Pull VLA removal from Kees Cook:
 "Globally warn on VLA use.

  This turns on "-Wvla" globally now that the last few trees with their
  VLA removals have landed (crypto, block, net, and powerpc).

  Arnd mentioned that there may be a couple more VLAs hiding in
  hard-to-find randconfigs, but nothing big has shaken out in the last
  month or so in linux-next.

  We should be basically VLA-free now! Wheee. :)

  Summary:

   - Remove unused fallback for BUILD_BUG_ON (which technically contains
     a VLA)

   - Lift -Wvla to the top-level Makefile"

* tag 'vla-v4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  Makefile: Globally enable VLA warning
  compiler.h: give up __compiletime_assert_fallback()

Pull Kbuild updates from Masahiro Yamada:

 - optimize kallsyms slightly

 - remove check for old CFLAGS usage

 - add some compiler flags unconditionally instead of evaluating
   $(call cc-option,...)

 - fix variable shadowing in host tools

 - refactor scripts/mkmakefile

 - refactor various makefiles

* tag 'kbuild-v4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  modpost: Create macro to avoid variable shadowing
  ASN.1: Remove unnecessary shadowed local variable
  kbuild: use 'else ifeq' for checksrc to improve readability
  kbuild: remove unneeded link_multi_deps
  kbuild: add -Wno-unused-but-set-variable flag unconditionally
  kbuild: add -Wdeclaration-after-statement flag unconditionally
  kbuild: add -Wno-pointer-sign flag unconditionally
  modpost: remove leftover symbol prefix handling for module device table
  kbuild: simplify command line creation in scripts/mkmakefile
  kbuild: do not pass $(objtree) to scripts/mkmakefile
  kbuild: remove user ID check in scripts/mkmakefile
  kbuild: remove VERSION and PATCHLEVEL from $(objtree)/Makefile
  kbuild: add --include-dir flag only for out-of-tree build
  kbuild: remove dead code in cmd_files calculation in top Makefile
  kbuild: hide most of targets when running config or mixed targets
  kbuild: remove old check for CFLAGS use
  kbuild: prefix Makefile.dtbinst path with $(srctree) unconditionally
  kallsyms: remove left-over Blackfin code
  kallsyms: reduce size a little on 64-bit

Merge tag 'linux-kselftest-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest

Pull kselftest updates from Shuah Khan:
 "This Kselftest update for Linux 4.20-rc1 consists of:

   - Improvements to ftrace test suite from Masami Hiramatsu.

   - Color coded ftrace PASS / FAIL results from Steven Rostedt (VMware)
     to improve readability of reports.

   - watchdog Fixes and enhancement to add gettimeout and get|set
     pretimeout options from Jerry Hoemann.

   - Several fixes to warnings and spelling etc"

* tag 'linux-kselftest-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest: (40 commits)
  selftests/ftrace: Strip escape sequences for log file
  selftests/ftrace: Use colored output when available
  selftests: fix warning: "_GNU_SOURCE" redefined
  selftests: kvm: Fix -Wformat warnings
  selftests/ftrace: Add color to the PASS / FAIL results
  kvm: selftests: fix spelling mistake "Insufficent" -> "Insufficient"
  selftests: gpio: Fix OUTPUT directory in Makefile
  selftests: gpio: restructure Makefile
  selftests: watchdog: Fix ioctl SET* error paths to take oneshot exit path
  selftests: watchdog: Add gettimeout and get|set pretimeout
  selftests: watchdog: Fix error message.
  selftests: watchdog: fix message when /dev/watchdog open fails
  selftests/ftrace: Add ftrace cpumask testcase
  selftests/ftrace: Add wakeup_rt tracer testcase
  selftests/ftrace: Add wakeup tracer testcase
  selftests/ftrace: Add stacktrace ftrace filter command testcase
  selftests/ftrace: Add trace_pipe testcase
  selftests/ftrace: Add function filter on module testcase
  selftests/ftrace: Add max stack tracer testcase
  selftests/ftrace: Add function profiling stat testcase
  ...

Pull XArray conversion from Matthew Wilcox:
 "The XArray provides an improved interface to the radix tree data
  structure, providing locking as part of the API, specifying GFP flags
  at allocation time, eliminating preloading, less re-walking the tree,
  more efficient iterations and not exposing RCU-protected pointers to
  its users.

  This patch set

   1. Introduces the XArray implementation

   2. Converts the pagecache to use it

   3. Converts memremap to use it

  The page cache is the most complex and important user of the radix
  tree, so converting it was most important. Converting the memremap
  code removes the only other user of the multiorder code, which allows
  us to remove the radix tree code that supported it.

  I have 40+ followup patches to convert many other users of the radix
  tree over to the XArray, but I'd like to get this part in first. The
  other conversions haven't been in linux-next and aren't suitable for
  applying yet, but you can see them in the xarray-conv branch if you're
  interested"

* 'xarray' of git://git.infradead.org/users/willy/linux-dax: (90 commits)
  radix tree: Remove multiorder support
  radix tree test: Convert multiorder tests to XArray
  radix tree tests: Convert item_delete_rcu to XArray
  radix tree tests: Convert item_kill_tree to XArray
  radix tree tests: Move item_insert_order
  radix tree test suite: Remove multiorder benchmarking
  radix tree test suite: Remove __item_insert
  memremap: Convert to XArray
  xarray: Add range store functionality
  xarray: Move multiorder_check to in-kernel tests
  xarray: Move multiorder_shrink to kernel tests
  xarray: Move multiorder account test in-kernel
  radix tree test suite: Convert iteration test to XArray
  radix tree test suite: Convert tag_tagged_items to XArray
  radix tree: Remove radix_tree_clear_tags
  radix tree: Remove radix_tree_maybe_preload_order
  radix tree: Remove split/join code
  radix tree: Remove radix_tree_update_node_t
  page cache: Finish XArray conversion
  dax: Convert page fault handlers to XArray
  ...

Create DEF_FIELD_ADDR_VAR as a more generic version of the DEF_FIELD_ADD
macro, allowing usage of a variable name other than the struct element name.
Also, sets DEF_FIELD_ADDR as a specific usage of DEF_FILD_ADDR_VAR in which
the var name is the same as the struct element name.
Then, makes use of DEF_FIELD_ADDR_VAR to create a variable of another name,
in order to avoid variable shadowing.
Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Remove an unnecessary shadowed local variable (start).
It was used only once, with the same value it was started before
the if block.
Signed-off-by: Leonardo Bras <leobras.c@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

.. even when that "default y" is hidden syntactically as a

	default !EXPERT

it's wrong.

The only reason something should be 'default y' is if it used to be
built-in, and it was made configurable, and the 'default y' is just
retaining the status quo.

Altheratively, the hardware for the driver has become _so_ common that
it really makes sense for everybody to build it.  Finally, one possible
reason for 'default y' is because the option is not enabling any new
code at all, but is just enabling other options (the networking people
do this for vendor options, for example, so that you can disable whole
vendors at a time).

Clearly, none of these cases hold for the BigBen Interactive Kids'
gamepad, and HID_BIGBEN_FF should thus most definitely not default
to on for everybody.

Cc: Hanno Zulla <kontakt@hanno.de>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull watchdog updates from Wim Van Sebroeck:

 - Add Armada 37xx CPU watchdog

 - w83627hf_wdt: Add Support for NCT6796D, NCT6797D, NCT6798D

 - hpwdt: several improvements

 - renesas_wdt: SPDX identifiers, stop when unregistering, support for
   R7S9210

 - rza_wdt: SPDX identifiers, support longer timeouts

 - core: fix null pointer dereference when releasing cdev

 - iTCO_wdt: Drop option vendorsupport=2

 - sama5d4: fix timeout-sec usage

 - lantiq_wdt: convert to watchdog framework

 - several small fixes

* tag 'linux-watchdog-4.20-rc1' of git://www.linux-watchdog.org/linux-watchdog: (30 commits)
  watchdog: ts4800: release syscon device node in ts4800_wdt_probe()
  watchdog: armada_37xx_wdt: use do_div for u64 division
  documentation: watchdog: add documentation for armada-37xx-wdt
  dt-bindings: watchdog: Document armada-37xx-wdt binding
  watchdog: Add support for Armada 37xx CPU watchdog
  dt-bindings: watchdog: add mpc8xxx-wdt support
  watchdog: mpc8xxx: provide boot status
  MAINTAINERS: Fix file pattern for MEN Z069 watchdog driver
  dt-bindings: watchdog: renesas-wdt: Add support for R7S9210
  watchdog: rza_wdt: Support longer timeouts
  watchdog: hpwdt: Disable PreTimeout when Timeout is smaller
  watchdog: w83627hf_wdt: Support NCT6796D, NCT6797D, NCT6798D
  watchdog: mpc8xxx: use dev_xxxx() instead of pr_xxxx()
  watchdog: lantiq: add get_timeleft callback
  watchdog: lantiq: Convert to watchdog_device
  watchdog: lantiq: update register names to better match spec
  watchdog: sama5d4: fix timeout-sec usage
  watchdog: fix a small number of "watchog" typos in comments
  watchdog: rza_wdt: convert to SPDX identifiers
  watchdog: iTCO_wdt: Remove unused hooks
  ...

Pull input updates from Dmitry Torokhov:
 "Just random driver fixups, nothing exiting"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Input: synaptics - avoid using uninitialized variable when probing
  Input: xen-kbdfront - mark expected switch fall-through
  Input: atmel_mxt_ts - mark expected switch fall-through
  Input: cyapa - mark expected switch fall-throughs
  Input: wm97xx-ts - fix exit path
  Input: of_touchscreen - add support for touchscreen-min-x|y
  Input: Fix DIR-685 touchkeys MAINTAINERS entry
  Input: elants_i2c - use DMA safe i2c when possible
  Input: silead - try firmware reload after unsuccessful resume
  Input: st1232 - set INPUT_PROP_DIRECT property
  Input: xilinx_ps2 - convert to using %pOFn instead of device_node.name
  Input: atmel_mxt_ts - fix multiple <linux/property.h> includes
  Input: sun4i-lradc - convert to using %pOFn instead of device_node.name
  Input: pwm-vibrator - correct pwms in DT binding example

Pull RTC updates from Alexandre Belloni:
 "This cycle, there were mostly non urgent fixes in drivers. I also
  finally unexported the non managed registration.

  Subsystem:

   - non devm managed registration is now removed from the driver API

   - all the unnecessary rtc_valid_tm() calls have been removed

  Drivers:

   - abx80X: watchdog support

   - cmos: fix non ACPI support

   - sc27xx: fix alarm support

   - Remove a possible sysfs race condition for ab8500, ds1307, ds1685,
     isl1208

   - Fix a possible race condition where an irq handler may be called
     before the rtc_device struct is allocated for mt6397, pl030,
     menelaus, armada38x"

* tag 'rtc-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux: (54 commits)
  rtc: sc27xx: Always read normal alarm when registering RTC device
  rtc: sc27xx: Add check to see if need to enable the alarm interrupt
  rtc: sc27xx: Remove interrupts disable and clear in probe()
  rtc: sc27xx: Clear SPG value update interrupt status
  rtc: sc27xx: Set wakeup capability before registering rtc device
  rtc: s35390a: Change buf's type to u8 in s35390a_init
  rtc: ds1307: fix ds1339 wakealarm support
  rtc: ds1685: simplify getting .driver_data
  rtc: m41t80: mark expected switch fall-through
  rtc: tegra: Propagate errors from platform_get_irq()
  rtc: cmos: Remove the `use_acpi_alarm' module parameter for !ACPI
  rtc: cmos: Fix non-ACPI undefined reference to `hpet_rtc_interrupt'
  rtc: mv: let the core handle invalid alarms
  rtc: vr41xx: switch to rtc_time64_to_tm/rtc_tm_to_time64
  rtc: ab8500: remove useless check
  rtc: ab8500: let the core handle range
  rtc: ab8500: use rtc_add_group
  rtc: rs5c348: report error when time is invalid
  rtc: rs5c348: remove forward declaration
  rtc: rs5c348: remove useless label
  ...

Merge tag 'led-fix-for-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds

Pull LED fix from Jacek Anaszewski.

* tag 'led-fix-for-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds:
  leds: gpio: set led_dat->gpiod pointer for OF defined GPIO leds

Commit 9ee3e066 ("HID: i2c-hid: override HID descriptors for certain
devices") added a new dmi_system_id quirk table to override certain HID
report descriptors for some systems that lack them.

But the table wasn't properly terminated, causing the dmi matching to
walk off into la-la-land, and starting to treat random data as dmi
descriptor pointers, causing boot-time oopses if you were at all
unlucky.

Terminate the array.

We really should have some way to just statically check that arrays that
should be terminated by an empty entry actually are so.  But the HID
people really should have caught this themselves, rather than have me
deal with an oops during the merge window.  Tssk, tssk.

Cc: Julian Sax <jsbc@gmx.de>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Merge updates from Andrew Morton:

 - a few misc things

 - ocfs2 updates

 - most of MM

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (132 commits)
  hugetlbfs: dirty pages as they are added to pagecache
  mm: export add_swap_extent()
  mm: split SWP_FILE into SWP_ACTIVATED and SWP_FS
  tools/testing/selftests/vm/map_fixed_noreplace.c: add test for MAP_FIXED_NOREPLACE
  mm: thp: relocate flush_cache_range() in migrate_misplaced_transhuge_page()
  mm: thp: fix mmu_notifier in migrate_misplaced_transhuge_page()
  mm: thp: fix MADV_DONTNEED vs migrate_misplaced_transhuge_page race condition
  mm/kasan/quarantine.c: make quarantine_lock a raw_spinlock_t
  mm/gup: cache dev_pagemap while pinning pages
  Revert "x86/e820: put !E820_TYPE_RAM regions into memblock.reserved"
  mm: return zero_resv_unavail optimization
  mm: zero remaining unavailable struct pages
  tools/testing/selftests/vm/gup_benchmark.c: add MAP_HUGETLB option
  tools/testing/selftests/vm/gup_benchmark.c: add MAP_SHARED option
  tools/testing/selftests/vm/gup_benchmark.c: allow user specified file
  tools/testing/selftests/vm/gup_benchmark.c: fix 'write' flag usage
  mm/gup_benchmark.c: add additional pinning methods
  mm/gup_benchmark.c: time put_page()
  mm: don't raise MEMCG_OOM event due to failed high-order allocation
  mm/page-writeback.c: fix range_cyclic writeback vs writepages deadlock
  ...

Pull networking fixes from David Miller:
 "What better way to start off a weekend than with some networking bug
  fixes:

  1) net namespace leak in dump filtering code of ipv4 and ipv6, fixed
     by David Ahern and Bjørn Mork.

  2) Handle bad checksums from hardware when using CHECKSUM_COMPLETE
     properly in UDP, from Sean Tranchetti.

  3) Remove TCA_OPTIONS from policy validation, it turns out we don't
     consistently use nested attributes for this across all packet
     schedulers. From David Ahern.

  4) Fix SKB corruption in cadence driver, from Tristram Ha.

  5) Fix broken WoL handling in r8169 driver, from Heiner Kallweit.

  6) Fix OOPS in pneigh_dump_table(), from Eric Dumazet"

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (28 commits)
  net/neigh: fix NULL deref in pneigh_dump_table()
  net: allow traceroute with a specified interface in a vrf
  bridge: do not add port to router list when receives query with source 0.0.0.0
  net/smc: fix smc_buf_unuse to use the lgr pointer
  ipv6/ndisc: Preserve IPv6 control buffer if protocol error handlers are called
  net/{ipv4,ipv6}: Do not put target net if input nsid is invalid
  lan743x: Remove SPI dependency from Microchip group.
  drivers: net: remove <net/busy_poll.h> inclusion when not needed
  net: phy: genphy_10g_driver: Avoid NULL pointer dereference
  r8169: fix broken Wake-on-LAN from S5 (poweroff)
  octeontx2-af: Use GFP_ATOMIC under spin lock
  net: ethernet: cadence: fix socket buffer corruption problem
  net/ipv6: Allow onlink routes to have a device mismatch if it is the default route
  net: sched: Remove TCA_OPTIONS from policy
  ice: Poll for link status change
  ice: Allocate VF interrupts and set queue map
  ice: Introduce ice_dev_onetime_setup
  net: hns3: Fix for warning uninitialized symbol hw_err_lst3
  octeontx2-af: Copy the right amount of memory
  net: udp: fix handling of CHECKSUM_COMPLETE packets
  ...

Pull sparc fixes from David Miller:
 "Some more sparc fixups, mostly aimed at getting the allmodconfig build
  up and clean again"

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc:
  sparc64: Rework xchg() definition to avoid warnings.
  sparc64: Export __node_distance.
  sparc64: Make corrupted user stacks more debuggable.

Some test systems were experiencing negative huge page reserve counts and
incorrect file block counts.  This was traced to /proc/sys/vm/drop_caches
removing clean pages from hugetlbfs file pagecaches.  When non-hugetlbfs
explicit code removes the pages, the appropriate accounting is not
performed.

This can be recreated as follows:
 fallocate -l 2M /dev/hugepages/foo
 echo 1 > /proc/sys/vm/drop_caches
 fallocate -l 2M /dev/hugepages/foo
 grep -i huge /proc/meminfo
   AnonHugePages:         0 kB
   ShmemHugePages:        0 kB
   HugePages_Total:    2048
   HugePages_Free:     2047
   HugePages_Rsvd:    18446744073709551615
   HugePages_Surp:        0
   Hugepagesize:       2048 kB
   Hugetlb:         4194304 kB
 ls -lsh /dev/hugepages/foo
   4.0M -rw-r--r--. 1 root root 2.0M Oct 17 20:05 /dev/hugepages/foo

To address this issue, dirty pages as they are added to pagecache.  This
can easily be reproduced with fallocate as shown above.  Read faulted
pages will eventually end up being marked dirty.  But there is a window
where they are clean and could be impacted by code such as drop_caches.
So, just dirty them all as they are added to the pagecache.

Link: http://lkml.kernel.org/r/b5be45b8-5afe-56cd-9482-28384699a049@oracle.com
Fixes: 6bda666a ("hugepages: fold find_or_alloc_pages into huge_no_page()")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Acked-by: Mihcla Hocko <mhocko@suse.com>
Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Btrfs currently does not support swap files because swap's use of bmap
does not work with copy-on-write and multiple devices.  See 35054394
("Btrfs: stop providing a bmap operation to avoid swapfile corruptions").

However, the swap code has a mechanism for the filesystem to manually add
swap extents using add_swap_extent() from the ->swap_activate() aop.
iomap has done this since 67482129 ("iomap: add a swapfile activation
function").  Btrfs will do the same in a later patch, so export
add_swap_extent().

Link: http://lkml.kernel.org/r/bb1208575e02829aae51b538709476964f97b1ea.1536704650.git.osandov@fb.comSigned-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: David Sterba <dsterba@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The SWP_FILE flag serves two purposes: to make swap_{read,write}page() go
through the filesystem, and to make swapoff() call ->swap_deactivate().
For Btrfs, we want the latter but not the former, so split this flag into
two.  This makes us always call ->swap_deactivate() if ->swap_activate()
succeeded, not just if it didn't add any swap extents itself.

This also resolves the issue of the very misleading name of SWP_FILE,
which is only used for swap files over NFS.

Link: http://lkml.kernel.org/r/6d63d8668c4287a4f6d203d65696e96f80abdfc7.1536704650.git.osandov@fb.comSigned-off-by: Omar Sandoval <osandov@fb.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Sterba <dsterba@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Add a test for MAP_FIXED_NOREPLACE, based on some code originally by Jann
Horn.  This would have caught the overlap bug reported by Daniel Micay.

I originally suggested to Michal that we create MAP_FIXED_NOREPLACE, but
instead of writing a selftest I spent my time bike-shedding whether it
should be called MAP_FIXED_SAFE/NOCLOBBER/WEAK/NEW ..  mea culpa.

Link: http://lkml.kernel.org/r/20181013133929.28653-1-mpe@ellerman.id.auSigned-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Jann Horn <jannh@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Cc: Joel Stanley <joel@jms.id.au>
Cc: Jason Evans <jasone@google.com>
Cc: David Goldblatt <davidtgoldblatt@gmail.com>
Cc: Daniel Micay <danielmicay@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

There should be no cache left by the time we overwrite the old transhuge
pmd with the new one.  It's already too late to flush through the virtual
address because we already copied the page data to the new physical
address.

So flush the cache before the data copy.

Also delete the "end" variable to shutoff a "unused variable" warning on
x86 where flush_cache_range() is a noop.

Link: http://lkml.kernel.org/r/20181015202311.7209-1-aarcange@redhat.comSigned-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

change_huge_pmd() after arming the numa/protnone pmd doesn't flush the TLB
right away.  do_huge_pmd_numa_page() flushes the TLB before calling
migrate_misplaced_transhuge_page().  By the time do_huge_pmd_numa_page()
runs some CPU could still access the page through the TLB.

change_huge_pmd() before arming the numa/protnone transhuge pmd calls
mmu_notifier_invalidate_range_start().  So there's no need of
mmu_notifier_invalidate_range_start()/mmu_notifier_invalidate_range_only_end()
sequence in migrate_misplaced_transhuge_page() too, because by the time
migrate_misplaced_transhuge_page() runs, the pmd mapping has already been
invalidated in the secondary MMUs.  It has to or if a secondary MMU can
still write to the page, the migrate_page_copy() would lose data.

However an explicit mmu_notifier_invalidate_range() is needed before
migrate_misplaced_transhuge_page() starts copying the data of the
transhuge page or the below can happen for MMU notifier users sharing the
primary MMU pagetables and only implementing ->invalidate_range:

CPU0		CPU1		GPU sharing linux pagetables using
                                only ->invalidate_range
-----------	------------	---------
				GPU secondary MMU writes to the page
				mapped by the transhuge pmd
change_pmd_range()
mmu..._range_start()
->invalidate_range_start() noop
change_huge_pmd()
set_pmd_at(numa/protnone)
pmd_unlock()
		do_huge_pmd_numa_page()
		CPU TLB flush globally (1)
		CPU cannot write to page
		migrate_misplaced_transhuge_page()
				GPU writes to the page...
		migrate_page_copy()
				...GPU stops writing to the page
CPU TLB flush (2)
mmu..._range_end() (3)
->invalidate_range_stop() noop
->invalidate_range()
				GPU secondary MMU is invalidated
				and cannot write to the page anymore
				(too late)

Just like we need a CPU TLB flush (1) because the TLB flush (2) arrives
too late, we also need a mmu_notifier_invalidate_range() before calling
migrate_misplaced_transhuge_page(), because the ->invalidate_range() in
(3) also arrives too late.

This requirement is the result of the lazy optimization in
change_huge_pmd() that releases the pmd_lock without first flushing the
TLB and without first calling mmu_notifier_invalidate_range().

Even converting the removed mmu_notifier_invalidate_range_only_end() into
a mmu_notifier_invalidate_range_end() would not have been enough to fix
this, because it run after migrate_page_copy().

After the hugepage data copy is done migrate_misplaced_transhuge_page()
can proceed and call set_pmd_at without having to flush the TLB nor any
secondary MMUs because the secondary MMU invalidate, just like the CPU TLB
flush, has to happen before the migrate_page_copy() is called or it would
be a bug in the first place (and it was for drivers using
->invalidate_range()).

KVM is unaffected because it doesn't implement ->invalidate_range().

The standard PAGE_SIZEd migrate_misplaced_page is less accelerated and
uses the generic migrate_pages which transitions the pte from
numa/protnone to a migration entry in try_to_unmap_one() and flushes TLBs
and all mmu notifiers there before copying the page.

Link: http://lkml.kernel.org/r/20181013002430.698-3-aarcange@redhat.comSigned-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "migrate_misplaced_transhuge_page race conditions".

Aaron found a new instance of the THP MADV_DONTNEED race against
pmdp_clear_flush* variants, that was apparently left unfixed.

While looking into the race found by Aaron, I may have found two more
issues in migrate_misplaced_transhuge_page.

These race conditions would not cause kernel instability, but they'd
corrupt userland data or leave data non zero after MADV_DONTNEED.

I did only minor testing, and I don't expect to be able to reproduce this
(especially the lack of ->invalidate_range before migrate_page_copy,
requires the latest iommu hardware or infiniband to reproduce).  The last
patch is noop for x86 and it needs further review from maintainers of
archs that implement flush_cache_range() (not in CC yet).

To avoid confusion, it's not the first patch that introduces the bug fixed
in the second patch, even before removing the
pmdp_huge_clear_flush_notify, that _notify suffix was called after
migrate_page_copy already run.

This patch (of 3):

This is a corollary of ced10803 ("thp: fix MADV_DONTNEED vs.  numa
balancing race"), 58ceeb6b ("thp: fix MADV_DONTNEED vs.  MADV_FREE
race") and 5b7abeae ("thp: fix MADV_DONTNEED vs clear soft dirty
race).

When the above three fixes where posted Dave asked
https://lkml.kernel.org/r/929b3844-aec2-0111-fef7-8002f9d4e2b9@intel.com
but apparently this was missed.

The pmdp_clear_flush* in migrate_misplaced_transhuge_page() was introduced
in a54a407f ("mm: Close races between THP migration and PMD numa
clearing").

The important part of such commit is only the part where the page lock is
not released until the first do_huge_pmd_numa_page() finished disarming
the pagenuma/protnone.

The addition of pmdp_clear_flush() wasn't beneficial to such commit and
there's no commentary about such an addition either.

I guess the pmdp_clear_flush() in such commit was added just in case for
safety, but it ended up introducing the MADV_DONTNEED race condition found
by Aaron.

At that point in time nobody thought of such kind of MADV_DONTNEED race
conditions yet (they were fixed later) so the code may have looked more
robust by adding the pmdp_clear_flush().

This specific race condition won't destabilize the kernel, but it can
confuse userland because after MADV_DONTNEED the memory won't be zeroed
out.

This also optimizes the code and removes a superfluous TLB flush.

[akpm@linux-foundation.org: reflow comment to 80 cols, fix grammar and typo (beacuse)]
Link: http://lkml.kernel.org/r/20181013002430.698-2-aarcange@redhat.comSigned-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: Aaron Tomlin <atomlin@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The static lock quarantine_lock is used in quarantine.c to protect the
quarantine queue datastructures.  It is taken inside quarantine queue
manipulation routines (quarantine_put(), quarantine_reduce() and
quarantine_remove_cache()), with IRQs disabled.  This is not a problem on
a stock kernel but is problematic on an RT kernel where spin locks are
sleeping spinlocks, which can sleep and can not be acquired with disabled
interrupts.

Convert the quarantine_lock to a raw spinlock_t.  The usage of
quarantine_lock is confined to quarantine.c and the work performed while
the lock is held is used for debug purpose.

[bigeasy@linutronix.de: slightly altered the commit message]
Link: http://lkml.kernel.org/r/20181010214945.5owshc3mlrh74z4b@linutronix.deSigned-off-by: Clark Williams <williams@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Getting pages from ZONE_DEVICE memory needs to check the backing device's
live-ness, which is tracked in the device's dev_pagemap metadata.  This
metadata is stored in a radix tree and looking it up adds measurable
software overhead.

This patch avoids repeating this relatively costly operation when
dev_pagemap is used by caching the last dev_pagemap while getting user
pages.  The gup_benchmark kernel self test reports this reduces time to
get user pages to as low as 1/3 of the previous time.

Link: http://lkml.kernel.org/r/20181012173040.15669-1-keith.busch@intel.comSigned-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

commit 124049de ("x86/e820: put !E820_TYPE_RAM regions into
memblock.reserved") breaks movable_node kernel option because it changed
the memory gap range to reserved memblock.  So, the node is marked as
Normal zone even if the SRAT has Hot pluggable affinity.

    =====================================================================
    kernel: BIOS-e820: [mem 0x0000180000000000-0x0000180fffffffff] usable
    kernel: BIOS-e820: [mem 0x00001c0000000000-0x00001c0fffffffff] usable
    ...
    kernel: reserved[0x12]#011[0x0000181000000000-0x00001bffffffffff], 0x000003f000000000 bytes flags: 0x0
    ...
    kernel: ACPI: SRAT: Node 2 PXM 6 [mem 0x180000000000-0x1bffffffffff] hotplug
    kernel: ACPI: SRAT: Node 3 PXM 7 [mem 0x1c0000000000-0x1fffffffffff] hotplug
    ...
    kernel: Movable zone start for each node
    kernel:  Node 3: 0x00001c0000000000
    kernel: Early memory node ranges
    ...
    =====================================================================

The original issue is fixed by the former patches, so let's revert commit
124049de ("x86/e820: put !E820_TYPE_RAM regions into
memblock.reserved").

Link: http://lkml.kernel.org/r/20181002143821.5112-4-msys.mizuma@gmail.comSigned-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Oscar Salvador <osalvador@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

When checking for valid pfns in zero_resv_unavail(), it is not necessary
to verify that pfns within pageblock_nr_pages ranges are valid, only the
first one needs to be checked.  This is because memory for pages are
allocated in contiguous chunks that contain pageblock_nr_pages struct
pages.

Link: http://lkml.kernel.org/r/20181002143821.5112-3-msys.mizuma@gmail.comSigned-off-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Reviewed-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Acked-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "mm: Fix for movable_node boot option", v3.

This patch series contains a fix for the movable_node boot option issue
which was introduced by commit 124049de ("x86/e820: put !E820_TYPE_RAM
regions into memblock.reserved").

The commit breaks the option because it changed the memory gap range to
reserved memblock.  So, the node is marked as Normal zone even if the SRAT
has Hot pluggable affinity.

First and second patch fix the original issue which the commit tried to
fix, then revert the commit.

This patch (of 3):

There is a kernel panic that is triggered when reading /proc/kpageflags on
the kernel booted with kernel parameter 'memmap=nn[KMG]!ss[KMG]':

  BUG: unable to handle kernel paging request at fffffffffffffffe
  PGD 9b20e067 P4D 9b20e067 PUD 9b210067 PMD 0
  Oops: 0000 [#1] SMP PTI
  CPU: 2 PID: 1728 Comm: page-types Not tainted 4.17.0-rc6-mm1-v4.17-rc6-180605-0816-00236-g2dfb086ef02c+ #160
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.fc28 04/01/2014
  RIP: 0010:stable_page_flags+0x27/0x3c0
  Code: 00 00 00 0f 1f 44 00 00 48 85 ff 0f 84 a0 03 00 00 41 54 55 49 89 fc 53 48 8b 57 08 48 8b 2f 48 8d 42 ff 83 e2 01 48 0f 44 c7 <48> 8b 00 f6 c4 01 0f 84 10 03 00 00 31 db 49 8b 54 24 08 4c 89 e7
  RSP: 0018:ffffbbd44111fde0 EFLAGS: 00010202
  RAX: fffffffffffffffe RBX: 00007fffffffeff9 RCX: 0000000000000000
  RDX: 0000000000000001 RSI: 0000000000000202 RDI: ffffed1182fff5c0
  RBP: ffffffffffffffff R08: 0000000000000001 R09: 0000000000000001
  R10: ffffbbd44111fed8 R11: 0000000000000000 R12: ffffed1182fff5c0
  R13: 00000000000bffd7 R14: 0000000002fff5c0 R15: ffffbbd44111ff10
  FS:  00007efc4335a500(0000) GS:ffff93a5bfc00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: fffffffffffffffe CR3: 00000000b2a58000 CR4: 00000000001406e0
  Call Trace:
   kpageflags_read+0xc7/0x120
   proc_reg_read+0x3c/0x60
   __vfs_read+0x36/0x170
   vfs_read+0x89/0x130
   ksys_pread64+0x71/0x90
   do_syscall_64+0x5b/0x160
   entry_SYSCALL_64_after_hwframe+0x44/0xa9
  RIP: 0033:0x7efc42e75e23
  Code: 09 00 ba 9f 01 00 00 e8 ab 81 f4 ff 66 2e 0f 1f 84 00 00 00 00 00 90 83 3d 29 0a 2d 00 00 75 13 49 89 ca b8 11 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 34 c3 48 83 ec 08 e8 db d3 01 00 48 89 04 24

According to kernel bisection, this problem became visible due to commit
f7f99100 which changes how struct pages are initialized.

Memblock layout affects the pfn ranges covered by node/zone.  Consider
that we have a VM with 2 NUMA nodes and each node has 4GB memory, and the
default (no memmap= given) memblock layout is like below:

  MEMBLOCK configuration:
   memory size = 0x00000001fff75c00 reserved size = 0x000000000300c000
   memory.cnt  = 0x4
   memory[0x0]     [0x0000000000001000-0x000000000009efff], 0x000000000009e000 bytes on node 0 flags: 0x0
   memory[0x1]     [0x0000000000100000-0x00000000bffd6fff], 0x00000000bfed7000 bytes on node 0 flags: 0x0
   memory[0x2]     [0x0000000100000000-0x000000013fffffff], 0x0000000040000000 bytes on node 0 flags: 0x0
   memory[0x3]     [0x0000000140000000-0x000000023fffffff], 0x0000000100000000 bytes on node 1 flags: 0x0
   ...

If you give memmap=1G!4G (so it just covers memory[0x2]),
the range [0x100000000-0x13fffffff] is gone:

  MEMBLOCK configuration:
   memory size = 0x00000001bff75c00 reserved size = 0x000000000300c000
   memory.cnt  = 0x3
   memory[0x0]     [0x0000000000001000-0x000000000009efff], 0x000000000009e000 bytes on node 0 flags: 0x0
   memory[0x1]     [0x0000000000100000-0x00000000bffd6fff], 0x00000000bfed7000 bytes on node 0 flags: 0x0
   memory[0x2]     [0x0000000140000000-0x000000023fffffff], 0x0000000100000000 bytes on node 1 flags: 0x0
   ...

This causes shrinking node 0's pfn range because it is calculated by the
address range of memblock.memory.  So some of struct pages in the gap
range are left uninitialized.

We have a function zero_resv_unavail() which does zeroing the struct pages
outside memblock.memory, but currently it covers only the reserved
unavailable range (i.e.  memblock.memory && !memblock.reserved).  This
patch extends it to cover all unavailable range, which fixes the reported
issue.

Link: http://lkml.kernel.org/r/20181002143821.5112-2-msys.mizuma@gmail.com
Fixes: f7f99100 ("mm: stop zeroing memory during allocation in vmemmap")
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Tested-by: Oscar Salvador <osalvador@suse.de>
Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Reviewed-by: Pavel Tatashin <pavel.tatashin@microsoft.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Add a new option '-H' to the gup benchmark to help understand how hugetlb
mapping pages compare with the default.

Link: http://lkml.kernel.org/r/20181010195605.10689-6-keith.busch@intel.comSigned-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Add a new benchmark option, -S, to request MAP_SHARED.  This can be used
to compare with MAP_PRIVATE, or for files that require this option, like
dax.

Link: http://lkml.kernel.org/r/20181010195605.10689-5-keith.busch@intel.comSigned-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Allow a user to specify a file to map by adding a new option, '-f',
providing a means to test various file backings.

If not specified, the benchmark will use a private mapping of /dev/zero,
which produces an anonymous mapping as before.

[akpm@linux-foundation.org: avoid using comma operator]
Link: http://lkml.kernel.org/r/20181010195605.10689-4-keith.busch@intel.comSigned-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

If the '-w' parameter was provided, the benchmark would exit due to a
mssing 'break'.

Link: http://lkml.kernel.org/r/20181010195605.10689-3-keith.busch@intel.comSigned-off-by: Keith Busch <keith.busch@intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Provide new gup benchmark ioctl commands to run different user page
pinning methods, get_user_pages_longterm() and get_user_pages(), in
addition to the existing get_user_pages_fast().

Link: http://lkml.kernel.org/r/20181010195605.10689-2-keith.busch@intel.comSigned-off-by: Keith Busch <keith.busch@intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

We'd like to measure time to unpin user pages, so this adds a second
benchmark timer on put_page, separate from get_page.

Adding the field breaks this ioctl ABI, but should be okay since this an
in-tree kernel selftest.

[akpm@linux-foundation.org: add expansion to struct gup_benchmark for future use]
Link: http://lkml.kernel.org/r/20181010195605.10689-1-keith.busch@intel.comSigned-off-by: Keith Busch <keith.busch@intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

It was reported that on some of our machines containers were restarted
with OOM symptoms without an obvious reason.  Despite there were almost no
memory pressure and plenty of page cache, MEMCG_OOM event was raised
occasionally, causing the container management software to think, that OOM
has happened.  However, no tasks have been killed.

The following investigation showed that the problem is caused by a failing
attempt to charge a high-order page.  In such case, the OOM killer is
never invoked.  As shown below, it can happen under conditions, which are
very far from a real OOM: e.g.  there is plenty of clean page cache and no
memory pressure.

There is no sense in raising an OOM event in this case, as it might
confuse a user and lead to wrong and excessive actions (e.g.  restart the
workload, as in my case).

Let's look at the charging path in try_charge().  If the memory usage is
about memory.max, which is absolutely natural for most memory cgroups, we
try to reclaim some pages.  Even if we were able to reclaim enough memory
for the allocation, the following check can fail due to a race with
another concurrent allocation:

    if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
        goto retry;

For regular pages the following condition will save us from triggering
the OOM:

   if (nr_reclaimed && nr_pages <= (1 << PAGE_ALLOC_COSTLY_ORDER))
       goto retry;

But for high-order allocation this condition will intentionally fail.  The
reason behind is that we'll likely fall to regular pages anyway, so it's
ok and even preferred to return ENOMEM.

In this case the idea of raising MEMCG_OOM looks dubious.

Fix this by moving MEMCG_OOM raising to mem_cgroup_oom() after allocation
order check, so that the event won't be raised for high order allocations.
This change doesn't affect regular pages allocation and charging.

Link: http://lkml.kernel.org/r/20181004214050.7417-1-guro@fb.comSigned-off-by: Roman Gushchin <guro@fb.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

We've recently seen a workload on XFS filesystems with a repeatable
deadlock between background writeback and a multi-process application
doing concurrent writes and fsyncs to a small range of a file.

range_cyclic
writeback		Process 1		Process 2

xfs_vm_writepages
  write_cache_pages
    writeback_index = 2
    cycled = 0
    ....
    find page 2 dirty
    lock Page 2
    ->writepage
      page 2 writeback
      page 2 clean
      page 2 added to bio
    no more pages
			write()
			locks page 1
			dirties page 1
			locks page 2
			dirties page 1
			fsync()
			....
			xfs_vm_writepages
			write_cache_pages
			  start index 0
			  find page 1 towrite
			  lock Page 1
			  ->writepage
			    page 1 writeback
			    page 1 clean
			    page 1 added to bio
			  find page 2 towrite
			  lock Page 2
			  page 2 is writeback
			  <blocks>
						write()
						locks page 1
						dirties page 1
						fsync()
						....
						xfs_vm_writepages
						write_cache_pages
						  start index 0

    !done && !cycled
      sets index to 0, restarts lookup
    find page 1 dirty
						  find page 1 towrite
						  lock Page 1
						  page 1 is writeback
						  <blocks>

    lock Page 1
    <blocks>

DEADLOCK because:

	- process 1 needs page 2 writeback to complete to make
	  enough progress to issue IO pending for page 1
	- writeback needs page 1 writeback to complete so process 2
	  can progress and unlock the page it is blocked on, then it
	  can issue the IO pending for page 2
	- process 2 can't make progress until process 1 issues IO
	  for page 1

The underlying cause of the problem here is that range_cyclic writeback is
processing pages in descending index order as we hold higher index pages
in a structure controlled from above write_cache_pages().  The
write_cache_pages() caller needs to be able to submit these pages for IO
before write_cache_pages restarts writeback at mapping index 0 to avoid
wcp inverting the page lock/writeback wait order.

generic_writepages() is not susceptible to this bug as it has no private
context held across write_cache_pages() - filesystems using this
infrastructure always submit pages in ->writepage immediately and so there
is no problem with range_cyclic going back to mapping index 0.

However:
	mpage_writepages() has a private bio context,
	exofs_writepages() has page_collect
	fuse_writepages() has fuse_fill_wb_data
	nfs_writepages() has nfs_pageio_descriptor
	xfs_vm_writepages() has xfs_writepage_ctx

All of these ->writepages implementations can hold pages under writeback
in their private structures until write_cache_pages() returns, and hence
they are all susceptible to this deadlock.

Also worth noting is that ext4 has it's own bastardised version of
write_cache_pages() and so it /may/ have an equivalent deadlock.  I looked
at the code long enough to understand that it has a similar retry loop for
range_cyclic writeback reaching the end of the file and then promptly ran
away before my eyes bled too much.  I'll leave it for the ext4 developers
to determine if their code is actually has this deadlock and how to fix it
if it has.

There's a few ways I can see avoid this deadlock.  There's probably more,
but these are the first I've though of:

1. get rid of range_cyclic altogether

2. range_cyclic always stops at EOF, and we start again from
writeback index 0 on the next call into write_cache_pages()

2a. wcp also returns EAGAIN to ->writepages implementations to
indicate range cyclic has hit EOF. writepages implementations can
then flush the current context and call wpc again to continue. i.e.
lift the retry into the ->writepages implementation

3. range_cyclic uses trylock_page() rather than lock_page(), and it
skips pages it can't lock without blocking. It will already do this
for pages under writeback, so this seems like a no-brainer

3a. all non-WB_SYNC_ALL writeback uses trylock_page() to avoid
blocking as per pages under writeback.

I don't think #1 is an option - range_cyclic prevents frequently
dirtied lower file offset from starving background writeback of
rarely touched higher file offsets.

#2 is simple, and I don't think it will have any impact on
performance as going back to the start of the file implies an
immediate seek. We'll have exactly the same number of seeks if we
switch writeback to another inode, and then come back to this one
later and restart from index 0.

#2a is pretty much "status quo without the deadlock". Moving the
retry loop up into the wcp caller means we can issue IO on the
pending pages before calling wcp again, and so avoid locking or
waiting on pages in the wrong order. I'm not convinced we need to do
this given that we get the same thing from #2 on the next writeback
call from the writeback infrastructure.

#3 is really just a band-aid - it doesn't fix the access/wait
inversion problem, just prevents it from becoming a deadlock
situation. I'd prefer we fix the inversion, not sweep it under the
carpet like this.

#3a is really an optimisation that just so happens to include the
band-aid fix of #3.

So it seems that the simplest way to fix this issue is to implement
solution #2

Link: http://lkml.kernel.org/r/20181005054526.21507-1-david@fromorbit.comSigned-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Jan Kara <jack@suse.de>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

memmap_init_zone, is getting complex, because it is called from different
contexts: hotplug, and during boot, and also because it must handle some
architecture quirks.  One of them is mirrored memory.

Move the code that decides whether to skip mirrored memory outside of
memmap_init_zone, into a separate function.

[pasha.tatashin@oracle.com: uninline overlap_memmap_init()]
  Link: http://lkml.kernel.org/r/20180726193509.3326-4-pasha.tatashin@oracle.com
Link: http://lkml.kernel.org/r/20180724235520.10200-4-pasha.tatashin@oracle.comSigned-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Cc: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

update_defer_init() should be called only when struct page is about to be
initialized. Because it counts number of initialized struct pages, but
there we may skip struct pages if there is some mirrored memory.

So move, update_defer_init() after checking for mirrored memory.

Also, rename update_defer_init() to defer_init() and reverse the return
boolean to emphasize that this is a boolean function, that tells that the
reset of memmap initialization should be deferred.

Make this function self-contained: do not pass number of already
initialized pages in this zone by using static counters.

I found this bug by reading the code.  The effect is that fewer than
expected struct pages are initialized early in boot, and it is possible
that in some corner cases we may fail to boot when mirrored pages are
used.  The deferred on demand code should somewhat mitigate this.  But
this still brings some inconsistencies compared to when booting without
mirrored pages, so it is better to fix.

[pasha.tatashin@oracle.com: add comment about defer_init's lack of locking]
  Link: http://lkml.kernel.org/r/20180726193509.3326-3-pasha.tatashin@oracle.com
[akpm@linux-foundation.org: make defer_init non-inline, __meminit]
Link: http://lkml.kernel.org/r/20180724235520.10200-3-pasha.tatashin@oracle.comSigned-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

memmap_init is sometimes a macro sometimes a function based on
__HAVE_ARCH_MEMMAP_INIT.  It is only a function on ia64.  Make memmap_init
a weak function instead, and let ia64 redefine it.

Link: http://lkml.kernel.org/r/20180724235520.10200-2-pasha.tatashin@oracle.comSigned-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

This will allow to use generic refcount_t interfaces to check counters
overflow instead of currently existing VM_BUG_ON().  The only difference
after the patch is VM_BUG_ON() may cause BUG(), while refcount_t fires
with WARN().  But this seems not to be significant here, since such the
problems are usually caught by syzbot with panic-on-warn enabled.

Link: http://lkml.kernel.org/r/153910718919.7006.13400779039257185427.stgit@localhost.localdomainSigned-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

If move_freepages_block() returns 0 because !zone_spans_pfn(),
*num_movable can hold the value from the stack because it does not get
initialized in move_freepages().

Move the initialization to move_freepages_block() to guarantee the value
actually makes sense.

This currently doesn't affect its only caller where num_movable != NULL,
so no bug fix, but just more robust.

Link: http://lkml.kernel.org/r/alpine.DEB.2.21.1810051355490.212229@chino.kir.corp.google.comSigned-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>