Instead of having various protocols provide <protocol>_supported()
functions, let's use IS_ENABLED() macro that works well in "if" statements.
Acked-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Merge bfin_rotary driver changes from Sonic Zhang.

Introduce open and close methods for the input device to postpone enabling
the device until it is needed.
Acked-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Use of managed resources simplifies error handling.
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Instead of using arch-specific accessors remap rotary register physical
address into kernel space in probe and use standard readw and writew to
access rotary MMRs.
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Newer Blackfin boards use pinctrl API to manage pins and the legacy
peripherial lists are not useful on them. Let's move pin lists into
platform data so older boards can still use them and newer boards can use
the modern API.
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

The platform data definition of the rotary driver should be generic for all
architectures.
Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Instead of using #ifdef to guard potentially unused suspend and resume code
let's mark them as __maybe_unused so they still get discarded if they are
not used but we do not get warning. This allows for better compile coverage.
Acked-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

The interrupt handler in the driver tries to fetch driver data from
platform device, unfortunately it is only set up after interrupt handler
is registered. Since interrupt handler does not really need to access
the platform device itself let's change it to get the driver data
instance instead.
Acked-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

This patch move all packet info from driver source code to documentation
and adds info about v6 packet format (from driver source code).
Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

The comment about suspicions entry 0x20, 0x02, 0x0e has over time drifted
away and it become hard to figure out what it meant. Let's move it back so
it is clear.
Reported-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Previously dev2 device was used for both external PS/2 mouse and internal
trackstick device (if available). This change introduces dev3 device which
is used for external PS/2 mouse data and dev2 is now used only for
trackstick.

In case that trackstick is not present dev2 is not created, so userspace
does not see non existent device in system.

Because laptops with ALPS devices often do not use i8042 active
multiplexing all data (from touchpad, trackstick and external PS/2 mouse)
come to one port.  So it is not possible to know if external PS/2 mouse is
connected or not. In most cases external PS/2 mouse is not connected so
driver will create dev3 input device after first bare PS/2 packet will be
received. So there will not be "ghost" input device.

This change also helps in identifying possible problems in future if driver
decides to report 6-bytes trackstick packets as 3-bytes bare PS/2 (data
will be reported to dev3 instead dev2).
Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

On some Dell Latitudes we fail to identify presence of trackstick unless we
reset the device. The issue is quite benign as we do perform reset in
alps_init(), so the trackstick ends up working, but mouse name reported to
userspace is not accurate.

In order to fix the issue while avoiding the additional lengthy reset we
move the resrt to alps_detect() and keep the discovered state to be used
later in alps_init().
Reported-by: Pali Rohár <pali.rohar@gmail.com>
Tested-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Move setting of all protocol properties into alps_set_protocol (former
alps_set_defaults) instead of having it split between several functions.
Tested-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

In preparation of reworking the way we set protocol parameters let's
split certain protocol items from alps_model_info into a separate
structure.
Tested-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Even though Rushmore is very close to V3 protocol it is sufficiently
different to warrant it's own protocol name.
Tested-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

In order to accommodate new protocol number for Rushmore touchpads
let's shift protocol numbers by 8 bits (i.e. 1 -> 0x100) - this way
we keep protocol version reported in input device id the same as it
was, but add some holes in numbering.
Tested-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

The input_free_device() function tests whether its argument is NULL and
then returns immediately. Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Static checkers complain about this NULL check because we dereference it
without checking a couple lines later.  This function is only called
when "keypad->pdata" is non-NULL so we can just delete the NULL test.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
[Dmitry: remove the variable altogether given that it is used just once and
 dereference directly.]
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

KEY_HOME is the key to go back to the beginning of the line, not the key to
get into an overview mode, as Windows does. GNOME can already make use of
the Windows key on multiple form factors, and other desktop environments
can use it depending on the form factor.

Using "Windows" as the emitted key also means that the keycode sent out
matches the symbol on the key itself.

So switch KEY_HOME to KEY_LEFTMETA ("Windows" key).
Signed-off-by: Bastien Nocera <hadess@hadess.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Pull nios2 fix from Ley Foon Tan:
 "This fixes incorrect behavior of some user programs"

* tag 'nios2-fixes-v3.19-final' of git://git.rocketboards.org/linux-socfpga-next:
  nios2: fix unhandled signals

Pull aio nested sleep annotation from Ben LaHaise,

* git://git.kvack.org/~bcrl/aio-fixes:
  aio: annotate aio_read_event_ring for sleep patterns

Merge tag 'trace-fixes-v3.19-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull ftrace fixes from Steven Rostedt:
 "During testing Sedat Dilek hit a "suspicious RCU usage" splat that
  pointed out a real bug.  During suspend and resume the tlb_flush
  tracepoint is called when the CPU is going offline.  As the CPU has
  been noted as offline, RCU is ignoring that CPU, which means that it
  can not use RCU protected locks.  When tracepoints are activated, they
  require RCU locking, and if RCU is ignoring a CPU that runs a
  tracepoint, there is a chance that the tracepoint could cause
  corruption.

  The solution was to change the tracepoint into a
  TRACE_EVENT_CONDITION() which allows us to check a condition to
  determine if the tracepoint should be called or not.  If the condition
  is not met, the rcu protected code will not be executed.  By adding
  the condition "cpu_online(smp_processor_id())", this will prevent the
  RCU protected code from being executed if the CPU is marked offline.

  After adding this, another bug was discovered.  As RCU checks rcu
  callers, if a rcu call is not done, there is no check (obviously).  We
  found that tracepoints could be added in RCU ignored locations and not
  have lockdep complain until the tracepoint is activated.  This missed
  places where tracepoints were added in places they should not have
  been.  To fix this, code was added in 3.18 that if lockdep is enabled,
  any tracepoint will still call the rcu checks even if the tracepoint
  is not enabled.  The bug here, is that the check does not take the
  CONDITION into account.  As the condition may prevent tracepoints from
  being activated in RCU ignored areas (as the one patch does), we get
  false positives when we enable lockdep and hit a tracepoint that the
  condition prevents it from being called in a RCU ignored location.

  The fix for this is to add the CONDITION to the rcu checks, even if
  the tracepoint is not enabled"

* tag 'trace-fixes-v3.19-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  x86/tlb/trace: Do not trace on CPU that is offline
  tracing: Add condition check to RCU lockdep checks

Follow other architectures for user fault handling.
Signed-off-by: Chung-Ling Tang <cltang@codesourcery.com>
Acked-by: Ley Foon Tan <lftan@altera.com>

When taking a CPU down for suspend and resume, a tracepoint may be called
when the CPU has been designated offline. As tracepoints require RCU for
protection, they must not be called if the current CPU is offline.

Unfortunately, trace_tlb_flush() is called in this scenario as was noted
by LOCKDEP:

...

 Disabling non-boot CPUs ...
 intel_pstate CPU 1 exiting

 ===============================
 smpboot: CPU 1 didn't die...
 [ INFO: suspicious RCU usage. ]
 3.19.0-rc7-next-20150204.1-iniza-small #1 Not tainted
 -------------------------------
 include/trace/events/tlb.h:35 suspicious rcu_dereference_check() usage!

 other info that might help us debug this:

 RCU used illegally from offline CPU!
 rcu_scheduler_active = 1, debug_locks = 0
 no locks held by swapper/1/0.

 stack backtrace:
 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 3.19.0-rc7-next-20150204.1-iniza-small #1
 Hardware name: SAMSUNG ELECTRONICS CO., LTD. 530U3BI/530U4BI/530U4BH/530U3BI/530U4BI/530U4BH, BIOS 13XK 03/28/2013
  0000000000000001 ffff88011a44fe18 ffffffff817e370d 0000000000000011
  ffff88011a448290 ffff88011a44fe48 ffffffff810d6847 ffff8800c66b9600
  0000000000000001 ffff88011a44c000 ffffffff81cb3900 ffff88011a44fe78
 Call Trace:
  [<ffffffff817e370d>] dump_stack+0x4c/0x65
  [<ffffffff810d6847>] lockdep_rcu_suspicious+0xe7/0x120
  [<ffffffff810b71a5>] idle_task_exit+0x205/0x2c0
  [<ffffffff81054c4e>] play_dead_common+0xe/0x50
  [<ffffffff81054ca5>] native_play_dead+0x15/0x140
  [<ffffffff8102963f>] arch_cpu_idle_dead+0xf/0x20
  [<ffffffff810cd89e>] cpu_startup_entry+0x37e/0x580
  [<ffffffff81053e20>] start_secondary+0x140/0x150
 intel_pstate CPU 2 exiting

...

By converting the tlb_flush tracepoint to a TRACE_EVENT_CONDITION where the
condition is cpu_online(smp_processor_id()), we can avoid calling RCU protected
code when the CPU is offline.

Link: http://lkml.kernel.org/r/CA+icZUUGiGDoL5NU8RuxKzFjoLjEKRtUWx=JB8B9a0EQv-eGzQ@mail.gmail.com

Cc: stable@vger.kernel.org # 3.17+
Fixes: d17d8f9d "x86/mm: Add tracepoints for TLB flushes"
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Suggested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Dave Hansen <dave@sr71.net>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

The trace_tlb_flush() tracepoint can be called when a CPU is going offline.
When a CPU is offline, RCU is no longer watching that CPU and since the
tracepoint is protected by RCU, it must not be called. To prevent the
tlb_flush tracepoint from being called when the CPU is offline, it was
converted to a TRACE_EVENT_CONDITION where the condition checks if the
CPU is online before calling the tracepoint.

Unfortunately, this was not enough to stop lockdep from complaining about
it. Even though the RCU protected code of the tracepoint will never be
called, the condition is hidden within the tracepoint, and even though the
condition prevents RCU code from being called, the lockdep checks are
outside the tracepoint (this is to test tracepoints even when they are not
enabled).

Even though tracepoints should be checked to be RCU safe when they are not
enabled, the condition should still be considered when checking RCU.

Link: http://lkml.kernel.org/r/CA+icZUUGiGDoL5NU8RuxKzFjoLjEKRtUWx=JB8B9a0EQv-eGzQ@mail.gmail.com

Fixes: 3a630178 "tracing: generate RCU warnings even when tracepoints are disabled"
Cc: stable@vger.kernel.org # 3.18+
Acked-by: Dave Hansen <dave@sr71.net>
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Pull one more infiniband revert from Roland Dreier:
 "One more last-second RDMA change for 3.19: Yann realized that the
  previous revert of new userspace ABI did not go far enough, and we're
  still exposing a change that we don't want.  Revert even closer to
  3.18 interface to make sure we get things right in the long run"

Yann Droneaud pipes up:
 "I hope this could go in v3.19 as, at this stage, we don't want to
  expose any bits of this ABI in a released kernel"

* tag 'rdma-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband:
  Revert "IB/core: Add support for extended query device caps"

Pull btrfs fix from Chris Mason:
 "Forrest Liu tracked down a missing blk_finish_plug in the btrfs
  logging code.  This isn't a new bug, and it's hard to hit.  But, it's
  safe enough for inclusion now, and in my for-linus branch"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
  Btrfs: add missing blk_finish_plug in btrfs_sync_log()

There's no %px extension. From the context I think the intention was to
dump the five bytes which were not as expected, and for that one should use
%ph.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Merge branches 'timers-urgent-for-linus' and 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer and x86 fix from Ingo Molnar:
 "A CLOCK_TAI early expiry fix and an x86 microcode driver oops fix"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  hrtimer: Fix incorrect tai offset calculation for non high-res timer systems

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, microcode: Return error from driver init code when loader is disabled

Pull scheduler fixes from Ingo Molnar:
 "Misc fixes"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/deadline: Fix deadline parameter modification handling
  sched/wait: Remove might_sleep() from wait_event_cmd()
  sched: Fix crash if cpuset_cpumask_can_shrink() is passed an empty cpumask
  sched/fair: Avoid using uninitialized variable in preferred_group_nid()

Pull core kernel fixes from Ingo Molnar:
 "Two liblockdep fixes and a CPU hotplug race fix"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  tools/liblockdep: don't include host headers
  tools/liblockdep: ignore generated .so file
  smpboot: Add missing get_online_cpus() in smpboot_register_percpu_thread()

Pull sound fixes from Takashi Iwai:
 "Hopefully the final pull request for 3.19: this ended up with a
  slightly higher volume than wished, but I put them all as they are
  either stable or 3.19 regression fixes.

  Most of commits are from ASoC, and have been stewed for a while in
  linux-next.  The only change in the common code is the regression
  fixes for ASoC AC97 stuff wrt device registrations.  The rest are
  device-specific, mostly small fixes in various ASoC drivers and ak411x
  on ice1724 boards"

* tag 'sound-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound:
  ASoC: Intel: fix sst firmware path for cht-bsw-rt5672
  ARM: dts: Fix I2S1, I2S2 compatible for exynos4 SoCs
  ASoC: sgtl5000: add delay before first I2C access
  MAINTAINERS: ASoC: add maintainer for Intel BDW/HSW ASoC driver
  ASoC: atmel_ssc_dai: fix the setting for DSP mode
  ASoC: sgtl5000: Use shift mask when setting codec mode
  ASoC: tlv320aic3x: Fix data delay configuration
  ALSA: ak411x: Fix stall in work callback
  ASoC: Intel: Used lock version to update shim registers
  ASoC: wm8731: init mutex in i2c init path
  ASoC: atmel_ssc_dai: fix start event for I2S mode
  ASoC: rt5640: Add RT5642 ACPI ID for Intel Baytrail
  ASoC: wm97xx: Reset AC'97 device before registering it
  ASoC: Add support for allocating AC'97 device before registering it

Merge misc fixes from Andrew Morton:
 "7 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm/debug_pagealloc: fix build failure on ppc and some other archs
  nilfs2: fix deadlock of segment constructor over I_SYNC flag
  MAINTAINERS: remove SUPERH website
  memcg, shmem: fix shmem migration to use lrucare
  mm: export "high_memory" symbol on !MMU
  .mailmap: update Konstantin Khlebnikov's email address
  mm: pagewalk: call pte_hole() for VM_PFNMAP during walk_page_range

Pull MIPS fixes from Ralf Baechle:
 "The pending MIPS fixes for 3.19.  All across the field and nothing
  particularly severe or dramatic"

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (23 commits)
  IRQCHIP: mips-gic: Avoid rerouting timer IRQs for smp-cmp
  MIPS: Fix syscall_get_nr for the syscall exit tracing.
  MIPS: elf2ecoff: Ignore PT_MIPS_ABIFLAGS program headers.
  MIPS: elf2ecoff: Rewrite main processing loop to switch.
  MIPS: fork: Fix MSA/FPU/DSP context duplication race
  MIPS: Fix C0_Pagegrain[IEC] support.
  MIPS: traps: Fix inline asm ctc1 missing .set hardfloat
  MIPS: mipsregs.h: Add write_32bit_cp1_register()
  MIPS: Fix kernel lockup or crash after CPU offline/online
  MIPS: OCTEON: fix kernel crash when offlining a CPU
  MIPS: ARC: Fix build error.
  MIPS: IRQ: Fix disable_irq on CPU IRQs
  MIPS: smp-mt,smp-cmp: Enable all HW IRQs on secondary CPUs
  MIPS: Fix restart of indirect syscalls
  MIPS: ELF: fix loading o32 binaries on 64-bit kernels
  MIPS: mips-cm: Fix sparse warnings
  MIPS: Kconfig: Fix recursive dependency.
  MIPS: Compat: Fix build error if CONFIG_MIPS32_COMPAT but no compat ABI.
  MIPS: JZ4740: Fixup #include's (sparse)
  MIPS: Wire up execveat(2).
  ...

While commit 7e36ef82 ("IB/core: Temporarily disable
ex_query_device uverb") is correct as it makes the extended
QUERY_DEVICE uverb (which came as part of commit 5a77abf9
("IB/core: Add support for extended query device caps") and commit
860f10a7 ("IB/core: Add flags for on demand paging support")) not
available to userspace, it doesn't address the initial issue regarding
ib_copy_to_udata() [1][2].

Additionally, further discussions around this new uverb seems to
conclude it would require a different data structure than the one
currently described in <rdma/ib_user_verbs.h> [3].

Both of these issues require a revert of the changes, so this patch
partially reverts commit 8cdd312c ("IB/mlx5: Implement the ODP
capability query verb") and commit 860f10a7 ("IB/core: Add flags
for on demand paging support") and fully reverts commit 5a77abf9
("IB/core: Add support for extended query device caps").

[1] "Re: [PATCH v3 06/17] IB/core: Add support for extended query device caps"
    http://mid.gmane.org/1418733236.2779.26.camel@opteya.com

[2] "Re: [PATCH] IB/core: Temporarily disable ex_query_device uverb"
    http://mid.gmane.org/1423067503.3030.83.camel@opteya.com

[3] "RE: [PATCH v1 1/5] IB/uverbs: ex_query_device: answer must not depend on request's comp_mask"
    http://mid.gmane.org/2807E5FD2F6FDA4886F6618EAC48510E0CC12C30@CRSMSX101.amr.corp.intel.com

Cc: Eli Cohen <eli@mellanox.com>
Cc: Haggai Eran <haggaie@mellanox.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: Sagi Grimberg <sagig@mellanox.com>
Cc: Shachar Raindel <raindel@mellanox.com>
Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

There is no point in queueing EV_SYN/SYN_DROPPED on clock type change when
there are no events in the client's queue and doing so confuses tests in
libinput package, so let's not do that.
Reported-and-tested-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Kim Phillips reported following build failure.

  LD      init/built-in.o
  mm/built-in.o: In function `free_pages_prepare':
  mm/page_alloc.c:770: undefined reference to `.kernel_map_pages'
  mm/built-in.o: In function `prep_new_page':
  mm/page_alloc.c:933: undefined reference to `.kernel_map_pages'
  mm/built-in.o: In function `map_pages':
  mm/compaction.c:61: undefined reference to `.kernel_map_pages'
  make: *** [vmlinux] Error 1

Reason for this problem is that commit 031bc574
("mm/debug-pagealloc: make debug-pagealloc boottime configurable")
forgot to remove the old declaration of kernel_map_pages() for some
architectures.  This patch removes them to fix build failure.
Reported-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: David Miller <davem@davemloft.net>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Nilfs2 eventually hangs in a stress test with fsstress program.  This
issue was caused by the following deadlock over I_SYNC flag between
nilfs_segctor_thread() and writeback_sb_inodes():

  nilfs_segctor_thread()
    nilfs_segctor_thread_construct()
      nilfs_segctor_unlock()
        nilfs_dispose_list()
          iput()
            iput_final()
              evict()
                inode_wait_for_writeback()  * wait for I_SYNC flag

  writeback_sb_inodes()
     * set I_SYNC flag on inode->i_state
    __writeback_single_inode()
      do_writepages()
        nilfs_writepages()
          nilfs_construct_dsync_segment()
            nilfs_segctor_sync()
               * wait for completion of segment constructor
    inode_sync_complete()
       * clear I_SYNC flag after __writeback_single_inode() completed

writeback_sb_inodes() calls do_writepages() for dirty inodes after
setting I_SYNC flag on inode->i_state.  do_writepages() in turn calls
nilfs_writepages(), which can run segment constructor and wait for its
completion.  On the other hand, segment constructor calls iput(), which
can call evict() and wait for the I_SYNC flag on
inode_wait_for_writeback().

Since segment constructor doesn't know when I_SYNC will be set, it
cannot know whether iput() will block or not unless inode->i_nlink has a
non-zero count.  We can prevent evict() from being called in iput() by
implementing sop->drop_inode(), but it's not preferable to leave inodes
with i_nlink == 0 for long periods because it even defers file
truncation and inode deallocation.  So, this instead resolves the
deadlock by calling iput() asynchronously with a workqueue for inodes
with i_nlink == 0.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>