In preparation for adding coordination between extent unmap operations
and busy dax-pages, update xfs_break_layouts() to permit it to be called
with the mmap lock held. This lock scheme will be required for
coordinating the break of 'dax layouts' (non-idle dax (ZONE_DEVICE)
pages mapped into the file's address space). Breaking dax layouts will
be added to xfs_break_layouts() in a future patch, for now this preps
the unmap call sites to take and hold XFS_MMAPLOCK_EXCL over the call to
xfs_break_layouts().

Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Suggested-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: N"Darrick J. Wong" <darrick.wong@oracle.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

Background:

get_user_pages() in the filesystem pins file backed memory pages for
access by devices performing dma. However, it only pins the memory pages
not the page-to-file offset association. If a file is truncated the
pages are mapped out of the file and dma may continue indefinitely into
a page that is owned by a device driver. This breaks coherency of the
file vs dma, but the assumption is that if userspace wants the
file-space truncated it does not matter what data is inbound from the
device, it is not relevant anymore. The only expectation is that dma can
safely continue while the filesystem reallocates the block(s).

Problem:

This expectation that dma can safely continue while the filesystem
changes the block map is broken by dax. With dax the target dma page
*is* the filesystem block. The model of leaving the page pinned for dma,
but truncating the file block out of the file, means that the filesytem
is free to reallocate a block under active dma to another file and now
the expected data-incoherency situation has turned into active
data-corruption.

Solution:

Defer all filesystem operations (fallocate(), truncate()) on a dax mode
file while any page/block in the file is under active dma. This solution
assumes that dma is transient. Cases where dma operations are known to
not be transient, like RDMA, have been explicitly disabled via
commits like 5f1d43de "IB/core: disable memory registration of
filesystem-dax vmas".

The dax_layout_busy_page() routine is called by filesystems with a lock
held against mm faults (i_mmap_lock) to find pinned / busy dax pages.
The process of looking up a busy page invalidates all mappings
to trigger any subsequent get_user_pages() to block on i_mmap_lock.
The filesystem continues to call dax_layout_busy_page() until it finally
returns no more active pages. This approach assumes that the page
pinning is transient, if that assumption is violated the system would
have likely hung from the uncompleted I/O.

Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Reported-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

get_user_pages_fast() for device pages is missing the typical validation
that all page references have been taken while the mapping was valid.
Without this validation truncate operations can not reliably coordinate
against new page reference events like O_DIRECT.

Cc: <stable@vger.kernel.org>
Fixes: 3565fce3 ("mm, x86: get_user_pages() for dax mappings")
Reported-by: NJan Kara <jack@suse.cz>
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

In preparation for fixing dax-dma-vs-unmap issues, filesystems need to
be able to rely on the fact that they will get wakeups on dev_pagemap
page-idle events. Introduce MEMORY_DEVICE_FS_DAX and
generic_dax_page_free() as common indicator / infrastructure for dax
filesytems to require. With this change there are no users of the
MEMORY_DEVICE_HOST designation, so remove it.

The HMM sub-system extended dev_pagemap to arrange a callback when a
dev_pagemap managed page is freed. Since a dev_pagemap page is free /
idle when its reference count is 1 it requires an additional branch to
check the page-type at put_page() time. Given put_page() is a hot-path
we do not want to incur that check if HMM is not in use, so a static
branch is used to avoid that overhead when not necessary.

Now, the FS_DAX implementation wants to reuse this mechanism for
receiving dev_pagemap ->page_free() callbacks. Rework the HMM-specific
static-key into a generic mechanism that either HMM or FS_DAX code paths
can enable.

For ARCH=um builds, and any other arch that lacks ZONE_DEVICE support,
care must be taken to compile out the DEV_PAGEMAP_OPS infrastructure.
However, we still need to support FS_DAX in the FS_DAX_LIMITED case
implemented by the s390/dcssblk driver.

Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Michal Hocko <mhocko@suse.com>
Reported-by: Nkbuild test robot <lkp@intel.com>
Reported-by: NThomas Meyer <thomas@m3y3r.de>
Reported-by: NDave Jiang <dave.jiang@intel.com>
Cc: "Jérôme Glisse" <jglisse@redhat.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

Currently, kernel/memremap.c contains generic code for supporting
memremap() (CONFIG_HAS_IOMEM) and devm_memremap_pages()
(CONFIG_ZONE_DEVICE). This causes ongoing build maintenance problems as
additions to memremap.c, especially for the ZONE_DEVICE case, need to be
careful about being placed in ifdef guards. Remove the need for these
ifdef guards by moving the ZONE_DEVICE support functions to their own
compilation unit.

Cc: "Jérôme Glisse" <jglisse@redhat.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJan Kara <jack@suse.cz>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>

Pull drm fixes from Dave Airlie:
 "Exynos, i915, vc4, amdgpu fixes.

  i915:
   - an oops fix
   - two race fixes
   - some gvt fixes

  amdgpu:
   - dark screen fix
   - clk/voltage fix
   - vega12 smu fix

  vc4:
   - memory leak fix

  exynos just drops some code"

* tag 'drm-fixes-for-v4.17-rc2' of git://people.freedesktop.org/~airlied/linux: (23 commits)
  drm/amd/powerplay: header file interface to SMU update
  drm/amd/pp: Fix bug voltage can't be OD separately on VI
  drm/amd/display: Don't program bypass on linear regamma LUT
  drm/i915: Fix LSPCON TMDS output buffer enabling from low-power state
  drm/i915/audio: Fix audio detection issue on GLK
  drm/i915: Call i915_perf_fini() on init_hw error unwind
  drm/i915/bios: filter out invalid DDC pins from VBT child devices
  drm/i915/pmu: Inspect runtime PM state more carefully while estimating RC6
  drm/i915: Do no use kfree() to free a kmem_cache_alloc() return value
  drm/exynos: exynos_drm_fb -> drm_framebuffer
  drm/exynos: Move dma_addr out of exynos_drm_fb
  drm/exynos: Move GEM BOs to drm_framebuffer
  drm: Fix HDCP downstream dev count read
  drm/vc4: Fix memory leak during BO teardown
  drm/i915/execlists: Clear user-active flag on preemption completion
  drm/i915/gvt: Add drm_format_mod update
  drm/i915/gvt: Disable primary/sprite/cursor plane at virtual display initialization
  drm/i915/gvt: Delete redundant error message in fb_decode.c
  drm/i915/gvt: Cancel dma map when resetting ggtt entries
  drm/i915/gvt: Missed to cancel dma map for ggtt entries
  ...

- Fix a dark screen issue in DC
- Fix clk/voltage dependency tracking for wattman
- Update SMU interface for vega12

* 'drm-next-4.17' of git://people.freedesktop.org/~agd5f/linux:
  drm/amd/powerplay: header file interface to SMU update
  drm/amd/pp: Fix bug voltage can't be OD separately on VI
  drm/amd/display: Don't program bypass on linear regamma LUT

Merge tag 'exynos-drm-fixes-for-v4.17-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos into drm-next

Remove Exynos specific framebuffer structure and
relevant functions.
- it removes exynos_drm_fb structure which is a wrapper of
  drm_framebuffer and unnecessary two exynos specific callback
  functions, exynos_drm_destory() and exynos_drm_fb_create_handle()
  because we can reuse existing drm common callback ones instead.

* tag 'exynos-drm-fixes-for-v4.17-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos:
  drm/exynos: exynos_drm_fb -> drm_framebuffer
  drm/exynos: Move dma_addr out of exynos_drm_fb
  drm/exynos: Move GEM BOs to drm_framebuffer
  drm/amdkfd: Deallocate SDMA queues correctly
  drm/amdkfd: Fix scratch memory with HWS enabled

Merge tag 'drm-intel-next-fixes-2018-04-19' of git://anongit.freedesktop.org/drm/drm-intel into drm-next

- Fix for FDO #105549: Avoid OOPS on bad VBT (Jani)
- Fix rare pre-emption race (Chris)
- Fix RC6 race against PM transitions (Tvrtko)

* tag 'drm-intel-next-fixes-2018-04-19' of git://anongit.freedesktop.org/drm/drm-intel:
  drm/i915/audio: Fix audio detection issue on GLK
  drm/i915: Call i915_perf_fini() on init_hw error unwind
  drm/i915/bios: filter out invalid DDC pins from VBT child devices
  drm/i915/pmu: Inspect runtime PM state more carefully while estimating RC6
  drm/i915: Do no use kfree() to free a kmem_cache_alloc() return value
  drm/i915/execlists: Clear user-active flag on preemption completion
  drm/i915/gvt: Add drm_format_mod update
  drm/i915/gvt: Disable primary/sprite/cursor plane at virtual display initialization
  drm/i915/gvt: Delete redundant error message in fb_decode.c
  drm/i915/gvt: Cancel dma map when resetting ggtt entries
  drm/i915/gvt: Missed to cancel dma map for ggtt entries
  drm/i915/gvt: Make MI_USER_INTERRUPT nop in cmd parser
  drm/i915/gvt: Mark expected switch fall-through in handle_g2v_notification
  drm/i915/gvt: throw error on unhandled vfio ioctls

drm-misc-fixes:

stable: vc4: Fix memory leak during BO teardown (Daniel)
dp: Add i2c retry for LSPCON adapters (Imre)
hdcp: Fix device count mask (Ramalingam)

Cc: Daniel J Blueman <daniel@quora.org
Cc: Imre Deak <imre.deak@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>

* tag 'drm-misc-fixes-2018-04-18-1' of git://anongit.freedesktop.org/drm/drm-misc:
  drm/i915: Fix LSPCON TMDS output buffer enabling from low-power state
  drm: Fix HDCP downstream dev count read
  drm/vc4: Fix memory leak during BO teardown

Pull cifs fixes from Steve French:
 "Various SMB3/CIFS fixes.

  There are three more security related fixes in progress that are not
  included in this set but they are still being tested and reviewed, so
  sending this unrelated set of smaller fixes now"

* tag '4.17-rc1-SMB3-CIFS' of git://git.samba.org/sfrench/cifs-2.6:
  CIFS: fix typo in cifs_dbg
  cifs: do not allow creating sockets except with SMB1 posix exensions
  cifs: smbd: Dump SMB packet when configured
  cifs: smbd: Check for iov length on sending the last iov
  fs: cifs: Adding new return type vm_fault_t
  cifs: smb2ops: Fix NULL check in smb2_query_symlink

Pull btrfs fixes from David Sterba:
 "This contains a few fixups to the qgroup patches that were merged this
  dev cycle, unaligned access fix, blockgroup removal corner case fix
  and a small debugging output tweak"

* tag 'for-4.17-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: print-tree: debugging output enhancement
  btrfs: Fix race condition between delayed refs and blockgroup removal
  btrfs: fix unaligned access in readdir
  btrfs: Fix wrong btrfs_delalloc_release_extents parameter
  btrfs: delayed-inode: Remove wrong qgroup meta reservation calls
  btrfs: qgroup: Use independent and accurate per inode qgroup rsv
  btrfs: qgroup: Commit transaction in advance to reduce early EDQUOT

Pull x86 fixes from Thomas Gleixner:
 "A small set of fixes for x86:

   - Prevent X2APIC ID 0xFFFFFFFF from being treated as valid, which
     causes the possible CPU count to be wrong.

   - Prevent 32bit truncation in calc_hpet_ref() which causes the TSC
     calibration to fail

   - Fix the page table setup for temporary text mappings in the resume
     code which causes resume failures

   - Make the page table dump code handle HIGHPTE correctly instead of
     oopsing

   - Support for topologies where NUMA nodes share an LLC to prevent a
     invalid topology warning and further malfunction on such systems.

   - Remove the now unused pci-nommu code

   - Remove stale function declarations"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/power/64: Fix page-table setup for temporary text mapping
  x86/mm: Prevent kernel Oops in PTDUMP code with HIGHPTE=y
  x86,sched: Allow topologies where NUMA nodes share an LLC
  x86/processor: Remove two unused function declarations
  x86/acpi: Prevent X2APIC id 0xffffffff from being accounted
  x86/tsc: Prevent 32bit truncation in calc_hpet_ref()
  x86: Remove pci-nommu.c

Pull timer fixes from Thomas Gleixner:
 "A small set of timer fixes:

   - Evaluate the -ETIME condition correctly in the imx tpm driver

   - Fix the evaluation order of a condition in posix cpu timers

   - Use pr_cont() in the clockevents code to prevent ugly message
     splitting

   - Remove __current_kernel_time() which is now unused to prevent that
     new users show up.

   - Remove a stale forward declaration"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  clocksource/imx-tpm: Correct -ETIME return condition check
  posix-cpu-timers: Ensure set_process_cpu_timer is always evaluated
  timekeeping: Remove __current_kernel_time()
  timers: Remove stale struct tvec_base forward declaration
  clockevents: Fix kernel messages split across multiple lines

Pull perf fixes from Thomas Gleixner:
 "A larger set of updates for perf.

  Kernel:

   - Handle the SBOX uncore monitoring correctly on Broadwell CPUs which
     do not have SBOX.

   - Store context switch out type in PERF_RECORD_SWITCH[_CPU_WIDE]. The
     percentage of preempting and non-preempting context switches help
     understanding the nature of workloads (CPU or IO bound) that are
     running on a machine. This adds the kernel facility and userspace
     changes needed to show this information in 'perf script' and 'perf
     report -D' (Alexey Budankov)

   - Remove a WARN_ON() in the trace/kprobes code which is pointless
     because the return error code is already telling the caller what's
     wrong.

   - Revert a fugly workaround for clang BPF targets.

   - Fix sample_max_stack maximum check and do not proceed when an error
     has been detect, return them to avoid misidentifying errors (Jiri
     Olsa)

   - Add SPDX idenitifiers and get rid of GPL boilderplate.

  Tools:

   - Synchronize kernel ABI headers, v4.17-rc1 (Ingo Molnar)

   - Support MAP_FIXED_NOREPLACE, noticed when updating the
     tools/include/ copies (Arnaldo Carvalho de Melo)

   - Add '\n' at the end of parse-options error messages (Ravi Bangoria)

   - Add s390 support for detailed/verbose PMU event description (Thomas
     Richter)

   - perf annotate fixes and improvements:

      * Allow showing offsets in more than just jump targets, use the
        new 'O' hotkey in the TUI, config ~/.perfconfig
        annotate.offset_level for it and for --stdio2 (Arnaldo Carvalho
        de Melo)

      * Use the resolved variable names from objdump disassembled lines
        to make them more compact, just like was already done for some
        instructions, like "mov", this eventually will be done more
        generally, but lets now add some more to the existing mechanism
        (Arnaldo Carvalho de Melo)

   - perf record fixes:

      * Change warning for missing topology sysfs entry to debug, as not
        all architectures have those files, s390 being one of those
        (Thomas Richter)

      * Remove old error messages about things that unlikely to be the
        root cause in modern systems (Andi Kleen)

   - perf sched fixes:

      * Fix -g/--call-graph documentation (Takuya Yamamoto)

   - perf stat:

      * Enable 1ms interval for printing event counters values in
        (Alexey Budankov)

   - perf test fixes:

      * Run dwarf unwind on arm32 (Kim Phillips)

      * Remove unused ptrace.h include from LLVM test, sidesteping older
        clang's lack of support for some asm constructs (Arnaldo
        Carvalho de Melo)

      * Fixup BPF test using epoll_pwait syscall function probe, to cope
        with the syscall routines renames performed in this development
        cycle (Arnaldo Carvalho de Melo)

   - perf version fixes:

      * Do not print info about HAVE_LIBAUDIT_SUPPORT in 'perf version
        --build-options' when HAVE_SYSCALL_TABLE_SUPPORT is true, as
        libaudit won't be used in that case, print info about
        syscall_table support instead (Jin Yao)

   - Build system fixes:

      * Use HAVE_..._SUPPORT used consistently (Jin Yao)

      * Restore READ_ONCE() C++ compatibility in tools/include (Mark
        Rutland)

      * Give hints about package names needed to build jvmti (Arnaldo
        Carvalho de Melo)"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (37 commits)
  perf/x86/intel/uncore: Fix SBOX support for Broadwell CPUs
  perf/x86/intel/uncore: Revert "Remove SBOX support for Broadwell server"
  coresight: Move to SPDX identifier
  perf test BPF: Fixup BPF test using epoll_pwait syscall function probe
  perf tests mmap: Show which tracepoint is failing
  perf tools: Add '\n' at the end of parse-options error messages
  perf record: Remove suggestion to enable APIC
  perf record: Remove misleading error suggestion
  perf hists browser: Clarify top/report browser help
  perf mem: Allow all record/report options
  perf trace: Support MAP_FIXED_NOREPLACE
  perf: Remove superfluous allocation error check
  perf: Fix sample_max_stack maximum check
  perf: Return proper values for user stack errors
  perf list: Add s390 support for detailed/verbose PMU event description
  perf script: Extend misc field decoding with switch out event type
  perf report: Extend raw dump (-D) out with switch out event type
  perf/core: Store context switch out type in PERF_RECORD_SWITCH[_CPU_WIDE]
  tools/headers: Synchronize kernel ABI headers, v4.17-rc1
  trace_kprobe: Remove warning message "Could not insert probe at..."
  ...

Pull objtool fix from Thomas Gleixner:
 "A single fix for objtool so it uses the host C and LD flags and not
  the target ones"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Support HOSTCFLAGS and HOSTLDFLAGS

Pull /dev/random fixes from Ted Ts'o:
 "Fix some bugs in the /dev/random driver which causes getrandom(2) to
  unblock earlier than designed.

  Thanks to Jann Horn from Google's Project Zero for pointing this out
  to me"

* tag 'random_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/random:
  random: add new ioctl RNDRESEEDCRNG
  random: crng_reseed() should lock the crng instance that it is modifying
  random: set up the NUMA crng instances after the CRNG is fully initialized
  random: use a different mixing algorithm for add_device_randomness()
  random: fix crng_ready() test

Pull libnvdimm fixes from Dan Williams:
 "A regression fix, new unit test infrastructure and a build fix:

   - Regression fix addressing support for the new NVDIMM label storage
     area access commands (_LSI, _LSR, and _LSW).

     The Intel specific version of these commands communicated the
     "Device Locked" status on the label-storage-information command.

     However, these new commands (standardized in ACPI 6.2) communicate
     the "Device Locked" status on the label-storage-read command, and
     the driver was missing the indication.

     Reading from locked persistent memory is similar to reading
     unmapped PCI memory space, returns all 1's.

   - Unit test infrastructure is added to regression test the "Device
     Locked" detection failure.

   - A build fix is included to allow the "of_pmem" driver to be built
     as a module and translate an Open Firmware described device to its
     local numa node"

* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  MAINTAINERS: Add backup maintainers for libnvdimm and DAX
  device-dax: allow MAP_SYNC to succeed
  Revert "libnvdimm, of_pmem: workaround OF_NUMA=n build error"
  libnvdimm, of_pmem: use dev_to_node() instead of of_node_to_nid()
  tools/testing/nvdimm: enable labels for nfit_test.1 dimms
  tools/testing/nvdimm: fix missing newline in nfit_test_dimm 'handle' attribute
  tools/testing/nvdimm: support nfit_test_dimm attributes under nfit_test.1
  tools/testing/nvdimm: allow custom error code injection
  libnvdimm, dimm: handle EACCES failures from label reads

Pull sound fixes from Takashi Iwai:
 "A few small fixes:

   - a fix for the NULL-dereference in rawmidi compat ioctls, triggered
     by fuzzer

   - HD-audio Realtek codec quirks, a VIA controller fixup

   - a long-standing bug fix in LINE6 MIDI"

* tag 'sound-4.17-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound:
  ALSA: rawmidi: Fix missing input substream checks in compat ioctls
  ALSA: hda/realtek - adjust the location of one mic
  ALSA: hda/realtek - set PINCFG_HEADSET_MIC to parse_flags
  ALSA: hda - New VIA controller suppor no-snoop path
  ALSA: line6: Use correct endpoint type for midi output

Pull watchdog fixes from Wim Van Sebroeck:

 - fall-through fixes

 - MAINTAINER change for hpwdt

 - renesas-wdt: Add support for WDIOF_CARDRESET

 - aspeed: set bootstatus during probe

* tag 'linux-watchdog-4.17-rc2' of git://www.linux-watchdog.org/linux-watchdog:
  aspeed: watchdog: Set bootstatus during probe
  watchdog: renesas-wdt: Add support for WDIOF_CARDRESET
  watchdog: wafer5823wdt: Mark expected switch fall-through
  watchdog: w83977f_wdt: Mark expected switch fall-through
  watchdog: sch311x_wdt: Mark expected switch fall-through
  watchdog: hpwdt: change maintainer.

Merge tag 'linux-kselftest-4.17-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest

Pull Kselftest fix from Shuah Khan:
 "A fix from Michael Ellerman to not run dnotify_test by default to
  prevent Kselftest running forever"

* tag 'linux-kselftest-4.17-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest:
  selftests/filesystems: Don't run dnotify_test by default

Pull arm64 fixes from Catalin Marinas:

 - kasan: avoid pfn_to_nid() before the page array is initialised

 - Fix typo causing the "upgrade" of known signals to SIGKILL

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: signal: don't force known signals to SIGKILL
  arm64: kasan: avoid pfn_to_nid() before page array is initialized

Merge misc fixes from Andrew Morton:

 - "fork: unconditionally clear stack on fork" is a non-bugfix which got
   lost during the merge window - performance concerns appear to have
   been adequately addressed.

 - and a bunch of fixes

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm/filemap.c: fix NULL pointer in page_cache_tree_insert()
  mm: memcg: add __GFP_NOWARN in __memcg_schedule_kmem_cache_create()
  fs, elf: don't complain MAP_FIXED_NOREPLACE unless -EEXIST error
  kexec_file: do not add extra alignment to efi memmap
  proc: fix /proc/loadavg regression
  proc: revalidate kernel thread inodes to root:root
  autofs: mount point create should honour passed in mode
  MAINTAINERS: add personal addresses for Sascha and Uwe
  kasan: add no_sanitize attribute for clang builds
  rapidio: fix rio_dma_transfer error handling
  mm: enable thp migration for shmem thp
  writeback: safer lock nesting
  mm, pagemap: fix swap offset value for PMD migration entry
  mm: fix do_pages_move status handling
  fork: unconditionally clear stack on fork

Merge tag 'perf-urgent-for-mingo-4.17-20180420' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/urgent

Pull perf/urgent fixes and improvements from Arnaldo Carvalho de Melo:

- Store context switch out type in PERF_RECORD_SWITCH[_CPU_WIDE].
  The percentage of preempting and non-preempting context switches help
  understanding the nature of workloads (CPU or IO bound) that are running
  on a machine. This adds the kernel facility and userspace changes needed
  to show this information in 'perf script' and 'perf report -D' (Alexey Budankov)

- Remove old error messages about things that unlikely to be the root cause
  in modern systems (Andi Kleen)

- Synchronize kernel ABI headers, v4.17-rc1 (Ingo Molnar)

- Support MAP_FIXED_NOREPLACE, noticed when updating the tools/include/
  copies (Arnaldo Carvalho de Melo)

- Fixup BPF test using epoll_pwait syscall function probe, to cope with
  the syscall routines renames performed in this development cycle (Arnaldo Carvalho de Melo)

- Fix sample_max_stack maximum check and do not proceed when an error
  has been detect, return them to avoid misidentifying errors (Jiri Olsa)

- Add '\n' at the end of parse-options error messages (Ravi Bangoria)

- Add s390 support for detailed/verbose PMU event description (Thomas Richter)
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: NIngo Molnar <mingo@kernel.org>

f2fs specifies the __GFP_ZERO flag for allocating some of its pages.
Unfortunately, the page cache also uses the mapping's GFP flags for
allocating radix tree nodes.  It always masked off the __GFP_HIGHMEM
flag, and masks off __GFP_ZERO in some paths, but not all.  That causes
radix tree nodes to be allocated with a NULL list_head, which causes
backtraces like:

  __list_del_entry+0x30/0xd0
  list_lru_del+0xac/0x1ac
  page_cache_tree_insert+0xd8/0x110

The __GFP_DMA and __GFP_DMA32 flags would also be able to sneak through
if they are ever used.  Fix them all by using GFP_RECLAIM_MASK at the
innermost location, and remove it from earlier in the callchain.

Link: http://lkml.kernel.org/r/20180411060320.14458-2-willy@infradead.org
Fixes: 449dd698 ("mm: keep page cache radix tree nodes in check")
Signed-off-by: NMatthew Wilcox <mawilcox@microsoft.com>
Reported-by: NChris Fries <cfries@google.com>
Debugged-by: NMinchan Kim <minchan@kernel.org>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Acked-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NJan Kara <jack@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If there is heavy memory pressure, page allocation with __GFP_NOWAIT
fails easily although it's order-0 request.  I got below warning 9 times
for normal boot.

     <snip >: page allocation failure: order:0, mode:0x2200000(GFP_NOWAIT|__GFP_NOTRACK)
     .. snip ..
     Call trace:
       dump_backtrace+0x0/0x4
       dump_stack+0xa4/0xc0
       warn_alloc+0xd4/0x15c
       __alloc_pages_nodemask+0xf88/0x10fc
       alloc_slab_page+0x40/0x18c
       new_slab+0x2b8/0x2e0
       ___slab_alloc+0x25c/0x464
       __kmalloc+0x394/0x498
       memcg_kmem_get_cache+0x114/0x2b8
       kmem_cache_alloc+0x98/0x3e8
       mmap_region+0x3bc/0x8c0
       do_mmap+0x40c/0x43c
       vm_mmap_pgoff+0x15c/0x1e4
       sys_mmap+0xb0/0xc8
       el0_svc_naked+0x24/0x28
     Mem-Info:
     active_anon:17124 inactive_anon:193 isolated_anon:0
      active_file:7898 inactive_file:712955 isolated_file:55
      unevictable:0 dirty:27 writeback:18 unstable:0
      slab_reclaimable:12250 slab_unreclaimable:23334
      mapped:19310 shmem:212 pagetables:816 bounce:0
      free:36561 free_pcp:1205 free_cma:35615
     Node 0 active_anon:68496kB inactive_anon:772kB active_file:31592kB inactive_file:2851820kB unevictable:0kB isolated(anon):0kB isolated(file):220kB mapped:77240kB dirty:108kB writeback:72kB shmem:848kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
     DMA free:142188kB min:3056kB low:3820kB high:4584kB active_anon:10052kB inactive_anon:12kB active_file:312kB inactive_file:1412620kB unevictable:0kB writepending:0kB present:1781412kB managed:1604728kB mlocked:0kB slab_reclaimable:3592kB slab_unreclaimable:876kB kernel_stack:400kB pagetables:52kB bounce:0kB free_pcp:1436kB local_pcp:124kB free_cma:142492kB
     lowmem_reserve[]: 0 1842 1842
     Normal free:4056kB min:4172kB low:5212kB high:6252kB active_anon:58376kB inactive_anon:760kB active_file:31348kB inactive_file:1439040kB unevictable:0kB writepending:180kB present:2000636kB managed:1923688kB mlocked:0kB slab_reclaimable:45408kB slab_unreclaimable:92460kB kernel_stack:9680kB pagetables:3212kB bounce:0kB free_pcp:3392kB local_pcp:688kB free_cma:0kB
     lowmem_reserve[]: 0 0 0
     DMA: 0*4kB 0*8kB 1*16kB (C) 0*32kB 0*64kB 0*128kB 1*256kB (C) 1*512kB (C) 0*1024kB 1*2048kB (C) 34*4096kB (C) = 142096kB
     Normal: 228*4kB (UMEH) 172*8kB (UMH) 23*16kB (UH) 24*32kB (H) 5*64kB (H) 1*128kB (H) 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 3872kB
     721350 total pagecache pages
     0 pages in swap cache
     Swap cache stats: add 0, delete 0, find 0/0
     Free swap  = 0kB
     Total swap = 0kB
     945512 pages RAM
     0 pages HighMem/MovableOnly
     63408 pages reserved
     51200 pages cma reserved

__memcg_schedule_kmem_cache_create() tries to create a shadow slab cache
and the worker allocation failure is not really critical because we will
retry on the next kmem charge.  We might miss some charges but that
shouldn't be critical.  The excessive allocation failure report is not
very helpful.

[mhocko@kernel.org: changelog update]
Link: http://lkml.kernel.org/r/20180418022912.248417-1-minchan@kernel.orgSigned-off-by: NMinchan Kim <minchan@kernel.org>
Acked-by: NJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit 4ed28639 ("fs, elf: drop MAP_FIXED usage from elf_map") is
printing spurious messages under memory pressure due to map_addr == -ENOMEM.

 9794 (a.out): Uhuuh, elf segment at 00007f2e34738000(fffffffffffffff4) requested but the memory is mapped already
 14104 (a.out): Uhuuh, elf segment at 00007f34fd76c000(fffffffffffffff4) requested but the memory is mapped already
 16843 (a.out): Uhuuh, elf segment at 00007f930ecc7000(fffffffffffffff4) requested but the memory is mapped already

Complain only if -EEXIST, and use %px for printing the address.

Link: http://lkml.kernel.org/r/201804182307.FAC17665.SFMOFJVFtHOLOQ@I-love.SAKURA.ne.jp
Fixes: 4ed28639 ("fs, elf: drop MAP_FIXED usage from elf_map") is
Signed-off-by: NTetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Andrei Vagin <avagin@openvz.org>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Kees Cook <keescook@chromium.org>
Cc: Abdul Haleem <abdhalee@linux.vnet.ibm.com>
Cc: Joel Stanley <joel@jms.id.au>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Chun-Yi reported a kernel warning message below:

  WARNING: CPU: 0 PID: 0 at ../mm/early_ioremap.c:182 early_iounmap+0x4f/0x12c()
  early_iounmap(ffffffffff200180, 00000118) [0] size not consistent 00000120

The problem is x86 kexec_file_load adds extra alignment to the efi
memmap: in bzImage64_load():

        efi_map_sz = efi_get_runtime_map_size();
        efi_map_sz = ALIGN(efi_map_sz, 16);

And __efi_memmap_init maps with the size including the alignment bytes
but efi_memmap_unmap use nr_maps * desc_size which does not include the
extra bytes.

The alignment in kexec code is only needed for the kexec buffer internal
use Actually kexec should pass exact size of the efi memmap to 2nd
kernel.

Link: http://lkml.kernel.org/r/20180417083600.GA1972@dhcp-128-65.nay.redhat.comSigned-off-by: NDave Young <dyoung@redhat.com>
Reported-by: Njoeyli <jlee@suse.com>
Tested-by: NRandy Wright <rwright@hpe.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit 95846ecf ("pid: replace pid bitmap implementation with IDR
API") changed last field of /proc/loadavg (last pid allocated) to be off
by one:

	# unshare -p -f --mount-proc cat /proc/loadavg
	0.00 0.00 0.00 1/60 2	<===

It should be 1 after first fork into pid namespace.

This is formally a regression but given how useless this field is I
don't think anyone is affected.

Bug was found by /proc testsuite!

Link: http://lkml.kernel.org/r/20180413175408.GA27246@avx2
Fixes: 95846ecf ("pid: replace pid bitmap implementation with IDR API")
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Gargi Sharma <gs051095@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

task_dump_owner() has the following code:

	mm = task->mm;
	if (mm) {
		if (get_dumpable(mm) != SUID_DUMP_USER) {
			uid = ...
		}
	}

Check for ->mm is buggy -- kernel thread might be borrowing mm
and inode will go to some random uid:gid pair.

Link: http://lkml.kernel.org/r/20180412220109.GA20978@avx2Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The autofs file system mkdir inode operation blindly sets the created
directory mode to S_IFDIR | 0555, ingoring the passed in mode, which can
cause selinux dac_override denials.

But the function also checks if the caller is the daemon (as no-one else
should be able to do anything here) so there's no point in not honouring
the passed in mode, allowing the daemon to set appropriate mode when
required.

Link: http://lkml.kernel.org/r/152361593601.8051.14014139124905996173.stgit@pluto.themaw.netSigned-off-by: NIan Kent <raven@themaw.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The idea behind using kernel@pengutronix.de (i.e. the mail alias for the
kernel people at Pengutronix) as email address was to have a backup when
a given developer is on vacation or run over by a bus. Make this more
explicit by adding the alias as reviewer and use the personal address
for Sascha and me.

Link: http://lkml.kernel.org/r/20180413083312.11213-1-u.kleine-koenig@pengutronix.deSigned-off-by: NUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: NSascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

KASAN uses the __no_sanitize_address macro to disable instrumentation of
particular functions.  Right now it's defined only for GCC build, which
causes false positives when clang is used.

This patch adds a definition for clang.

Note, that clang's revision 329612 or higher is required.

[andreyknvl@google.com: remove redundant #ifdef CONFIG_KASAN check]
  Link: http://lkml.kernel.org/r/c79aa31a2a2790f6131ed607c58b0dd45dd62a6c.1523967959.git.andreyknvl@google.com
Link: http://lkml.kernel.org/r/4ad725cc903f8534f8c8a60f0daade5e3d674f8d.1523554166.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Acked-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Paul Lawrence <paullawrence@google.com>
Cc: Sandipan Das <sandipan@linux.vnet.ibm.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Some of the mport_dma_req structure members were initialized late
inside the do_dma_request() function, just before submitting the
request to the dma engine. But we have some error branches before
that. In case of such an error, the code would return on the error
path and trigger the calling of dma_req_free() with a req structure
which is not completely initialized. This causes a NULL pointer
dereference in dma_req_free().

This patch fixes these error branches by making sure that all
necessary mport_dma_req structure members are initialized in
rio_dma_transfer() immediately after the request structure gets
allocated.

Link: http://lkml.kernel.org/r/20180412150605.GA31409@nokia.com
Fixes: bbd876ad ("rapidio: use a reference count for struct mport_dma_req")
Signed-off-by: NIoan Nicu <ioan.nicu.ext@nokia.com>
Tested-by: NAlexander Sverdlin <alexander.sverdlin@nokia.com>
Acked-by: NAlexandre Bounine <alex.bou9@gmail.com>
Cc: Barry Wood <barry.wood@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Frank Kunz <frank.kunz@nokia.com>
Cc: <stable@vger.kernel.org>	[4.6+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

My testing for the latest kernel supporting thp migration showed an
infinite loop in offlining the memory block that is filled with shmem
thps.  We can get out of the loop with a signal, but kernel should return
with failure in this case.

What happens in the loop is that scan_movable_pages() repeats returning
the same pfn without any progress.  That's because page migration always
fails for shmem thps.

In memory offline code, memory blocks containing unmovable pages should be
prevented from being offline targets by has_unmovable_pages() inside
start_isolate_page_range().  So it's possible to change migratability for
non-anonymous thps to avoid the issue, but it introduces more complex and
thp-specific handling in migration code, so it might not good.

So this patch is suggesting to fix the issue by enabling thp migration for
shmem thp.  Both of anon/shmem thp are migratable so we don't need
precheck about the type of thps.

Link: http://lkml.kernel.org/r/20180406030706.GA2434@hori1.linux.bs1.fc.nec.co.jp
Fixes: commit 72b39cfc ("mm, memory_hotplug: do not fail offlining too early")
Signed-off-by: NNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: NKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Zi Yan <zi.yan@sent.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

lock_page_memcg()/unlock_page_memcg() use spin_lock_irqsave/restore() if
the page's memcg is undergoing move accounting, which occurs when a
process leaves its memcg for a new one that has
memory.move_charge_at_immigrate set.

unlocked_inode_to_wb_begin,end() use spin_lock_irq/spin_unlock_irq() if
the given inode is switching writeback domains.  Switches occur when
enough writes are issued from a new domain.

This existing pattern is thus suspicious:
    lock_page_memcg(page);
    unlocked_inode_to_wb_begin(inode, &locked);
    ...
    unlocked_inode_to_wb_end(inode, locked);
    unlock_page_memcg(page);

If both inode switch and process memcg migration are both in-flight then
unlocked_inode_to_wb_end() will unconditionally enable interrupts while
still holding the lock_page_memcg() irq spinlock.  This suggests the
possibility of deadlock if an interrupt occurs before unlock_page_memcg().

    truncate
    __cancel_dirty_page
    lock_page_memcg
    unlocked_inode_to_wb_begin
    unlocked_inode_to_wb_end
    <interrupts mistakenly enabled>
                                    <interrupt>
                                    end_page_writeback
                                    test_clear_page_writeback
                                    lock_page_memcg
                                    <deadlock>
    unlock_page_memcg

Due to configuration limitations this deadlock is not currently possible
because we don't mix cgroup writeback (a cgroupv2 feature) and
memory.move_charge_at_immigrate (a cgroupv1 feature).

If the kernel is hacked to always claim inode switching and memcg
moving_account, then this script triggers lockup in less than a minute:

  cd /mnt/cgroup/memory
  mkdir a b
  echo 1 > a/memory.move_charge_at_immigrate
  echo 1 > b/memory.move_charge_at_immigrate
  (
    echo $BASHPID > a/cgroup.procs
    while true; do
      dd if=/dev/zero of=/mnt/big bs=1M count=256
    done
  ) &
  while true; do
    sync
  done &
  sleep 1h &
  SLEEP=$!
  while true; do
    echo $SLEEP > a/cgroup.procs
    echo $SLEEP > b/cgroup.procs
  done

The deadlock does not seem possible, so it's debatable if there's any
reason to modify the kernel.  I suggest we should to prevent future
surprises.  And Wang Long said "this deadlock occurs three times in our
environment", so there's more reason to apply this, even to stable.
Stable 4.4 has minor conflicts applying this patch.  For a clean 4.4 patch
see "[PATCH for-4.4] writeback: safer lock nesting"
https://lkml.org/lkml/2018/4/11/146

Wang Long said "this deadlock occurs three times in our environment"

[gthelen@google.com: v4]
  Link: http://lkml.kernel.org/r/20180411084653.254724-1-gthelen@google.com
[akpm@linux-foundation.org: comment tweaks, struct initialization simplification]
Change-Id: Ibb773e8045852978f6207074491d262f1b3fb613
Link: http://lkml.kernel.org/r/20180410005908.167976-1-gthelen@google.com
Fixes: 682aa8e1 ("writeback: implement unlocked_inode_to_wb transaction and use it for stat updates")
Signed-off-by: NGreg Thelen <gthelen@google.com>
Reported-by: NWang Long <wanglong19@meituan.com>
Acked-by: NWang Long <wanglong19@meituan.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: <stable@vger.kernel.org>	[v4.2+]
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The swap offset reported by /proc/<pid>/pagemap may be not correct for
PMD migration entries.  If addr passed into pagemap_pmd_range() isn't
aligned with PMD start address, the swap offset reported doesn't
reflect this.  And in the loop to report information of each sub-page,
the swap offset isn't increased accordingly as that for PFN.

This may happen after opening /proc/<pid>/pagemap and seeking to a page
whose address doesn't align with a PMD start address.  I have verified
this with a simple test program.

BTW: migration swap entries have PFN information, do we need to restrict
whether to show them?

[akpm@linux-foundation.org: fix typo, per Huang, Ying]
Link: http://lkml.kernel.org/r/20180408033737.10897-1-ying.huang@intel.comSigned-off-by: N"Huang, Ying" <ying.huang@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andrei Vagin <avagin@openvz.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: "Jerome Glisse" <jglisse@redhat.com>
Cc: Daniel Colascione <dancol@google.com>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Li Wang has reported that LTP move_pages04 test fails with the current
tree:

LTP move_pages04:
   TFAIL  :  move_pages04.c:143: status[1] is EPERM, expected EFAULT

The test allocates an array of two pages, one is present while the other
is not (resp.  backed by zero page) and it expects EFAULT for the second
page as the man page suggests.  We are reporting EPERM which doesn't make
any sense and this is a result of a bug from cf5f16b23ec9 ("mm: unclutter
THP migration").

do_pages_move tries to handle as many pages in one batch as possible so we
queue all pages with the same node target together and that corresponds to
[start, i] range which is then used to update status array.
add_page_for_migration will correctly notice the zero (resp.  !present)
page and returns with EFAULT which gets written to the status.  But if
this is the last page in the array we do not update start and so the last
store_status after the loop will overwrite the range of the last batch
with NUMA_NO_NODE (which corresponds to EPERM).

Fix this by simply bailing out from the last flush if the pagelist is
empty as there is clearly nothing more to do.

Link: http://lkml.kernel.org/r/20180418121255.334-1-mhocko@kernel.org
Fixes: cf5f16b23ec9 ("mm: unclutter THP migration")
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Reported-by: NLi Wang <liwang@redhat.com>
Tested-by: NLi Wang <liwang@redhat.com>
Cc: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

One of the classes of kernel stack content leaks[1] is exposing the
contents of prior heap or stack contents when a new process stack is
allocated.  Normally, those stacks are not zeroed, and the old contents
remain in place.  In the face of stack content exposure flaws, those
contents can leak to userspace.

Fixing this will make the kernel no longer vulnerable to these flaws, as
the stack will be wiped each time a stack is assigned to a new process.
There's not a meaningful change in runtime performance; it almost looks
like it provides a benefit.

Performing back-to-back kernel builds before:
	Run times: 157.86 157.09 158.90 160.94 160.80
	Mean: 159.12
	Std Dev: 1.54

and after:
	Run times: 159.31 157.34 156.71 158.15 160.81
	Mean: 158.46
	Std Dev: 1.46

Instead of making this a build or runtime config, Andy Lutomirski
recommended this just be enabled by default.

[1] A noisy search for many kinds of stack content leaks can be seen here:
https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=linux+kernel+stack+leak

I did some more with perf and cycle counts on running 100,000 execs of
/bin/true.

before:
Cycles: 218858861551 218853036130 214727610969 227656844122 224980542841
Mean:  221015379122.60
Std Dev: 4662486552.47

after:
Cycles: 213868945060 213119275204 211820169456 224426673259 225489986348
Mean:  217745009865.40
Std Dev: 5935559279.99

It continues to look like it's faster, though the deviation is rather
wide, but I'm not sure what I could do that would be less noisy.  I'm
open to ideas!

Link: http://lkml.kernel.org/r/20180221021659.GA37073@beastSigned-off-by: NKees Cook <keescook@chromium.org>
Acked-by: NMichal Hocko <mhocko@suse.com>
Reviewed-by: NAndrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>