This patch add new 'rcuboost' to each flavor's folder, now we could use:
	'cat /debugfs/rcu/rsp/rcuboost'
to get the selected rsp info.
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This patch add new 'rcubarrier' to each flavor's folder, now we could use:
	'cat /debugfs/rcu/rsp/rcubarrier'
to get the selected rsp info.
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The rcu_state structure's ->completed field is unsigned long, so this
commit adjusts show_one_rcugp()'s printf() format to suit.  Also add
the required ACCESS_ONCE() directives while we are in this function.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This patch removes the interface "rcudata.csv" since it is apparently
not used.
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This patch removed the old RCU debugfs interface and replaced it with
the new one.
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This patch implements the new 'rcu_pending' interface under each rsp
directory, by using the 'CPU units sequence reading', thus avoiding loss
of tracing data.
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This patch implements the new 'rcudata.csv' interface under each rsp
directory, by using the 'CPU units sequence reading', thus avoiding loss
of tracing data.
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This patch implements the new 'rcudata' interface under each rsp
directory, by using the 'CPU units sequence reading', thus avoiding loss
of tracing data.
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This patch add the fundamental facility used by the following patches, so we
can implement the 'CPU units sequence reading' later.

This helps us avoid losing data when there are too many CPUs and too
small of a buffer, since this new approach allows userspace to read out
the data one CPU at a time.  Thus, if the buffer is not large enough,
userspace will get whatever CPUs fit, and can then issue another read
for the remainder of the data.
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This patch will create subdirectory according to each flavor of rcu, the new
structure will be:

	/debugfs/rcu/ -> rsp_0
		      -> rsp_1
		      -> ...

So we can go to '/debugfs/rcu/rsp_0' and get the cpu info of rsp_0 there.
The flavors of RCU are currently rcu_bh, rcu_preempt, and rcu_sched.
Signed-off-by: Michael Wang <wangyun@linux.vnet.ibm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This commit adds the counters to rcu_state and updates them in
synchronize_rcu_expedited() to provide the data needed for debugfs
tracing.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Tracing (debugfs) of expedited RCU primitives is required, which in turn
requires that the relevant data be located where the tracing code can find
it, not in its current static global variables in kernel/rcutree.c.
This commit therefore moves sync_sched_expedited_started and
sync_sched_expedited_done to the rcu_state structure, as fields
->expedited_start and ->expedited_done, respectively.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

There is a counter scheme similar to ticket locking that
synchronize_sched_expedited() uses to service multiple concurrent
callers with the same expedited grace period.  Upon entry, a
sync_sched_expedited_started variable is atomically incremented,
and upon completion of a expedited grace period a separate
sync_sched_expedited_done variable is atomically incremented.

However, if a synchronize_sched_expedited() is delayed while
in try_stop_cpus(), concurrent invocations will increment the
sync_sched_expedited_started counter, which will eventually overflow.
If the original synchronize_sched_expedited() resumes execution just
as the counter overflows, a concurrent invocation could incorrectly
conclude that an expedited grace period elapsed in zero time, which
would be bad.  One could rely on counter size to prevent this from
happening in practice, but the goal is to formally validate this
code, so it needs to be fixed anyway.

This commit therefore checks the gap between the two counters before
incrementing sync_sched_expedited_started, and if the gap is too
large, does a normal grace period instead.  Overflow is thus only
possible if there are more than about 3.5 billion threads on 32-bit
systems, which can be excluded until such time as task_struct fits
into a single byte and 4G/4G patches are accepted into mainline.
It is also easy to encode this limitation into mechanical theorem
provers.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

The ->onofflock field in the rcu_state structure at one time synchronized
CPU-hotplug operations for RCU.  However, its scope has decreased over time
so that it now only protects the lists of orphaned RCU callbacks.  This
commit therefore renames it to ->orphan_lock to reflect its current use.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

This commit causes rcutorture to print the errno if cpu_down() fails
when the rcutorture "verbose" module parameter is specified.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

In the old days, _rcu_barrier() acquired ->onofflock to exclude
rcu_send_cbs_to_orphanage(), which allowed the latter to avoid memory
barriers in callback handling.  However, _rcu_barrier() recently started
doing get_online_cpus() to lock out CPU-hotplug operations entirely, which
means that the comment in rcu_send_cbs_to_orphanage() that talks about
->onofflock is now obsolete.  This commit therefore fixes the comment.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Pull arm64 fixes from Catalin Marinas:
 "Main changes:
   - AArch64 Linux compilation fixes following 3.7-rc1 changes
     (MODULES_USE_ELF_RELA, update_vsyscall() prototype)
   - Unnecessary register setting in start_thread() (thanks to Al Viro)
   - ptrace fixes"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/cmarinas/linux-aarch64:
  arm64: fix alignment padding in assembly code
  arm64: ptrace: use HW_BREAKPOINT_EMPTY type for disabled breakpoints
  arm64: ptrace: make structure padding explicit for debug registers
  arm64: No need to set the x0-x2 registers in start_thread()
  arm64: Ignore memory blocks below PHYS_OFFSET
  arm64: Fix the update_vsyscall() prototype
  arm64: Select MODULES_USE_ELF_RELA
  arm64: Remove duplicate inclusion of mmu_context.h in smp.c

An interesting effect of using the generic version of linkage.h
is that the padding is defined in terms of x86 NOPs, which can have
even more interesting effects when the assembly code looks like this:

ENTRY(func1)
	mov	x0, xzr
ENDPROC(func1)
	// fall through
ENTRY(func2)
	mov	x0, #1
	ret
ENDPROC(func2)

Admittedly, the code is not very nice. But having code from another
architecture doesn't look completely sane either.

The fix is to add arm64's version of linkage.h, which causes the insertion
of proper AArch64 NOPs.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

The min/max call needed to have explicit types on some architectures
(e.g. mn10300). Use clamp_t instead to avoid the warning:

  kernel/sys.c: In function 'override_release':
  kernel/sys.c:1287:10: warning: comparison of distinct pointer types lacks a cast [enabled by default]
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull perf fixes from Ingo Molnar:
 "Assorted small fixes"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf python: Properly link with libtraceevent
  perf hists browser: Add back callchain folding symbol
  perf tools: Fix build on sparc.
  perf python: Link with libtraceevent
  perf python: Initialize 'page_size' variable
  tools lib traceevent: Fix missed freeing of subargs in free_arg() in filter
  lib tools traceevent: Add back pevent assignment in __pevent_parse_format()
  perf hists browser: Fix off-by-two bug on the first column
  perf tools: Remove warnings on JIT samples for srcline sort key
  perf tools: Fix segfault when using srcline sort key
  perf: Require exclude_guest to use PEBS - kernel side enforcement
  perf tool: Precise mode requires exclude_guest

Namhyung Kim reported that the build fails with:

  GEN python/perf.so
  gcc: error: python_ext_build/tmp//../../libtraceevent.a: No such file or directory
  error: command 'gcc' failed with exit status 1
  cp: cannot stat `python_ext_build/lib/perf.so': No such file or directory
  make: *** [python/perf.so] Error 1

We need to propagate the TE_PATH variable to the setup.py file.
Reported-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: http://lkml.kernel.org/n/tip-8umiPbm4sxpknKivbjgykhut@git.kernel.org
[ Fixed superfluous variable build error. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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

Pull perf/urgent fixes from Arnaldo Carvalho de Melo:

* The python binding needs to link with libtraceevent and to initialize
  the 'page_size' variable so that mmaping works again.

* The callchain folding character that appears on the TUI just before
  the overhead had disappeared due to recent changes, add it back.

* Intel PEBS in VT-x context uses the DS address as a guest linear address,
  even though its programmed by the host as a host linear address. This either
  results in guest memory corruption and or the hardware faulting and 'crashing'
  the virtual machine.  Therefore we have to disable PEBS on VT-x enter and
  re-enable on VT-x exit, enforcing a strict exclude_guest.

  Kernel side enforcement fix by Peter Zijlstra, tooling side fix by David Ahern.

* Fix build on sparc due to UAPI, fix from David Miller.

* Fixes for the srclike sort key for unresolved symbols and when processing
  samples in JITted code, where we don't have an ELF file, just an special
  symbol table, fixes from Namhyung Kim.

* Fix some leaks in libtraceevent, from Steven Rostedt.
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Pull ARM soc fixes from Olof Johansson:
 "A set of fixes and some minor cleanups for -rc2:

   - A series from Arnd that fixes warnings in drivers and other code
     included by ARM defconfigs.  Most have been acked by corresponding
     maintainers (and seem quite hard to argue not picking up anyway in
     the few exception cases).
   - A few misc patches from the list for integrator/vt8500/i.MX
   - A batch of fixes to OMAP platforms, fixing:
     - boot problems on beaglebone,
     - regression fixes for local timers
     - clockdomain locking fixes
     - a few boot/sparse warnings
   - For Tegra:
     - Clock rate calculation overflow fix
     - Revert a change that removed timer clocks and a fix for symbol
       name clashes
   - For Renesas:
     - IO accessor / annotation cleanups to remove warnings
   - For Kirkwood/Dove/mvebu:
     - Fixes for device trees for Dove (some minor cleanups, some fixes)
     - Fixes for the mvebu gpio driver
     - Fix build problem for Feroceon due to missing ifdefs
     - Fix lsxl DTS files"

* tag 'fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc: (31 commits)
  ARM: kirkwood: fix buttons on lsxl boards
  ARM: kirkwood: fix LEDs names for lsxl boards
  ARM: Kirkwood: fix disabling CACHE_FEROCEON_L2
  gpio: mvebu: Add missing breaks in mvebu_gpio_irq_set_type
  ARM: dove: Add crypto engine to DT
  ARM: dove: Remove watchdog from DT
  ARM: dove: Restructure SoC device tree descriptor
  ARM: dove: Fix clock names of sata and gbe
  ARM: dove: Fix tauros2 device tree init
  ARM: dove: Add pcie clock support
  ARM: OMAP2+: Allow kernel to boot even if GPMC fails to reserve memory
  ARM: OMAP: clockdomain: Fix locking on _clkdm_clk_hwmod_enable / disable
  ARM: s3c: mark s3c2440_clk_add as __init_refok
  spi/s3c64xx: use correct dma_transfer_direction type
  ARM: OMAP4: devices: fixup OMAP4 DMIC platform device error message
  ARM: OMAP2+: clock data: Add dev-id for the omap-gpmc dummy fck
  ARM: OMAP: resolve sparse warning concerning debug_card_init()
  ARM: OMAP4: Fix twd_local_timer_register regression
  ARM: tegra: add tegra_timer clock
  ARM: tegra: rename tegra system timer
  ...

Emit the magic string that indicates a module has a signature after the
signature data instead of before it.  This allows module_sig_check() to
be made simpler and faster by the elimination of the search for the
magic string.  Instead we just need to do a single memcmp().

This works because at the end of the signature data there is the
fixed-length signature information block.  This block then falls
immediately prior to the magic number.

From the contents of the information block, it is trivial to calculate
the size of the signature data and thus the size of the actual module
data.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

From Jason Cooper:
 - improve #ifdef logic to prevent linker errors with CACHE_FEROCEON_L2
 - lsxl board dts fixes

* tag 'kirkwood_fixes_for_v3.7' of git://git.infradead.org/users/jcooper/linux:
  ARM: kirkwood: fix buttons on lsxl boards
  ARM: kirkwood: fix LEDs names for lsxl boards
  ARM: Kirkwood: fix disabling CACHE_FEROCEON_L2

The module build process no longer creates intermediate files for module
signing, so remove them from .gitignore.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Turn sign-file into perl and merge in x509keyid.  The latter doesn't
need to be a separate script as it doesn't actually need to work out the
SHA1 sum of the X.509 certificate itself, since it can get that from the
X.509 certificate.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Merge branch 'testing/driver-warnings' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc into fixes

A collection of warning fixes on non-ARM code from Arnd Bergmann:

* 'testing/driver-warnings' of git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc:
  ARM: s3c: mark s3c2440_clk_add as __init_refok
  spi/s3c64xx: use correct dma_transfer_direction type
  pcmcia: sharpsl: don't discard sharpsl_pcmcia_ops
  USB: EHCI: mark ehci_orion_conf_mbus_windows __devinit
  mm/slob: use min_t() to compare ARCH_SLAB_MINALIGN
  SCSI: ARM: make fas216_dumpinfo function conditional
  SCSI: ARM: ncr5380/oak uses no interrupts

  /proc/<pid>/numa_maps scans vma and show mempolicy under
  mmap_sem. It sometimes accesses task->mempolicy which can
  be freed without mmap_sem and numa_maps can show some
  garbage while scanning.

This patch tries to take reference count of task->mempolicy at reading
numa_maps before calling get_vma_policy(). By this, task->mempolicy
will not be freed until numa_maps reaches its end.

V2->v3
  -  updated comments to be more verbose.
  -  removed task_lock() in numa_maps code.
V1->V2
  -  access task->mempolicy only once and remember it.  Becase kernel/exit.c
     can overwrite it.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull miscellaneous x86 fixes from Peter Anvin:
 "The biggest ones are fixing suspend/resume breakage on 32 bits, and an
  interrim fix for mapping over holes that allows AMD kit with more than
  1 TB.

  A final solution for the latter is in the works, but involves some
  fairly invasive changes that will probably mean it will only be
  appropriate for 3.8."

* 'x86/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, MCE: Remove bios_cmci_threshold sysfs attribute
  x86, amd, mce: Avoid NULL pointer reference on CPU northbridge lookup
  x86: Exclude E820_RESERVED regions and memory holes above 4 GB from direct mapping.
  x86/cache_info: Use ARRAY_SIZE() in amd_l3_attrs()
  x86/reboot: Remove quirk entry for SBC FITPC
  x86, suspend: Correct the restore of CR4, EFER; skip computing EFLAGS.ID

Merge misc fixes from Andrew Morton:
 "Seven fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (7 patches)
  lib/dma-debug.c: fix __hash_bucket_find()
  mm: compaction: correct the nr_strict va isolated check for CMA
  firmware/memmap: avoid type conflicts with the generic memmap_init()
  pidns: remove recursion from free_pid_ns()
  drivers/video/backlight/lm3639_bl.c: return proper error in lm3639_bled_mode_store() error paths
  kernel/sys.c: fix stack memory content leak via UNAME26
  linux/coredump.h needs asm/siginfo.h

If there is only one match, the unique matched entry should be returned.

Without the fix, the upcoming dma debug interfaces ("dma-debug: new
interfaces to debug dma mapping errors") can't work reliably because
only device and dma_addr are passed to dma_mapping_error().
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Reported-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Joerg Roedel <joerg.roedel@amd.com>
Tested-by: Shuah Khan <shuah.khan@hp.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Jakub Kicinski <kubakici@wp.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Thierry reported that the "iron out" patch for isolate_freepages_block()
had problems due to the strict check being too strict with "mm:
compaction: Iron out isolate_freepages_block() and
isolate_freepages_range() -fix1".  It's possible that more pages than
necessary are isolated but the check still fails and I missed that this
fix was not picked up before RC1.  This same problem has been identified
in 3.7-RC1 by Tony Prisk and should be addressed by the following patch.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Tested-by: Tony Prisk <linux@prisktech.co.nz>
Reported-by: Thierry Reding <thierry.reding@avionic-design.de>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Richard Davies <richard@arachsys.com>
Cc: Shaohua Li <shli@kernel.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Fix this build error:

  drivers/firmware/memmap.c:240:19: error: conflicting types for 'memmap_init'
  arch/ia64/include/asm/pgtable.h:565:17: note: previous declaration of 'memmap_init' was here
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Bernhard Walle <bwalle@suse.de>
Cc: Glauber Costa <glommer@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

free_pid_ns() operates in a recursive fashion:

free_pid_ns(parent)
  put_pid_ns(parent)
    kref_put(&ns->kref, free_pid_ns);
      free_pid_ns

thus if there was a huge nesting of namespaces the userspace may trigger
avalanche calling of free_pid_ns leading to kernel stack exhausting and a
panic eventually.

This patch turns the recursion into an iterative loop.

Based on a patch by Andrew Vagin.

[akpm@linux-foundation.org: export put_pid_ns() to modules]
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Andrew Vagin <avagin@openvz.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Calling uname() with the UNAME26 personality set allows a leak of kernel
stack contents.  This fixes it by defensively calculating the length of
copy_to_user() call, making the len argument unsigned, and initializing
the stack buffer to zero (now technically unneeded, but hey, overkill).

CVE-2012-0957
Reported-by: PaX Team <pageexec@freemail.hu>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit 5ab1c309 ("coredump: pass siginfo_t* to do_coredump() and
below, not merely signr") added siginfo_t to linux/coredump.h but forgot
to include asm/siginfo.h.  This breaks the build for UML/i386.  (And any
other arch where asm/siginfo.h is not magically preincluded...)

  In file included from arch/x86/um/elfcore.c:2:0: include/linux/coredump.h:15:25: error: unknown type name 'siginfo_t'
  make[1]: *** [arch/x86/um/elfcore.o] Error 1
Signed-off-by: Richard Weinberger <richard@nod.at>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Amerigo Wang <amwang@redhat.com>
Cc: "Jonathan M. Foote" <jmfoote@cert.org>
Cc: Roland McGrath <roland@hack.frob.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

In commit 0b173bc4 ("mm: kill vma flag VM_CAN_NONLINEAR") we
replaced the VM_CAN_NONLINEAR test with checking whether the mapping has
a '->remap_pages()' vm operation, but there is no guarantee that there
it even has a vm_ops pointer at all.

Add the appropriate test for NULL vm_ops.
Reported-by: Sasha Levin <levinsasha928@gmail.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>