So that the hwpoison injector can get mem_cgroup for arbitrary page
and thus know whether it is owned by some mem_cgroup task(s).

[AK: Merged with latest git tree]

CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
CC: Hugh Dickins <hugh.dickins@tiscali.co.uk>
CC: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
CC: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

When specified, only poison pages if ((page_flags & mask) == value).

-       corrupt-filter-flags-mask
-       corrupt-filter-flags-value

This allows stress testing of many kinds of pages.

Strictly speaking, the buddy pages requires taking zone lock, to avoid
setting PG_hwpoison on a "was buddy but now allocated to someone" page.
However we can just do nothing because we set PG_locked in the beginning,
this prevents the page allocator from allocating it to someone. (It will
BUG() on the unexpected PG_locked, which is fine for hwpoison testing.)

[AK: Add select PROC_PAGE_MONITOR to satisfy dependency]

CC: Nick Piggin <npiggin@suse.de>
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

__memory_failure()'s workflow is

	set PG_hwpoison
	//...
	unset PG_hwpoison if didn't pass hwpoison filter

That could kill unrelated process if it happens to page fault on the
page with the (temporary) PG_hwpoison. The race should be big enough to
appear in stress tests.

Fix it by grabbing the page and checking filter at inject time.  This
also avoids the very noisy "Injecting memory failure..." messages.

- we don't touch madvise() based injection, because the filters are
  generally not necessary for it.
- if we want to apply the filters to h/w aided injection, we'd better to
  rearrange the logic in __memory_failure() instead of this patch.

AK: fix documentation, use drain all, cleanups

CC: Haicheng Li <haicheng.li@intel.com>
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

Filesystem data/metadata present the most tricky-to-isolate pages.
It requires careful code review and stress testing to get them right.

The fs/device filter helps to target the stress tests to some specific
filesystem pages. The filter condition is block device's major/minor
numbers:
        - corrupt-filter-dev-major
        - corrupt-filter-dev-minor
When specified (non -1), only page cache pages that belong to that
device will be poisoned.

The filters are checked reliably on the locked and refcounted page.

Haicheng: clear PG_hwpoison and drop bad page count if filter not OK
AK: Add documentation

CC: Haicheng Li <haicheng.li@intel.com>
CC: Nick Piggin <npiggin@suse.de>
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

Return 0 to indicate success, when
- action result is RECOVERED or DELAYED
- no extra page reference

Note that dirty swapcache pages are kept in swapcache, so can have one
more reference count.
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

Change semantics for
- IGNORED: not handled; it may well be _unsafe_
- DELAYED: to be handled later; it is _safe_

With this change,
- IGNORED/FAILED mean (maybe) Error
- DELAYED/RECOVERED mean Success
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

The unpoisoning interface is useful for stress testing tools to
reclaim poisoned pages (to prevent OOM)

There is no hardware level unpoisioning, so this
cannot be used for real memory errors, only for software injected errors.

Note that it may leak pages silently - those who have been removed from
LRU cache, but not isolated from page cache/swap cache at hwpoison time.
Especially the stress test of dirty swap cache pages shall reboot system
before exhausting memory.

AK: Fix comments, add documentation, add printks, rename symbol
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

Most free pages in the buddy system have no PG_buddy set.
Introduce is_free_buddy_page() for detecting them reliably.

CC: Nick Piggin <npiggin@suse.de>
CC: Mel Gorman <mel@linux.vnet.ibm.com>
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

The buddy page has already be handled in the very beginning.
So remove redundant code.
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

Introduce delete_from_lru_cache() to
- clear PG_active, PG_unevictable to avoid complains at unpoison time
- move the isolate_lru_page() call back to the handlers instead of the
  entrance of __memory_failure(), this is more hwpoison filter friendly
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

AK: Improve comment
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

Don't try to isolate a still mapped page. Otherwise we will hit the
BUG_ON(page_mapped(page)) in __remove_from_page_cache().
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

Now that "ref" is just a boolean turn it into
a flags argument. First step is only a single flag
that makes the code's intention more clear, but more
may follow.
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

If page is double referenced in madvise_hwpoison() and __memory_failure(),
remove_mapping() will fail because it expects page_count=2. Fix it by
not grabbing extra page count in __memory_failure().
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

Use a different errno than the usual EIO for invalid page numbers.
This is mainly for better reporting for the injector.

This also avoids calling action_result() with invalid pfn.
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

(PG_swapbacked && !PG_lru) pages should not happen.
Better to treat them as unknown pages.
Signed-off-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

shake_page handles more types of page caches than lru_drain_all()

- per cpu page allocator pages
- per CPU LRU

Stops early when the page became free.

Used in followon patches.
Signed-off-by: NAndi Kleen <ak@linux.intel.com>

The NOMMU code currently clears all anonymous mmapped memory.  While this
is what we want in the default case, all memory allocation from userspace
under NOMMU has to go through this interface, including malloc() which is
allowed to return uninitialized memory.  This can easily be a significant
performance penalty.  So for constrained embedded systems were security is
irrelevant, allow people to avoid clearing memory unnecessarily.

This also alters the ELF-FDPIC binfmt such that it obtains uninitialised
memory for the brk and stack region.
Signed-off-by: NJie Zhang <jie.zhang@analog.com>
Signed-off-by: NRobin Getz <rgetz@blackfin.uclinux.org>
Signed-off-by: NMike Frysinger <vapier@gentoo.org>
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Acked-by: NPaul Mundt <lethal@linux-sh.org>
Acked-by: NGreg Ungerer <gerg@snapgear.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This patch enables extraction of the pfn of a hugepage from
/proc/pid/pagemap in an architecture independent manner.

Details
-------
My test program (leak_pagemap) works as follows:
 - creat() and mmap() a file on hugetlbfs (file size is 200MB == 100 hugepages,)
 - read()/write() something on it,
 - call page-types with option -p,
 - munmap() and unlink() the file on hugetlbfs

Without my patches
------------------
$ ./leak_pagemap
             flags page-count       MB  symbolic-flags                     long-symbolic-flags
0x0000000000000000          1        0  __________________________________
0x0000000000000804          1        0  __R________M______________________ referenced,mmap
0x000000000000086c         81        0  __RU_lA____M______________________ referenced,uptodate,lru,active,mmap
0x0000000000005808          5        0  ___U_______Ma_b___________________ uptodate,mmap,anonymous,swapbacked
0x0000000000005868         12        0  ___U_lA____Ma_b___________________ uptodate,lru,active,mmap,anonymous,swapbacked
0x000000000000586c          1        0  __RU_lA____Ma_b___________________ referenced,uptodate,lru,active,mmap,anonymous,swapbacked
             total        101        0

The output of page-types don't show any hugepage.

With my patches
---------------
$ ./leak_pagemap
             flags page-count       MB  symbolic-flags                     long-symbolic-flags
0x0000000000000000          1        0  __________________________________
0x0000000000030000      51100      199  ________________TG________________ compound_tail,huge
0x0000000000028018        100        0  ___UD__________H_G________________ uptodate,dirty,compound_head,huge
0x0000000000000804          1        0  __R________M______________________ referenced,mmap
0x000000000000080c          1        0  __RU_______M______________________ referenced,uptodate,mmap
0x000000000000086c         80        0  __RU_lA____M______________________ referenced,uptodate,lru,active,mmap
0x0000000000005808          4        0  ___U_______Ma_b___________________ uptodate,mmap,anonymous,swapbacked
0x0000000000005868         12        0  ___U_lA____Ma_b___________________ uptodate,lru,active,mmap,anonymous,swapbacked
0x000000000000586c          1        0  __RU_lA____Ma_b___________________ referenced,uptodate,lru,active,mmap,anonymous,swapbacked
             total      51300      200

The output of page-types shows 51200 pages contributing to hugepages,
containing 100 head pages and 51100 tail pages as expected.

[akpm@linux-foundation.org: build fix]
Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Most callers of pmd_none_or_clear_bad() check whether the target page is
in a hugepage or not, but walk_page_range() do not check it.  So if we
read /proc/pid/pagemap for the hugepage on x86 machine, the hugepage
memory is leaked as shown below.  This patch fixes it.

Details
=======
My test program (leak_pagemap) works as follows:
 - creat() and mmap() a file on hugetlbfs (file size is 200MB == 100 hugepages,)
 - read()/write() something on it,
 - call page-types with option -p (walk around the page tables),
 - munmap() and unlink() the file on hugetlbfs

Without my patches
------------------
$ cat /proc/meminfo |grep "HugePage"
HugePages_Total:    1000
HugePages_Free:     1000
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ./leak_pagemap
[snip output]
$ cat /proc/meminfo |grep "HugePage"
HugePages_Total:    1000
HugePages_Free:      900
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ls /hugetlbfs/
$

100 hugepages are accounted as used while there is no file on hugetlbfs.

With my patches
---------------
$ cat /proc/meminfo |grep "HugePage"
HugePages_Total:    1000
HugePages_Free:     1000
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ./leak_pagemap
[snip output]
$ cat /proc/meminfo |grep "HugePage"
HugePages_Total:    1000
HugePages_Free:     1000
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ls /hugetlbfs
$

No memory leaks.
Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: David Rientjes <rientjes@google.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Most callers of pmd_none_or_clear_bad() check whether the target page is
in a hugepage or not, but mincore() and walk_page_range() do not check it.
 So if we use mincore() on a hugepage on x86 machine, the hugepage memory
is leaked as shown below.  This patch fixes it by extending mincore()
system call to support hugepages.

Details
=======
My test program (leak_mincore) works as follows:
 - creat() and mmap() a file on hugetlbfs (file size is 200MB == 100 hugepages,)
 - read()/write() something on it,
 - call mincore() for first ten pages and printf() the values of *vec
 - munmap() and unlink() the file on hugetlbfs

Without my patch
----------------
$ cat /proc/meminfo| grep "HugePage"
HugePages_Total:    1000
HugePages_Free:     1000
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ./leak_mincore
vec[0] 0
vec[1] 0
vec[2] 0
vec[3] 0
vec[4] 0
vec[5] 0
vec[6] 0
vec[7] 0
vec[8] 0
vec[9] 0
$ cat /proc/meminfo |grep "HugePage"
HugePages_Total:    1000
HugePages_Free:      999
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ls /hugetlbfs/
$

Return values in *vec from mincore() are set to 0, while the hugepage
should be in memory, and 1 hugepage is still accounted as used while
there is no file on hugetlbfs.

With my patch
-------------
$ cat /proc/meminfo| grep "HugePage"
HugePages_Total:    1000
HugePages_Free:     1000
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ./leak_mincore
vec[0] 1
vec[1] 1
vec[2] 1
vec[3] 1
vec[4] 1
vec[5] 1
vec[6] 1
vec[7] 1
vec[8] 1
vec[9] 1
$ cat /proc/meminfo |grep "HugePage"
HugePages_Total:    1000
HugePages_Free:     1000
HugePages_Rsvd:        0
HugePages_Surp:        0
$ ls /hugetlbfs/
$

Return value in *vec set to 1 and no memory leaks.

[akpm@linux-foundation.org: cleanup]
[akpm@linux-foundation.org: build fix]
Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: David Rientjes <rientjes@google.com>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If a user asks for a hugepage pool resize but specified a large number,
the machine can begin trashing.  In response, they might hit ctrl-c but
signals are ignored and the pool resize continues until it fails an
allocation.  This can take a considerable amount of time so this patch
aborts a pool resize if a signal is pending.

Suggested by Dave Hansen.
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Cleanup stale comments on munlock_vma_page().
Signed-off-by: NLee Schermerhorn <lee.schermerhorn@hp.com>
Acked-by: NHugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

unevictable_migrate_page() in mm/internal.h is a relic of the since
removed UNEVICTABLE_LRU Kconfig option.  This patch removes the function
and open codes the test in migrate_page_copy().
Signed-off-by: NLee Schermerhorn <lee.schermerhorn@hp.com>
Reviewed-by: NChristoph Lameter <cl@linux-foundation.org>
Acked-by: NHugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When the owner of a mapping fails COW because a child process is holding a
reference, the children VMAs are walked and the page is unmapped.  The
i_mmap_lock is taken for the unmapping of the page but not the walking of
the prio_tree.  In theory, that tree could be changing if the lock is not
held.  This patch takes the i_mmap_lock properly for the duration of the
prio_tree walk.

[hugh.dickins@tiscali.co.uk: Spotted the problem in the first place]
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Acked-by: NHugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Modify the generic mmap() code to keep the cache attribute in
vma->vm_page_prot regardless if writenotify is enabled or not.  Without
this patch the cache configuration selected by f_op->mmap() is overwritten
if writenotify is enabled, making it impossible to keep the vma uncached.

Needed by drivers such as drivers/video/sh_mobile_lcdcfb.c which uses
deferred io together with uncached memory.
Signed-off-by: NMagnus Damm <damm@opensource.se>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Jaya Kumar <jayakumar.lkml@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Simplify the code for shrink_inactive_list().
Signed-off-by: NHuang Shijie <shijie8@gmail.com>
Reviewed-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: NWu Fengguang <fengguang.wu@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

In AIM7 runs, recent kernels start swapping out anonymous pages well
before they should.  This is due to shrink_list falling through to
shrink_inactive_list if !inactive_anon_is_low(zone, sc), when all we
really wanted to do is pre-age some anonymous pages to give them extra
time to be referenced while on the inactive list.

The obvious fix is to make sure that shrink_list does not fall through to
scanning/reclaiming inactive pages when we called it to scan one of the
active lists.

This change should be safe because the loop in shrink_zone ensures that we
will still shrink the anon and file inactive lists whenever we should.

[kosaki.motohiro@jp.fujitsu.com: inactive_file_is_low() should be inactive_anon_is_low()]
Reported-by: NLarry Woodman <lwoodman@redhat.com>
Signed-off-by: NRik van Riel <riel@redhat.com>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Cc: Tomasz Chmielewski <mangoo@wpkg.org>
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NJan Beulich <jbeulich@novell.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

SWAP_MLOCK mean "We marked the page as PG_MLOCK, please move it to
unevictable-lru". So, following code is easy confusable.

        if (vma->vm_flags & VM_LOCKED) {
                ret = SWAP_MLOCK;
                goto out_unmap;
        }

Plus, if the VMA doesn't have VM_LOCKED, We don't need to check
the needed of calling mlock_vma_page().

Also, add some commentary to try_to_unmap_one().
Acked-by: NHugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

__free_pages_bootmem() is a __meminit function - which has been called
from put_pages_bootmem thus causes a section mismatch warning.

 We were warned by the following warning:

  LD      mm/built-in.o
WARNING: mm/built-in.o(.text+0x26b22): Section mismatch in reference
from the function put_page_bootmem() to the function
.meminit.text:__free_pages_bootmem()
The function put_page_bootmem() references
the function __meminit __free_pages_bootmem().
This is often because put_page_bootmem lacks a __meminit
annotation or the annotation of __free_pages_bootmem is wrong.
Signed-off-by: NRakib Mullick <rakib.mullick@gmail.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

hugetlb_fault() takes the mm->page_table_lock spinlock then calls
hugetlb_cow().  If the alloc_huge_page() in hugetlb_cow() fails due to an
insufficient huge page pool it calls unmap_ref_private() with the
mm->page_table_lock held.  unmap_ref_private() then calls
unmap_hugepage_range() which tries to acquire the mm->page_table_lock.

[<ffffffff810928c3>] print_circular_bug_tail+0x80/0x9f
 [<ffffffff8109280b>] ? check_noncircular+0xb0/0xe8
 [<ffffffff810935e0>] __lock_acquire+0x956/0xc0e
 [<ffffffff81093986>] lock_acquire+0xee/0x12e
 [<ffffffff8111a7a6>] ? unmap_hugepage_range+0x3e/0x84
 [<ffffffff8111a7a6>] ? unmap_hugepage_range+0x3e/0x84
 [<ffffffff814c348d>] _spin_lock+0x40/0x89
 [<ffffffff8111a7a6>] ? unmap_hugepage_range+0x3e/0x84
 [<ffffffff8111afee>] ? alloc_huge_page+0x218/0x318
 [<ffffffff8111a7a6>] unmap_hugepage_range+0x3e/0x84
 [<ffffffff8111b2d0>] hugetlb_cow+0x1e2/0x3f4
 [<ffffffff8111b935>] ? hugetlb_fault+0x453/0x4f6
 [<ffffffff8111b962>] hugetlb_fault+0x480/0x4f6
 [<ffffffff8111baee>] follow_hugetlb_page+0x116/0x2d9
 [<ffffffff814c31a7>] ? _spin_unlock_irq+0x3a/0x5c
 [<ffffffff81107b4d>] __get_user_pages+0x2a3/0x427
 [<ffffffff81107d0f>] get_user_pages+0x3e/0x54
 [<ffffffff81040b8b>] get_user_pages_fast+0x170/0x1b5
 [<ffffffff81160352>] dio_get_page+0x64/0x14a
 [<ffffffff8116112a>] __blockdev_direct_IO+0x4b7/0xb31
 [<ffffffff8115ef91>] blkdev_direct_IO+0x58/0x6e
 [<ffffffff8115e0a4>] ? blkdev_get_blocks+0x0/0xb8
 [<ffffffff810ed2c5>] generic_file_aio_read+0xdd/0x528
 [<ffffffff81219da3>] ? avc_has_perm+0x66/0x8c
 [<ffffffff81132842>] do_sync_read+0xf5/0x146
 [<ffffffff8107da00>] ? autoremove_wake_function+0x0/0x5a
 [<ffffffff81211857>] ? security_file_permission+0x24/0x3a
 [<ffffffff81132fd8>] vfs_read+0xb5/0x126
 [<ffffffff81133f6b>] ? fget_light+0x5e/0xf8
 [<ffffffff81133131>] sys_read+0x54/0x8c
 [<ffffffff81011e42>] system_call_fastpath+0x16/0x1b

This can be fixed by dropping the mm->page_table_lock around the call to
unmap_ref_private() if alloc_huge_page() fails, its dropped right below in
the normal path anyway.  However, earlier in the that function, it's also
possible to call into the page allocator with the same spinlock held.

What this patch does is drop the spinlock before the page allocator is
potentially entered.  The check for page allocation failure can be made
without the page_table_lock as well as the copy of the huge page.  Even if
the PTE changed while the spinlock was held, the consequence is that a
huge page is copied unnecessarily.  This resolves both the double taking
of the lock and sleeping with the spinlock held.

[mel@csn.ul.ie: Cover also the case where process can sleep with spinlock]
Signed-off-by: NLarry Woodman <lwooman@redhat.com>
Signed-off-by: NMel Gorman <mel@csn.ul.ie>
Acked-by: NAdam Litke <agl@us.ibm.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

It has no references outside memory_hotplug.c.

Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Yasunori Goto <y-goto@jp.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Now that ksm pages are swappable, and the known holes plugged, remove
mention of unswappable kernel pages from KSM documentation and comments.

Remove the totalram_pages/4 initialization of max_kernel_pages.  In fact,
remove max_kernel_pages altogether - we can reinstate it if removal turns
out to break someone's script; but if we later want to limit KSM's memory
usage, limiting the stable nodes would not be an effective approach.
Signed-off-by: NHugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Chris Wright <chrisw@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The previous patch enables page migration of ksm pages, but that soon gets
into trouble: not surprising, since we're using the ksm page lock to lock
operations on its stable_node, but page migration switches the page whose
lock is to be used for that.  Another layer of locking would fix it, but
do we need that yet?

Do we actually need page migration of ksm pages?  Yes, memory hotremove
needs to offline sections of memory: and since we stopped allocating ksm
pages with GFP_HIGHUSER, they will tend to be GFP_HIGHUSER_MOVABLE
candidates for migration.

But KSM is currently unconscious of NUMA issues, happily merging pages
from different NUMA nodes: at present the rule must be, not to use
MADV_MERGEABLE where you care about NUMA.  So no, NUMA page migration of
ksm pages does not make sense yet.

So, to complete support for ksm swapping we need to make hotremove safe.
ksm_memory_callback() take ksm_thread_mutex when MEM_GOING_OFFLINE and
release it when MEM_OFFLINE or MEM_CANCEL_OFFLINE.  But if mapped pages
are freed before migration reaches them, stable_nodes may be left still
pointing to struct pages which have been removed from the system: the
stable_node needs to identify a page by pfn rather than page pointer, then
it can safely prune them when MEM_OFFLINE.

And make NUMA migration skip PageKsm pages where it skips PageReserved.
But it's only when we reach unmap_and_move() that the page lock is taken
and we can be sure that raised pagecount has prevented a PageAnon from
being upgraded: so add offlining arg to migrate_pages(), to migrate ksm
page when offlining (has sufficient locking) but reject it otherwise.
Signed-off-by: NHugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Chris Wright <chrisw@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

A side-effect of making ksm pages swappable is that they have to be placed
on the LRUs: which then exposes them to isolate_lru_page() and hence to
page migration.

Add rmap_walk() for remove_migration_ptes() to use: rmap_walk_anon() and
rmap_walk_file() in rmap.c, but rmap_walk_ksm() in ksm.c.  Perhaps some
consolidation with existing code is possible, but don't attempt that yet
(try_to_unmap needs to handle nonlinears, but migration pte removal does
not).

rmap_walk() is sadly less general than it appears: rmap_walk_anon(), like
remove_anon_migration_ptes() which it replaces, avoids calling
page_lock_anon_vma(), because that includes a page_mapped() test which
fails when all migration ptes are in place.  That was valid when NUMA page
migration was introduced (holding mmap_sem provided the missing guarantee
that anon_vma's slab had not already been destroyed), but I believe not
valid in the memory hotremove case added since.

For now do the same as before, and consider the best way to fix that
unlikely race later on.  When fixed, we can probably use rmap_walk() on
hwpoisoned ksm pages too: for now, they remain among hwpoison's various
exceptions (its PageKsm test comes before the page is locked, but its
page_lock_anon_vma fails safely if an anon gets upgraded).
Signed-off-by: NHugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Chris Wright <chrisw@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

But ksm swapping does require one small change in mem cgroup handling.
When do_swap_page()'s call to ksm_might_need_to_copy() does indeed
substitute a duplicate page to accommodate a different anon_vma (or a the
!PageSwapCache check in mem_cgroup_try_charge_swapin().

That was returning success without charging, on the assumption that
pte_same() would fail after, which is not the case here.  Originally I
proposed that success, so that an unshrinkable mem cgroup at its limit
would not fail unnecessarily; but that's a minor point, and there are
plenty of other places where we may fail an overallocation which might
later prove unnecessary.  So just go ahead and do what all the other
exceptions do: proceed to charge current mm.
Signed-off-by: NHugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Chris Wright <chrisw@redhat.com>
Acked-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: NBalbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

When ksm pages were unswappable, it made no sense to include them in mem
cgroup accounting; but now that they are swappable (although I see no
strict logical connection) the principle of least surprise implies that
they should be accounted (with the usual dissatisfaction, that a shared
page is accounted to only one of the cgroups using it).

This patch was intended to add mem cgroup accounting where necessary; but
turned inside out, it now avoids allocating a ksm page, instead upgrading
an anon page to ksm - which brings its existing mem cgroup accounting with
it.  Thus mem cgroups don't appear in the patch at all.

This upgrade from PageAnon to PageKsm takes place under page lock (via a
somewhat hacky NULL kpage interface), and audit showed only one place
which needed to cope with the race - page_referenced() is sometimes used
without page lock, so page_lock_anon_vma() needs an ACCESS_ONCE() to be
sure of getting anon_vma and flags together (no problem if the page goes
ksm an instant after, the integrity of that anon_vma list is unaffected).
Signed-off-by: NHugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Chris Wright <chrisw@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

There's a lamentable flaw in KSM swapping: the stable_node holds a
reference to the ksm page, so the page to be freed cannot actually be
freed until ksmd works its way around to removing the last rmap_item from
its stable_node.  Which in some configurations may take minutes: not quite
responsive enough for memory reclaim.  And we don't want to twist KSM and
its locking more tightly into the rest of mm.  What a pity.

But although the stable_node needs to hold a pointer to the ksm page, does
it actually need to raise the reference count of that page?

No.  It would need to do so if struct pages were ordinary kmalloc'ed
objects; but they are more stable than that, and reused in particular ways
according to particular rules.

Access to stable_node from its pointer in struct page is no problem, so
long as we never free a stable_node before the ksm page itself has been
freed.  Access to struct page from its pointer in stable_node: reintroduce
get_ksm_page(), and let that peep out through its keyhole (the stable_node
pointer to ksm page), to see if that struct page still holds the right key
to open it (the ksm page mapping pointer back to this stable_node).

This relies upon the established way in which free_hot_cold_page() sets an
anon (including ksm) page->mapping to NULL; and relies upon no other user
of a struct page to put something which looks like the original
stable_node pointer (with two low bits also set) into page->mapping.  It
also needs get_page_unless_zero() technique pioneered by speculative
pagecache; and uses rcu_read_lock() to keep the guarantees that gives.

There are several drivers which put pointers of their own into page->
mapping; but none of those could coincide with our stable_node pointers,
since KSM won't free a stable_node until it sees that the page has gone.

The only problem case found is the pagetable spinlock USE_SPLIT_PTLOCKS
places in struct page (my own abuse): to accommodate GENERIC_LOCKBREAK's
break_lock on 32-bit, that spans both page->private and page->mapping.
Since break_lock is only 0 or 1, again no confusion for get_ksm_page().

But what of DEBUG_SPINLOCK on 64-bit bigendian?  When owner_cpu is 3
(matching PageKsm low bits), it might see 0xdead4ead00000003 in page->
mapping, which might coincide?  We could get around that by...  but a
better answer is to suppress USE_SPLIT_PTLOCKS when DEBUG_SPINLOCK or
DEBUG_LOCK_ALLOC, to stop bloating sizeof(struct page) in their case -
already proposed in an earlier mm/Kconfig patch.
Signed-off-by: NHugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Chris Wright <chrisw@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>