Reshuffle the comment at the top of the source
dropping filenames and moving up human readable strings.

This seems to be somewhat more useful information to start the
source file with. It is also less fragile, f.e. to file renames.
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

This reverts commit a6db2c86 ("mmc: dw_mmc: Don't allow Runtime PM for
SDIO cards")'

As dw_mmc now is capable of preventing runtime PM suspend while SDIO IRQs
are enabled, let's drop the less fine-grained method, which is preventing
runtime PM suspend for all SDIO cards - no matter of whether SDIO IRQs are
being enabled or not.

In this way we don't keep the host runtime PM resumed, unless it's really
needed, thus avoiding to waste power.

Especially when SDIO IRQs is supported via a separate out-of-band IRQ line,
which isn't defined by the SDIO standard, typically the SDIO func driver
doesn't enable SDIO IRQs via sdio_claim_irq(). So, for these cases we can
now allow the dwmmc device to be runtime PM suspended in-between requests.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>

To be able to handle SDIO IRQs the dw_mmc device needs to be powered and
providing clock to the SDIO card. Therefore, we must not allow the device
to be runtime PM suspended while SDIO IRQs are enabled.

To fix this, let's increase the runtime PM usage count while the mmc core
enables SDIO IRQs. Later when the mmc core tells dw_mmc to disable SDIO
IRQs, we drop the usage count to again allow runtime PM suspend.

This now becomes the default behaviour for dw_mmc. In cases where SDIO IRQs
can be re-routed as GPIO wake-ups during runtime PM suspend, one could
potentially allow runtime PM suspend. However, that will have to be
addressed as a separate change on top of this one.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>

Convert to use the more lightweight method for processing SDIO IRQs, which
involves the following changes:

- Enable MMC_CAP2_SDIO_IRQ_NOTHREAD when SDIO IRQ is supported and use
  sdio_signal_irq() instead of mmc_signal_sdio_irq().
- Mask the SDIO IRQ before signaling a new one to be processed.
- Implement the ->ack_sdio_irq() callback to unmask the SDIO IRQ.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>

For hosts not supporting MMC_CAP2_SDIO_IRQ_NOTHREAD but MMC_CAP_SDIO_IRQ,
the SDIO IRQs are processed from a dedicated kernel thread. For these
cases, the host calls mmc_signal_sdio_irq() from its ISR to signal a new
SDIO IRQ.

Signaling an SDIO IRQ makes the host's ->enable_sdio_irq() callback to be
invoked to temporary disable the IRQs, before the kernel thread is woken up
to process it. When processing of the IRQs are completed, they are
re-enabled by the kernel thread, again via invoking the host's
->enable_sdio_irq().

The observation from this, is that the execution path is being unnecessary
complex, as the host driver already knows that it needs to temporary
disable the IRQs before signaling a new one. Moreover, replacing the kernel
thread with a work/workqueue would not only greatly simplify the code, but
also make it more robust.

To address the above problems, let's continue to build upon the support for
MMC_CAP2_SDIO_IRQ_NOTHREAD, as it already implements SDIO IRQs to be
processed without using the clumsy kernel thread and without the ping-pong
calls of the host's ->enable_sdio_irq() callback for each processed IRQ.

Therefore, let's add new API sdio_signal_irq(), which enables hosts to
signal/process SDIO IRQs by using a work/workqueue, rather than using the
kernel thread.

Add also a new host callback ->ack_sdio_irq(), which the work invokes when
the SDIO IRQs have been processed. This informs the host about when it
shall re-enable the SDIO IRQs. Potentially, we could re-use the existing
->enable_sdio_irq() callback instead of adding a new one, however it has
turned out that it's more convenient for hosts to get this information via
a separate callback.

Hosts that wants to use this new method to signal/process SDIO IRQs, must
enable MMC_CAP2_SDIO_IRQ_NOTHREAD and implement the ->ack_sdio_irq()
callback.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>

In cases when MMC_CAP2_SDIO_IRQ_NOTHREAD is set, there is a minor window
for when the mmc host could call sdio_run_irqs(), while in fact an SDIO
func driver could have decided to released the SDIO IRQ via a call to
sdio_release_irq(). In this scenario, processing of the SDIO IRQs are done
even if there is none IRQ claimed, which is not what we want.

To prevent this from happen, close the window by validating that at least
one SDIO IRQs is claimed, before deciding to process them.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>

In case if a pwrseq-emmc has been bound to the host, a call to
mmc_power_up() triggers an eMMC HW reset via the pwrseq_emmc's
->post_power_on() callback. This isn't really what we want, as
mmc_power_up() is called each time when resuming the card.

As a matter of fact, the current approach may also violate the eMMC spec,
as the involved delays managed in pwrseq_emmc assumes both VCC and VCCQ has
been turned on, which isn't the case for VCCQ, unless the regulator is
always on.

Fix this behaviour by aligning to the same procedure used when the mmc host
implements the ->hw_reset() callback and has the MMC_CAP_HW_RESET flag set.
In this way the eMMC HW reset is issued at card detection scan, to cope
with bogus bootloaders and in the error recovery path via the mmc specific
bus_ops->reset() callback.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

The ->reset() callback is needed to implement a better support for eMMC HW
reset. The following changes will take advantage of the new callback.
Suggested-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>

Add the missing endianness conversions when printing the USB
device-descriptor idVendor and idProduct fields during probe.
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

AVR32 is gone. Now it's time to clean up the driver by removing
leftovers that was used by AVR32 related code.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

At the end of either of the read or write loops len is always zero
and hence the non-zero check on len and return of -EIO is redundant
and can be removed.

Detected by CoverityScan, CID#114293 ("Logically dead code")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

ret is signed however is printed as unsigned fix the same.
If printed as a negative number the result is easier to read.
No functional change.
Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.

This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.

Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.

One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications.  For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).

Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.

Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.
Original-patch-by: Oleg Nesterov <oleg@redhat.com>
Original-patch-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull ARM SoC fixes from Olof Johansson:
 "Stream of fixes has slowed down, only a few this week:

   - Some DT fixes for Allwinner platforms, and addition of a clock to
     the R_CCU clock controller that had been missed.

   - A couple of small DT fixes for am335x-sl50"

* tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc:
  arm64: allwinner: a64: Add PLL_PERIPH0 clock to the R_CCU
  ARM: sunxi: h3-h5: Add PLL_PERIPH0 clock to the R_CCU
  ARM: dts: am335x-sl50: Fix cannot claim requested pins for spi0
  ARM: dts: am335x-sl50: Fix card detect pin for mmc1
  arm64: allwinner: h5: Remove syslink to shared DTSI
  ARM: sunxi: h3/h5: fix the compatible of R_CCU

Merge tag 'sunxi-fixes-for-4.12' of https://git.kernel.org/pub/scm/linux/kernel/git/sunxi/linux into fixes

Allwinner fixes for 4.12

A few fixes around the PRCM support that got in 4.12 with a wrong
compatible, and a missing clock in the binding.

* tag 'sunxi-fixes-for-4.12' of https://git.kernel.org/pub/scm/linux/kernel/git/sunxi/linux:
  arm64: allwinner: a64: Add PLL_PERIPH0 clock to the R_CCU
  ARM: sunxi: h3-h5: Add PLL_PERIPH0 clock to the R_CCU
  arm64: allwinner: h5: Remove syslink to shared DTSI
  ARM: sunxi: h3/h5: fix the compatible of R_CCU
Signed-off-by: Olof Johansson <olof@lixom.net>

Merge tag 'omap-for-v4.12/fixes-sl50' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap into fixes

Two fixes for am335x-sl50 to fix a boot time error
for claiming SPI pins, and to fix a SDIO card detect
pin for production version of the device.

* tag 'omap-for-v4.12/fixes-sl50' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap:
  ARM: dts: am335x-sl50: Fix cannot claim requested pins for spi0
  ARM: dts: am335x-sl50: Fix card detect pin for mmc1
Signed-off-by: Olof Johansson <olof@lixom.net>

Pull virtio bugfix from Michael Tsirkin:
 "It turns out balloon does not handle IOMMUs correctly. We should fix
  that at some point, for now let's just disable this configuration"

* tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost:
  virtio_balloon: disable VIOMMU support

Pull i2c fixes from Wolfram Sang:
 "Two driver bugfixes"

* 'i2c/for-current-fixed' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: ismt: fix wrong device address when unmap the data buffer
  i2c: rcar: use correct length when unmapping DMA

Pull MIPS fixes from Ralf Baechle:

 - Three highmem fixes:
    + Fixed mapping initialization
    + Adjust the pkmap location
    + Ensure we use at most one page for PTEs

 - Fix makefile dependencies for .its targets to depend on vmlinux

 - Fix reversed condition in BNEZC and JIALC software branch emulation

 - Only flush initialized flush_insn_slot to avoid NULL pointer
   dereference

 - perf: Remove incorrect odd/even counter handling for I6400

 - ftrace: Fix init functions tracing

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus:
  MIPS: .its targets depend on vmlinux
  MIPS: Fix bnezc/jialc return address calculation
  MIPS: kprobes: flush_insn_slot should flush only if probe initialised
  MIPS: ftrace: fix init functions tracing
  MIPS: mm: adjust PKMAP location
  MIPS: highmem: ensure that we don't use more than one page for PTEs
  MIPS: mm: fixed mappings: correct initialisation
  MIPS: perf: Remove incorrect odd/even counter handling for I6400

virtio balloon bypasses the DMA API entirely so does not support the
VIOMMU right now.  It's not clear we need that support, for now let's
just make sure we don't pretend to support it.

Cc: stable@vger.kernel.org
Cc: Wei Wang <wei.w.wang@intel.com>
Fixes: 1a937693 ("virtio: new feature to detect IOMMU device quirk")
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

Pull x86 fixes from Thomas Gleixner:
 "Two fixlets for x86:

   - Handle WARN_ONs proper with the new UD based WARN implementation

   - Disable 1G mappings when 2M mappings are disabled by kmemleak or
     debug_pagealloc. Otherwise 1G mappings might still be used,
     confusing the debug mechanisms"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/mm: Disable 1GB direct mappings when disabling 2MB mappings
  x86/debug: Handle early WARN_ONs proper

Pull timer fixes from Thomas Gleixner:
 "Three fixlets for timers:

   - Two hot-fixes for the alarmtimer based posix timers, which prevent
     a nasty DOS by self rescheduling timers. The proper cleanup of that
     mess is queued for 4.13

   - Make a function static"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  tick/broadcast: Make tick_broadcast_setup_oneshot() static
  alarmtimer: Rate limit periodic intervals
  alarmtimer: Prevent overflow of relative timers

Pull scheduler fixes from Thomas Gleixner:
 "Two small fixes for the schedulre core:

   - Use the proper switch_mm() variant in idle_task_exit() because that
     code is not called with interrupts disabled.

   - Fix a confusing typo in a printk"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/core: Idle_task_exit() shouldn't use switch_mm_irqs_off()
  sched/fair: Fix typo in printk message

Pull perf fixes from Thomas Gleixner:
 "Three fixes for the perf user space side:

   - Fix the probing of precise_ip level, which got broken recently for
     x86.

   - Unbreak the ARCH=x86_64 build

   - Report module before trying to unwind into the module code, which
     avoids broken stack frames displayed"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf unwind: Report module before querying isactivation in dwfl unwind
  perf tools: Fix build with ARCH=x86_64
  perf evsel: Fix probing of precise_ip level for default cycles event

Pull irq fix from Thomas Gleixner:
 "Add a missing resource release to an error path"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  genirq: Release resources in __setup_irq() error path

Pull objtool fix from Thomas Gleixner:
 "A single fix which adds fortify_panic to the list of no return
  functions"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Add fortify_panic as __noreturn function

Merge tag 'led_fixes_for_4.12-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds

Pull LED fixes from Jacek Anaszewski:
 "Two LED fixes:

   - fix signal source assignment for leds-bcm6328

   - revert patch that intended to fix LED behavior on suspend but it
     had a side effect preventing suspend at all due to uevent being
     sent on trigger removal"

* tag 'led_fixes_for_4.12-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszewski/linux-leds:
  Revert "leds: handle suspend/resume in heartbeat trigger"
  leds: bcm6328: fix signal source assignment for leds 4 to 7

Pull USB fixes from Greg KH:
 "Here are some small gadget and xhci USB fixes for 4.12-rc6.

  Nothing major, but one of the gadget patches does fix a reported oops,
  and the xhci ones resolve reported problems. All have been in
  linux-next with no reported issues"

* tag 'usb-4.12-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
  USB: gadgetfs, dummy-hcd, net2280: fix locking for callbacks
  usb: xhci: ASMedia ASM1042A chipset need shorts TX quirk
  usb: xhci: Fix USB 3.1 supported protocol parsing
  USB: gadget: fix GPF in gadgetfs
  usb: gadget: composite: make sure to reactivate function on unbind

Pull staging and IIO fixes from Greg KH:
 "Here are some small staging and IIO driver fixes for 4.12-rc6.

  Nothing huge, just a few small driver fixes for reported issues. All
  have been in linux-next with no reported issues"

* tag 'staging-4.12-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
  Staging: rtl8723bs: fix an error code in isFileReadable()
  iio: buffer-dmaengine: Add missing header buffer_impl.h
  iio: buffer-dma: Add missing header buffer_impl.h
  iio: adc: meson-saradc: fix potential crash in meson_sar_adc_clear_fifo
  iio: adc: mxs-lradc: Fix return value check in mxs_lradc_adc_probe()
  iio: imu: inv_mpu6050: add accel lpf setting for chip >= MPU6500
  staging: iio: ad7152: Fix deadlock in ad7152_write_raw_samp_freq()

Pull ceph fixes from Ilya Dryomov:
 "A fix for an old ceph ->fh_to_* bug from Luis and two timestamp fixups
  from Zheng, prompted by the ongoing y2038 work"

* tag 'ceph-for-4.12-rc6' of git://github.com/ceph/ceph-client:
  ceph: unify inode i_ctime update
  ceph: use current_kernel_time() to get request time stamp
  ceph: check i_nlink while converting a file handle to dentry

Pull xfs fix from Darrick Wong:
 "One more bugfix for you for 4.12-rc6 to fix something that came up in
  an earlier rc:

   - Fix some bogus ASSERT failures on CONFIG_SMP=n and CONFIG_XFS_DEBUG=y"

* tag 'xfs-4.12-fixes-4' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: fix spurious spin_is_locked() assert failures on non-smp kernels

Pull ufs fixes from Al Viro:
 "Fix assorted ufs bugs: a couple of deadlocks, fs corruption in
  truncate(), oopsen on tail unpacking and truncate when racing with
  vmscan, mild fs corruption (free blocks stats summary buggered, *BSD
  fsck would complain and fix), several instances of broken logics
  around reserved blocks (starting with "check almost never triggers
  when it should" and then there are issues with sufficiently large
  UFS2)"

[ Note: ufs hasn't gotten any loving in a long time, because nobody
  really seems to use it. These ufs fixes are triggered by people
  actually caring now, not some sudden influx of new bugs.  - Linus ]

* 'ufs-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  ufs_truncate_blocks(): fix the case when size is in the last direct block
  ufs: more deadlock prevention on tail unpacking
  ufs: avoid grabbing ->truncate_mutex if possible
  ufs_get_locked_page(): make sure we have buffer_heads
  ufs: fix s_size/s_dsize users
  ufs: fix reserved blocks check
  ufs: make ufs_freespace() return signed
  ufs: fix logics in "ufs: make fsck -f happy"

Pull vfs fixes from Al Viro:
 "A couple of fixes; a leak in mntns_install() caught by Andrei (this
  cycle regression) + d_invalidate() softlockup fix - that had been
  reported by a bunch of people lately, but the problem is pretty old"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fs: don't forget to put old mntns in mntns_install
  Hang/soft lockup in d_invalidate with simultaneous calls

Pull PCI fixes from Bjorn Helgaas:

 - fix another PCI_ENDPOINT build error (merged for v4.12)

 - fix error codes added to config accessors for v4.12

* tag 'pci-v4.12-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci:
  PCI: endpoint: Select CRC32 to fix test build error
  PCI: Make error code types consistent in pci_{read,write}_config_*

Pull fbdev fixes from Bartlomiej Zolnierkiewicz:

 - fix udlfb driver to stop spamming logs (Mike Gerow)

 - add missing endianness conversions in smscufx & udlfb drivers (Johan
   Hovold)

 - fix few gcc warnings/errors (Arnd Bergmann)

* tag 'fbdev-v4.12-rc6' of git://github.com/bzolnier/linux:
  video: fbdev: udlfb: drop log level for blanking
  video: fbdev: via: remove possibly unused variables
  video: fbdev: add missing USB-descriptor endianness conversions
  video: fbdev: avoid int-in-bool-context warning

Merge misc fixes from Andrew Morton:
 "5 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm: correct the comment when reclaimed pages exceed the scanned pages
  userfaultfd: shmem: handle coredumping in handle_userfault()
  mm: numa: avoid waiting on freed migrated pages
  swap: cond_resched in swap_cgroup_prepare()
  mm/memory-failure.c: use compound_head() flags for huge pages

Commit e1587a49 ("mm: vmpressure: fix sending wrong events on
underflow") declared that reclaimed pages exceed the scanned pages due
to the thp reclaim.

That is incorrect because THP will be spilt to normal page and loop
again, which will result in the scanned pages increment.

[akpm@linux-foundation.org: tweak comment text]
Link: http://lkml.kernel.org/r/1496824266-25235-1-git-send-email-zhongjiang@huawei.comSigned-off-by: zhongjiang <zhongjiang@huawei.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Anon and hugetlbfs handle FOLL_DUMP set by get_dump_page() internally to
__get_user_pages().

shmem as opposed has no special FOLL_DUMP handling there so
handle_mm_fault() is invoked without mmap_sem and ends up calling
handle_userfault() that isn't expecting to be invoked without mmap_sem
held.

This makes handle_userfault() fail immediately if invoked through
shmem_vm_ops->fault during coredumping and solves the problem.

The side effect is a BUG_ON with no lock held triggered by the
coredumping process which exits.  Only 4.11 is affected, pre-4.11 anon
memory holes are skipped in __get_user_pages by checking FOLL_DUMP
explicitly against empty pagetables (mm/gup.c:no_page_table()).

It's zero cost as we already had a check for current->flags to prevent
futex to trigger userfaults during exit (PF_EXITING).

Link: http://lkml.kernel.org/r/20170615214838.27429-1-aarcange@redhat.comSigned-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: <stable@vger.kernel.org>	[4.11+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

In do_huge_pmd_numa_page(), we attempt to handle a migrating thp pmd by
waiting until the pmd is unlocked before we return and retry.  However,
we can race with migrate_misplaced_transhuge_page():

    // do_huge_pmd_numa_page                // migrate_misplaced_transhuge_page()
    // Holds 0 refs on page                 // Holds 2 refs on page

    vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd);
    /* ... */
    if (pmd_trans_migrating(*vmf->pmd)) {
            page = pmd_page(*vmf->pmd);
            spin_unlock(vmf->ptl);
                                            ptl = pmd_lock(mm, pmd);
                                            if (page_count(page) != 2)) {
                                                    /* roll back */
                                            }
                                            /* ... */
                                            mlock_migrate_page(new_page, page);
                                            /* ... */
                                            spin_unlock(ptl);
                                            put_page(page);
                                            put_page(page); // page freed here
            wait_on_page_locked(page);
            goto out;
    }

This can result in the freed page having its waiters flag set
unexpectedly, which trips the PAGE_FLAGS_CHECK_AT_PREP checks in the
page alloc/free functions.  This has been observed on arm64 KVM guests.

We can avoid this by having do_huge_pmd_numa_page() take a reference on
the page before dropping the pmd lock, mirroring what we do in
__migration_entry_wait().

When we hit the race, migrate_misplaced_transhuge_page() will see the
reference and abort the migration, as it may do today in other cases.

Fixes: b8916634 ("mm: Prevent parallel splits during THP migration")
Link: http://lkml.kernel.org/r/1497349722-6731-2-git-send-email-will.deacon@arm.comSigned-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Steve Capper <steve.capper@arm.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>