When STM32_THERMAL is enabled, this overrides all previously
enabled files in the same directory, as seen from this link failure:

ERROR: "st_thermal_pm_ops" [drivers/thermal/st/st_thermal_syscfg.ko] undefined!
ERROR: "st_thermal_register" [drivers/thermal/st/st_thermal_syscfg.ko] undefined!
ERROR: "st_thermal_unregister" [drivers/thermal/st/st_thermal_syscfg.ko] undefined!

The correct syntax in Makefile requires using += instead of :=.

Fixes: 1d693155 ("thermal: add stm32 thermal driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

This converts license boilerplate to SPDX identifier, and removes
unnecessary lines.
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

Use macro to simplify the code.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

Use macro to simplify the code.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

The thermal controller implementation on Tegra194 is very similar to the
implementation on Tegra186. Add a compatible string for the new
generation.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

Put return value checks of calling imx_init_from_nvmem_cells()
into one block to save one condition block for normal case.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

The thermal driver is a standalone driver for monitoring SoC temperature
by enabling thermal sensor, so it can be enabled even when CONFIG_CPU_FREQ
is NOT set. So remove the dependency with CPU_THERMAL.

Introduce dummy function of legacy cooling register/unregister to make
thermal driver probe successfully when CONFIG_CPU_FREQ is NOT set.
Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

Regmap would use device name to create debugfs entries. If the device
has multiple regmaps it is recommended to use name field in regmap_config.
Fix this by providing name to the regmap configs correctly.

Without this patch we would see below error on DB820c.

qcom-tsens 4a9000.thermal-sensor: Failed to create 4a9000.thermal-sensor
debugfs directory
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Acked-by: Amit Kucheria <amit.kucheria@linaro.org>
Tested-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

RZ/G2M also has 3 interrupts routed to the TSC, but the list was not
updated to reflect this.

Just drop the list, as this is the case for this TSC variant in all
R-Car Gen3 and RZ/G2 SoCs.

Fixes: be6af481 ("dt-bindings: thermal: rcar-gen3-thermal: Add r8a774a1 support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

Using devm_thermal_zone_of_sensor_register allows to simplify some
error handling code, drop a label, and drop the remove function.
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

By defaul of-based thermal driver do not enable hwmon.
This patch does this explicitly, so that the temperature can be read
through the common hwmon sysfs.
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

Avoid warnings like this:
thermal_hwmon.h:29:1: warning: ‘thermal_remove_hwmon_sysfs’ defined but not used [-Wunused-function]
 thermal_remove_hwmon_sysfs(struct thermal_zone_device *tz)

Fixes: 0dd88793 ("thermal: hwmon: move hwmon support to single file")
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

Pull media fixes from Mauro Carvalho Chehab:

 - Revert a dt-bindings patch whose driver didn't make for 4.20

 - fix a kernel oops at vicodec driver

 - fix a frame overflow at gspca with was causing regressions on some
   cameras, making them to not work

 - use the proper type for wait_queue head

 - make media request API compatible with 32-bit userspace on 64-bit
   kernel

 - fix a regression on Kernel 4.19 at dvb-pll

 - don't use SPDX headers yet for GFDL

* tag 'media/v4.20-4' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media:
  media: mediactl docs: Fix licensing message
  media: dvb-pll: don't re-validate tuner frequencies
  media: dvb-pll: fix tuner frequency ranges
  media: Revert "media: dt-bindings: Document the Rockchip VPU bindings"
  media: gspca: fix frame overflow error
  media: vicodec: fix memchr() kernel oops
  media: cedrus: add action item to the TODO
  media: media-request: Add compat ioctl
  media: Use wait_queue_head_t for media_request

Pull IDE fixes from David Miller:
 "A missing of_node_put() and a small cleanup"

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/ide:
  ide: Change to use DEFINE_SHOW_ATTRIBUTE macro
  ide: pmac: add of_node_put()

Pull sparc fixes from David Miller:

 1) Some implicit switch fallthrough fixes from Stephen Rothwell.

 2) Missing of_node_put() in various sparc drivers from Yangtao Li.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc:
  drivers/tty: add missing of_node_put()
  drivers/sbus/char: add of_node_put()
  sbus: char: add of_node_put()
  sparc32: supress another implicit-fallthrough warning
  sparc32: suppress an implicit-fallthrough warning
  sparc: suppress the implicit-fallthrough warning
  arch/sparc: Use kzalloc_node

Use DEFINE_SHOW_ATTRIBUTE macro to simplify the code.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

use of_node_put() to release the refcount.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

of_find_node_by_path() acquires a reference to the node
returned by it and that reference needs to be dropped by its caller.
This place is not doing this, so fix it.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

use of_node_put() to release the refcount.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

use of_node_put() to release the refcount.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Pull ARM SoC fixes from Olof Johansson:
 "Volume is a little higher than usual due to a set of gpio fixes for
  Davinci platforms that's been around a while, still seemed appropriate
  to not hold off until next merge window.

  Besides that it's the usual mix of minor fixes, mostly corrections of
  small stuff in device trees.

  Major stability-related one is the removal of a regulator from DT on
  Rock960, since DVFS caused undervoltage. I expect it'll be restored
  once they figure out the underlying issue"

* tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc: (28 commits)
  MAINTAINERS: Remove unused Qualcomm SoC mailing list
  ARM: davinci: dm644x: set the GPIO base to 0
  ARM: davinci: da830: set the GPIO base to 0
  ARM: davinci: dm355: set the GPIO base to 0
  ARM: davinci: dm646x: set the GPIO base to 0
  ARM: davinci: dm365: set the GPIO base to 0
  ARM: davinci: da850: set the GPIO base to 0
  gpio: davinci: restore a way to manually specify the GPIO base
  ARM: davinci: dm644x: define gpio interrupts as separate resources
  ARM: davinci: dm355: define gpio interrupts as separate resources
  ARM: davinci: dm646x: define gpio interrupts as separate resources
  ARM: davinci: dm365: define gpio interrupts as separate resources
  ARM: davinci: da8xx: define gpio interrupts as separate resources
  ARM: dts: at91: sama5d2: use the divided clock for SMC
  ARM: dts: imx51-zii-rdu1: Remove EEPROM node
  ARM: dts: rockchip: Remove @0 from the veyron memory node
  arm64: dts: rockchip: Fix PCIe reset polarity for rk3399-puma-haikou.
  arm64: dts: qcom: msm8998: Reserve gpio ranges on MTP
  arm64: dts: sdm845-mtp: Reserve reserved gpios
  arm64: dts: ti: k3-am654: Fix wakeup_uart reg address
  ...

Pull xen fixes from Juergen Gross:

 - A revert of a previous commit as it is no longer necessary and has
   shown to cause problems in some memory hotplug cases.

 - Some small fixes and a minor cleanup.

 - A patch for adding better diagnostic data in a very rare failure
   case.

* tag 'for-linus-4.20a-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  pvcalls-front: fixes incorrect error handling
  Revert "xen/balloon: Mark unallocated host memory as UNUSABLE"
  xen: xlate_mmu: add missing header to fix 'W=1' warning
  xen/x86: add diagnostic printout to xen_mc_flush() in case of error
  x86/xen: cleanup includes in arch/x86/xen/spinlock.c

Pull dmaengine fixes from Vinod Koul:
 "This contains two fixes to at_hdmac which fixes long standing bus
  reported recently on serial transfers causing memory leak. These fixes
  were done by Richard Genoud"

* tag 'dmaengine-fix-4.20-rc5' of git://git.infradead.org/users/vkoul/slave-dma:
  dmaengine: at_hdmac: fix module unloading
  dmaengine: at_hdmac: fix memory leak in at_dma_xlate()

Pull STIBP fallout fixes from Thomas Gleixner:
 "The performance destruction department finally got it's act together
  and came up with a cure for the STIPB regression:

   - Provide a command line option to control the spectre v2 user space
     mitigations. Default is either seccomp or prctl (if seccomp is
     disabled in Kconfig). prctl allows mitigation opt-in, seccomp
     enables the migitation for sandboxed processes.

   - Rework the code to handle the conditional STIBP/IBPB control and
     remove the now unused ptrace_may_access_sched() optimization
     attempt

   - Disable STIBP automatically when SMT is disabled

   - Optimize the switch_to() logic to avoid MSR writes and invocations
     of __switch_to_xtra().

   - Make the asynchronous speculation TIF updates synchronous to
     prevent stale mitigation state.

  As a general cleanup this also makes retpoline directly depend on
  compiler support and removes the 'minimal retpoline' option which just
  pretended to provide some form of security while providing none"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (31 commits)
  x86/speculation: Provide IBPB always command line options
  x86/speculation: Add seccomp Spectre v2 user space protection mode
  x86/speculation: Enable prctl mode for spectre_v2_user
  x86/speculation: Add prctl() control for indirect branch speculation
  x86/speculation: Prepare arch_smt_update() for PRCTL mode
  x86/speculation: Prevent stale SPEC_CTRL msr content
  x86/speculation: Split out TIF update
  ptrace: Remove unused ptrace_may_access_sched() and MODE_IBRS
  x86/speculation: Prepare for conditional IBPB in switch_mm()
  x86/speculation: Avoid __switch_to_xtra() calls
  x86/process: Consolidate and simplify switch_to_xtra() code
  x86/speculation: Prepare for per task indirect branch speculation control
  x86/speculation: Add command line control for indirect branch speculation
  x86/speculation: Unify conditional spectre v2 print functions
  x86/speculataion: Mark command line parser data __initdata
  x86/speculation: Mark string arrays const correctly
  x86/speculation: Reorder the spec_v2 code
  x86/l1tf: Show actual SMT state
  x86/speculation: Rework SMT state change
  sched/smt: Expose sched_smt_present static key
  ...

Pull block layer fixes from Jens Axboe:

 - Single range elevator discard merge fix, that caused crashes (Ming)

 - Fix for a regression in O_DIRECT, where we could potentially lose the
   error value (Maximilian Heyne)

 - NVMe pull request from Christoph, with little fixes all over the map
   for NVMe.

* tag 'for-linus-20181201' of git://git.kernel.dk/linux-block:
  block: fix single range discard merge
  nvme-rdma: fix double freeing of async event data
  nvme: flush namespace scanning work just before removing namespaces
  nvme: warn when finding multi-port subsystems without multipathing enabled
  fs: fix lost error code in dio_complete
  nvme-pci: fix surprise removal
  nvme-fc: initialize nvme_req(rq)->ctrl after calling __nvme_fc_init_request()
  nvme: Free ctrl device name on init failure

Pull PCI fixes from Bjorn Helgaas:

 - Fix a link speed checking interface that broke PCIe gen3 cards in
   gen1 slots (Mikulas Patocka)

 - Fix an imx6 link training error (Trent Piepho)

 - Fix a layerscape outbound window accessor calling error (Hou
   Zhiqiang)

 - Fix a DesignWare endpoint MSI-X address calculation error (Gustavo
   Pimentel)

* tag 'pci-v4.20-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci:
  PCI: Fix incorrect value returned from pcie_get_speed_cap()
  PCI: dwc: Fix MSI-X EP framework address calculation bug
  PCI: layerscape: Fix wrong invocation of outbound window disable accessor
  PCI: imx6: Fix link training status detection in link up check

  - Fix DesignWare endpoint MSI-X address calculation bug (Gustavo
    Pimentel)

  - Fix Layerscape outbound window disable usage (Hou Zhiqiang)

  - Fix imx6 link up detection (Trent Piepho)

* lorenzo/pci/controller-fixes:
  PCI: dwc: Fix MSI-X EP framework address calculation bug
  PCI: layerscape: Fix wrong invocation of outbound window disable accessor
  PCI: imx6: Fix link training status detection in link up check

The macros PCI_EXP_LNKCAP_SLS_*GB are values, not bit masks.  We must mask
the register and compare it against them.

This fixes errors like this:

  amdgpu: [powerplay] failed to send message 261 ret is 0

when a PCIe-v3 card is plugged into a PCIe-v1 slot, because the slot is
being incorrectly reported as PCIe-v3 capable.

6cf57be0, which appeared in v4.17, added pcie_get_speed_cap() with the
incorrect test of PCI_EXP_LNKCAP_SLS as a bitmask.  5d9a6330, which
appeared in v4.19, changed amdgpu to use pcie_get_speed_cap(), so the
amdgpu bug reports below are regressions in v4.19.

Fixes: 6cf57be0 ("PCI: Add pcie_get_speed_cap() to find max supported link speed")
Fixes: 5d9a6330 ("drm/amdgpu: use pcie functions for link width and speed")
Link: https://bugs.freedesktop.org/show_bug.cgi?id=108704
Link: https://bugs.freedesktop.org/show_bug.cgi?id=108778Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
[bhelgaas: update comment, remove use of PCI_EXP_LNKCAP_SLS_8_0GB and
PCI_EXP_LNKCAP_SLS_16_0GB since those should be covered by PCI_EXP_LNKCAP2,
remove test of PCI_EXP_LNKCAP for zero, since that register is required]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org	# v4.17+

Merge misc fixes from Andrew Morton:
 "31 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (31 commits)
  ocfs2: fix potential use after free
  mm/khugepaged: fix the xas_create_range() error path
  mm/khugepaged: collapse_shmem() do not crash on Compound
  mm/khugepaged: collapse_shmem() without freezing new_page
  mm/khugepaged: minor reorderings in collapse_shmem()
  mm/khugepaged: collapse_shmem() remember to clear holes
  mm/khugepaged: fix crashes due to misaccounted holes
  mm/khugepaged: collapse_shmem() stop if punched or truncated
  mm/huge_memory: fix lockdep complaint on 32-bit i_size_read()
  mm/huge_memory: splitting set mapping+index before unfreeze
  mm/huge_memory: rename freeze_page() to unmap_page()
  initramfs: clean old path before creating a hardlink
  kernel/kcov.c: mark funcs in __sanitizer_cov_trace_pc() as notrace
  psi: make disabling/enabling easier for vendor kernels
  proc: fixup map_files test on arm
  debugobjects: avoid recursive calls with kmemleak
  userfaultfd: shmem: UFFDIO_COPY: set the page dirty if VM_WRITE is not set
  userfaultfd: shmem: add i_size checks
  userfaultfd: shmem/hugetlbfs: only allow to register VM_MAYWRITE vmas
  userfaultfd: shmem: allocate anonymous memory for MAP_PRIVATE shmem
  ...

Pull few more MIPS fixes from Paul Burton:

 - Fix mips_get_syscall_arg() to operate on the task specified when
   detecting o32 tasks running on MIPS64 kernels.

 - Fix some incorrect GPIO pin muxing for the MT7620 SoC.

 - Update the linux-mips mailing list address.

* tag 'mips_fixes_4.20_4' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux:
  MAINTAINERS: Update linux-mips mailing list address
  MIPS: ralink: Fix mt7620 nd_sd pinmux
  mips: fix mips_get_syscall_arg o32 check

Pull arm64 fixes from Catalin Marinas:

 - Cortex-A76 erratum workaround

 - ftrace fix to enable syscall events on arm64

 - Fix uninitialised pointer in iort_get_platform_device_domain()

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  ACPI/IORT: Fix iort_get_platform_device_domain() uninitialized pointer value
  arm64: ftrace: Fix to enable syscall events on arm64
  arm64: Add workaround for Cortex-A76 erratum 1286807

Pull stackleak plugin fix from Kees Cook:
 "Fix crash by not allowing kprobing of stackleak_erase() (Alexander
  Popov)"

* tag 'gcc-plugins-v4.20-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  stackleak: Disable function tracing and kprobes for stackleak_erase()

Merge tag 'fscache-fixes-20181130' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull fscache and cachefiles fixes from David Howells:
 "Misc fixes:

   - Fix an assertion failure at fs/cachefiles/xattr.c:138 caused by a
     race between a cache object lookup failing and someone attempting
     to reenable that object, thereby triggering an update of the
     object's attributes.

   - Fix an assertion failure at fs/fscache/operation.c:449 caused by a
     split atomic subtract and atomic read that allows a race to happen.

   - Fix a leak of backing pages when simultaneously reading the same
     page from the same object from two or more threads.

   - Fix a hang due to a race between a cache object being discarded and
     the corresponding cookie being reenabled.

  There are also some minor cleanups:

   - Cast an enum value to a different enum type to prevent clang from
     generating a warning. This shouldn't cause any sort of change in
     the emitted code.

   - Use ktime_get_real_seconds() instead of get_seconds(). This is just
     used to uniquify a filename for an object to be placed in the
     graveyard. Objects placed there are deleted by cachfilesd in
     userspace immediately thereafter.

   - Remove an initialised, but otherwise unused variable. This should
     have been entirely optimised away anyway"

* tag 'fscache-fixes-20181130' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  fscache, cachefiles: remove redundant variable 'cache'
  cachefiles: avoid deprecated get_seconds()
  cachefiles: Explicitly cast enumerated type in put_object
  fscache: fix race between enablement and dropping of object
  cachefiles: Fix page leak in cachefiles_read_backing_file while vmscan is active
  fscache: Fix race in fscache_op_complete() due to split atomic_sub & read
  cachefiles: Fix an assertion failure when trying to update a failed object

The linux-mips.org infrastructure has been unreliable recently & nobody
with sufficient access to fix it is around to do so. As a result we're
moving away from it, and part of this is migrating our mailing list to
kernel.org.

Replace all instances of linux-mips@linux-mips.org in MAINTAINERS with
the shiny new linux-mips@vger.kernel.org address.

The new list is now being archived on kernel.org at
https://lore.kernel.org/linux-mips/ which also holds the history of the
old linux-mips.org list.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: linux-mips@linux-mips.org

ocfs2_get_dentry() calls iput(inode) to drop the reference count of
inode, and if the reference count hits 0, inode is freed.  However, in
this function, it then reads inode->i_generation, which may result in a
use after free bug.  Move the put operation later.

Link: http://lkml.kernel.org/r/1543109237-110227-1-git-send-email-bianpan2016@163.com
Fixes: 781f200c("ocfs2: Remove masklog ML_EXPORT.")
Signed-off-by: Pan Bian <bianpan2016@163.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <ge.changwei@h3c.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

collapse_shmem()'s xas_nomem() is very unlikely to fail, but it is
rightly given a failure path, so move the whole xas_create_range() block
up before __SetPageLocked(new_page): so that it does not need to
remember to unlock_page(new_page).

Add the missing mem_cgroup_cancel_charge(), and set (currently unused)
result to SCAN_FAIL rather than SCAN_SUCCEED.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261531200.2275@eggly.anvils
Fixes: 77da9389 ("mm: Convert collapse_shmem to XArray")
Signed-off-by: Hugh Dickins <hughd@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

collapse_shmem()'s VM_BUG_ON_PAGE(PageTransCompound) was unsafe: before
it holds page lock of the first page, racing truncation then extension
might conceivably have inserted a hugepage there already.  Fail with the
SCAN_PAGE_COMPOUND result, instead of crashing (CONFIG_DEBUG_VM=y) or
otherwise mishandling the unexpected hugepage - though later we might
code up a more constructive way of handling it, with SCAN_SUCCESS.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261529310.2275@eggly.anvils
Fixes: f3f0e1d2 ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>	[4.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

khugepaged's collapse_shmem() does almost all of its work, to assemble
the huge new_page from 512 scattered old pages, with the new_page's
refcount frozen to 0 (and refcounts of all old pages so far also frozen
to 0).  Including shmem_getpage() to read in any which were out on swap,
memory reclaim if necessary to allocate their intermediate pages, and
copying over all the data from old to new.

Imagine the frozen refcount as a spinlock held, but without any lock
debugging to highlight the abuse: it's not good, and under serious load
heads into lockups - speculative getters of the page are not expecting
to spin while khugepaged is rescheduled.

One can get a little further under load by hacking around elsewhere; but
fortunately, freezing the new_page turns out to have been entirely
unnecessary, with no hacks needed elsewhere.

The huge new_page lock is already held throughout, and guards all its
subpages as they are brought one by one into the page cache tree; and
anything reading the data in that page, without the lock, before it has
been marked PageUptodate, would already be in the wrong.  So simply
eliminate the freezing of the new_page.

Each of the old pages remains frozen with refcount 0 after it has been
replaced by a new_page subpage in the page cache tree, until they are
all unfrozen on success or failure: just as before.  They could be
unfrozen sooner, but cause no problem once no longer visible to
find_get_entry(), filemap_map_pages() and other speculative lookups.

Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261527570.2275@eggly.anvils
Fixes: f3f0e1d2 ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org>	[4.8+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>