linux.git/Documentation/sysctl/vm.txt, branch v4.6

Documentation/sysctl/vm.txt: update numa_zonelist_order description

2016-04-29T02:34:04+00:00

Commit 3193913ce62c ("mm: page_alloc: default node-ordering on 64-bit
NUMA, zone-ordering on 32-bit") changes the default value of
numa_zonelist_order.  Update the document.

Signed-off-by: Xishi Qiu 
Cc: Mel Gorman 
Cc: Johannes Weiner 
Cc: Rik van Riel 
Cc: David Rientjes 
Cc: Kamezawa Hiroyuki 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: scale kswapd watermarks in proportion to memory

2016-03-17T22:09:34+00:00

In machines with 140G of memory and enterprise flash storage, we have
seen read and write bursts routinely exceed the kswapd watermarks and
cause thundering herds in direct reclaim.  Unfortunately, the only way
to tune kswapd aggressiveness is through adjusting min_free_kbytes - the
system's emergency reserves - which is entirely unrelated to the
system's latency requirements.  In order to get kswapd to maintain a
250M buffer of free memory, the emergency reserves need to be set to 1G.
That is a lot of memory wasted for no good reason.

On the other hand, it's reasonable to assume that allocation bursts and
overall allocation concurrency scale with memory capacity, so it makes
sense to make kswapd aggressiveness a function of that as well.

Change the kswapd watermark scale factor from the currently fixed 25% of
the tunable emergency reserve to a tunable 0.1% of memory.

Beyond 1G of memory, this will produce bigger watermark steps than the
current formula in default settings.  Ensure that the new formula never
chooses steps smaller than that, i.e.  25% of the emergency reserve.

On a 140G machine, this raises the default watermark steps - the
distance between min and low, and low and high - from 16M to 143M.

Signed-off-by: Johannes Weiner 
Acked-by: Mel Gorman 
Acked-by: Rik van Riel 
Acked-by: David Rientjes 
Cc: Joonsoo Kim 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'akpm' (patches from Andrew)

2016-01-15T19:41:44+00:00

Merge first patch-bomb from Andrew Morton:

 - A few hotfixes which missed 4.4 becasue I was asleep.  cc'ed to
   -stable

 - A few misc fixes

 - OCFS2 updates

 - Part of MM.  Including pretty large changes to page-flags handling
   and to thp management which have been buffered up for 2-3 cycles now.

  I have a lot of MM material this time.

[ It turns out the THP part wasn't quite ready, so that got dropped from
  this series  - Linus ]

* emailed patches from Andrew Morton : (117 commits)
  zsmalloc: reorganize struct size_class to pack 4 bytes hole
  mm/zbud.c: use list_last_entry() instead of list_tail_entry()
  zram/zcomp: do not zero out zcomp private pages
  zram: pass gfp from zcomp frontend to backend
  zram: try vmalloc() after kmalloc()
  zram/zcomp: use GFP_NOIO to allocate streams
  mm: add tracepoint for scanning pages
  drivers/base/memory.c: fix kernel warning during memory hotplug on ppc64
  mm/page_isolation: use macro to judge the alignment
  mm: fix noisy sparse warning in LIBCFS_ALLOC_PRE()
  mm: rework virtual memory accounting
  include/linux/memblock.h: fix ordering of 'flags' argument in comments
  mm: move lru_to_page to mm_inline.h
  Documentation/filesystems: describe the shared memory usage/accounting
  memory-hotplug: don't BUG() in register_memory_resource()
  hugetlb: make mm and fs code explicitly non-modular
  mm/swapfile.c: use list_for_each_entry_safe in free_swap_count_continuations
  mm: /proc/pid/clear_refs: no need to clear VM_SOFTDIRTY in clear_soft_dirty_pmd()
  mm: make sure isolate_lru_page() is never called for tail page
  vmstat: make vmstat_updater deferrable again and shut down on idle
  ...

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial

2016-01-15T01:04:19+00:00

Pull trivial tree updates from Jiri Kosina.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial:
  floppy: make local variable non-static
  exynos: fixes an incorrect header guard
  dt-bindings: fixes some incorrect header guards
  cpufreq-dt: correct dead link in documentation
  cpufreq: ARM big LITTLE: correct dead link in documentation
  treewide: Fix typos in printk
  Documentation: filesystem: Fix typo in fs/eventfd.c
  fs/super.c: use && instead of & for warn_on condition
  Documentation: fix sysfs-ptp
  lib: scatterlist: fix Kconfig description

mm: mmap: add new /proc tunable for mmap_base ASLR

2016-01-15T00:00:49+00:00

Address Space Layout Randomization (ASLR) provides a barrier to
exploitation of user-space processes in the presence of security
vulnerabilities by making it more difficult to find desired code/data
which could help an attack.  This is done by adding a random offset to
the location of regions in the process address space, with a greater
range of potential offset values corresponding to better protection/a
larger search-space for brute force, but also to greater potential for
fragmentation.

The offset added to the mmap_base address, which provides the basis for
the majority of the mappings for a process, is set once on process exec
in arch_pick_mmap_layout() and is done via hard-coded per-arch values,
which reflect, hopefully, the best compromise for all systems.  The
trade-off between increased entropy in the offset value generation and
the corresponding increased variability in address space fragmentation
is not absolute, however, and some platforms may tolerate higher amounts
of entropy.  This patch introduces both new Kconfig values and a sysctl
interface which may be used to change the amount of entropy used for
offset generation on a system.

The direct motivation for this change was in response to the
libstagefright vulnerabilities that affected Android, specifically to
information provided by Google's project zero at:

  http://googleprojectzero.blogspot.com/2015/09/stagefrightened.html

The attack presented therein, by Google's project zero, specifically
targeted the limited randomness used to generate the offset added to the
mmap_base address in order to craft a brute-force-based attack.
Concretely, the attack was against the mediaserver process, which was
limited to respawning every 5 seconds, on an arm device.  The hard-coded
8 bits used resulted in an average expected success rate of defeating
the mmap ASLR after just over 10 minutes (128 tries at 5 seconds a
piece).  With this patch, and an accompanying increase in the entropy
value to 16 bits, the same attack would take an average expected time of
over 45 hours (32768 tries), which makes it both less feasible and more
likely to be noticed.

The introduced Kconfig and sysctl options are limited by per-arch
minimum and maximum values, the minimum of which was chosen to match the
current hard-coded value and the maximum of which was chosen so as to
give the greatest flexibility without generating an invalid mmap_base
address, generally a 3-4 bits less than the number of bits in the
user-space accessible virtual address space.

When decided whether or not to change the default value, a system
developer should consider that mmap_base address could be placed
anywhere up to 2^(value) bits away from the non-randomized location,
which would introduce variable-sized areas above and below the mmap_base
address such that the maximum vm_area_struct size may be reduced,
preventing very large allocations.

This patch (of 4):

ASLR only uses as few as 8 bits to generate the random offset for the
mmap base address on 32 bit architectures.  This value was chosen to
prevent a poorly chosen value from dividing the address space in such a
way as to prevent large allocations.  This may not be an issue on all
platforms.  Allow the specification of a minimum number of bits so that
platforms desiring greater ASLR protection may determine where to place
the trade-off.

Signed-off-by: Daniel Cashman 
Cc: Russell King 
Acked-by: Kees Cook 
Cc: Ingo Molnar 
Cc: Jonathan Corbet 
Cc: Don Zickus 
Cc: Eric W. Biederman 
Cc: Heinrich Schuchardt 
Cc: Josh Poimboeuf 
Cc: Kirill A. Shutemov 
Cc: Naoya Horiguchi 
Cc: Andrea Arcangeli 
Cc: Mel Gorman 
Cc: Thomas Gleixner 
Cc: David Rientjes 
Cc: Mark Salyzyn 
Cc: Jeff Vander Stoep 
Cc: Nick Kralevich 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: "H. Peter Anvin" 
Cc: Hector Marco-Gisbert 
Cc: Borislav Petkov 
Cc: Ralf Baechle 
Cc: Heiko Carstens 
Cc: Martin Schwidefsky 
Cc: Benjamin Herrenschmidt 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Documentation: fix sysfs-ptp

2015-12-08T13:50:12+00:00

s/avaiable/available/g

This fixup is already in scripts/spelling.txt.

The fix in Documentation/ABI/testing/sysfs-ptp affects documentation of
a /sys entry: the /sys entry itself is correct.

Signed-off-by: Chris Dunlop 
Signed-off-by: Jiri Kosina

Documentation/sysctl/vm.txt: fix misleading code reference of overcommit_memory

2015-11-09T23:11:24+00:00

The origin document references to cap_vm_enough_memory is because
cap_vm_enough_memory invoked __vm_enough_memory before and it no longer
does now.

Signed-off-by: Chun Chen 
Acked-by: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/page_alloc.c: fix a misleading comment

2015-09-08T22:35:28+00:00

The comment says that the per-cpu batchsize and zone watermarks are
determined by present_pages which is definitely wrong, they are both
calculated from managed_pages.  Fix it.

Signed-off-by: Yaowei Bai 
Acked-by: Michal Hocko 
Cc: David Rientjes 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Documentation: mm: fix location of extfrag_index

2015-07-24T13:05:56+00:00

/proc/extfrag_index does not exist.  This file is in debugfs.  Fix the
description of extfrag_threshold to reflect this.

Signed-off-by: Rabin Vincent 
Signed-off-by: Jonathan Corbet

mm: allow compaction of unevictable pages

2015-04-15T23:35:17+00:00

Currently, pages which are marked as unevictable are protected from
compaction, but not from other types of migration.  The POSIX real time
extension explicitly states that mlock() will prevent a major page
fault, but the spirit of this is that mlock() should give a process the
ability to control sources of latency, including minor page faults.
However, the mlock manpage only explicitly says that a locked page will
not be written to swap and this can cause some confusion.  The
compaction code today does not give a developer who wants to avoid swap
but wants to have large contiguous areas available any method to achieve
this state.  This patch introduces a sysctl for controlling compaction
behavior with respect to the unevictable lru.  Users who demand no page
faults after a page is present can set compact_unevictable_allowed to 0
and users who need the large contiguous areas can enable compaction on
locked memory by leaving the default value of 1.

To illustrate this problem I wrote a quick test program that mmaps a
large number of 1MB files filled with random data.  These maps are
created locked and read only.  Then every other mmap is unmapped and I
attempt to allocate huge pages to the static huge page pool.  When the
compact_unevictable_allowed sysctl is 0, I cannot allocate hugepages
after fragmenting memory.  When the value is set to 1, allocations
succeed.

Signed-off-by: Eric B Munson 
Acked-by: Michal Hocko 
Acked-by: Vlastimil Babka 
Acked-by: Christoph Lameter 
Acked-by: David Rientjes 
Acked-by: Rik van Riel 
Cc: Vlastimil Babka 
Cc: Thomas Gleixner 
Cc: Christoph Lameter 
Cc: Peter Zijlstra 
Cc: Mel Gorman 
Cc: David Rientjes 
Cc: Michal Hocko 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds