ARM: pxa: fixes for v4.6

There is only a single fix for dma requestor lines initial
setup, triggered by dmaengine previous fix.

* tag 'pxa-fixes-v4.6' of https://github.com/rjarzmik/linux:
  ARM: pxa: fix the number of DMA requestor lines
Signed-off-by: Olof Johansson <olof@lixom.net>

Merge tag 'omap-for-v4.6/fixes-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap into fixes

Fixes for omaps against v4.6-rc1. Mostly minor fixes for the newer
SoCs with few board fixes and a fix for a long time hwmod bug:

- Fix cpsw_emac0 link type for baltos-ir5221
- Fix interrupt type for TWD
- Fix edma memcpy channel allocation for am43x
- Fix am43x-epos sycntimer32k by using the correct assigned clock
- Fix interconnect barrier for dra7
- Fix a long time hwmod bug for updating sysconfig register properly
- Fix flakey booting on dm814x where USB reset needs a delay

And there is one minor change that is not strictly a fix, but is
good to have for proper hardware detection:

- Detect dra7 silicon revision 2.0 properly

* tag 'omap-for-v4.6/fixes-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap:
  ARM: dts: am335x-baltos-ir5221: fix cpsw_emac0 link type
  ARM: OMAP: Correct interrupt type for ARM TWD
  ARM: DRA722: Add ID detect for Silicon Rev 2.0
  ARM: dts: am43xx: fix edma memcpy channel allocation
  ARM: dts: AM43x-epos: Fix clk parent for synctimer
  ARM: OMAP2: Fix up interconnect barrier initialization for DRA7
  ARM: OMAP2+: hwmod: Fix updating of sysconfig register
  ARM: OMAP2+: Use srst_udelay for USB on dm814x
Signed-off-by: Olof Johansson <olof@lixom.net>

This patch fixes condition whether the specified address ranges
overlap each other.

Fixes: 4b7f48d3 ("bus: uniphier-system-bus: add UniPhier System Bus driver")
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

My intention was to ioremap a 4-byte register.  Coincidentally enough,
sizeof(SZ_4) equals to SZ_4, but this code is weird anyway.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

With http://www.spinics.net/lists/devicetree/msg116771.html we split / refactor
the pinctrl driver to have two different pinctrl devices for each bus on the
Amlogic Meson8 / Meson8b SoCs.
These are the missing patches for documentation and DT that weren't pulled into
mainline with the driver changes.

* tag 'meson8-dt-fix' of https://github.com/carlocaione/linux-meson:
  documentation: Fix pinctrl documentation for Meson8 / Meson8b
  ARM: dts: amlogic: Split pinctrl device for Meson8 / Meson8b

In Baltos iR5221 cpsw_emac0 is connected directly to the switch IC and
hence needs to be configured as "fixed-link".
Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Tony Lindgren <tony@atomide.com>

The ARM TWD interrupt is a private peripheral interrupt (PPI) and per
the ARM GIC documentation, whether the type for PPIs can be set is
IMPLEMENTATION DEFINED. For OMAP4 devices the PPI type cannot be set and
so when we attempt to set the type for the ARM TWD interrupt it fails.
This has done unnoticed because it fails silently and because we cannot
re-configure the type it has had no impact. Nevertheless fix the type
for the TWD interrupt so that it matches the hardware configuration.
Reported-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Tested-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Silicon Rev 2.0 is a minor variant of Rev 1.0. Rev 2.0 is an incremental revision
with various fixes including the following:
    - Reset logic fixes
    - Few asymmetric aging logic fixes
    - Ethernet speed fixes
    - EDMA fixes for McASP
Signed-off-by: Vishal Mahaveer <vishalm@ti.com>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

EDMA was allocating DMA channels 32 and 33 for memcpy usage, out of which
channel 33 is actually used by DES crypto engine. This bad allocation of
the channel causes a crash in the DES crypto engine, as the channel
gets configured for memcpy usage instead of hardware <-> memory DMA.

Fixed by allocating DMA channels 58 and 59 for memcpy usage (I2C0 RX/TX),
which are not used by anybody.

Fixes: cce1ee00 ("ARM: DTS: am437x: Use the new DT bindings for
the eDMA3")
Cc: stable@vger.kernel.org # v4.4+
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Suggested-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

commit 55ee7017 ("arm: omap2: board-generic: use omap4_local_timer_init
for AM437x") makes synctimer32k as the clocksource on AM43xx. By default
the synctimer32k is clocked by 32K RTC OSC on AM43xx. But this 32K RTC OSC
is not available on epos boards which makes it fail to boot.

Synctimer32k can also be clocked by a peripheral PLL, so making this as
clock parent for synctimer3k on epos boards.

Fixes: 55ee7017 ("arm: omap2: board-generic: use omap4_local_timer_init for AM437x")
Cc: stable@vger.kernel.org # v4.4+
Reported-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

The following commits:
commit 3fa60975 ("ARM: omap2: restore OMAP4 barrier behaviour")
commit f746929f ("Revert "ARM: OMAP4: remove dead kconfig option OMAP4_ERRATA_I688"")
and
commit ea827ad5 ("ARM: DRA7: Provide proper IO map table")
came in around the same time, unfortunately this seem to have missed
initializing the barrier for DRA7 platforms - omap5_map_io was reused
for dra7 till it was split out by the last patch. barrier_init
needs to be hence carried forward as it is valid for DRA7 family of
processors as they are for OMAP5.

Fixes: ea827ad5 ("ARM: DRA7: Provide proper IO map table")
Cc: stable@vger.kernel.org # v4.1+
Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reported-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Fix pin controller documentation introducing the new compatibles for
the pinctrl drivers specific for aobus / cbus.

This is needed because we have changed the pin controller driver: we
have now a single specialized pinctrl driver / compatible for each bus
the controller is attached to, instead of one single driver dealing with
all the controllers we have on different buses.
Signed-off-by: Carlo Caione <carlo@endlessm.com>
Acked-by: Rob Herring <robh@kernel.org>

Signed-off-by: Carlo Caione <carlo@endlessm.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Tested-by: Kevin Hilman <khilman@baylibre.com>

Merge tag 'for-v4.6-rc/omap-fixes-a' of git://git.kernel.org/pub/scm/linux/kernel/git/pjw/omap-pending into omap-for-v4.6/fixes

ARM: OMAP2+: first hwmod fix for v4.6-rc

Fix a longstanding bug in the hwmod code that could cause
hardware SYSCONFIG register values to not match the kernel's
idea of what they should be, and that could result in lower
performance during IP block idle entry.

Basic build, boot, and PM test logs are available here:

http://www.pwsan.com/omap/testlogs/omap-hwmod-fixes-a-for-v4.6-rc/20160326231727/

The PCI memory windows available in vulcan.dtsi are limited to 128MB
for 32-bit BARs, and 4GB for 64-bit BARs. Given the memory mapped IO
space available in arm64, these windows can be increased substantially
to support more use cases.

The change increases the 32-bit window to 256MB and the 64-bit window
to 128 GB. The firmware on vulcan boards will use these ranges as well.

PCI IO windows are not supported on Vulcan, so remove them instead of
keeping an unused value.
Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

The Ux500 boards may have an RMI4 unit, and the DT fragments for
them have been merged upstream. Add it to the defconfig.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

The number of requestor lines was clamped to 0 for all pxa architectures
in the requestor declaration. Fix this by using the value.

Fixes: 72b195cb ("ARM: pxa: add the number of DMA requestor lines")
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>

Commit 127500cc ("ARM: OMAP2+: Only write the sysconfig on idle
when necessary") talks about verification of sysconfig cache value before
updating it, only during idle path. But the patch is adding the
verification in the enable path. So, adding the check in a proper place
as per the commit description.

Not keeping this check during enable path as there is a chance of losing
context and it is safe to do on idle as the context of the register will
never be lost while the device is active.
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Acked-by: Tero Kristo <t-kristo@ti.com>
Cc: Jon Hunter <jonathanh@nvidia.com>
Cc: <stable@vger.kernel.org> # 3.12+
Fixes: commit 127500cc "ARM: OMAP2+: Only write the sysconfig on idle when necessary"
[paul@pwsan.com: appears to have been caused by my own mismerge of the
 originally posted patch]
Signed-off-by: Paul Walmsley <paul@pwsan.com>

Pull Ceph updates from Sage Weil:
 "There is quite a bit here, including some overdue refactoring and
  cleanup on the mon_client and osd_client code from Ilya, scattered
  writeback support for CephFS and a pile of bug fixes from Zheng, and a
  few random cleanups and fixes from others"

[ I already decided not to pull this because of it having been rebased
  recently, but ended up changing my mind after all.  Next time I'll
  really hold people to it.  Oh well.   - Linus ]

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: (34 commits)
  libceph: use KMEM_CACHE macro
  ceph: use kmem_cache_zalloc
  rbd: use KMEM_CACHE macro
  ceph: use lookup request to revalidate dentry
  ceph: kill ceph_get_dentry_parent_inode()
  ceph: fix security xattr deadlock
  ceph: don't request vxattrs from MDS
  ceph: fix mounting same fs multiple times
  ceph: remove unnecessary NULL check
  ceph: avoid updating directory inode's i_size accidentally
  ceph: fix race during filling readdir cache
  libceph: use sizeof_footer() more
  ceph: kill ceph_empty_snapc
  ceph: fix a wrong comparison
  ceph: replace CURRENT_TIME by current_fs_time()
  ceph: scattered page writeback
  libceph: add helper that duplicates last extent operation
  libceph: enable large, variable-sized OSD requests
  libceph: osdc->req_mempool should be backed by a slab pool
  libceph: make r_request msg_size calculation clearer
  ...

Pull orangefs filesystem from Mike Marshall.

This finally merges the long-pending orangefs filesystem, which has been
much cleaned up with input from Al Viro over the last six months.  From
the documentation file:

 "OrangeFS is an LGPL userspace scale-out parallel storage system.  It
  is ideal for large storage problems faced by HPC, BigData, Streaming
  Video, Genomics, Bioinformatics.

  Orangefs, originally called PVFS, was first developed in 1993 by Walt
  Ligon and Eric Blumer as a parallel file system for Parallel Virtual
  Machine (PVM) as part of a NASA grant to study the I/O patterns of
  parallel programs.

  Orangefs features include:

    - Distributes file data among multiple file servers
    - Supports simultaneous access by multiple clients
    - Stores file data and metadata on servers using local file system
      and access methods
    - Userspace implementation is easy to install and maintain
    - Direct MPI support
    - Stateless"

see Documentation/filesystems/orangefs.txt for more in-depth details.

* tag 'ofs-pull-tag-1' of git://git.kernel.org/pub/scm/linux/kernel/git/hubcap/linux: (174 commits)
  orangefs: fix orangefs_superblock locking
  orangefs: fix do_readv_writev() handling of error halfway through
  orangefs: have ->kill_sb() evict the VFS side of things first
  orangefs: sanitize ->llseek()
  orangefs-bufmap.h: trim unused junk
  orangefs: saner calling conventions for getting a slot
  orangefs_copy_{to,from}_bufmap(): don't pass bufmap pointer
  orangefs: get rid of readdir_handle_s
  ornagefs: ensure that truncate has an up to date inode size
  orangefs: move code which sets i_link to orangefs_inode_getattr
  orangefs: remove needless wrapper around GFP_KERNEL
  orangefs: remove wrapper around mutex_lock(&inode->i_mutex)
  orangefs: refactor inode type or link_target change detection
  orangefs: use new getattr for revalidate and remove old getattr
  orangefs: use new getattr in inode getattr and permission
  orangefs: use new orangefs_inode_getattr to get size in write and llseek
  orangefs: use new orangefs_inode_getattr to create new inodes
  orangefs: rename orangefs_inode_getattr to orangefs_inode_old_getattr
  orangefs: remove inode->i_lock wrapper
  orangefs: put register_chrdev immediately before register_filesystem
  ...

Pull NTB bug fixes from Jon Mason:
 "NTB bug fixes for tasklet from spinning forever, link errors,
  translation window setup, NULL ptr dereference, and ntb-perf errors.

  Also, a modification to the driver API that makes _addr functions
  optional"

* tag 'ntb-4.6' of git://github.com/jonmason/ntb:
  NTB: Remove _addr functions from ntb_hw_amd
  NTB: Make _addr functions optional in the API
  NTB: Fix incorrect clean up routine in ntb_perf
  NTB: Fix incorrect return check in ntb_perf
  ntb: fix possible NULL dereference
  ntb: add missing setup of translation window
  ntb: stop link work when we do not have memory
  ntb: stop tasklet from spinning forever during shutdown.
  ntb: perf test: fix address space confusion

Pull more SCSI updates from James Bottomley:
 "The only new stuff which missed the first pull request is an update to
  the UFS driver.

  The rest is an assortment of bug fixes and minor tweaks which appeared
  recently (some are fixes for recent code and some are stuff spotted
  recently by the checkers or the new gcc-6 compiler [most of Arnd's
  stuff])"

* tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: (32 commits)
  scsi_common: do not clobber fixed sense information
  scsi: ufs: select CONFIG_NLS
  scsi: fc: use get/put_unaligned64 for wwn access
  fnic: move printk()s outside of the critical code section.
  qla2xxx: avoid maybe_uninitialized warning
  megaraid_sas: add missing curly braces in ioctl handler
  lpfc: fix misleading indentation
  scsi_transport_sas: add 'scsi_target_id' sysfs attribute
  scsi_dh_alua: uninitialized variable in alua_check_vpd()
  scsi: ufs-qcom: add printouts of testbus debug registers
  scsi: ufs-qcom: enable/disable the device ref clock
  scsi: ufs-qcom: set PA_Local_TX_LCC_Enable before link startup
  scsi: ufs: add device quirk delay before putting UFS rails in LPM
  scsi: ufs: fix leakage during link off state
  scsi: ufs: tune UniPro parameters to optimize hibern8 exit time
  scsi: ufs: handle non spec compliant bkops behaviour by device
  scsi: ufs: add retry for query descriptors
  scsi: ufs: add error recovery after DL NAC error
  scsi: ufs: make error handling bit faster
  scsi: ufs: disable vccq if it's not needed by UFS device
  ...

Commit 0b81d077 ("fs crypto: move per-file encryption from f2fs
tree to fs/crypto") moved the f2fs crypto files to fs/crypto/ and
renamed the symbol prefixes from "f2fs_" to "fscrypt_" (and from "F2FS_"
to just "FS" for preprocessor symbols).

Because of the symbol renaming, it's a bit hard to see it as a file
move: use

    git show -M30 0b81d077

to lower the rename detection to just 30% similarity and make git show
the files as renamed (the header file won't be shown as a rename even
then - since all it contains is symbol definitions, it looks almost
completely different).

Even with the renames showing as renames, the diffs are not all that
easy to read, since so much is just the renames.  But Eric Biggers
noticed that it's not just all renames: the initialization of the
xts_tweak had been broken too, using the inode number rather than the
page offset.

That's not right - it makes the xfs_tweak the same for all pages of each
inode.  It _might_ make sense to make the xfs_tweak contain both the
offset _and_ the inode number, but not just the inode number.
Reported-by: Eric Biggers <ebiggers3@gmail.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Kernel zero day testing warned about address space confusion.  A virtual
iomem address was used where a physical address is expected.  The
offending functions implement an optional part of the api, so they are
removed.  They can be added later, after testing.

Fixes: a1b36958Signed-off-by: Allen Hubbe <Allen.Hubbe@emc.com>
Acked-by: Xiangliang Yu <Xiangliang.Yu@amd.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

* switch orangefs_remount() to taking ORANGEFS_SB(sb) instead of sb
* remove from the list _before_ orangefs_unmount() - request_mutex
in the latter will make sure that nothing observed in the loop in
ORANGEFS_DEV_REMOUNT_ALL handling will get freed until the end
of loop
* on removal, keep the forward pointer and zero the back one.  That
way we can drop and regain the spinlock in the loop body (again,
ORANGEFS_DEV_REMOUNT_ALL one) and still be able to get to the
rest of the list.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>

Error should only be returned if nothing had been read/written.
Otherwise we need to report a short read/write instead.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>

a) open files can't have NULL inodes
b) it's SEEK_END, not ORANGEFS_SEEK_END; no need to get cute.
c) make_bad_inode() on lseek()?
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>

just have it return the slot number or -E... - the caller checks
the sign anyway
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>

it's always __orangefs_bufmap
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>

no point, really - we couldn't keep those across the calls of
getdents(); it would be too easy to DoS, having all slots exhausted.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>

Merge fourth patch-bomb from Andrew Morton:
 "A lot more stuff than expected, sorry.  A bunch of ocfs2 reviewing was
  finished off.

   - mhocko's oom-reaper out-of-memory-handler changes

   - ocfs2 fixes and features

   - KASAN feature work

   - various fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (42 commits)
  thp: fix typo in khugepaged_scan_pmd()
  MAINTAINERS: fill entries for KASAN
  mm/filemap: generic_file_read_iter(): check for zero reads unconditionally
  kasan: test fix: warn if the UAF could not be detected in kmalloc_uaf2
  mm, kasan: stackdepot implementation. Enable stackdepot for SLAB
  arch, ftrace: for KASAN put hard/soft IRQ entries into separate sections
  mm, kasan: add GFP flags to KASAN API
  mm, kasan: SLAB support
  kasan: modify kmalloc_large_oob_right(), add kmalloc_pagealloc_oob_right()
  include/linux/oom.h: remove undefined oom_kills_count()/note_oom_kill()
  mm/page_alloc: prevent merging between isolated and other pageblocks
  drivers/memstick/host/r592.c: avoid gcc-6 warning
  ocfs2: extend enough credits for freeing one truncate record while replaying truncate records
  ocfs2: extend transaction for ocfs2_remove_rightmost_path() and ocfs2_update_edge_lengths() before to avoid inconsistency between inode and et
  ocfs2/dlm: move lock to the tail of grant queue while doing in-place convert
  ocfs2: solve a problem of crossing the boundary in updating backups
  ocfs2: fix occurring deadlock by changing ocfs2_wq from global to local
  ocfs2/dlm: fix BUG in dlm_move_lockres_to_recovery_list
  ocfs2/dlm: fix race between convert and recovery
  ocfs2: fix a deadlock issue in ocfs2_dio_end_io_write()
  ...

Pull power management fixlet from Rafael Wysocki:
 "One of commits in my previous pull request changed the permissions of
  drivers/power/avs/rockchip-io-domain.c to executable by mistake"

* tag 'pm+acpi-4.6-rc1-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
  Fix permissions of drivers/power/avs/rockchip-io-domain.c

Pull ia64 update from Tony Luck:
 "Wire up new system calls p{read,write}v2 for ia64"

* tag 'please-pull-preadv2' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux:
  [IA64] Enable preadv2 and pwritev2 syscalls for ia64

Pull more input updates from Dmitry Torokhov:
 "Second round of updates for the input subsystem.

  The BYD PS/2 protocol driver now uses absolute reporting mode and
  should behave more like other touchpads; Synaptics driver needed to
  extend one of its quirks to a newer firmware version, and a few USB
  drivers got tightened up checks for the contents of their descriptors"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input:
  Input: sur40 - fix DMA on stack
  Input: ati_remote2 - fix crashes on detecting device with invalid descriptor
  Input: synaptics - handle spurious release of trackstick buttons, again
  Input: synaptics-rmi4 - remove check of Non-NULL array
  Input: byd - enable absolute mode
  Input: ims-pcu - sanity check against missing interfaces
  Input: melfas_mip4 - add hw_version sysfs attribute

!PageLRU should lead to SCAN_PAGE_LRU, not SCAN_SCAN_ABORT result.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

If
 - generic_file_read_iter() gets called with a zero read length,
 - the read offset is at a page boundary,
 - IOCB_DIRECT is not set
-  and the page in question hasn't made it into the page cache yet,
then do_generic_file_read() will trigger a readahead with a req_size hint
of zero.

Since roundup_pow_of_two(0) is undefined, UBSAN reports

  UBSAN: Undefined behaviour in include/linux/log2.h:63:13
  shift exponent 64 is too large for 64-bit type 'long unsigned int'
  CPU: 3 PID: 1017 Comm: sa1 Tainted: G L 4.5.0-next-20160318+ #14
  [...]
  Call Trace:
   [...]
   [<ffffffff813ef61a>] ondemand_readahead+0x3aa/0x3d0
   [<ffffffff813ef61a>] ? ondemand_readahead+0x3aa/0x3d0
   [<ffffffff813c73bd>] ? find_get_entry+0x2d/0x210
   [<ffffffff813ef9c3>] page_cache_sync_readahead+0x63/0xa0
   [<ffffffff813cc04d>] do_generic_file_read+0x80d/0xf90
   [<ffffffff813cc955>] generic_file_read_iter+0x185/0x420
   [...]
   [<ffffffff81510b06>] __vfs_read+0x256/0x3d0
   [...]

when get_init_ra_size() gets called from ondemand_readahead().

The net effect is that the initial readahead size is arch dependent for
requested read lengths of zero: for example, since

  1UL << (sizeof(unsigned long) * 8)

evaluates to 1 on x86 while its result is 0 on ARMv7, the initial readahead
size becomes 4 on the former and 0 on the latter.

What's more, whether or not the file access timestamp is updated for zero
length reads is decided differently for the two cases of IOCB_DIRECT
being set or cleared: in the first case, generic_file_read_iter()
explicitly skips updating that timestamp while in the latter case, it is
always updated through the call to do_generic_file_read().

According to POSIX, zero length reads "do not modify the last data access
timestamp" and thus, the IOCB_DIRECT behaviour is POSIXly correct.

Let generic_file_read_iter() unconditionally check the requested read
length at its entry and return immediately with success if it is zero.
Signed-off-by: Nicolai Stange <nicstange@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>