If the driver is built as a module, autoload won't work because the module
alias information is not filled. So user-space can't match the registered
device with the corresponding module.

Export the module alias information using the MODULE_DEVICE_TABLE() macro.

Before this patch:

$ modinfo drivers/input/misc/da9063_onkey.ko | grep alias
alias:          platform:da9063-onkey

After this patch:

$ modinfo drivers/input/misc/da9063_onkey.ko | grep alias
alias:          platform:da9063-onkey
alias:          of:N*T*Cdlg,da9062-onkeyC*
alias:          of:N*T*Cdlg,da9062-onkey
alias:          of:N*T*Cdlg,da9063-onkeyC*
alias:          of:N*T*Cdlg,da9063-onkey
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

If the driver is built as a module, autoload won't work because the module
alias information is not filled. So user-space can't match the registered
device with the corresponding module.

Export the module alias information using the MODULE_DEVICE_TABLE() macro.

Before this patch:

$ modinfo drivers/input/touchscreen/fsl-imx25-tcq.ko | grep alias

After this patch:

$ modinfo drivers/input/touchscreen/fsl-imx25-tcq.ko | grep alias
alias:          of:N*T*Cfsl,imx25-tcqC*
alias:          of:N*T*Cfsl,imx25-tcq
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

it's always easier to retrieve these information in bug reports when
it is always printed in the dmesg.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Older versions of gcc warn about the tca8418_irq_handler function
as they can't keep track of the variable assignment inside of the
loop when using the -Wmaybe-unintialized flag:

drivers/input/keyboard/tca8418_keypad.c: In function ‘tca8418_irq_handler’:
drivers/input/keyboard/tca8418_keypad.c:172:9: error: ‘reg’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
drivers/input/keyboard/tca8418_keypad.c:165:5: note: ‘reg’ was declared here

This is fixed in gcc-6, but it's possible to rearrange the code
in a way that avoids the warning on older compilers as well.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Use product id for firmware name to request compatible firmware.
Signed-off-by: Sangwon Jee <jeesw@melfas.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Copyright header is updated to add DA9061 in its description and the module
description macro is extended to include DA9061.

Minor change to the code, alters dev_dbg() statements to report a generic
"PMIC" instead of DA9063. This device driver is compatible with DA9061,
DA9062 and DA9063.

Kconfig is updated to reflect support for DA9061/62/63.
Signed-off-by: Steve Twiss <stwiss.opensource@diasemi.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Trivial fix to typo in dev_err message
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Instead of relying on this model zoo let's skip selftest on all newer Asus
laptops (newer as in when they changed "Computer" -> "COMPUTER" in their
DMI data).
Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Add product_id sysfs attribute and update protocol version to support it.
Signed-off-by: Sangwon Jee <jeesw@melfas.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Sync up with mainline to bring in I2C host notify changes and other
updates.

On suspend/resume cycle, selftest is executed to reset i8042 controller.
But when this is done in Asus devices, subsequent calls to detect/init
functions to elantech driver fails. Skipping selftest fixes this problem.

An easier step to reproduce this problem is adding i8042.reset=1 as a
kernel parameter. On Asus laptops, it'll make the system to start with the
touchpad already stuck, since psmouse_probe forcibly calls the selftest
function.

This patch was inspired by John Hiesey's change[1], but, since this problem
affects a lot of models of Asus, let's avoid running selftests on them.

All models affected by this problem:
A455LD
K401LB
K501LB
K501LX
R409L
V502LX
X302LA
X450LCP
X450LD
X455LAB
X455LDB
X455LF
Z450LA

[1]: https://marc.info/?l=linux-input&m=144312209020616&w=2

Fixes: "ETPS/2 Elantech Touchpad dies after resume from suspend"
(https://bugzilla.kernel.org/show_bug.cgi?id=107971)
Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Add ic_name sysfs attribute for retrieving IC model name.
Signed-off-by: Sangwon Jee <jeesw@melfas.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Add maintainer information.
Signed-off-by: Sangwon Jee <jeesw@melfas.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Add devicetree binding documentations.
Signed-off-by: Sangwon Jee <jeesw@melfas.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Another Lifebook machine that needs the same quirk as other similar
models to make the driver working.

Also let's reorder elantech_dmi_force_crc_enabled list so LIfebook enries
are in alphabetical order.
Reported-by: William Linna <william.linna@gmail.com>
Tested-by: William Linna <william.linna@gmail.com>
Reviewed-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Instantiating the rmi4 I2C transport driver without interrupts assigned
(for example using manual i2c instantiation from the command line)
caused the driver to fail to load, but it does not clean up its regulator
or transport device registrations. Result is a crash at a later time,
for example when rebooting the system.

Fixes: 946c8432 ("Input: synaptics-rmi4 - support regulator supplies")
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Instantiating the rmi4 SPI transport driver without an interrupt assigned
caused the driver to fail to load, but it does not clean up its transport
device registration. Result may be a crash at a later time, for example
when rebooting the system.

Fixes: 8d99758d ("Input: synaptics-rmi4 - add SPI transport driver")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Tested-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Ben Gamari <ben@smart-cactus.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Here we introduce logic in alps_identify to set the ALPS_DUALPOINT flag
for touchpad hardware responding to E7 report with 73 03 28, as is found
in the Dell Latitude E7470.
Tested-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Ben Gamari <ben@smart-cactus.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

The SS5 hardware can report this.
Tested-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Ben Gamari <ben@smart-cactus.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

While a button is held SS5 hardware will give us single-finger packets
with x, y, and pressure equal to zero. This causes annoying jumps in
pointer position if a touch is released while the button is held. Handle
this by claiming zero contacts to ensure that no position events are
provided to the user.
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Tested-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Ben Gamari <ben@smart-cactus.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Add touchstick support for the so-called SS5 hardware, which uses a
variant of the SS4 protocol.
Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Tested-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Ben Gamari <ben@smart-cactus.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Just like Fujitsu CELSIUS H730, the H760 also has an Elantech touchpad with
the same quirks. Without this patch, the touchpad is useless out-of-the-box
as the mouse pointer won't move.

This patch makes the driver aware of both the crc_enabled=1 requirement and
the middle button, making the touchpad fully functional out-of-the-box.
Signed-off-by: Matti Kurkela <Matti.Kurkela@iki.fi>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com>
Reviewed-by: Ulrik De Bie <ulrik.debie-os@e2big.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

i2c_smbus_read_block_data() returns negative errno else the number of
data bytes in the slave's response.

Checking for error not null means the function always fails if the device
answers properly.

So given that we read 3 bytes and access those, better check that we
actually read those 3 bytes.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

The newly added ektf2127 driver uses the SIMPLE_DEV_PM_OPS macro
to conditionally refer to the resume/suspend functions, which
causes a warning when CONFIG_PM_SLEEP is disabled:

drivers/input/touchscreen/ektf2127.c:168:12: error: 'ektf2127_resume' defined but not used [-Werror=unused-function]
drivers/input/touchscreen/ektf2127.c:156:12: error: 'ektf2127_suspend' defined but not used [-Werror=unused-function]

We could either put these functions inside of an #ifdef or
add __maybe_unused annotations. This uses the second approach,
which is generally more foolproof.

Fixes: 9ca5bf50 ("Input: add support for Elan eKTF2127 touchscreen controller")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

Pull ARM fixes from Russell King:
 "Three relatively small fixes for ARM:

   - Roger noticed that dma_max_pfn() was calculating the upper limit
     wrongly, by adding the PFN offset of memory twice.

   - A fix from Robin to correct parsing of MPIDR values when the
     address size is larger than one BE32 unit.

   - A fix from Srinivas to ensure that we do not rely on the boot
     loader (or previous Linux kernel) setting the translation table
     base register a certain way in the decompressor, which can lead to
     crashes"

* 'fixes' of git://git.armlinux.org.uk/~rmk/linux-arm:
  ARM: 8618/1: decompressor: reset ttbcr fields to use TTBR0 on ARMv7
  ARM: 8617/1: dma: fix dma_max_pfn()
  ARM: 8616/1: dt: Respect property size when parsing CPUs

If the bootloader uses the long descriptor format and jumps to
kernel decompressor code, TTBCR may not be in a right state.
Before enabling the MMU, it is required to clear the TTBCR.PD0
field to use TTBR0 for translation table walks.

The commit dbece458 ("ARM: 7501/1: decompressor:
reset ttbcr for VMSA ARMv7 cores") does the reset of TTBCR.N, but
doesn't consider all the bits for the size of TTBCR.N.

Clear TTBCR.PD0 field and reset all the three bits of TTBCR.N to
indicate the use of TTBR0 and the correct base address width.

Fixes: dbece458 ("ARM: 7501/1: decompressor: reset ttbcr for VMSA ARMv7 cores")
Acked-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Srinivas Ramana <sramana@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

Pull x86 fixes from Thomas Gleixner:
 "The last regression fixes for 4.8 final:

   - Two patches addressing the fallout of the CR4 optimizations which
     caused CR4-less machines to fail.

   - Fix the VDSO build on big endian machines

   - Take care of FPU initialization if no CPUID is available otherwise
     task struct size ends up being zero

   - Fix up context tracking in case load_gs_index fails"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/entry/64: Fix context tracking state warning when load_gs_index fails
  x86/boot: Initialize FPU and X86_FEATURE_ALWAYS even if we don't have CPUID
  x86/vdso: Fix building on big endian host
  x86/boot: Fix another __read_cr4() case on 486
  x86/init: Fix cr4_init_shadow() on CR4-less machines

Pull MIPS fixes from Ralf Baechle:
 "Another round of fixes:

   - CM: Fix mips_cm_max_vp_width for non-MT kernels on MT systems
   - CPS: Avoid BUG() when offlining pre-r6 CPUs
   - DEC: Avoid gas warnings due to suspicious instruction scheduling by
     manually expanding assembler macros.
   - FTLB: Fix configuration by moving confiuguratoin after probing
   - FTLB: clear execution hazard after changing FTLB enable
   - Highmem: Fix detection of unsupported highmem with cache aliases
   - I6400: Don't touch FTLBP chicken bits
   - microMIPS: Fix BUILD_ROLLBACK_PROLOGUE
   - Malta: Fix IOCU disable switch read for MIPS64
   - Octeon: Fix probing of devices attached to GPIO lines
   - uprobes: Misc small fixes"

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus:
  MIPS: CM: Fix mips_cm_max_vp_width for non-MT kernels on MT systems
  MIPS: Fix detection of unsupported highmem with cache aliases
  MIPS: Malta: Fix IOCU disable switch read for MIPS64
  MIPS: Fix BUILD_ROLLBACK_PROLOGUE for microMIPS
  MIPS: clear execution hazard after changing FTLB enable
  MIPS: Configure FTLB after probing TLB sizes from config4
  MIPS: Stop setting I6400 FTLBP
  MIPS: DEC: Avoid la pseudo-instruction in delay slots
  MIPS: Octeon: mark GPIO controller node not populated after IRQ init.
  MIPS: uprobes: fix use of uninitialised variable
  MIPS: uprobes: remove incorrect set_orig_insn
  MIPS: fix uretprobe implementation
  MIPS: smp-cps: Avoid BUG() when offlining pre-r6 CPUs

Pull sparc fixes from David Miller:

 1) Fix section mismatches in some builds, from Paul Gortmaker.

 2) Need to count huge zero page mappings when doing TSB sizing, from
    Mike Kravetz.

 3) Fix handing of cpu_possible_mask when nr_cpus module option is
    specified, from Atish Patra.

 4) Don't allocate irq stacks until nr_irqs has been processed, also
    from Atish Patra.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc:
  sparc64: Fix non-SMP build.
  sparc64: Fix irq stack bootmem allocation.
  sparc64: Fix cpu_possible_mask if nr_cpus is set
  sparc64 mm: Fix more TSB sizing issues
  sparc64: fix section mismatch in find_numa_latencies_for_group

Pull networking fixes from David Miller:

 1) Fix wrong TCP checksums on MTU probing when checksum offloading is
    disabled, from Douglas Caetano dos Santos.

 2) Fix qdisc backlog updates in qfq and sfb schedulers, from Cong Wang.

 3) Route lookup flow key protocol value is wrong in ip6gre_xmit_other(),
    fix from Lance Richardson.

 4) Scheduling while atomic in multicast routing code of ipv4 and ipv6,
    fix from Nikolay Aleksandrov.

 5) Fix packet alignment in fec driver, from Eric Nelson.

 6) Fix perf regression in sctp due to struct layout and cache misses,
    from Xin Long.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net:
  sctp: fix the issue sctp_diag uses lock_sock in rcu_read_lock
  sctp: change to check peer prsctp_capable when using prsctp polices
  sctp: remove prsctp_param from sctp_chunk
  sctp: move sent_count to the memory hole in sctp_chunk
  tg3: Avoid NULL pointer dereference in tg3_io_error_detected()
  act_ife: Fix false encoding
  act_ife: Fix external mac header on encode
  VSOCK: Don't dec ack backlog twice for rejected connections
  Revert "net: ethernet: bcmgenet: use phydev from struct net_device"
  net: fec: align IP header in hardware
  net: fec: remove QUIRK_HAS_RACC from i.mx27
  net: fec: remove QUIRK_HAS_RACC from i.mx25
  ipmr, ip6mr: fix scheduling while atomic and a deadlock with ipmr_get_route
  ip6_gre: fix flowi6_proto value in ip6gre_xmit_other()
  tcp: fix a compile error in DBGUNDO()
  tcp: fix wrong checksum calculation on MTU probing
  sch_sfb: keep backlog updated with qlen
  sch_qfq: keep backlog updated with qlen
  can: dev: fix deadlock reported after bus-off

When discovering the number of VPEs per core, smp_num_siblings will be
incorrect for kernels built without support for the MIPS MultiThreading
(MT) ASE running on systems which implement said ASE. This leads to
accesses to VPEs in secondary cores being performed incorrectly since
mips_cm_vp_id calculates the wrong ID to write to the local "other"
registers. Fix this by examining the number of VPEs in the core as
reported by the CM.

This patch presumes that the number of VPEs will be the same in each
core of the system. As this path only applies to systems with CM version
2.5 or lower, and this property is true of all such known systems, this
is likely to be fine but is described in a comment for good measure.
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14338/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

Pull SCSI fix from James Bottomley:
 "One final fix before 4.8.

  There was a memory leak triggered by turning scsi mq off due to the
  fact that we assume on host release that the already running hosts
  weren't mq based because that's the state of the global flag (even
  though they were).

  Fix it by tracking this on a per host host basis"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: Avoid that toggling use_blk_mq triggers a memory leak

Pull input fix from Dmitry Torokhov:
 "One small change to make joydev (which is used by older games) to bind
  to devices that export Z axis but not X or Y (such as TRC rudder)"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Input: joydev - recognize devices with Z axis as joysticks

Merge more fixes from Andrew Morton:
 "Three fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  include/linux/property.h: fix typo/compile error
  ocfs2: fix deadlock on mmapped page in ocfs2_write_begin_nolock()
  mm: workingset: fix crash in shadow node shrinker caused by replace_page_cache_page()

This fixes commit d76eebfa ("include/linux/property.h: fix build
issues with gcc-4.4.4").

With that commit we get the following compile error when using the
PROPERTY_ENTRY_INTEGER_ARRAY macro.

 include/linux/property.h:201:39: error: `u32_data' undeclared (first
                 use in this function)
  PROPERTY_ENTRY_INTEGER_ARRAY(_name_, u32, _val_)
                                       ^
 include/linux/property.h:193:17: note: in definition of macro
                 `PROPERTY_ENTRY_INTEGER_ARRAY'
  { .pointer = { _type_##_data = _val_ } },  \
                 ^

This needs a '.' to reference the union member.  It seems this was just
overlooked here since it is done correctly in similar constructs in
other parts of the original commit.

This fix is in preparation of upcoming commits that will use this macro.

Fixes: commit d76eebfa ("include/linux/property.h: fix build issues with gcc-4.4.4")
Link: http://lkml.kernel.org/r/2de3b929290d88a723ed829a3e3cbd02044714df.1475114627.git.johnyoun@synopsys.comSigned-off-by: John Youn <johnyoun@synopsys.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The testcase "mmaptruncate" of ocfs2-test deadlocks occasionally.

In this testcase, we create a 2*CLUSTER_SIZE file and mmap() on it;
there are 2 process repeatedly performing the following operations
respectively: one is doing memset(mmaped_addr + 2*CLUSTER_SIZE - 1, 'a',
1), while the another is playing ftruncate(fd, 2*CLUSTER_SIZE) and then
ftruncate(fd, CLUSTER_SIZE) again and again.

This is the backtrace when the deadlock happens:

   __wait_on_bit_lock+0x50/0xa0
   __lock_page+0xb7/0xc0
   ocfs2_write_begin_nolock+0x163f/0x1790 [ocfs2]
   ocfs2_page_mkwrite+0x1c7/0x2a0 [ocfs2]
   do_page_mkwrite+0x66/0xc0
   handle_mm_fault+0x685/0x1350
   __do_page_fault+0x1d8/0x4d0
   trace_do_page_fault+0x37/0xf0
   do_async_page_fault+0x19/0x70
   async_page_fault+0x28/0x30

In ocfs2_write_begin_nolock(), we first grab the pages and then allocate
disk space for this write; ocfs2_try_to_free_truncate_log() will be
called if -ENOSPC is returned; if we're lucky to get enough clusters,
which is usually the case, we start over again.

But in ocfs2_free_write_ctxt() the target page isn't unlocked, so we
will deadlock when trying to grab the target page again.

Also, -ENOMEM might be returned in ocfs2_grab_pages_for_write().
Another deadlock will happen in __do_page_mkwrite() if
ocfs2_page_mkwrite() returns non-VM_FAULT_LOCKED, and along with a
locked target page.

These two errors fail on the same path, so fix them by unlocking the
target page manually before ocfs2_free_write_ctxt().

Jan Kara helps me clear out the JBD2 part, and suggest the hint for root
cause.

Changes since v1:
1. Also put ENOMEM error case into consideration.

Link: http://lkml.kernel.org/r/1474173902-32075-1-git-send-email-zren@suse.comSigned-off-by: Eric Ren <zren@suse.com>
Reviewed-by: He Gang <ghe@suse.com>
Acked-by: Joseph Qi <joseph.qi@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Antonio reports the following crash when using fuse under memory pressure:

  kernel BUG at /build/linux-a2WvEb/linux-4.4.0/mm/workingset.c:346!
  invalid opcode: 0000 [#1] SMP
  Modules linked in: all of them
  CPU: 2 PID: 63 Comm: kswapd0 Not tainted 4.4.0-36-generic #55-Ubuntu
  Hardware name: System manufacturer System Product Name/P8H67-M PRO, BIOS 3904 04/27/2013
  task: ffff88040cae6040 ti: ffff880407488000 task.ti: ffff880407488000
  RIP: shadow_lru_isolate+0x181/0x190
  Call Trace:
    __list_lru_walk_one.isra.3+0x8f/0x130
    list_lru_walk_one+0x23/0x30
    scan_shadow_nodes+0x34/0x50
    shrink_slab.part.40+0x1ed/0x3d0
    shrink_zone+0x2ca/0x2e0
    kswapd+0x51e/0x990
    kthread+0xd8/0xf0
    ret_from_fork+0x3f/0x70

which corresponds to the following sanity check in the shadow node
tracking:

  BUG_ON(node->count & RADIX_TREE_COUNT_MASK);

The workingset code tracks radix tree nodes that exclusively contain
shadow entries of evicted pages in them, and this (somewhat obscure)
line checks whether there are real pages left that would interfere with
reclaim of the radix tree node under memory pressure.

While discussing ways how fuse might sneak pages into the radix tree
past the workingset code, Miklos pointed to replace_page_cache_page(),
and indeed there is a problem there: it properly accounts for the old
page being removed - __delete_from_page_cache() does that - but then
does a raw raw radix_tree_insert(), not accounting for the replacement
page.  Eventually the page count bits in node->count underflow while
leaving the node incorrectly linked to the shadow node LRU.

To address this, make sure replace_page_cache_page() uses the tracked
page insertion code, page_cache_tree_insert().  This fixes the page
accounting and makes sure page-containing nodes are properly unlinked
from the shadow node LRU again.

Also, make the sanity checks a bit less obscure by using the helpers for
checking the number of pages and shadows in a radix tree node.

Fixes: 449dd698 ("mm: keep page cache radix tree nodes in check")
Link: http://lkml.kernel.org/r/20160919155822.29498-1-hannes@cmpxchg.orgSigned-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Antonio SJ Musumeci <trapexit@spawn.link>
Debugged-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <stable@vger.kernel.org>	[3.15+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>