so, we need give a protection and return a error value.
[ 7341.474236] [drm:do_intel_finish_page_flip] *ERROR* invalid or inactive unpin_work!
[ 7341.494464] atomisp-css2400b0_v21 0000:00:03.0: unhandled css stored event: 0x20
[ 7341.503627] vmap allocation for size 208896 failed: use vmalloc=<size> to increase size.<=================== map failed
[ 7341.507135] [drm:do_intel_finish_page_flip] *ERROR* invalid or inactive unpin_work!
[ 7341.503848] BUG: unable to handle kernel NULL pointer dereference at   (null)
[ 7341.520394] IP: [<c18f5c1b>] sst_load_all_modules_elf+0x1bb/0x850
[ 7341.527216] *pdpt = 0000000030dfe001 *pde = 0000000000000000
[ 7341.533640] Oops: 0000 [#1] PREEMPT SMP
[ 7341.540360] [drm:do_intel_finish_page_flip] *ERROR* invalid or inactive unpin_work!
[ 7341.538037] Modules linked in: atomisp_css2400b0_v21 lm3554 ov2722 imx1x5 atmel_mxt_ts vxd392 videobuf_vmalloc videobuf_core lm_dump(O) bcm_bt_lpm hdmi_audio bcm4334x(O)
[ 7341.563531] CPU: 1 PID: 525 Comm: mediaserver Tainted: G        W  O 3.10.20-262518-ga83c053 #1
[ 7341.573253] task: f0994ec0 ti: f09f0000 task.ti: f09f0000
[ 7341.579284] EIP: 0060:[<c18f5c1b>] EFLAGS: 00010246 CPU: 1
[ 7341.585415] EIP is at sst_load_all_modules_elf+0x1bb/0x850
[ 7341.591541] EAX: 00000000 EBX: e3595ba0 ECX: 00000000 EDX: 00031c1c
[ 7341.598541] ESI: e04a0000 EDI: 00000000 EBP: f09f1d80 ESP: f09f1cf4
[ 7341.605542]  DS: 007b ES: 007b FS: 00d8 GS: 003b SS: 0068
[ 7341.611573] CR0: 80050033 CR2: 00000000 CR3: 30db4000 CR4: 001007f0
[ 7341.618573] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
[ 7341.625575] DR6: ffff0ff0 DR7: 00000400
[ 7341.629856] Stack:
[ 7341.632097]  f09f1d57 00000019 c1d656d7 c1d658d3 c1d56409 00000f28 c1d64af9 18000103
[ 7341.640766]  01000001 00080000 c1f910a0 f326f4c8 00000034 f326f520 00000002 e04a02bc
[ 7341.649465]  00000001 f326e014 c1f910b0 e04a0000 c0080100 00031c1c e3595ba0 c0080100
[ 7341.658149] Call Trace:
[ 7341.660888]  [<c18f6308>] sst_post_download_byt+0x58/0xb0
[ 7341.666925]  [<c18f4fbc>] sst_load_fw+0xdc/0x510
[ 7341.672086]  [<c1a7b2c0>] ? __mutex_lock_slowpath+0x250/0x370
[ 7341.678507]  [<c1a80e05>] ? sub_preempt_count+0x55/0xe0
[ 7341.684346]  [<c18f1294>] sst_download_fw+0x14/0x60
[ 7341.689796]  [<c1a7b403>] ? mutex_lock+0x23/0x30
[ 7341.694954]  [<c18f191c>] intel_sst_check_device+0x6c/0x120
[ 7341.701181]  [<c18f1d08>] sst_set_generic_params+0x1b8/0x4a0
[ 7341.707504]  [<c1a80e05>] ? sub_preempt_count+0x55/0xe0
[ 7341.713341]  [<c1a80e05>] ? sub_preempt_count+0x55/0xe0
[ 7341.719178]  [<c1a7b2c0>] ? __mutex_lock_slowpath+0x250/0x370
[ 7341.725600]  [<c1320d84>] ? __kmalloc_track_caller+0xe4/0x1d0
[ 7341.732022]  [<c18e35f5>] sst_set_mixer_param+0x25/0x40
[ 7341.737859]  [<c18e3853>] lpe_mixer_ihf_set+0xb3/0x160
[ 7341.743602]  [<c1855b99>] snd_ctl_ioctl+0xa89/0xb40
[ 7341.749052]  [<c1331e65>] ? path_openat+0xa5/0x3d0
[ 7341.754409]  [<c1447857>] ? avc_has_perm_flags+0xc7/0x170
[ 7341.760441]  [<c1855110>] ? snd_ctl_elem_add_user+0x540/0x540
[ 7341.766862]  [<c1334047>] do_vfs_ioctl+0x77/0x5e0
[ 7341.772117]  [<c144842a>] ? inode_has_perm.isra.42.constprop.79+0x3a/0x50
[ 7341.779705]  [<c14490a0>] ? file_has_perm+0xa0/0xb0
[ 7341.785155]  [<c14493b8>] ? selinux_file_ioctl+0x48/0xe0
[ 7341.791090]  [<c1334628>] SyS_ioctl+0x78/0x90
[ 7341.795958]  [<c1a7dde8>] syscall_call+0x7/0xb
[ 7341.800925]  [<c1a70000>] ? mm_fault_error+0x13c/0x198
Signed-off-by: Nzhang jun <jun.zhang@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The google memconsole driver is currently broken upstream, as it tries
to read memory that is described as reserved in /proc/iomem, by
dereferencing a pointer obtained through phys_to_virt(). This triggers
a kernel fault as such regions are unmapped after early boot.

The proper workaround is to use ioremap_cache() / iounmap() around such
accesses.

As some unrelated changes, I also converted some printks to use pr_info()
and added some missing __init annotations.

Tested: booted dbg build, verified I could read /sys/firmware/log
Signed-off-by: NMichel Lespinasse <walken@google.com>
Acked-by: NMike Waychison <mikew@google.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Starting in commit e14ab23d,
efivars_sysfs_init() is called both by itself as an init function,
and by drivers/firmware/google/gsmi.c gsmi_init().

This results in runtime warnings such as the following:
[    5.651330] WARNING: at fs/sysfs/dir.c:530 sysfs_add_one+0xbd/0xe0()
[    5.657699] sysfs: cannot create duplicate filename '/firmware/gsmi/vars'

Fixing this by removing the redundant efivars_sysfs_init() call in
gsmi_init().

Tested: booted, checked that /firmware/gsmi/vars was still present and
showed the expected contents.
Signed-off-by: NMichel Lespinasse <walken@google.com>
Acked-by: NMatt Fleming <matt.fleming@intel.com>
Acked-by: NMike Waychison <mikew@google.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

None of these files are actually using any __init type directives
and hence don't need to include <linux/init.h>.  Most are just a
left over from __devinit and __cpuinit removal, or simply due to
code getting copied from one driver to the next.

Cc: Len Brown <len.brown@intel.com>
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: NPavel Machek <pavel@ucw.cz>
Acked-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: NMark Brown <broonie@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently kernfs_node_from_dentry() returns NULL for root dentry,
because root_dentry->d_op == NULL.

Due to this bug cgroupstats_build() returns -EINVAL for root cgroup.

  # mount -t cgroup -o cpuacct /cgroup
  # Documentation/accounting/getdelays -C /cgroup
  fatal reply error,  errno -22

With this fix:

  # Documentation/accounting/getdelays -C /cgroup
  sleeping 305, blocked 0, running 1, stopped 0, uninterruptible 1
Signed-off-by: NLi Zefan <lizefan@huawei.com>
Acked-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The acpi_dev_pm_attach/_detach functions perform their own checks to
ensure the device has an ACPI companion.  It is not necessary for the
caller to do so.

This mirrors what other busses with ACPI dev PM support do (i2c, spi,
sdio).

Cc: Len Brown <lenb@kernel.org>
Acked-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: NJosh Cartwright <joshc@codeaurora.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

da9846ae ("kernfs: make kernfs_deactivate() honor KERNFS_LOCKDEP
flag") in driver-core-linus conflicts with kernfs_drain() updates in
driver-core-next.  The former just adds the missing KERNFS_LOCKDEP
checks which are already handled by kernfs_lockdep() checks in
driver-core-next.  The conflict can be resolved by taking code from
driver-core-next.

Conflicts:
	fs/kernfs/dir.c

3eef34ad ("kernfs: implement kernfs_get_parent(),
kernfs_name/path() and friends") restructured kernfs_rename_ns() such
that new name assignment happens under kernfs_rename_lock;
unfortunately, it mistakenly passed NULL to kernfs_name_hash() to
calculate the new hash if the name hasn't changed, which can lead to
oops.

Fix it by using kn->name and kn->ns when calculating the new hash.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: Dan Carpenter dan.carpenter@oracle.com
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull SELinux fixes from James Morris.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  SELinux:  Fix kernel BUG on empty security contexts.
  selinux: add SOCK_DIAG_BY_FAMILY to the list of netlink message types

Pull vfs fixes from Al Viro:
 "A couple of fixes, both -stable fodder.  The O_SYNC bug is fairly
  old..."

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  fix a kmap leak in virtio_console
  fix O_SYNC|O_APPEND syncing the wrong range on write()

While we are at it, don't do kmap() under kmap_atomic(), *especially*
for a page we'd allocated with GFP_KERNEL.  It's spelled "page_address",
and had that been more than that, we'd have a real trouble - kmap_high()
can block, and doing that while holding kmap_atomic() is a Bad Idea(tm).
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

It actually goes back to 2004 ([PATCH] Concurrent O_SYNC write support)
when sync_page_range() had been introduced; generic_file_write{,v}() correctly
synced
	pos_after_write - written .. pos_after_write - 1
but generic_file_aio_write() synced
	pos_before_write .. pos_before_write + written - 1
instead.  Which is not the same thing with O_APPEND, obviously.
A couple of years later correct variant had been killed off when
everything switched to use of generic_file_aio_write().

All users of generic_file_aio_write() are affected, and the same bug
has been copied into other instances of ->aio_write().

The fix is trivial; the only subtle point is that generic_write_sync()
ought to be inlined to avoid calculations useless for the majority of
calls.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Pull btrfs fixes from Chris Mason:
 "This is a small collection of fixes"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs:
  Btrfs: fix data corruption when reading/updating compressed extents
  Btrfs: don't loop forever if we can't run because of the tree mod log
  btrfs: reserve no transaction units in btrfs_ioctl_set_features
  btrfs: commit transaction after setting label and features
  Btrfs: fix assert screwup for the pending move stuff

Pull perf fixes from Ingo Molnar:
 "Tooling fixes, mostly related to the KASLR fallout, but also other
  fixes"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf buildid-cache: Check relocation when checking for existing kcore
  perf tools: Adjust kallsyms for relocated kernel
  perf tests: No need to set up ref_reloc_sym
  perf symbols: Prevent the use of kcore if the kernel has moved
  perf record: Get ref_reloc_sym from kernel map
  perf machine: Set up ref_reloc_sym in machine__create_kernel_maps()
  perf machine: Add machine__get_kallsyms_filename()
  perf tools: Add kallsyms__get_function_start()
  perf symbols: Fix symbol annotation for relocated kernel
  perf tools: Fix include for non x86 architectures
  perf tools: Fix AAAAARGH64 memory barriers
  perf tools: Demangle kernel and kernel module symbols too
  perf/doc: Remove mention of non-existent set_perf_event_pending() from design.txt

When using a mix of compressed file extents and prealloc extents, it
is possible to fill a page of a file with random, garbage data from
some unrelated previous use of the page, instead of a sequence of zeroes.

A simple sequence of steps to get into such case, taken from the test
case I made for xfstests, is:

   _scratch_mkfs
   _scratch_mount "-o compress-force=lzo"
   $XFS_IO_PROG -f -c "pwrite -S 0x06 -b 18670 266978 18670" $SCRATCH_MNT/foobar
   $XFS_IO_PROG -c "falloc 26450 665194" $SCRATCH_MNT/foobar
   $XFS_IO_PROG -c "truncate 542872" $SCRATCH_MNT/foobar
   $XFS_IO_PROG -c "fsync" $SCRATCH_MNT/foobar

This results in the following file items in the fs tree:

   item 4 key (257 INODE_ITEM 0) itemoff 15879 itemsize 160
       inode generation 6 transid 6 size 542872 block group 0 mode 100600
   item 5 key (257 INODE_REF 256) itemoff 15863 itemsize 16
       inode ref index 2 namelen 6 name: foobar
   item 6 key (257 EXTENT_DATA 0) itemoff 15810 itemsize 53
       extent data disk byte 0 nr 0 gen 6
       extent data offset 0 nr 24576 ram 266240
       extent compression 0
   item 7 key (257 EXTENT_DATA 24576) itemoff 15757 itemsize 53
       prealloc data disk byte 12849152 nr 241664 gen 6
       prealloc data offset 0 nr 241664
   item 8 key (257 EXTENT_DATA 266240) itemoff 15704 itemsize 53
       extent data disk byte 12845056 nr 4096 gen 6
       extent data offset 0 nr 20480 ram 20480
       extent compression 2
   item 9 key (257 EXTENT_DATA 286720) itemoff 15651 itemsize 53
       prealloc data disk byte 13090816 nr 405504 gen 6
       prealloc data offset 0 nr 258048

The on disk extent at offset 266240 (which corresponds to 1 single disk block),
contains 5 compressed chunks of file data. Each of the first 4 compress 4096
bytes of file data, while the last one only compresses 3024 bytes of file data.
Therefore a read into the file region [285648 ; 286720[ (length = 4096 - 3024 =
1072 bytes) should always return zeroes (our next extent is a prealloc one).

The solution here is the compression code path to zero the remaining (untouched)
bytes of the last page it uncompressed data into, as the information about how
much space the file data consumes in the last page is not known in the upper layer
fs/btrfs/extent_io.c:__do_readpage(). In __do_readpage we were correctly zeroing
the remainder of the page but only if it corresponds to the last page of the inode
and if the inode's size is not a multiple of the page size.

This would cause not only returning random data on reads, but also permanently
storing random data when updating parts of the region that should be zeroed.
For the example above, it means updating a single byte in the region [285648 ; 286720[
would store that byte correctly but also store random data on disk.

A test case for xfstests follows soon.
Signed-off-by: NFilipe David Borba Manana <fdmanana@gmail.com>
Signed-off-by: NChris Mason <clm@fb.com>

A user reported a 100% cpu hang with my new delayed ref code.  Turns out I
forgot to increase the count check when we can't run a delayed ref because of
the tree mod log.  If we can't run any delayed refs during this there is no
point in continuing to look, and we need to break out.  Thanks,
Signed-off-by: NJosef Bacik <jbacik@fb.com>
Signed-off-by: NChris Mason <clm@fb.com>

Added in patch "btrfs: add ioctls to query/change feature bits online"
modifications to superblock don't need to reserve metadata blocks when
starting a transaction.
Signed-off-by: NDavid Sterba <dsterba@suse.cz>
Signed-off-by: NChris Mason <clm@fb.com>

The set_fslabel ioctl uses btrfs_end_transaction, which means it's
possible that the change will be lost if the system crashes, same for
the newly set features. Let's use btrfs_commit_transaction instead.
Signed-off-by: NJeff Mahoney <jeffm@suse.com>
Signed-off-by: NDavid Sterba <dsterba@suse.cz>
Signed-off-by: NChris Mason <clm@fb.com>

Wang noticed that he was failing btrfs/030 even though me and Filipe couldn't
reproduce.  Turns out this is because Wang didn't have CONFIG_BTRFS_ASSERT set,
which meant that a key part of Filipe's original patch was not being built in.
This appears to be a mess up with merging Filipe's patch as it does not exist in
his original patch.  Fix this by changing how we make sure del_waiting_dir_move
asserts that it did not error and take the function out of the ifdef check.
This makes btrfs/030 pass with the assert on or off.  Thanks,
Signed-off-by: NJosef Bacik <jbacik@fb.com>
Reviewed-by: NFilipe Manana <fdmanana@gmail.com>
Signed-off-by: NChris Mason <clm@fb.com>

Pull pinctrl fixes from Linus Walleij:
 "First round of pin control fixes for v3.14:

   - Protect pinctrl_list_add() with the proper mutex.  This was
     identified by RedHat.  Caused nasty locking warnings was rootcased
     by Stanislaw Gruszka.

   - Avoid adding dangerous debugfs files when either half of the
     subsystem is unused: pinmux or pinconf.

   - Various fixes to various drivers: locking, hardware particulars, DT
     parsing, error codes"

* tag 'pinctrl-v3.14-2' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl:
  pinctrl: tegra: return correct error type
  pinctrl: do not init debugfs entries for unimplemented functionalities
  pinctrl: protect pinctrl_list add
  pinctrl: sirf: correct the pin index of ac97_pins group
  pinctrl: imx27: fix offset calculation in imx_read_2bit
  pinctrl: vt8500: Change devicetree data parsing
  pinctrl: imx27: fix wrong offset to ICONFB
  pinctrl: at91: use locked variant of irq_set_handler

Pull irq fix from Thomas Gleixner:
 "Add a missing Kconfig dependency"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  genirq: Generic irq chip requires IRQ_DOMAIN

Pull x86 fixes from Peter Anvin:
 "Quite a varied little collection of fixes.  Most of them are
  relatively small or isolated; the biggest one is Mel Gorman's fixes
  for TLB range flushing.

  A couple of AMD-related fixes (including not crashing when given an
  invalid microcode image) and fix a crash when compiled with gcov"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86, microcode, AMD: Unify valid container checks
  x86, hweight: Fix BUG when booting with CONFIG_GCOV_PROFILE_ALL=y
  x86/efi: Allow mapping BGRT on x86-32
  x86: Fix the initialization of physnode_map
  x86, cpu hotplug: Fix stack frame warning in check_irq_vectors_for_cpu_disable()
  x86/intel/mid: Fix X86_INTEL_MID dependencies
  arch/x86/mm/srat: Skip NUMA_NO_NODE while parsing SLIT
  mm, x86: Revisit tlb_flushall_shift tuning for page flushes except on IvyBridge
  x86: mm: change tlb_flushall_shift for IvyBridge
  x86/mm: Eliminate redundant page table walk during TLB range flushing
  x86/mm: Clean up inconsistencies when flushing TLB ranges
  mm, x86: Account for TLB flushes only when debugging
  x86/AMD/NB: Fix amd_set_subcaches() parameter type
  x86/quirks: Add workaround for AMD F16h Erratum792
  x86, doc, kconfig: Fix dud URL for Microcode data

Pull jfs fix from David Kleikamp:
 "Fix regression"

* tag 'jfs-3.14-rc2' of git://github.com/kleikamp/linux-shaggy:
  jfs: fix generic posix ACL regression

I missed a couple errors in reviewing the patches converting jfs
to use the generic posix ACL function. Setting ACL's currently
fails with -EOPNOTSUPP.
Signed-off-by: NDave Kleikamp <dave.kleikamp@oracle.com>
Reported-by: NMichael L. Semon <mlsemon35@gmail.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>

On archs like S390 or um this driver cannot build nor work.
Make it depend on HAS_IOMEM to bypass build failures.

drivers/built-in.o: In function `dw_wdt_drv_probe':
drivers/watchdog/dw_wdt.c:302: undefined reference to `devm_ioremap_resource'
Signed-off-by: NRichard Weinberger <richard@nod.at>
Signed-off-by: NWim Van Sebroeck <wim@iguana.be>

As sysfs was kernfs's only user, kernfs has been piggybacking on
CONFIG_SYSFS; however, kernfs is scheduled to grow a new user very
soon.  Introduce a separate config option CONFIG_KERNFS which is to be
selected by kernfs users.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently, kobject is invoking kernfs_enable_ns() directly.  This is
fine now as sysfs and kernfs are enabled and disabled together.  If
sysfs is disabled, kernfs_enable_ns() is switched to dummy
implementation too and everything is fine; however, kernfs will soon
have its own config option CONFIG_KERNFS and !SYSFS && KERNFS will be
possible, which can make kobject call into non-dummy
kernfs_enable_ns() with NULL kernfs_node pointers leading to an oops.

Introduce sysfs_enable_ns() which is a wrapper around
kernfs_enable_ns() so that it can be made a noop depending only on
CONFIG_SYSFS regardless of the planned CONFIG_KERNFS.
Signed-off-by: NTejun Heo <tj@kernel.org>
Reported-by: NFengguang Wu <fengguang.wu@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

kernfs_node->parent and ->name are currently marked as "published"
indicating that kernfs users may access them directly; however, those
fields may get updated by kernfs_rename[_ns]() and unrestricted access
may lead to erroneous values or oops.

Protect ->parent and ->name updates with a irq-safe spinlock
kernfs_rename_lock and implement the following accessors for these
fields.

* kernfs_name()		- format the node's name into the specified buffer
* kernfs_path()		- format the node's path into the specified buffer
* pr_cont_kernfs_name()	- pr_cont a node's name (doesn't need buffer)
* pr_cont_kernfs_path()	- pr_cont a node's path (doesn't need buffer)
* kernfs_get_parent()	- pin and return a node's parent

All can be called under any context.  The recursive sysfs_pathname()
in fs/sysfs/dir.c is replaced with kernfs_path() and
sysfs_rename_dir_ns() is updated to use kernfs_get_parent() instead of
dereferencing parent directly.

v2: Dummy definition of kernfs_path() for !CONFIG_KERNFS was missing
    static inline making it cause a lot of build warnings.  Add it.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Implement helpers to determine node from dentry and root from
super_block.  Also add a kernfs_rename_ns() wrapper which assumes NULL
namespace.  These generally make sense and will be used by cgroup.

v2: Some dummy implementations for !CONFIG_SYSFS was missing.  Fixed.
    Reported by kbuild test robot.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add a private data field to be used by kernfs file operations.  This
generally makes sense and will be used by cgroup.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

A write to a kernfs_node is buffered through a kernel buffer.  Writes
<= PAGE_SIZE are performed atomically, while larger ones are executed
in PAGE_SIZE chunks.  While this is enough for sysfs, cgroup which is
scheduled to be converted to use kernfs needs a bit more control over
it.

This patch adds kernfs_ops->atomic_write_len.  If not set (zero), the
behavior stays the same.  If set, writes upto the size are executed
atomically and larger writes are rejected with -E2BIG.

A different implementation strategy would be allowing configuring
chunking size while making the original write size available to the
write method; however, such strategy, while being more complicated,
doesn't really buy anything.  If the write implementation has to
handle chunking, the specific chunk size shouldn't matter all that
much.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently, kernfs_nodes are made visible to userland on creation,
which makes it difficult for kernfs users to atomically succeed or
fail creation of multiple nodes.  In addition, if something fails
after creating some nodes, the created nodes might already be in use
and their active refs need to be drained for removal, which has the
potential to introduce tricky reverse locking dependency on active_ref
depending on how the error path is synchronized.

This patch introduces per-root flag KERNFS_ROOT_CREATE_DEACTIVATED.
If set, all nodes under the root are created in the deactivated state
and stay invisible to userland until explicitly enabled by the new
kernfs_activate() API.  Also, nodes which have never been activated
are guaranteed to bypass draining on removal thus allowing error paths
to not worry about lockding dependency on active_ref draining.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

kernfs_iop_lookup(), kernfs_dir_pos() and kernfs_dir_next_pos() were
missing kernfs_active() tests before using the found kernfs_node.  As
deactivated state is currently visible only while a node is being
removed, this doesn't pose an actual problem.  e.g. lookup succeeding
on a deactivated node doesn't harm anything as the eventual file
operations are gonna fail and those failures are indistinguishible
from the cases in which the lookups had happened before the node was
deactivated.

However, we're gonna allow new nodes to be created deactivated and
then activated explicitly by the kernfs user when it sees fit.  This
is to support atomically making multiple nodes visible to userland and
thus those nodes must not be visible to userland before activated.

Let's plug the lookup and readdir holes so that deactivated nodes are
invisible to userland.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add two super_block related syscall callbacks ->remount_fs() and
->show_options() to kernfs_syscall_ops.  These simply forward the
matching super_operations.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

We're gonna need non-dir syscall callbacks, which will make dir_ops a
misnomer.  Let's rename kernfs_dir_ops to kernfs_syscall_ops.

This is pure rename.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

kernfs_dir_ops are currently being invoked without any active
reference, which makes it tricky for the invoked operations to
determine whether the objects associated those nodes are safe to
access and will remain that way for the duration of such operations.

kernfs already has active_ref mechanism to deal with this which makes
the removal of a given node the synchronization point for gating the
file operations.  There's no reason for dir_ops to be any different.
Update the dir_ops handling so that active_ref is held while the
dir_ops are executing.  This guarantees that while a dir_ops is
executing the target nodes stay alive.

As kernfs_dir_ops doesn't have any in-kernel user at this point, this
doesn't affect anybody.
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

All device_schedule_callback_owner() users are converted to use
device_remove_file_self().  Remove now unused
{sysfs|device}_schedule_callback_owner().
Signed-off-by: NTejun Heo <tj@kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

driver-core now supports synchrnous self-deletion of attributes and
the asynchrnous removal mechanism is scheduled for removal.  Use it
instead of device_schedule_callback().

* Conversions in arch/s390/pci/pci_sysfs.c and
  drivers/s390/block/dcssblk.c are straightforward.

* drivers/s390/cio/ccwgroup.c is a bit more tricky because
  ccwgroup_notifier() was (ab)using device_schedule_callback() to
  purely obtain a process context to kick off ungroup operation which
  may block from a notifier callback.

  Rename ccwgroup_ungroup_callback() to ccwgroup_ungroup() and make it
  take ccwgroup_device * instead.  The new function is now called
  directly from ccwgroup_ungroup_store().

  ccwgroup_notifier() chain is updated to explicitly bounce through
  ccwgroup_device->ungroup_work.  This also removes possible failure
  from memory pressure.

Only compile-tested.
Signed-off-by: NTejun Heo <tj@kernel.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux390@de.ibm.com
Cc: linux-s390@vger.kernel.org
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>