mem;

	mem = mmap(NULL, PAGES_TO_TEST * PAGE_SIZE,
			PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);

	if (madvise(mem, PAGES_TO_TEST * PAGE_SIZE, MADV_HWPOISON) == -1)
		return -1;

	munmap(mem, PAGES_TO_TEST * PAGE_SIZE);

	return 0;
}

There is one page reference count for default empty zero page,
madvise_hwpoison add another one by get_user_pages_fast.  memory_hwpoison
reduce one page reference count since it's a non LRU page.
unpoison_memory release the last page reference count and free empty zero
page to buddy system which is not correct since empty zero page has
PG_reserved flag.  This patch fix it by don't reduce the page reference
count under 1 against empty zero page.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Hwpoison injection doesn't implement read method for
corrupt-pfn/unpoison-pfn attributes:

# cat /sys/kernel/debug/hwpoison/corrupt-pfn
cat: /sys/kernel/debug/hwpoison/corrupt-pfn: Permission denied
# cat /sys/kernel/debug/hwpoison/unpoison-pfn
cat: /sys/kernel/debug/hwpoison/unpoison-pfn: Permission denied

This patch changes the permission of corrupt-pfn/unpoison-pfn to 0200.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

madvise hwpoison inject will poison the read-only empty zero page if there
is no write access before poison.  Empty zero page reference count will be
increased for hwpoison, subsequent poison zero page will return directly
since page has already been set PG_hwpoison, however, page reference count
is still increased by get_user_pages_fast.  The unpoison process will
unpoison the empty zero page and decrease the reference count successfully
for the fist time, however, subsequent unpoison empty zero page will
return directly since page has already been unpoisoned and without
decrease the page reference count of empty zero page.

This patch fixes it by make madvise_hwpoison() put a page and return
immediately (without calling memory_failure() or soft_offline_page()) when
the page is already hwpoisoned.

Testcase:

#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <sys/mman.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <errno.h>

#define PAGES_TO_TEST 3
#define PAGE_SIZE	4096

int main(void)
{
	char *mem;
	int i;

	mem = mmap(NULL, PAGES_TO_TEST * PAGE_SIZE,
			PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);

	if (madvise(mem, PAGES_TO_TEST * PAGE_SIZE, MADV_HWPOISON) == -1)
		return -1;

	munmap(mem, PAGES_TO_TEST * PAGE_SIZE);

	return 0;
}

Add printk to dump page reference count:

[   93.075959] Injecting memory failure for page 0x19d0 at 0xb77d8000
[   93.076207] MCE 0x19d0: non LRU page recovery: Ignored
[   93.076209] pfn 0x19d0, page count = 1 after memory failure
[   93.076220] Injecting memory failure for page 0x19d0 at 0xb77d9000
[   93.076221] MCE 0x19d0: already hardware poisoned
[   93.076222] pfn 0x19d0, page count = 2 after memory failure
[   93.076224] Injecting memory failure for page 0x19d0 at 0xb77da000
[   93.076224] MCE 0x19d0: already hardware poisoned
[   93.076225] pfn 0x19d0, page count = 3 after memory failure

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Suggested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Add '#' to madvise_hwpoison.

Before patch:

[   95.892866] Injecting memory failure for page 19d0 at b7786000
[   95.893151] MCE 0x19d0: non LRU page recovery: Ignored

After patch:

[   95.892866] Injecting memory failure for page 0x19d0 at 0xb7786000
[   95.893151] MCE 0x19d0: non LRU page recovery: Ignored

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Drop forward reference declarations __soft_offline_page.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Set pageblock migration type will hold zone->lock which is heavy contended
in system to avoid race.  However, soft offline page will set pageblock
migration type twice during get page if the page is in used, not hugetlbfs
page and not on lru list.  There is unnecessary to set the pageblock
migration type and hold heavy contended zone->lock again if the first
round get page have already set the pageblock to right migration type.

The trick here is migration type is MIGRATE_ISOLATE.  There are other two
parts can change MIGRATE_ISOLATE except hwpoison.  One is memory hoplug,
however, we hold lock_memory_hotplug() which avoid race.  The second is
CMA which umovable page allocation requst can't fallback to.  So it's safe
here.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Replace atomic_long_sub() with atomic_long_dec() since the page is normal
page instead of hugetlbfs page or thp.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

There is a race between hwpoison page and unpoison page, memory_failure
set the page hwpoison and increase num_poisoned_pages without hold page
lock, and one page count will be accounted against thp for
num_poisoned_pages.  However, unpoison can occur before memory_failure
hold page lock and split transparent hugepage, unpoison will decrease
num_poisoned_pages by 1 << compound_order since memory_failure has not yet
split transparent hugepage with page lock held.  That means we account one
page for hwpoison and 1 << compound_order for unpoison.  This patch fix it
by inserting a PageTransHuge check before doing TestClearPageHWPoison,
unpoison failed without clearing PageHWPoison and decreasing
num_poisoned_pages.

            A                                                 	B
    	memory_failue
        TestSetPageHWPoison(p);
        if (PageHuge(p))
            nr_pages = 1 << compound_order(hpage);
        else
            nr_pages = 1;
        atomic_long_add(nr_pages, &num_poisoned_pages);
                                                            unpoison_memory
	                                                        nr_pages = 1<< compound_trans_order(page);
                                                            if(TestClearPageHWPoison(p))
                                                            atomic_long_sub(nr_pages, &num_poisoned_pages);
        lock page
        if (!PageHWPoison(p))
        	unlock page and return
        hwpoison_user_mappings
        if (PageTransHuge(hpage))
        	split_huge_page(hpage);

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Suggested-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

compound lock is introduced by commit e9da73d6

("thp: compound_lock."), it
is used to serialize put_page against __split_huge_page_refcount().  In
addition, transparent hugepages will be splitted in hwpoison handler and
just one subpage will be poisoned.  There is unnecessary to hold compound
lock for hugetlbfs page.  This patch replace compound_trans_order by
compond_order in the place where the page is hugetlbfs page.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

memory_failure() store the page flag of the error page before doing unmap,
and (only) if the first check with page flags at the time decided the
error page is unknown, it do the second check with the stored page flag
since memory_failure() does unmapping of the error pages before doing
page_action().  This unmapping changes the page state, especially
page_remove_rmap() (called from try_to_unmap_one()) clears PG_mlocked, so
page_action() can't catch mlocked pages after that.

However, memory_failure() can't handle memory errors on dirty mlocked
pages correctly.  try_to_unmap_one will move the dirty bit from pte to the
physical page, the second check lose it since it check the stored page
flag.  This patch fix it by restore PG_dirty flag to stored page flag if
the page is dirty.

Testcase:

#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <errno.h>

#define PAGES_TO_TEST 2
#define PAGE_SIZE	4096

int main(void)
{
	char *mem;
	int i;

	mem = mmap(NULL, PAGES_TO_TEST * PAGE_SIZE,
			PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_LOCKED, 0, 0);

	for (i = 0; i < PAGES_TO_TEST; i++)
		mem[i * PAGE_SIZE] = 'a';

	if (madvise(mem, PAGES_TO_TEST * PAGE_SIZE, MADV_HWPOISON) == -1)
		return -1;

	return 0;
}

Before patch:

[  912.839247] Injecting memory failure for page 7dfb8 at 7f6b4e37b000
[  912.839257] MCE 0x7dfb8: clean mlocked LRU page recovery: Recovered
[  912.845550] MCE 0x7dfb8: clean mlocked LRU page still referenced by 1 users
[  912.852586] Injecting memory failure for page 7e6aa at 7f6b4e37c000
[  912.852594] MCE 0x7e6aa: clean mlocked LRU page recovery: Recovered
[  912.858936] MCE 0x7e6aa: clean mlocked LRU page still referenced by 1 users

After patch:

[  163.590225] Injecting memory failure for page 91bc2f at 7f9f5b0e5000
[  163.590264] MCE 0x91bc2f: dirty mlocked LRU page recovery: Recovered
[  163.596680] MCE 0x91bc2f: dirty mlocked LRU page still referenced by 1 users
[  163.603831] Injecting memory failure for page 91cdd3 at 7f9f5b0e6000
[  163.603852] MCE 0x91cdd3: dirty mlocked LRU page recovery: Recovered
[  163.610305] MCE 0x91cdd3: dirty mlocked LRU page still referenced by 1 users

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Soft offline code expects that MIGRATE_ISOLATE is set on the target page
only during soft offlining work.  But currenly it doesn't work as expected
when get_any_page() fails and returns negative value.  In the result, end
users can have unexpectedly isolated pages.  This patch just fixes it.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Set _mapcount PAGE_BUDDY_MAPCOUNT_VALUE to make the page buddy.  Not the
magic number -2.

Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
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>

_PAGE_SOFT_DIRTY bit should never be set on present pte so add VM_BUG_ON
to catch any potential future abuse.

Also add a comment on _PAGE_SWP_SOFT_DIRTY definition explaining scope of
its usage.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The feature prevents mistrusted filesystems (ie: FUSE mounts created by
unprivileged users) to grow a large number of dirty pages before
throttling.  For such filesystems balance_dirty_pages always check bdi
counters against bdi limits.  I.e.  even if global "nr_dirty" is under
"freerun", it's not allowed to skip bdi checks.  The only use case for now
is fuse: it sets bdi max_ratio to 1% by default and system administrators
are supposed to expect that this limit won't be exceeded.

The feature is on if a BDI is marked by BDI_CAP_STRICTLIMIT flag.  A
filesystem may set the flag when it initializes its BDI.

The problematic scenario comes from the fact that nobody pays attention to
the NR_WRITEBACK_TEMP counter (i.e.  number of pages under fuse
writeback).  The implementation of fuse writeback releases original page
(by calling end_page_writeback) almost immediately.  A fuse request queued
for real processing bears a copy of original page.  Hence, if userspace
fuse daemon doesn't finalize write requests in timely manner, an
aggressive mmap writer can pollute virtually all memory by those temporary
fuse page copies.  They are carefully accounted in NR_WRITEBACK_TEMP, but
nobody cares.

To make further explanations shorter, let me use "NR_WRITEBACK_TEMP
problem" as a shortcut for "a possibility of uncontrolled grow of amount
of RAM consumed by temporary pages allocated by kernel fuse to process
writeback".

The problem was very easy to reproduce.  There is a trivial example
filesystem implementation in fuse userspace distribution: fusexmp_fh.c.  I
added "sleep(1);" to the write methods, then recompiled and mounted it.
Then created a huge file on the mount point and run a simple program which
mmap-ed the file to a memory region, then wrote a data to the region.  An
hour later I observed almost all RAM consumed by fuse writeback.  Since
then some unrelated changes in kernel fuse made it more difficult to
reproduce, but it is still possible now.

Putting this theoretical happens-in-the-lab thing aside, there is another
thing that really hurts real world (FUSE) users.  This is write-through
page cache policy FUSE currently uses.  I.e.  handling write(2), kernel
fuse populates page cache and flushes user data to the server
synchronously.  This is excessively suboptimal.  Pavel Emelyanov's patches
("writeback cache policy") solve the problem, but they also make resolving
NR_WRITEBACK_TEMP problem absolutely necessary.  Otherwise, simply copying
a huge file to a fuse mount would result in memory starvation.  Miklos,
the maintainer of FUSE, believes strictlimit feature the way to go.

And eventually putting FUSE topics aside, there is one more use-case for
strictlimit feature.  Using a slow USB stick (mass storage) in a machine
with huge amount of RAM installed is a well-known pain.  Let's make simple
computations.  Assuming 64GB of RAM installed, existing implementation of
balance_dirty_pages will start throttling only after 9.6GB of RAM becomes
dirty (freerun == 15% of total RAM).  So, the command "cp 9GB_file
/media/my-usb-storage/" may return in a few seconds, but subsequent
"umount /media/my-usb-storage/" will take more than two hours if effective
throughput of the storage is, to say, 1MB/sec.

After inclusion of strictlimit feature, it will be trivial to add a knob
(e.g.  /sys/devices/virtual/bdi/x:y/strictlimit) to enable it on demand.
Manually or via udev rule.  May be I'm wrong, but it seems to be quite a
natural desire to limit the amount of dirty memory for some devices we are
not fully trust (in the sense of sustainable throughput).

[akpm@linux-foundation.org: fix warning in page-writeback.c]
Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

'*lenp' may be less than "sizeof(kbuf)" so we must check this before the
next copy_to_user().

pdflush_proc_obsolete() is called by sysctl which 'procname' is
"nr_pdflush_threads", if the user passes buffer length less than
"sizeof(kbuf)", it will cause issue.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

In alloc_new_pmd(), if pud_alloc() was called successfully, but
pmd_alloc() fails, avoid leaking `pud'.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Use wrapper function get_vm_area_size to calculate size of vm area.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

It's not used globally and could be static.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

After commit 9bdac914

 ("sparsemem: Put mem map for one node
together."), vmemmap for one node will be allocated together, its logic
is similar as memory allocation for pageblock flags.  This patch
introduces alloc_usemap_and_memmap to extract the same logic of memory
alloction for pageblock flags and vmemmap.

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This patch is based on KOSAKI's work and I add a little more description,
please refer https://lkml.org/lkml/2012/6/14/74.

Currently, I found system can enter a state that there are lots of free
pages in a zone but only order-0 and order-1 pages which means the zone is
heavily fragmented, then high order allocation could make direct reclaim
path's long stall(ex, 60 seconds) especially in no swap and no compaciton
enviroment.  This problem happened on v3.4, but it seems issue still lives
in current tree, the reason is do_try_to_free_pages enter live lock:

kswapd will go to sleep if the zones have been fully scanned and are still
not balanced.  As kswapd thinks there's little point trying all over again
to avoid infinite loop.  Instead it changes order from high-order to
0-order because kswapd think order-0 is the most important.  Look at
73ce02e9 in detail.  If watermarks are ok, kswapd will go back to sleep
and may leave zone->all_unreclaimable =3D 0.  It assume high-order users
can still perform direct reclaim if they wish.

Direct reclaim continue to reclaim for a high order which is not a
COSTLY_ORDER without oom-killer until kswapd turn on
zone->all_unreclaimble= .  This is because to avoid too early oom-kill.
So it means direct_reclaim depends on kswapd to break this loop.

In worst case, direct-reclaim may continue to page reclaim forever when
kswapd sleeps forever until someone like watchdog detect and finally kill
the process.  As described in:
http://thread.gmane.org/gmane.linux.kernel.mm/103737

We can't turn on zone->all_unreclaimable from direct reclaim path because
direct reclaim path don't take any lock and this way is racy.  Thus this
patch removes zone->all_unreclaimable field completely and recalculates
zone reclaimable state every time.

Note: we can't take the idea that direct-reclaim see zone->pages_scanned
directly and kswapd continue to use zone->all_unreclaimable.  Because, it
is racy.  commit 929bea7c

 (vmscan: all_unreclaimable() use
zone->all_unreclaimable as a name) describes the detail.

[akpm@linux-foundation.org: uninline zone_reclaimable_pages() and zone_reclaimable()]
Cc: Aaditya Kumar <aaditya.kumar.30@gmail.com>
Cc: Ying Han <yinghan@google.com>
Cc: Nick Piggin <npiggin@gmail.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Bob Liu <lliubbo@gmail.com>
Cc: Neil Zhang <zhangwm@marvell.com>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Lisa Du <cldu@marvell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Currently munlock_vma_pages_range() calls follow_page_mask() to obtain
each individual struct page.  This entails repeated full page table
translations and page table lock taken for each page separately.

This patch avoids the costly follow_page_mask() where possible, by
iterating over ptes within single pmd under single page table lock.  The
first pte is obtained by get_locked_pte() for non-THP page acquired by the
initial follow_page_mask().  The rest of the on-stack pagevec for munlock
is filled up using pte_walk as long as pte_present() and vm_normal_page()
are sufficient to obtain the struct page.

After this patch, a 14% speedup was measured for munlocking a 56GB large
memory area with THP disabled.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Jörn Engel <joern@logfs.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michel Lespinasse <walken@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The performance of the fast path in munlock_vma_range() can be further
improved by avoiding atomic ops of a redundant get_page()/put_page() pair.

When calling get_page() during page isolation, we already have the pin
from follow_page_mask().  This pin will be then returned by
__pagevec_lru_add(), after which we do not reference the pages anymore.

After this patch, an 8% speedup was measured for munlocking a 56GB large
memory area with THP disabled.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Jörn Engel <joern@logfs.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michel Lespinasse <walken@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

After introducing batching by pagevecs into munlock_vma_range(), we can
further improve performance by bypassing the copying into per-cpu pagevec
and the get_page/put_page pair associated with that.  Instead we perform
LRU putback directly from our pagevec.  However, this is possible only for
single-mapped pages that are evictable after munlock.  Unevictable pages
require rechecking after putting on the unevictable list, so for those we
fallback to putback_lru_page(), hich handles that.

After this patch, a 13% speedup was measured for munlocking a 56GB large
memory area with THP disabled.

[akpm@linux-foundation.org:clarify comment]
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Jörn Engel <joern@logfs.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michel Lespinasse <walken@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Depending on previous batch which introduced batched isolation in
munlock_vma_range(), we can batch also the updates of NR_MLOCK page stats.
 After the whole pagevec is processed for page isolation, the stats are
updated only once with the number of successful isolations.  There were
however no measurable perfomance gains.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Jörn Engel <joern@logfs.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michel Lespinasse <walken@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Currently, munlock_vma_range() calls munlock_vma_page on each page in a
loop, which results in repeated taking and releasing of the lru_lock
spinlock for isolating pages one by one.  This patch batches the munlock
operations using an on-stack pagevec, so that isolation is done under
single lru_lock.  For THP pages, the old behavior is preserved as they
might be split while putting them into the pagevec.  After this patch, a
9% speedup was measured for munlocking a 56GB large memory area with THP
disabled.

A new function __munlock_pagevec() is introduced that takes a pagevec and:
1) It clears PageMlocked and isolates all pages under lru_lock.  Zone page
stats can be also updated using the variant which assumes disabled
interrupts.  2) It finishes the munlock and lru putback on all pages under
their lock_page.  Note that previously, lock_page covered also the
PageMlocked clearing and page isolation, but it is not needed for those
operations.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Jörn Engel <joern@logfs.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michel Lespinasse <walken@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

In munlock_vma_range(), lru_add_drain() is currently called in a loop
before each munlock_vma_page() call.

This is suboptimal for performance when munlocking many pages.  The
benefits of per-cpu pagevec for batching the LRU putback are removed since
the pagevec only holds at most one page from the previous loop's
iteration.

The lru_add_drain() call also does not serve any purposes for correctness
- it does not even drain pagavecs of all cpu's.  The munlock code already
expects and handles situations where a page cannot be isolated from the
LRU (e.g.  because it is on some per-cpu pagevec).

The history of the (not commented) call also suggest that it appears there
as an oversight rather than intentionally.  Before commit ff6a6da6 ("mm:
accelerate munlock() treatment of THP pages") the call happened only once
upon entering the function.  The commit has moved the call into the while
loope.  So while the other changes in the commit improved munlock
performance for THP pages, it introduced the abovementioned suboptimal
per-cpu pagevec usage.

Further in history, before commit 408e82b7 ("mm: munlock use
follow_page"), munlock_vma_pages_range() was just a wrapper around
__mlock_vma_pages_range which performed both mlock and munlock depending
on a flag.  However, before ba470de4 ("mmap: handle mlocked pages during
map, remap, unmap") the function handled only mlock, not munlock.  The
lru_add_drain call thus comes from the implementation in commit b291f000


("mlock: mlocked pages are unevictable" and was intended only for
mlocking, not munlocking.  The original intention of draining the LRU
pagevec at mlock time was to ensure the pages were on the LRU before the
lock operation so that they could be placed on the unevictable list
immediately.  There is very little motivation to do the same in the
munlock path this, particularly for every single page.

This patch therefore removes the call completely.  After removing the
call, a 10% speedup was measured for munlock() of a 56GB large memory area
with THP disabled.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Jörn Engel <joern@logfs.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michel Lespinasse <walken@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The goal of this patch series is to improve performance of munlock() of
large mlocked memory areas on systems without THP.  This is motivated by
reported very long times of crash recovery of processes with such areas,
where munlock() can take several seconds.  See
http://lwn.net/Articles/548108/

The work was driven by a simple benchmark (to be included in mmtests) that
mmaps() e.g.  56GB with MAP_LOCKED | MAP_POPULATE and measures the time of
munlock().  Profiling was performed by attaching operf --pid to the
process and sending a signal to trigger the munlock() part and then notify
bach the monitoring wrapper to stop operf, so that only munlock() appears
in the profile.

The profiles have shown that CPU time is spent mostly by atomic operations
and repeated locking per single pages. This series aims to reduce both, starting
from simpler to more complex changes.

Patch 1 performs a simple cleanup in putback_lru_page() so that page lru base
	type is not determined without being actually needed.

Patch 2 removes an unnecessary call to lru_add_drain() which drains the per-cpu
	pagevec after each munlocked page is put there.

Patch 3 changes munlock_vma_range() to use an on-stack pagevec for isolating
	multiple non-THP pages under a single lru_lock instead of locking and
	processing each page separately.

Patch 4 changes the NR_MLOCK accounting to be called only once per the pvec
	introduced by previous patch.

Patch 5 uses the introduced pagevec to batch also the work of putback_lru_page
	when possible, bypassing the per-cpu pvec and associated overhead.

Patch 6 removes a redundant get_page/put_page pair which saves costly atomic
	operations.

Patch 7 avoids calling follow_page_mask() on each individual page, and obtains
	multiple page references under a single page table lock where possible.

Measurements were made using 3.11-rc3 as a baseline.  The first set of
measurements shows the possibly ideal conditions where batching should
help the most.  All memory is allocated from a single NUMA node and THP is
disabled.

timedmunlock
                            3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3
                                   0                     1                     2                     3                     4                     5                     6                     7
Elapsed min           3.38 (  0.00%)        3.39 ( -0.13%)        3.00 ( 11.33%)        2.70 ( 20.20%)        2.67 ( 21.11%)        2.37 ( 29.88%)        2.20 ( 34.91%)        1.91 ( 43.59%)
Elapsed mean          3.39 (  0.00%)        3.40 ( -0.23%)        3.01 ( 11.33%)        2.70 ( 20.26%)        2.67 ( 21.21%)        2.38 ( 29.88%)        2.21 ( 34.93%)        1.92 ( 43.46%)
Elapsed stddev        0.01 (  0.00%)        0.01 (-43.09%)        0.01 ( 15.42%)        0.01 ( 23.42%)        0.00 ( 89.78%)        0.01 ( -7.15%)        0.00 ( 76.69%)        0.02 (-91.77%)
Elapsed max           3.41 (  0.00%)        3.43 ( -0.52%)        3.03 ( 11.29%)        2.72 ( 20.16%)        2.67 ( 21.63%)        2.40 ( 29.50%)        2.21 ( 35.21%)        1.96 ( 42.39%)
Elapsed range         0.03 (  0.00%)        0.04 (-51.16%)        0.02 (  6.27%)        0.02 ( 14.67%)        0.00 ( 88.90%)        0.03 (-19.18%)        0.01 ( 73.70%)        0.06 (-113.35%

The second set of measurements simulates the worst possible conditions for
batching by using numactl --interleave, so that there is in fact only one
page per pagevec.  Even in this case the series seems to improve
performance thanks to reduced atomic operations and removal of
lru_add_drain().

timedmunlock
                            3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3
                                   0                     1                     2                     3                     4                     5                     6                     7
Elapsed min           4.00 (  0.00%)        4.04 ( -0.93%)        3.87 (  3.37%)        3.72 (  6.94%)        3.81 (  4.72%)        3.69 (  7.82%)        3.64 (  8.92%)        3.41 ( 14.81%)
Elapsed mean          4.17 (  0.00%)        4.15 (  0.51%)        4.03 (  3.49%)        3.89 (  6.84%)        3.86 (  7.48%)        3.89 (  6.69%)        3.70 ( 11.27%)        3.48 ( 16.59%)
Elapsed stddev        0.16 (  0.00%)        0.08 ( 50.76%)        0.10 ( 41.58%)        0.16 (  4.59%)        0.05 ( 72.38%)        0.19 (-12.91%)        0.05 ( 68.09%)        0.06 ( 66.03%)
Elapsed max           4.34 (  0.00%)        4.32 (  0.56%)        4.19 (  3.62%)        4.12 (  5.15%)        3.91 (  9.88%)        4.12 (  5.25%)        3.80 ( 12.58%)        3.56 ( 18.08%)
Elapsed range         0.34 (  0.00%)        0.28 ( 17.91%)        0.32 (  6.45%)        0.40 (-15.73%)        0.10 ( 70.06%)        0.43 (-24.84%)        0.15 ( 55.32%)        0.15 ( 56.16%)

For completeness, a third set of measurements shows the situation where
THP is enabled and allocations are again done on a single NUMA node.  Here
munlock() is already very fast thanks to huge pages, and this series does
not compromise that performance.  It seems that the removal of call to
lru_add_drain() still helps a bit.

timedmunlock
                            3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3              3.11-rc3
                                   0                     1                     2                     3                     4                     5                     6                     7
Elapsed min           0.01 (  0.00%)        0.01 ( -0.11%)        0.01 (  6.59%)        0.01 (  5.41%)        0.01 (  5.45%)        0.01 (  5.03%)        0.01 (  6.08%)        0.01 (  5.20%)
Elapsed mean          0.01 (  0.00%)        0.01 ( -0.27%)        0.01 (  6.39%)        0.01 (  5.30%)        0.01 (  5.32%)        0.01 (  5.03%)        0.01 (  5.97%)        0.01 (  5.22%)
Elapsed stddev        0.00 (  0.00%)        0.00 ( -9.59%)        0.00 ( 10.77%)        0.00 (  3.24%)        0.00 ( 24.42%)        0.00 ( 31.86%)        0.00 ( -7.46%)        0.00 (  6.11%)
Elapsed max           0.01 (  0.00%)        0.01 ( -0.01%)        0.01 (  6.83%)        0.01 (  5.42%)        0.01 (  5.79%)        0.01 (  5.53%)        0.01 (  6.08%)        0.01 (  5.26%)
Elapsed range         0.00 (  0.00%)        0.00 (  7.30%)        0.00 ( 24.38%)        0.00 (  6.10%)        0.00 ( 30.79%)        0.00 ( 42.52%)        0.00 (  6.11%)        0.00 ( 10.07%)

This patch (of 7):

In putback_lru_page() since commit c53954a0

 (""mm: remove lru parameter
from __lru_cache_add and lru_cache_add_lru") it is no longer needed to
determine lru list via page_lru_base_type().

This patch replaces it with simple flag is_unevictable which says that the
page was put on the inevictable list.  This is the only information that
matters in subsequent tests.

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Jörn Engel <joern@logfs.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michel Lespinasse <walken@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>