Use irq_set_handler_locked() as it avoids a redundant lookup of the
irq descriptor.

Search and replacement was done with coccinelle.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: LKML <linux-kernel@vger.kernel.org>
Patchwork: https://patchwork.linux-mips.org/patch/10701/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Hand in irq_data and avoid the redundant lookup of irq_desc.

Originally-from: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10700/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

This is a preparatory patch for moving irq_data struct members.
Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mips@linux-mips.org
Cc: LKML <linux-kernel@vger.kernel.org>
Patchwork: https://patchwork.linux-mips.org/patch/10699/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Chained irq handlers usually set up handler data as well. We now have
a function to set both under irq_desc->lock. Replace the two calls
with one.

Search and conversion was done with coccinelle.
Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Patchwork: https://patchwork.linux-mips.org/patch/10698/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Chained irq handlers usually set up handler data as well. We now have
a function to set both under irq_desc->lock. Replace the two calls
with one.

Search and conversion was done with coccinelle.
Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: linux-mips@linux-mips.org
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Patchwork: https://patchwork.linux-mips.org/patch/10697/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Chained irq handlers usually set up handler data as well. We now have
a function to set both under irq_desc->lock. Replace the two calls
with one.

Search and conversion was done with coccinelle.
Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: linux-mips@linux-mips.org
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Patchwork: https://patchwork.linux-mips.org/patch/10696/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Chained irq handlers usually set up handler data as well. We now have
a function to set both under irq_desc->lock. Replace the two calls
with one.

Search and conversion was done with coccinelle.
Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Julia Lawall <Julia.Lawall@lip6.fr>
Cc: linux-mips@linux-mips.org
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Patchwork: https://patchwork.linux-mips.org/patch/10695/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Set up the I6400 FTLB probability similar to P5600 and proAptiv.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10652/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

R6 has dropped the MMUExtDef field from the config4 register and it
now returns 0. However, the return value means nothing in that case
and the only supported configuration for R6 is the VTLB+FTLB
(MMUextDef == 3). As a result, rework the code so that the correct
value is set for R6 cores.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10651/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Add a default case for the FTLB enable/disable code. This will be used
to detect that something went wrong in the set_ftlb_enable() function
either because that function knows nothing about the running core, or
simply because the core can't turn its FTLB on/off.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10650/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

We are so early in the boot process where we really don't want to
stall and wait for CP0 FTLB related changes become visible so just drop
the cp0 hazard barrier.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10649/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

CM3 uses a 64-bit counter and compare registers so add support for
them in the GIC counter interrupt.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10648/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Previously, the GIC accessors were only accessing u32 registers but
newer CMs may actually be 64-bit on MIPS64 cores. As a result of which,
extended these accessors to support 64-bit reads and writes.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10709/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

The CM cache error reporting code is not Malta specific and as such it
should live in the mips-cm.c file. Moreover, CM2 and CM3 differ in the
way cache errors are being recorded to the registers so extend the
previous code to add support for the CM3 as well.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10646/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

The GCR CPC base register is 64-bit on 64-bit processors so use the
appropriate field.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10645/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

The CMGCRBase register (CP0, 15, 3) register is 64-bit on MIPS64
so we change its type to unsigned long.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10644/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Previously, the CM accessors were only accessing CM registers as u32
types instead of using the native CM register with. However, newer CMs
may actually be 64-bit on MIPS64 cores. Fortunately, current 64-bit CMs
(CM3) hold all the useful configuration bits in the lower half of the
64-bit registers (at least most of them) so they can still be accessed
using the current 32-bit accessors.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10707/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Allow platforms to perform platform-specific steps before configuring
the L2 cache. This is necessary for platforms with CM3 since the L2
parameters no longer live in the Config2 register.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10642/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Detect the L2 cache configuration from GCR_L2_CONFIG when a CM3 is
present in the system, rather than from Config2 which does not expose
the L2 configuration on I6400.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10641/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Provide accessor functions for the GCR_L2_CONFIG register introduced
with CM3, and define the bits included in the register.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10639/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Provide a function to trivially return the version of the CM present in
the system, or 0 if no CM is present. The mips_cm_revision() will be
used later on to determine the CM register width, so it must not use
the regular CM accessors to read the revision register since that will
lead to build failures due to recursive inlines.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10655/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

R6 does not support the MIPS MT ASE and the CMP/SMP options so
restrict them in order to prevent users from selecting incompatible
SMP configuration for R6 cores. We also disable the CPS/SMP option
because its support hasn't been added to the CPS code yet.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10637/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Add a case in cpu_probe_mips for the MIPS I6400 processor ID, which sets
the CPU type to the new CPU_I6400.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10636/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Add a CPU_I6400 case to various switch statements, doing the same thing
as for CPU_P5600.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10635/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Add a Processor ID and CPU type for the MIPS I6400 core.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10634/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Remove the ugly cross tree include now that IRQCHIP_DECLARE moved to
linux/irqchip.h.
Signed-off-by: Alban Bedel <albeu@free.fr>
Cc: linux-mips@linux-mips.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: Qais Yousef <qais.yousef@imgtec.com>
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/10633/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Pull SCSI fixes from James Bottomley:
 "A couple of major (hang and deadlock) fixes with fortunately fairly
  rare triggering conditions.  The PM oops is only really triggered by
  people using enclosure services (rare) and the fnic driver is mostly
  used in enterprise environments"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  SCSI: Fix NULL pointer dereference in runtime PM
  fnic: Use the local variable instead of I/O flag to acquire io_req_lock in fnic_queuecommand() to avoid deadloack

Pull MIPS bug fixes from Ralf Baechle:
 "Two more fixes for 4.2.

  One fixes a build issue with the LLVM assembler - LLVM assembler macro
  names are case sensitive, GNU as macro names are insensitive; the
  other corrects a license string (GPL v2, not GPLv2) such that the
  module loader will recognice the license correctly"

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus:
  FIRMWARE: bcm47xx_nvram: Fix module license.
  MIPS: Fix LLVM build issue.

Pull 9p regression fix from Al Viro:
 "Fix for breakage introduced when switching p9_client_{read,write}() to
  struct iov_iter * (went into 4.1)"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  9p: ensure err is initialized to 0 in p9_client_read/write

Some use of those functions were providing unitialized values to those
functions. Notably, when reading 0 bytes from an empty file on a 9P
filesystem, the return code of read() was not 0.

Tested with this simple program:

    #include <assert.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    #include <unistd.h>

    int main(int argc, const char **argv)
    {
        assert(argc == 2);
        char buffer[256];
        int fd = open(argv[1], O_RDONLY|O_NOCTTY);
        assert(fd >= 0);
        assert(read(fd, buffer, 0) == 0);
        return 0;
    }

Cc: stable@vger.kernel.org # v4.1
Signed-off-by: Vincent Bernat <vincent@bernat.im>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Pull ARM fixes from Russell King:
 "Another couple of small ARM fixes.

  A patch from Masahiro Yamada who noticed that "make -jN all zImage"
  would end up generating bad images where N > 1, and a patch from
  Nicolas to fix the Marvell CPU user access optimisation code when page
  faults are disabled"

* 'fixes' of git://ftp.arm.linux.org.uk/~rmk/linux-arm:
  ARM: 8418/1: add boot image dependencies to not generate invalid images
  ARM: 8414/1: __copy_to_user_memcpy: fix mmap semaphore usage

Pull x86 fixes from Ingo Molnar:
 "Various low level fixes: fix more fallout from the FPU rework and the
  asm entry code rework, plus an MSI rework fix, and an idle-tracing fix"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/fpu/math-emu: Fix crash in fork()
  x86/fpu/math-emu: Fix math-emu boot crash
  x86/idle: Restore trace_cpu_idle to mwait_idle() calls
  x86/irq: Build correct vector mapping for multiple MSI interrupts
  Revert "sched/x86_64: Don't save flags on context switch"

Pull perf fixes from Ingo Molnar:
 "Tooling fixes: a 'perf record' deadlock fix plus debuggability fixes"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf top: Show backtrace when handling a SIGSEGV on --stdio mode
  perf tools: Fix buildid processing
  perf tools: Make fork event processing more resilient
  perf tools: Avoid deadlock when map_groups are broken

Pull irq fixes from Thomas Gleixner:
 "A series of small fixlets for a regression visible on OMAP devices
  caused by the conversion of the OMAP interrupt chips to hierarchical
  interrupt domains.  Mostly one liners on the driver side plus a small
  helper function in the core to avoid open coded mess in the drivers"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irqchip/crossbar: Restore set_wake functionality
  irqchip/crossbar: Restore the mask on suspend behaviour
  ARM: OMAP: wakeupgen: Restore the irq_set_type() mechanism
  irqchip/crossbar: Restore the irq_set_type() mechanism
  genirq: Introduce irq_chip_set_type_parent() helper
  genirq: Don't return ENOSYS in irq_chip_retrigger_hierarchy

Pull timer fixes from Thomas Gleixner:
 "Two minimalistic fixes for 4.2 regressions:

   - Eric fixed a thinko in the timer_list base switching code caused by
     the overhaul of the timer wheel.  It can cause a cpu to see the
     wrong base for a timer while we move the timer around.

   - Guenter fixed a regression for IMX if booted w/o device tree, where
     the timer interrupt is not initialized and therefor the machine
     fails to boot"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  clocksource/imx: Fix boot with non-DT systems
  timer: Write timer->flags atomically

During later stages of math-emu bootup the following crash triggers:

	 math_emulate: 0060:c100d0a8
	 Kernel panic - not syncing: Math emulation needed in kernel
	 CPU: 0 PID: 1511 Comm: login Not tainted 4.2.0-rc7+ #1012
	 [...]
	 Call Trace:
	  [<c181d50d>] dump_stack+0x41/0x52
	  [<c181c918>] panic+0x77/0x189
	  [<c1003530>] ? math_error+0x140/0x140
	  [<c164c2d7>] math_emulate+0xba7/0xbd0
	  [<c100d0a8>] ? fpu__copy+0x138/0x1c0
	  [<c1109c3c>] ? __alloc_pages_nodemask+0x12c/0x870
	  [<c136ac20>] ? proc_clear_tty+0x40/0x70
	  [<c136ac6e>] ? session_clear_tty+0x1e/0x30
	  [<c1003530>] ? math_error+0x140/0x140
	  [<c1003575>] do_device_not_available+0x45/0x70
	  [<c100d0a8>] ? fpu__copy+0x138/0x1c0
	  [<c18258e6>] error_code+0x5a/0x60
	  [<c1003530>] ? math_error+0x140/0x140
	  [<c100d0a8>] ? fpu__copy+0x138/0x1c0
	  [<c100c205>] arch_dup_task_struct+0x25/0x30
	  [<c1048cea>] copy_process.part.51+0xea/0x1480
	  [<c115a8e5>] ? dput+0x175/0x200
	  [<c136af70>] ? no_tty+0x30/0x30
	  [<c1157242>] ? do_vfs_ioctl+0x322/0x540
	  [<c104a21a>] _do_fork+0xca/0x340
	  [<c1057b06>] ? SyS_rt_sigaction+0x66/0x90
	  [<c104a557>] SyS_clone+0x27/0x30
	  [<c1824a80>] sysenter_do_call+0x12/0x12

The reason is the incorrect assumption in fpu_copy(), that FNSAVE
can be executed from math-emu kernels as well.

Don't try to copy the registers, the soft state will be copied
by fork anyway, so the child task inherits the parent task's
soft math state.

With this fix applied math-emu kernels boot up fine on modern
hardware and the 'no387 nofxsr' boot options.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

On a math-emu bootup the following crash occurs:

	Initializing CPU#0
	------------[ cut here ]------------
	kernel BUG at arch/x86/kernel/traps.c:779!
	invalid opcode: 0000 [#1] SMP
	[...]
	EIP is at do_device_not_available+0xe/0x70
	[...]
	Call Trace:
	 [<c18238e6>] error_code+0x5a/0x60
	 [<c1002bd0>] ? math_error+0x140/0x140
	 [<c100bbd9>] ? fpu__init_cpu+0x59/0xa0
	 [<c1012322>] cpu_init+0x202/0x330
	 [<c104509f>] ? __native_set_fixmap+0x1f/0x30
	 [<c1b56ab0>] trap_init+0x305/0x346
	 [<c1b548af>] start_kernel+0x1a5/0x35d
	 [<c1b542b4>] i386_start_kernel+0x82/0x86

The reason is that in the following commit:

  b1276c48 ("x86/fpu: Initialize fpregs in fpu__init_cpu_generic()")

I failed to consider math-emu's limitation that it cannot execute the
FNINIT instruction in kernel mode.

The long term fix might be to allow math-emu to execute (certain) kernel
mode FPU instructions, but for now apply the safe (albeit somewhat ugly)
fix: initialize the emulation state explicitly without trapping out to
the FPU emulator.

Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

While the idea behind get_maintainer seems highly useful it's
unfortunately way to trigger happy to grab people that once had a few
commits to files.  For someone like me who does a lot of tree-wide API
work that leads to an incredible amount of Cc spam.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Commit c48a11c7 ("netvm: propagate page->pfmemalloc to skb") added
checks for page->pfmemalloc to __skb_fill_page_desc():

        if (page->pfmemalloc && !page->mapping)
                skb->pfmemalloc = true;

It assumes page->mapping == NULL implies that page->pfmemalloc can be
trusted.  However, __delete_from_page_cache() can set set page->mapping
to NULL and leave page->index value alone.  Due to being in union, a
non-zero page->index will be interpreted as true page->pfmemalloc.

So the assumption is invalid if the networking code can see such a page.
And it seems it can.  We have encountered this with a NFS over loopback
setup when such a page is attached to a new skbuf.  There is no copying
going on in this case so the page confuses __skb_fill_page_desc which
interprets the index as pfmemalloc flag and the network stack drops
packets that have been allocated using the reserves unless they are to
be queued on sockets handling the swapping which is the case here and
that leads to hangs when the nfs client waits for a response from the
server which has been dropped and thus never arrive.

The struct page is already heavily packed so rather than finding another
hole to put it in, let's do a trick instead.  We can reuse the index
again but define it to an impossible value (-1UL).  This is the page
index so it should never see the value that large.  Replace all direct
users of page->pfmemalloc by page_is_pfmemalloc which will hide this
nastiness from unspoiled eyes.

The information will get lost if somebody wants to use page->index
obviously but that was the case before and the original code expected
that the information should be persisted somewhere else if that is
really needed (e.g.  what SLAB and SLUB do).

[akpm@linux-foundation.org: fix blooper in slub]
Fixes: c48a11c7 ("netvm: propagate page->pfmemalloc to skb")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Debugged-by: Vlastimil Babka <vbabka@suse.com>
Debugged-by: Jiri Bohac <jbohac@suse.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: <stable@vger.kernel.org>	[3.6+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>