Numeric assembly arguments are hard to understand and assembly code that
uses them is hard to modify. Use named arguments in BIT_OP and
TEST_AND_BIT_OP macros.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Parameterize macros with function name, opcode and inversion pattern.
This reduces code duplication removing 2/3 of definitions.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Use "m" constraint instead of "r" for the address, as "m" allows
compiler to access adjacent locations using base + offset, while "r"
requires updating the base register every time.
Use %[mem] * 0 + v to replace offset part of %[mem] expansion with v.
It is impossible to change address alignment through the offset part on
xtensa, so just ignore offset in alignment checks.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Section .fixup contains pieces of code, merge it with the rest of the
.text section.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

XIP (eXecute In Place) kernel image is the image that can be run
directly from ROM, using RAM only for writable data.

XIP xtensa kernel differs from regular xtensa kernel in the following
ways:
- it has exception/IRQ vectors merged into text section. No vectors
  relocation takes place at kernel startup.
- .data/.bss location must be specified in the kernel configuration,
  its content is copied there in the _startup function.
- .init.text is merged with the rest of text and is executed from ROM.
- when MMU is used the virtual address where the kernel will be mapped
  must be specified in the kernel configuration. It may be in the KSEG
  or in the KIO, __pa macro is adjusted to be able to handle both.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Currently kernel memory layout settings are split between "Processor
type and features" and "Platform options" menus. Consolidate them under
"Platform options".
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Use correct symbol for the end of .rodata section when dumping virtual
memory layout. This fixes odd rodata size with XIP kernel.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

.data.init.refok has been removed from the kernel long ago, replaced
with __REFDATA. Fix start_info definition.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

MPU attribute mapping table is R/O, move it from .data to __REFCONST
(as the rest of the _startup code where initialize_cacheattr is used is
in the __REF section). This allows executing initialize_cacheattr before
the data section of the XIP kernel is relocated to its place.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

These address and size definitions define xtensa kernel memory layout,
move them from vectors.h to the kmem_layout.h
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Remove empty hw_irq.h and user.h from arch/xtensa/include/asm and use
generic versions instead.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

xtensa now supports tracehook, queued spinlocks and rwlocks. Update
corresponding Documentation/features entries.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

Merge tag 'kbuild-fixes-v5.4-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull more Kbuild fixes from Masahiro Yamada:

 - fix a bashism of setlocalversion

 - do not use the too new --sort option of tar

* tag 'kbuild-fixes-v5.4-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kheaders: substituting --sort in archive creation
  scripts: setlocalversion: fix a bashism
  kbuild: update comment about KBUILD_ALLDIRS

Pull x86 fixes from Thomas Gleixner:
 "A small set of x86 fixes:

   - Prevent a NULL pointer dereference in the X2APIC code in case of a
     CPU hotplug failure.

   - Prevent boot failures on HP superdome machines by invalidating the
     level2 kernel pagetable entries outside of the kernel area as
     invalid so BIOS reserved space won't be touched unintentionally.

     Also ensure that memory holes are rounded up to the next PMD
     boundary correctly.

   - Enable X2APIC support on Hyper-V to prevent boot failures.

   - Set the paravirt name when running on Hyper-V for consistency

   - Move a function under the appropriate ifdef guard to prevent build
     warnings"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/boot/acpi: Move get_cmdline_acpi_rsdp() under #ifdef guard
  x86/hyperv: Set pv_info.name to "Hyper-V"
  x86/apic/x2apic: Fix a NULL pointer deref when handling a dying cpu
  x86/hyperv: Make vapic support x2apic mode
  x86/boot/64: Round memory hole size up to next PMD page
  x86/boot/64: Make level2_kernel_pgt pages invalid outside kernel area

Pull irq fixes from Thomas Gleixner:
 "A small set of irq chip driver fixes and updates:

   - Update the SIFIVE PLIC interrupt driver to use the fasteoi handler
     to address the shortcomings of the existing flow handling which was
     prone to lose interrupts

   - Use the proper limit for GIC interrupt line numbers

   - Add retrigger support for the recently merged Anapurna Labs Fabric
     interrupt controller to make it complete

   - Enable the ATMEL AIC5 interrupt controller driver on the new
     SAM9X60 SoC"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irqchip/sifive-plic: Switch to fasteoi flow
  irqchip/gic-v3: Fix GIC_LINE_NR accessor
  irqchip/atmel-aic5: Add support for sam9x60 irqchip
  irqchip/al-fic: Add support for irq retrigger

Pull hrtimer fixlet from Thomas Gleixner:
 "A single commit annotating the lockcless access to timer->base with
  READ_ONCE() and adding the WRITE_ONCE() counterparts for completeness"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  hrtimer: Annotate lockless access to timer->base

Pull stop-machine fix from Thomas Gleixner:
 "A single fix, amending stop machine with WRITE/READ_ONCE() to address
  the fallout of KCSAN"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  stop_machine: Avoid potential race behaviour

Pull networking fixes from David Miller:
 "I was battling a cold after some recent trips, so quite a bit piled up
  meanwhile, sorry about that.

  Highlights:

   1) Fix fd leak in various bpf selftests, from Brian Vazquez.

   2) Fix crash in xsk when device doesn't support some methods, from
      Magnus Karlsson.

   3) Fix various leaks and use-after-free in rxrpc, from David Howells.

   4) Fix several SKB leaks due to confusion of who owns an SKB and who
      should release it in the llc code. From Eric Biggers.

   5) Kill a bunc of KCSAN warnings in TCP, from Eric Dumazet.

   6) Jumbo packets don't work after resume on r8169, as the BIOS resets
      the chip into non-jumbo mode during suspend. From Heiner Kallweit.

   7) Corrupt L2 header during MPLS push, from Davide Caratti.

   8) Prevent possible infinite loop in tc_ctl_action, from Eric
      Dumazet.

   9) Get register bits right in bcmgenet driver, based upon chip
      version. From Florian Fainelli.

  10) Fix mutex problems in microchip DSA driver, from Marek Vasut.

  11) Cure race between route lookup and invalidation in ipv4, from Wei
      Wang.

  12) Fix performance regression due to false sharing in 'net'
      structure, from Eric Dumazet"

* git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (145 commits)
  net: reorder 'struct net' fields to avoid false sharing
  net: dsa: fix switch tree list
  net: ethernet: dwmac-sun8i: show message only when switching to promisc
  net: aquantia: add an error handling in aq_nic_set_multicast_list
  net: netem: correct the parent's backlog when corrupted packet was dropped
  net: netem: fix error path for corrupted GSO frames
  macb: propagate errors when getting optional clocks
  xen/netback: fix error path of xenvif_connect_data()
  net: hns3: fix mis-counting IRQ vector numbers issue
  net: usb: lan78xx: Connect PHY before registering MAC
  vsock/virtio: discard packets if credit is not respected
  vsock/virtio: send a credit update when buffer size is changed
  mlxsw: spectrum_trap: Push Ethernet header before reporting trap
  net: ensure correct skb->tstamp in various fragmenters
  net: bcmgenet: reset 40nm EPHY on energy detect
  net: bcmgenet: soft reset 40nm EPHYs before MAC init
  net: phy: bcm7xxx: define soft_reset for 40nm EPHY
  net: bcmgenet: don't set phydev->link from MAC
  net: Update address for MediaTek ethernet driver in MAINTAINERS
  ipv4: fix race condition between route lookup and invalidation
  ...

Intel test robot reported a ~7% regression on TCP_CRR tests
that they bisected to the cited commit.

Indeed, every time a new TCP socket is created or deleted,
the atomic counter net->count is touched (via get_net(net)
and put_net(net) calls)

So cpus might have to reload a contended cache line in
net_hash_mix(net) calls.

We need to reorder 'struct net' fields to move @hash_mix
in a read mostly cache line.

We move in the first cache line fields that can be
dirtied often.

We probably will have to address in a followup patch
the __randomize_layout that was added in linux-4.13,
since this might break our placement choices.

Fixes: 355b9855 ("netns: provide pure entropy for net_hash_mix()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

If there are multiple switch trees on the device, only the last one
will be listed, because the arguments of list_add_tail are swapped.

Fixes: 83c0afae ("net: dsa: Add new binding implementation")
Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Printing the info message every time more than the max number of mac
addresses are requested generates unnecessary log spam.  Showing it only
when the hw is not already in promiscous mode is equally informative
without being annoying.
Signed-off-by: Mans Rullgard <mans@mansr.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

add an error handling in aq_nic_set_multicast_list, it may not
work when hw_multicast_list_set error; and at the same time
it will remove gcc Wunused-but-set-variable warning.
Signed-off-by: Chenwandun <chenwandun@huawei.com>
Reviewed-by: Igor Russkikh <igor.russkikh@aquantia.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

Jakub Kicinski says:

====================
net: netem: fix further issues with packet corruption

This set is fixing two more issues with the netem packet corruption.

First patch (which was previously posted) avoids NULL pointer dereference
if the first frame gets freed due to allocation or checksum failure.
v2 improves the clarity of the code a little as requested by Cong.

Second patch ensures we don't return SUCCESS if the frame was in fact
dropped. Thanks to this commit message for patch 1 no longer needs the
"this will still break with a single-frame failure" disclaimer.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

If packet corruption failed we jump to finish_segs and return
NET_XMIT_SUCCESS. Seeing success will make the parent qdisc
increment its backlog, that's incorrect - we need to return
NET_XMIT_DROP.

Fixes: 6071bd1a ("netem: Segment GSO packets on enqueue")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

To corrupt a GSO frame we first perform segmentation.  We then
proceed using the first segment instead of the full GSO skb and
requeue the rest of the segments as separate packets.

If there are any issues with processing the first segment we
still want to process the rest, therefore we jump to the
finish_segs label.

Commit 177b8007 ("net: netem: fix backlog accounting for
corrupted GSO frames") started using the pointer to the first
segment in the "rest of segments processing", but as mentioned
above the first segment may had already been freed at this point.

Backlog corrections for parent qdiscs have to be adjusted.

Fixes: 177b8007 ("net: netem: fix backlog accounting for corrupted GSO frames")
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

The tx_clk, rx_clk, and tsu_clk are optional. Currently the macb driver
marks clock as not available if it receives an error when trying to get
a clock. This is wrong, because a clock controller might return
-EPROBE_DEFER if a clock is not available, but will eventually become
available.

In these cases, the driver would probe successfully but will never be
able to adjust the clocks, because the clocks were not available during
probe, but became available later.

For example, the clock controller for the ZynqMP is implemented in the
PMU firmware and the clocks are only available after the firmware driver
has been probed.

Use devm_clk_get_optional() in instead of devm_clk_get() to get the
optional clock and propagate all errors to the calling function.
Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Tested-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

xenvif_connect_data() calls module_put() in case of error. This is
wrong as there is no related module_get().

Remove the superfluous module_put().

Fixes: 279f438e ("xen-netback: Don't destroy the netdev until the vif is shut down")
Cc: <stable@vger.kernel.org> # 3.12
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Reviewed-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Currently, the num_msi_left means the vector numbers of NIC,
but if the PF supported RoCE, it contains the vector numbers
of NIC and RoCE(Not expected).

This may cause interrupts lost in some case, because of the
NIC module used the vector resources which belongs to RoCE.

This patch adds a new variable num_nic_msi to store the vector
numbers of NIC, and adjust the default TQP numbers and rss_size
according to the value of num_nic_msi.

Fixes: 46a3df9f ("net: hns3: Add HNS3 Acceleration Engine & Compatibility Layer Support")
Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Merge misc fixes from Andrew Morton:
 "Rather a lot of fixes, almost all affecting mm/"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (26 commits)
  scripts/gdb: fix debugging modules on s390
  kernel/events/uprobes.c: only do FOLL_SPLIT_PMD for uprobe register
  mm/thp: allow dropping THP from page cache
  mm/vmscan.c: support removing arbitrary sized pages from mapping
  mm/thp: fix node page state in split_huge_page_to_list()
  proc/meminfo: fix output alignment
  mm/init-mm.c: include <linux/mman.h> for vm_committed_as_batch
  mm/filemap.c: include <linux/ramfs.h> for generic_file_vm_ops definition
  mm: include <linux/huge_mm.h> for is_vma_temporary_stack
  zram: fix race between backing_dev_show and backing_dev_store
  mm/memcontrol: update lruvec counters in mem_cgroup_move_account
  ocfs2: fix panic due to ocfs2_wq is null
  hugetlbfs: don't access uninitialized memmaps in pfn_range_valid_gigantic()
  mm: memblock: do not enforce current limit for memblock_phys* family
  mm: memcg: get number of pages on the LRU list in memcgroup base on lru_zone_size
  mm/gup: fix a misnamed "write" argument, and a related bug
  mm/gup_benchmark: add a missing "w" to getopt string
  ocfs2: fix error handling in ocfs2_setattr()
  mm: memcg/slab: fix panic in __free_slab() caused by premature memcg pointer release
  mm/memunmap: don't access uninitialized memmap in memunmap_pages()
  ...

Currently lx-symbols assumes that module text is always located at
module->core_layout->base, but s390 uses the following layout:

  +------+  <- module->core_layout->base
  | GOT  |
  +------+  <- module->core_layout->base + module->arch->plt_offset
  | PLT  |
  +------+  <- module->core_layout->base + module->arch->plt_offset +
  | TEXT |     module->arch->plt_size
  +------+

Therefore, when trying to debug modules on s390, all the symbol
addresses are skewed by plt_offset + plt_size.

Fix by adding plt_offset + plt_size to module_addr in
load_module_symbols().

Link: http://lkml.kernel.org/r/20191017085917.81791-1-iii@linux.ibm.comSigned-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Kieran Bingham <kbingham@kernel.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Attaching uprobe to text section in THP splits the PMD mapped page table
into PTE mapped entries.  On uprobe detach, we would like to regroup PMD
mapped page table entry to regain performance benefit of THP.

However, the regroup is broken For perf_event based trace_uprobe.  This
is because perf_event based trace_uprobe calls uprobe_unregister twice
on close: first in TRACE_REG_PERF_CLOSE, then in
TRACE_REG_PERF_UNREGISTER.  The second call will split the PMD mapped
page table entry, which is not the desired behavior.

Fix this by only use FOLL_SPLIT_PMD for uprobe register case.

Add a WARN() to confirm uprobe unregister never work on huge pages, and
abort the operation when this WARN() triggers.

Link: http://lkml.kernel.org/r/20191017164223.2762148-6-songliubraving@fb.com
Fixes: 5a52c9df ("uprobe: use FOLL_SPLIT_PMD instead of FOLL_SPLIT")
Signed-off-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: William Kucharski <william.kucharski@oracle.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Once a THP is added to the page cache, it cannot be dropped via
/proc/sys/vm/drop_caches.  Fix this issue with proper handling in
invalidate_mapping_pages().

Link: http://lkml.kernel.org/r/20191017164223.2762148-5-songliubraving@fb.com
Fixes: 99cb0dbd ("mm,thp: add read-only THP support for (non-shmem) FS")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Tested-by: Song Liu <songliubraving@fb.com>
Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

__remove_mapping() assumes that pages can only be either base pages or
HPAGE_PMD_SIZE.  Ask the page what size it is.

Link: http://lkml.kernel.org/r/20191017164223.2762148-4-songliubraving@fb.com
Fixes: 99cb0dbd ("mm,thp: add read-only THP support for (non-shmem) FS")
Signed-off-by: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Song Liu <songliubraving@fb.com>
Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Make sure split_huge_page_to_list() handles the state of shmem THP and
file THP properly.

Link: http://lkml.kernel.org/r/20191017164223.2762148-3-songliubraving@fb.com
Fixes: 60fbf0ab ("mm,thp: stats for file backed THP")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Tested-by: Song Liu <songliubraving@fb.com>
Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Patch series "Fixes for THP in page cache", v2.

This patch (of 5):

Add extra space for FileHugePages and FilePmdMapped, so the output is
aligned with other rows.

Link: http://lkml.kernel.org/r/20191017164223.2762148-2-songliubraving@fb.com
Fixes: 60fbf0ab ("mm,thp: stats for file backed THP")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Tested-by: Song Liu <songliubraving@fb.com>
Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: William Kucharski <william.kucharski@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm_init.c needs to include <linux/mman.h> for the definition of
vm_committed_as_batch.  Fixes the following sparse warning:

  mm/mm_init.c:141:5: warning: symbol 'vm_committed_as_batch' was not declared. Should it be static?

Link: http://lkml.kernel.org/r/20191016091509.26708-1-ben.dooks@codethink.co.ukSigned-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The generic_file_vm_ops is defined in <linux/ramfs.h> so include it to
fix the following warning:

  mm/filemap.c:2717:35: warning: symbol 'generic_file_vm_ops' was not declared. Should it be static?

Link: http://lkml.kernel.org/r/20191008102311.25432-1-ben.dooks@codethink.co.ukSigned-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Include <linux/huge_mm.h> for the definition of is_vma_temporary_stack
to fix the following sparse warning:

  mm/rmap.c:1673:6: warning: symbol 'is_vma_temporary_stack' was not declared. Should it be static?

Link: http://lkml.kernel.org/r/20191009151155.27763-1-ben.dooks@codethink.co.ukSigned-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Reviewed-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

CPU0:				       CPU1:
backing_dev_show		       backing_dev_store
    ......				   ......
    file = zram->backing_dev;
    down_read(&zram->init_lock);	   down_read(&zram->init_init_lock)
    file_path(file, ...);		   zram->backing_dev = backing_dev;
    up_read(&zram->init_lock);		   up_read(&zram->init_lock);

gets the value of zram->backing_dev too early in backing_dev_show, which
resultin the value being NULL at the beginning, and not NULL later.

backtrace:
  d_path+0xcc/0x174
  file_path+0x10/0x18
  backing_dev_show+0x40/0xb4
  dev_attr_show+0x20/0x54
  sysfs_kf_seq_show+0x9c/0x10c
  kernfs_seq_show+0x28/0x30
  seq_read+0x184/0x488
  kernfs_fop_read+0x5c/0x1a4
  __vfs_read+0x44/0x128
  vfs_read+0xa0/0x138
  SyS_read+0x54/0xb4

Link: http://lkml.kernel.org/r/1571046839-16814-1-git-send-email-chenwandun@huawei.comSigned-off-by: Chenwandun <chenwandun@huawei.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <stable@vger.kernel.org>	[4.14+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>