At Connectathon 2016, we found that recent upstream Linux clients
would occasionally send a LOCK operation with a zero stateid. This
appeared to happen in close proximity to another thread returning
a delegation before unlinking the same file while it remained open.

Earlier, the client received a write delegation on this file and
returned the open stateid. Now, as it is getting ready to unlink the
file, it returns the write delegation. But there is still an open
file descriptor on that file, so the client must OPEN the file
again before it returns the delegation.

Since commit 24311f88 ('NFSv4: Recovery of recalled read
delegations is broken'), nfs_open_delegation_recall() clears the
NFS_DELEGATED_STATE flag _before_ it sends the OPEN. This allows a
racing LOCK on the same inode to be put on the wire before the OPEN
operation has returned a valid open stateid.

To eliminate this race, serialize delegation return with the
acquisition of a file lock on the same file. Adopt the same approach
as is used in the unlock path.

This patch also eliminates a similar race seen when sending a LOCK
operation at the same time as returning a delegation on the same file.

Fixes: 24311f88 ('NFSv4: Recovery of recalled read ... ')
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
[Anna: Add sentence about LOCK / delegation race]
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

A mirror can be shared between multiple layouts, even with different
iomodes. That makes stats gathering simpler, but it causes a problem
when we get different creds in READ vs. RW layouts.

The current code drops the newer credentials onto the floor when this
occurs. That's problematic when you fetch a READ layout first, and then
a RW. If the READ layout doesn't have the correct creds to do a write,
then writes will fail.

We could just overwrite the READ credentials with the RW ones, but that
would break the ability for the server to fence the layout for reads if
things go awry. We need to be able to revert to the earlier READ creds
if the RW layout is returned afterward.

The simplest fix is to just keep two sets of creds per mirror. One for
READ layouts and one for RW, and then use the appropriate set depending
on the iomode of the layout segment.

Also fix up some RCU nits that sparse found.
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

We're just as likely to have allocation problems here as we would if we
delay looking up the credential like we currently do. Fix the code to
get a rpc_cred reference early, as soon as the mirror is set up.

This allows us to eliminate the mirror early if there is a problem
getting an rpc credential. This also allows us to drop the uid/gid
from the layout_mirror struct as well.

In the event that we find an existing mirror where this one would go, we
swap in the new creds unconditionally, and drop the reference to the old
one.

Note that the old ff_layout_update_mirror_cred function wouldn't set
this pointer unless the DS version was 3, but we don't know what the DS
version is at this point. I'm a little unclear on why it did that as you
still need creds to talk to v4 servers as well. I have the code set
it regardless of the DS version here.

Also note the change to using generic creds instead of calling
lookup_cred directly. With that change, we also need to populate the
group_info pointer in the acred as some functions expect that to never
be NULL. Instead of allocating one every time however, we can allocate
one when the module is loaded and share it since the group_info is
refcounted.
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

In later patches, we're going to want to allow the creds to be updated
when we get a new layout with updated creds. Have this function take
a reference to the cred that is later put once the call has been
dispatched.

Also, prepare for this change by ensuring we follow RCU rules when
getting a reference to the cred as well.
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

All the callers already call that function before calling into here,
so it ends up being a no-op anyway.
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Sometimes we might have a RCU managed credential pointer and don't want
to use locking to handle it. Add a function that will take a reference
to the cred iff the refcount is not already zero. Callers can dereference
the pointer under the rcu_read_lock and use that function to take a
reference only if the cred is not on its way to destruction.
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Add function rpc_lookup_generic_cred, which allows lookups of a generic
credential that's not current_cred().

[jlayton: add gfp_t parm]
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

We need to be able to call the generic_cred creator from different
contexts. Add a gfp_t parm to the crcreate operation and to
rpcauth_lookup_credcache. For now, we just push the gfp_t parms up
one level to the *_lookup_cred functions.
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

An xdr_buf with head[0].iov_len = 0 and page_len = 0 will cause
xdr_init_decode() to incorrectly setup the xdr_stream.  Specifically,
xdr->end is never initialized.
Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Commit ea2cf228 created nfs_commit_info and saved &inode->i_lock inside
this NFS specific structure.  This obscures the usage of i_lock.
Instead, save struct inode * so later it's clear the spinlock taken is
i_lock.

Should be no functional change.
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

This will pop a warning if we count too many good bytes.
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Like other resend paths, mark the (old) hdr as NFS_IOHDR_REDO. This
ensures the hdr completion function will not count the (old) hdr
as good bytes.

Also, vector the error back through the hdr->task.tk_status like other
retry calls.

This fixes a bug with the FlexFiles layout where libaio was reporting more
bytes read than requested.
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

Pull misc driver fixes from Gfreg KH:
 "Here are three small fixes for some driver problems that were
  reported.  Full details in the shortlog below.

  All of these have been in linux-next with no reported issues"

* tag 'char-misc-4.6-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
  nvmem: mxs-ocotp: fix buffer overflow in read
  Drivers: hv: vmbus: Fix signaling logic in hv_need_to_signal_on_read()
  misc: mic: Fix for double fetch security bug in VOP driver

Pull IIO driver fixes from Grek KH:
 "It's really just IIO drivers here, some small fixes that resolve some
  'crash on boot' errors that have shown up in the -rc series, and other
  bugfixes that are required.

  All have been in linux-next with no reported problems"

* tag 'staging-4.6-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
  iio: imu: mpu6050: Fix name/chip_id when using ACPI
  iio: imu: mpu6050: fix possible NULL dereferences
  iio:adc:at91-sama5d2: Repair crash on module removal
  iio: ak8975: fix maybe-uninitialized warning
  iio: ak8975: Fix NULL pointer exception on early interrupt

Pull USB fixes from Greg KH:
 "Here are some last-remaining fixes for USB drivers to resolve issues
  that have shown up in testing.  And two new device ids as well.

  All of these have been in linux-next with no reported issues"

* tag 'usb-4.6-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb:
  Revert "USB / PM: Allow USB devices to remain runtime-suspended when sleeping"
  usb: musb: jz4740: fix error check of usb_get_phy()
  Revert "usb: musb: musb_host: Enable HCD_BH flag to handle urb return in bottom half"
  usb: musb: gadget: nuke endpoint before setting its descriptor to NULL
  USB: serial: cp210x: add Straizona Focusers device ids
  USB: serial: cp210x: add ID for Link ECU

Pull ARM fixes from Russell King:
 "These are a number of updates to fix a few problems found in the ARM
  nommu code over the last couple of years, caused mostly by changes on
  the mmu side"

* 'fixes' of git://git.armlinux.org.uk/~rmk/linux-arm:
  ARM: 8573/1: domain: move {set,get}_domain under config guard
  ARM: 8572/1: nommu: change memory reserve for the vectors
  ARM: 8571/1: nommu: fix PMSAv7 setup

Pull media fixes from Mauro Carvalho Chehab:

  - deadlock fixes on driver probe at exynos4-is and s43-camif drivers

  - a build breakage if media controller is enabled and USB or PCI is
   built as module.

* tag 'media/v4.6-5' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media:
  [media] media-device: fix builds when USB or PCI is compiled as module
  [media] media: s3c-camif: fix deadlock on driver probe()
  [media] media: exynos4-is: fix deadlock on driver probe

Pull libata fixes from Tejun Heo:
 "An ahci driver addition and updates to ahci port enable handling for
  some platform devices"

* 'for-4.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata:
  ata: add AMD Seattle platform driver
  ARM: dts: apq8064: add ahci ports-implemented mask
  ata: ahci-platform: Add ports-implemented DT bindings.
  libahci: save port map for forced port map

Pull rdma fix from Doug Ledford:
 "Fix for max sector calculation in iSER"

* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dledford/rdma:
  IB/iser: Fix max_sectors calculation

Pull writeback fix from Jens Axboe:
 "Just a single fix for domain aware writeback, fixing a regression that
  can cause balance_dirty_pages() to keep looping while not getting any
  work done"

* 'for-linus' of git://git.kernel.dk/linux-block:
  writeback: Fix performance regression in wb_over_bg_thresh()

Pull x86 fixes from Ingo Molnar:
 "This contains two fixes: a boot fix for older SGI/UV systems, and an
  APIC calibration fix"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/tsc: Read all ratio bits from MSR_PLATFORM_INFO
  x86/platform/UV: Bring back the call to map_low_mmrs in uv_system_init

Pull power management and ACPI fixes from Rafael Wysocki:
 "Fixes for problems introduced or discovered recently (intel_pstate,
  sti-cpufreq, ARM64 cpuidle, Operating Performance Points framework,
  generic device properties framework) and one fix for a hotplug-related
  deadlock in ACPICA that's been there forever, but is nasty enough.

  Specifics:

   - Fix for a recent regression in the intel_pstate driver causing it
     to fail to restore the HWP (HW-managed P-states) configuration of
     the boot CPU after suspend-to-RAM (Rafael Wysocki).

   - Fix for two recent regressions in the intel_pstate driver, one that
     can trigger a divide by zero if the driver is accessed via sysfs
     before it manages to take the first sample and one causing it to
     fail to update a structure field used in a trace point, so the
     information coming from it is less useful (Rafael Wysocki).

   - Fix for a problem in the sti-cpufreq driver introduced during the
     4.5 cycle that causes it to break CPU PM in multi-platform kernels
     by registering cpufreq-dt (which subsequently doesn't work)
     unconditionally and preventing the driver that would actually work
     from registering (Sudeep Holla).

   - Stable-candidate fix for an ARM64 cpuidle issue causing idle state
     usage counters to be incorrectly updated for idle states that were
     not entered due to errors (James Morse).

   - Fix for a recently introduced issue in the OPP (Operating
     Performance Points) framework causing it to print bogus error
     messages for missing optional regulators (Viresh Kumar).

   - Fix for a recently introduced issue in the generic device
     properties framework that may cause it to attempt to dereferece and
     invalid pointer in some cases (Heikki Krogerus).

   - Fix for a deadlock in the ACPICA core that may be triggered by
     device (eg Thunderbolt) hotplug (Prarit Bhargava)"

* tag 'pm+acpi-4.6-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  PM / OPP: Remove useless check
  ACPICA: Dispatcher: Update thread ID for recursive method calls
  intel_pstate: Fix intel_pstate_get()
  cpufreq: intel_pstate: Fix HWP on boot CPU after system resume
  cpufreq: st: enable selective initialization based on the platform
  ARM: cpuidle: Pass on arm_cpuidle_suspend()'s return value
  device property: Avoid potential dereferences of invalid pointers

Pull scheduler fix from Ingo Molnar:
 "This contains a single fix that fixes a nohz tick stopping bug when
  mixed-poliocy SCHED_FIFO and SCHED_RR tasks are present on a runqueue"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  nohz/full, sched/rt: Fix missed tick-reenabling bug in sched_can_stop_tick()

Pull perf fixes from Ingo Molnar:
 "This tree contains two fixes: new Intel CPU model numbers and an
  AMD/iommu uncore PMU driver fix"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/amd/iommu: Do not register a task ctx for uncore like PMUs
  perf/x86: Add model numbers for Kabylake CPUs

Pull EFI fixes from Ingo Molnar:
 "This tree contains three fixes: a console spam fix, a file pattern fix
  and a sysfb_efi fix for a bug that triggered on older ThinkPads"

* 'efi-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/sysfb_efi: Fix valid BAR address range check
  x86/efi-bgrt: Switch all pr_err() to pr_notice() for invalid BGRT
  MAINTAINERS: Remove asterisk from EFI directory names

Pull parisc fix from Helge Deller:
 "Patch from Dmitry V Levin to fix a kernel crash when a straced process
  calls the (invalid) syscall which is equal to value of __NR_Linux_syscalls"

* 'parisc-4.6-5' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  parisc: fix a bug when syscall number of tracee is __NR_Linux_syscalls

Pull ARC fixes from Vineet Gupta:
 "Late in the cycle, but this has fixes for couple of issues: a PAE40
  boot crash and Arnd spotting lack of barriers in BE io-accessors.

  The 3rd patch for enabling highmem in low physical mem ;-) honestly is
  more than a "fix" but its been in works for some time, seems to be
  stable in testing and enables 2 of our customers to go forward with
  4.6 kernel.

   - Fix for PTE truncation in PAE40 builds
   - Fix for big endian IO accessors lacking IO barrier
   - Allow HIGHMEM to work with low physical addresses"

* tag 'arc-4.6-rc7-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARC: support HIGHMEM even without PAE40
  ARC: Fix PAE40 boot failures due to PTE truncation
  ARC: Add missing io barriers to io{read,write}{16,32}be()

Pull powerpc fix from Michael Ellerman:
 "Fix bad inline asm constraint in create_zero_mask() from Anton
  Blanchard"

* tag 'powerpc-4.6-5' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc: Fix bad inline asm constraint in create_zero_mask()

Pull drm fixes from Dave Airlie:
 "Fixes for i915, amdgpu/radeon and imx.

  The IMX fix is for an autoloading regression found in Fedora.  The
  radeon fixes, are the same fix to amdgpu/radeon to avoid a hardware
  lockup in some circumstances with a bad mode, and a double free bug I
  took a few hours chasing down the other morning.

  The i915 fixes are across the board, all stable material, and fixing
  some hangs and suspend/resume issues, along with a live status
  regressions"

* 'drm-fixes' of git://people.freedesktop.org/~airlied/linux:
  gpu: ipu-v3: Fix imx-ipuv3-crtc module autoloading
  drm/amdgpu: make sure vertical front porch is at least 1
  drm/radeon: make sure vertical front porch is at least 1
  drm/amdgpu: set metadata pointer to NULL after freeing.
  drm/i915: Make RPS EI/thresholds multiple of 25 on SNB-BDW
  drm/i915: Fake HDMI live status
  drm/i915: Fix eDP low vswing for Broadwell
  drm/i915/ddi: Fix eDP VDD handling during booting and suspend/resume
  drm/i915: Fix system resume if PCI device remained enabled
  drm/i915: Avoid stalling on pending flips for legacy cursor updates

Do not load one entry beyond the end of the syscall table when the
syscall number of a traced process equals to __NR_Linux_syscalls.
Similar bug with regular processes was fixed by commit 3bb457af
("[PARISC] Fix bug when syscall nr is __NR_Linux_syscalls").

This bug was found by strace test suite.

Cc: stable@vger.kernel.org
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Helge Deller <deller@gmx.de>

* pm-opp-fixes:
  PM / OPP: Remove useless check

* pm-cpufreq-fixes:
  intel_pstate: Fix intel_pstate_get()
  cpufreq: intel_pstate: Fix HWP on boot CPU after system resume
  cpufreq: st: enable selective initialization based on the platform

* pm-cpuidle-fixes:
  ARM: cpuidle: Pass on arm_cpuidle_suspend()'s return value

* acpica-fixes:
  ACPICA: Dispatcher: Update thread ID for recursive method calls

* device-properties-fixes:
  device property: Avoid potential dereferences of invalid pointers

Currently we read the tsc radio: ratio = (MSR_PLATFORM_INFO >> 8) & 0x1f;

Thus we get bit 8-12 of MSR_PLATFORM_INFO, however according to the SDM
(35.5), the ratio bits are bit 8-15.

Ignoring the upper bits can result in an incorrect tsc ratio, which causes the
TSC calibration and the Local APIC timer frequency to be incorrect.

Fix this problem by masking 0xff instead.

[ tglx: Massaged changelog ]

Fixes: 7da7c156 "x86, tsc: Add static (MSR) TSC calibration on Intel Atom SoCs"
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: stable@vger.kernel.org
Cc: Bin Gao <bin.gao@intel.com>
Cc: Len Brown <lenb@kernel.org>
Link: http://lkml.kernel.org/r/1462505619-5516-1-git-send-email-yu.c.chen@intel.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

Merge fixes from Andrew Morton:
 "14 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  byteswap: try to avoid __builtin_constant_p gcc bug
  lib/stackdepot: avoid to return 0 handle
  mm: fix kcompactd hang during memory offlining
  modpost: fix module autoloading for OF devices with generic compatible property
  proc: prevent accessing /proc/<PID>/environ until it's ready
  mm/zswap: provide unique zpool name
  mm: thp: kvm: fix memory corruption in KVM with THP enabled
  MAINTAINERS: fix Rajendra Nayak's address
  mm, cma: prevent nr_isolated_* counters from going negative
  mm: update min_free_kbytes from khugepaged after core initialization
  huge pagecache: mmap_sem is unlocked when truncation splits pmd
  rapidio/mport_cdev: fix uapi type definitions
  mm: memcontrol: let v2 cgroups follow changes in system swappiness
  mm: thp: correct split_huge_pages file permission

Apparently patchwork ended up truncating the full name.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull libnvdimm fixes from Dan Williams:

 - a fix for the persistent memory 'struct page' driver.  The
   implementation overlooked the fact that pages are allocated in 2MB
   units leading to -ENOMEM when establishing some configurations.

   It's tagged for -stable as the problem was introduced with the
   initial implementation in 4.5.

 - The new "error status translation" routine, introduced with the 4.6
   updates to the nfit driver, missed a necessary path in
   acpi_nfit_ctl().

   The end result is that we are falsely assuming commands complete
   successfully when the embedded status says otherwise.

* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  nfit: fix translation of command status results
  libnvdimm, pfn: fix memmap reservation sizing

This is another attempt to avoid a regression in wwn_to_u64() after that
started using get_unaligned_be64(), which in turn ran into a bug on
gcc-4.9 through 6.1.

The regression got introduced due to the combination of two separate
workarounds (commits e3bde956: "include/linux/unaligned: force
inlining of byteswap operations" and ef3fb242: "scsi: fc: use
get/put_unaligned64 for wwn access") that each try to sidestep distinct
problems with gcc behavior (code growth and increased stack usage).

Unfortunately after both have been applied, a more serious gcc bug has
been uncovered, leading to incorrect object code that discards part of a
function and causes undefined behavior.

As part of this problem is how __builtin_constant_p gets evaluated on an
argument passed by reference into an inline function, this avoids the
use of __builtin_constant_p() for all architectures that set
CONFIG_ARCH_USE_BUILTIN_BSWAP.  Most architectures do not set
ARCH_SUPPORTS_OPTIMIZED_INLINING, which means they probably do not
suffer from the problem in the qla2xxx driver, but they might still run
into it elsewhere.

Both of the original workarounds were only merged in the 4.6 kernel, and
the bug that is fixed by this patch should only appear if both are
there, so we probably don't need to backport the fix.  On the other
hand, it works by simplifying the code path and should not have any
negative effects.

[arnd@arndb.de: fix older gcc warnings]
  (http://lkml.kernel.org/r/12243652.bxSxEgjgfk@wuerfel)
Link: https://lkml.org/lkml/headers/2016/4/12/1103
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70232
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646
Fixes: e3bde956 ("include/linux/unaligned: force inlining of byteswap operations")
Fixes: ef3fb242 ("scsi: fc: use get/put_unaligned64 for wwn access")
Link: http://lkml.kernel.org/r/1780465.XdtPJpi8Tt@wuerfelSigned-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Josh Poimboeuf <jpoimboe@redhat.com> # on gcc-5.3
Tested-by: Quinn Tran <quinn.tran@qlogic.com>
Cc: Martin Jambor <mjambor@suse.cz>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Himanshu Madhani <himanshu.madhani@qlogic.com>
Cc: Jan Hubicka <hubicka@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Recently, we allow to save the stacktrace whose hashed value is 0.  It
causes the problem that stackdepot could return 0 even if in success.
User of stackdepot cannot distinguish whether it is success or not so we
need to solve this problem.  In this patch, 1 bit are added to handle
and make valid handle none 0 by setting this bit.  After that, valid
handle will not be 0 and 0 handle will represent failure correctly.

Fixes: 33334e25 ("lib/stackdepot.c: allow the stack trace hash to be zero")
Link: http://lkml.kernel.org/r/1462252403-1106-1-git-send-email-iamjoonsoo.kim@lge.comSigned-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Assume memory47 is the last online block left in node1.  This will hang:

  # echo offline > /sys/devices/system/node/node1/memory47/state

After a couple of minutes, the following pops up in dmesg:

  INFO: task bash:957 blocked for more than 120 seconds.
         Not tainted 4.6.0-rc6+ #6
  "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  bash            D ffff8800b7adbaf8     0   957    951 0x00000000
  Call Trace:
    schedule+0x35/0x80
    schedule_timeout+0x1ac/0x270
    wait_for_completion+0xe1/0x120
    kthread_stop+0x4f/0x110
    kcompactd_stop+0x26/0x40
    __offline_pages.constprop.28+0x7e6/0x840
    offline_pages+0x11/0x20
    memory_block_action+0x73/0x1d0
    memory_subsys_offline+0x47/0x60
    device_offline+0x86/0xb0
    store_mem_state+0xda/0xf0
    dev_attr_store+0x18/0x30
    sysfs_kf_write+0x37/0x40
    kernfs_fop_write+0x11d/0x170
    __vfs_write+0x37/0x120
    vfs_write+0xa9/0x1a0
    SyS_write+0x55/0xc0
    entry_SYSCALL_64_fastpath+0x1a/0xa4

kcompactd is waiting for kcompactd_max_order > 0 when it's woken up to
actually exit.  Check kthread_should_stop() to break out of the wait.

Fixes: 698b1b30 ("mm, compaction: introduce kcompactd").
Reported-by: Reza Arbab <arbab@linux.vnet.ibm.com>
Tested-by: Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: David Rientjes <rientjes@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>