PMD faults on a zero length file on a file system mounted with -o dax
will not generate SIGBUS as expected.

	fd = open(...O_TRUNC);
	addr = mmap(NULL, 2*1024*1024, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
	*addr = 'a';
        <expect SIGBUS>

The problem is this code in dax_iomap_pmd_fault:

	max_pgoff = (i_size_read(inode) - 1) >> PAGE_SHIFT;

If the inode size is zero, we end up with a max_pgoff that is way larger
than 0.  :)  Fix it by using DIV_ROUND_UP, as is done elsewhere in the
kernel.

I tested this with some simple test code that ensured that SIGBUS was
received where expected.

Cc: <stable@vger.kernel.org>
Fixes: 642261ac ("dax: add struct iomap based DAX PMD support")
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Now that dax_flush() is no longer a driver callback (commit c3ca015f
"dax: remove the pmem_dax_ops->flush abstraction"), stop requiring the
dax_read_lock() to be held and the device to be alive.  This is in
preparation for switching filesystem-dax to store pfns instead of
sectors in the radix.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

DAX support in brd is awkward because its backing page frames are
distinct from the ones provided by pmem, dcssblk, or axonram. We need
pfn_t_devmap() entries to fully support DAX, and the limited DAX support
for pfn_t_special() page frames is not interesting for brd when pmem is
already a superset of brd.  Lastly, brd is the only dax capable driver
that may sleep in its ->direct_access() implementation. So it causes a
global burden with no net gain of kernel functionality.

For all these reasons, remove DAX support.

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Before we add another failure reason, quiet the existing log messages.
Leave it to the caller to decide if bdev_dax_supported() failures are
errors worth emitting to the log.
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

While reviewing whether MAP_SYNC should strengthen its current guarantee
of syncing writes from the initiating process to also include
third-party readers observing dirty metadata, Dave pointed out that the
check of IOMAP_WRITE is misplaced.

The policy of what to with IOMAP_F_DIRTY should be separated from the
generic filesystem mechanism of reporting dirty metadata. Move this
policy to the fs-dax core to simplify the per-filesystem iomap handlers,
and further centralize code that implements the MAP_SYNC policy. This
otherwise should not change behavior, it just makes it easier to change
behavior in the future.
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reported-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Return IOMAP_F_DIRTY from xfs_file_iomap_begin() when asked to prepare
blocks for writing and the inode is pinned, and has dirty fields other
than the timestamps.  In __xfs_filemap_fault() we then detect this case
and call dax_finish_sync_fault() to make sure all metadata is committed,
and to insert the page table entry.

Note that this will also dirty corresponding radix tree entry which is
what we want - fsync(2) will still provide data integrity guarantees for
applications not using userspace flushing. And applications using
userspace flushing can avoid calling fsync(2) and thus avoid the
performance overhead.

[JK: Added VM_SYNC flag handling]
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

xfs_filemap_pfn_mkwrite() duplicates a lot of __xfs_filemap_fault().
It will also need to handle flushing for synchronous page faults. So
just make that function use __xfs_filemap_fault().
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

We return IOMAP_F_DIRTY flag from ext4_iomap_begin() when asked to
prepare blocks for writing and the inode has some uncommitted metadata
changes. In the fault handler ext4_dax_fault() we then detect this case
(through VM_FAULT_NEEDDSYNC return value) and call helper
dax_finish_sync_fault() to flush metadata changes and insert page table
entry. Note that this will also dirty corresponding radix tree entry
which is what we want - fsync(2) will still provide data integrity
guarantees for applications not using userspace flushing. And
applications using userspace flushing can avoid calling fsync(2) and
thus avoid the performance overhead.
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

If transaction starting fails, just bail out of the function immediately
instead of checking for that condition throughout the function.
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Implement a function that filesystems can call to finish handling of
synchronous page faults. It takes care of syncing appropriare file range
and insertion of page table entry.
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Add a flag to iomap interface informing the caller that inode needs
fdstasync(2) for returned extent to become persistent and use it in DAX
fault code so that we don't map such extents into page tables
immediately. Instead we propagate the information that fdatasync(2) is
necessary from dax_iomap_fault() with a new VM_FAULT_NEEDDSYNC flag.
Filesystem fault handler is then responsible for calling fdatasync(2)
and inserting pfn into page tables.
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Define new MAP_SYNC flag and corresponding VMA VM_SYNC flag. As the
MAP_SYNC flag is not part of LEGACY_MAP_MASK, currently it will be
refused by all MAP_SHARED_VALIDATE map attempts and silently ignored for
everything else.
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Currently we dirty radix tree entry whenever dax_insert_mapping_entry()
gets called for a write fault. With synchronous page faults we would
like to insert clean radix tree entry and dirty it only once we call
fdatasync() and update page tables to save some unnecessary cache
flushing. Add 'dirty' argument to dax_insert_mapping_entry() for that.
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

For synchronous page fault dax_iomap_fault() will need to return PFN
which will then need to be inserted into page tables after fsync()
completes. Add necessary parameter to dax_iomap_fault().
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Add missing argument description.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

dax_pmd_insert_mapping() has only one callsite and we will need to
further fine tune what it does for synchronous faults. Just inline it
into the callsite so that we don't have to pass awkward bools around.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

dax_insert_mapping() has only one callsite and we will need to further
fine tune what it does for synchronous faults. Just inline it into the
callsite so that we don't have to pass awkward bools around.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

There are already two users and more are coming.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

There are already two users and more are coming.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Factor out code to get pfn out of iomap that is shared between PTE and
PMD fault path.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

dax_insert_mapping() has lots of arguments and a lot of them is actuall
duplicated by passing vm_fault structure as well. Change the function to
take the same arguments as dax_pmd_insert_mapping().
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

It is unused.
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

The mmap(2) syscall suffers from the ABI anti-pattern of not validating
unknown flags. However, proposals like MAP_SYNC need a mechanism to
define new behavior that is known to fail on older kernels without the
support. Define a new MAP_SHARED_VALIDATE flag pattern that is
guaranteed to fail on all legacy mmap implementations.

It is worth noting that the original proposal was for a standalone
MAP_VALIDATE flag. However, when that  could not be supported by all
archs Linus observed:

    I see why you *think* you want a bitmap. You think you want
    a bitmap because you want to make MAP_VALIDATE be part of MAP_SYNC
    etc, so that people can do

    ret = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED
		    | MAP_SYNC, fd, 0);

    and "know" that MAP_SYNC actually takes.

    And I'm saying that whole wish is bogus. You're fundamentally
    depending on special semantics, just make it explicit. It's already
    not portable, so don't try to make it so.

    Rename that MAP_VALIDATE as MAP_SHARED_VALIDATE, make it have a value
    of 0x3, and make people do

    ret = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED_VALIDATE
		    | MAP_SYNC, fd, 0);

    and then the kernel side is easier too (none of that random garbage
    playing games with looking at the "MAP_VALIDATE bit", but just another
    case statement in that map type thing.

    Boom. Done.

Similar to ->fallocate() we also want the ability to validate the
support for new flags on a per ->mmap() 'struct file_operations'
instance basis.  Towards that end arrange for flags to be generically
validated against a mmap_supported_flags exported by 'struct
file_operations'. By default all existing flags are implicitly
supported, but new flags require MAP_SHARED_VALIDATE and
per-instance-opt-in.

Cc: Jan Kara <jack@suse.cz>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Christoph Hellwig <hch@lst.de>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

_calc_vm_trans() does not handle the situation when some of the passed
flags are 0 (which can happen if these VM flags do not make sense for
the architecture). Improve the _calc_vm_trans() macro to return 0 in
such situation. Since all passed flags are constant, this does not add
any runtime overhead.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Pull SCSI fixes from James Bottomley:

 - a couple of serious fixes: use after free and blacklist for WRITE
   SAME

 - one error leg fix: write_pending failure

 - one user experience problem: do not override max_sectors_kb

 - one minor unused function removal

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: ibmvscsis: Fix write_pending failure path
  scsi: libiscsi: Remove iscsi_destroy_session
  scsi: libiscsi: Fix use-after-free race during iscsi_session_teardown
  scsi: sd: Do not override max_sectors_kb sysfs setting
  scsi: sd: Implement blacklist option for WRITE SAME w/ UNMAP

Pull i2c fixes from Wolfram Sang:
 "I2C has three driver fixes for the newly introduced drivers and one ID
  addition for the i801 driver"

* 'i2c/for-current-4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: i2c-stm32f7: make structure stm32f7_setup static const
  i2c: ensure termination of *_device_id tables
  i2c: i801: Add support for Intel Cedar Fork
  i2c: stm32f7: fix setup structure

Pull MMC fixes from Ulf Hansson:
 "MMC core:

   - Fix driver strength selection when selecting hs400es

   - Delete bounce buffer handling:

     This change fixes a problem related to how bounce buffers are being
     allocated. However, instead of trying to fix that, let's just
     remove the mmc bounce buffer code altogether, as it has practically
     no use.

  MMC host:

   - meson-gx: A couple of fixes related to clock/phase/tuning

   - sdhci-xenon: Fix clock resource by adding an optional bus clock"

* tag 'mmc-v4.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc:
  mmc: sdhci-xenon: Fix clock resource by adding an optional bus clock
  mmc: meson-gx: include tx phase in the tuning process
  mmc: meson-gx: fix rx phase reset
  mmc: meson-gx: make sure the clock is rounded down
  mmc: Delete bounce buffer handling
  mmc: core: add driver strength selection when selecting hs400es

Merge tag 'hwmon-for-linus-v4.14-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging

Pull hwmon fix from Guenter Roeck:
 "Fix up error path in xgene driver"

* tag 'hwmon-for-linus-v4.14-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging:
  hwmon: (xgene) Fix up error handling path mixup in 'xgene_hwmon_probe()'

Pull clk fixes from Stephen Boyd:

 - build fix to export the clk_bulk_prepare() symbol

 - suspend fix for Samsung Exynos SoCs where we need to keep clks on
   across suspend

 - two critical clk markings for clks that shouldn't ever turn off on
   Rockchip SoCs

 - a fix for a copy-paste mistake on Rockchip rk3128 causing some clks
   to touch the same bit and trample over one another

* tag 'clk-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux:
  clk: samsung: exynos4: Enable VPLL and EPLL clocks for suspend/resume cycle
  clk: Export clk_bulk_prepare()
  clk: rockchip: add sclk_timer5 as critical clock on rk3128
  clk: rockchip: fix up rk3128 pvtm and mipi_24m gate regs error
  clk: rockchip: add pclk_pmu as critical clock on rk3128

Pull ARC udpates from Vineet Gupta:

 - updates for various platforms

 - boot log updates for upcoming HS48 family of cores (dual issue)

* tag 'arc-4.14-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARC: [plat-hsdk]: Add reset controller node to manage ethernet reset
  ARC: [plat-hsdk]: Temporary fix to set CPU frequency to 1GHz
  ARC: fix allnoconfig build warning
  ARCv2: boot log: identify HS48 cores (dual issue)
  ARC: boot log: decontaminate ARCv2 ISA_CONFIG register
  arc: remove redundant UTS_MACHINE define in arch/arc/Makefile
  ARC: [plat-eznps] Update platform maintainer as Noam left
  ARC: [plat-hsdk] use actual clk driver to manage cpu clk
  ARC: [*defconfig] Reenable soft lock-up detector
  ARC: [plat-axs10x] sdio: Temporary fix of sdio ciu frequency
  ARC: [plat-hsdk] sdio: Temporary fix of sdio ciu frequency
  ARC: [plat-axs103] Add temporary quirk to reset ethernet IP

Pull xfs fixes from Darrick Wong:

 - fix a race between overlapping copy on write aio

 - fix cow fork swapping when we defragment reflinked files

* tag 'xfs-4.14-fixes-4' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: handle racy AIO in xfs_reflink_end_cow
  xfs: always swap the cow forks when swapping extents

Pull block fixes from Jens Axboe:
 "A collection of fixes for this series. This contains:

   - NVMe pull request from Christoph, one uuid attribute fix, and one
     fix for the controller memory buffer address for remapped BARs.

   - use-after-free fix for bsg, from Benjamin Block.

   - bcache race/use-after-free fix for a list traversal, fixing a
     regression in this merge window. From Coly Li.

   - null_blk change configfs dependency change from a 'depends' to a
     'select'. This is a change from this merge window as well. From me.

   - nbd signal fix from Josef, fixing a regression introduced with the
     status code changes.

   - nbd MAINTAINERS mailing list entry update.

   - blk-throttle stall fix from Joseph Qi.

   - blk-mq-debugfs fix from Omar, fixing an issue where we don't
     register the IO scheduler debugfs directory, if the driver is
     loaded with it. Only shows up if you switch through the sysfs
     interface"

* 'for-linus' of git://git.kernel.dk/linux-block:
  bsg-lib: fix use-after-free under memory-pressure
  nvme-pci: Use PCI bus address for data/queues in CMB
  blk-mq-debugfs: fix device sched directory for default scheduler
  null_blk: change configfs dependency to select
  blk-throttle: fix possible io stall when upgrade to max
  MAINTAINERS: update list for NBD
  nbd: fix -ERESTARTSYS handling
  nvme: fix visibility of "uuid" ns attribute
  bcache: use llist_for_each_entry_safe() in __closure_wake_up()

Pull PCI fixes from Bjorn Helgaas:
 "Fix legacy IDE probe issues exposed by recent PCI core IRQ mapping
  changes (Bartlomiej Zolnierkiewicz, Lorenzo Pieralisi)"

* tag 'pci-v4.14-fixes-4' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci:
  ide: fix IRQ assignment for PCI bus order probing
  ide: pci: free PCI BARs on initialization failure
  ide: free hwif->portdev on hwif_init() failure

Pull arm64 fixes from Catalin Marinas:

 - Bring initialisation of user space undefined instruction handling
   early (core_initcall) since late_initcall() happens after modprobe in
   initramfs is invoked. Similar fix for fpsimd initialisation

 - Increase the kernel stack when KASAN is enabled

 - Bring the PCI ACS enabling earlier via the
   iort_init_platform_devices()

 - Fix misleading data abort address printing (decimal vs hex)

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: Ensure fpsimd support is ready before userspace is active
  arm64: Ensure the instruction emulation is ready for userspace
  arm64: Use larger stacks when KASAN is selected
  ACPI/IORT: Fix PCI ACS enablement
  arm64: fix misleading data abort decoding

Pull KVM fixes from Radim Krčmář:

 - fix PPC XIVE interrupt delivery

 - fix x86 RCU breakage from asynchronous page faults when built without
   PREEMPT_COUNT

 - fix x86 build with -frecord-gcc-switches

 - fix x86 build without X86_LOCAL_APIC

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: add X86_LOCAL_APIC dependency
  x86/kvm: Move kvm_fastop_exception to .fixup section
  kvm/x86: Avoid async PF preempting the kernel incorrectly
  KVM: PPC: Book3S: Fix server always zero from kvmppc_xive_get_xive()

Pull rdma fixes from Doug Ledford:
 "This is a pretty small pull request. Only 6 patches in total. There
  are no outstanding -rc patches on the mailing list after this pull
  request, so only if some new issues are discovered in the remainder of
  the rc cycles will you hear from me again.

  Summary:
   - a fix for iwpm netlink usage
   - a fix for error unwinding in mlx5
   - two fixes to vlan handling in qedr
   - a couple small i40iw fixes"

* tag 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dledford/rdma:
  i40iw: Fix port number for query QP
  i40iw: Add missing memory barriers
  RDMA/qedr: Parse vlan priority as sl
  RDMA/qedr: Parse VLAN ID correctly and ignore the value of zero
  IB/mlx5: Fix label order in error path handling
  RDMA/iwpm: Properly mark end of NL messages

Pull btrfs fixes from David Sterba:
 "Two more fixes for bugs introduced in 4.13.

  The sector_t problem with 32bit architecture and !LBDAF config seems
  serious but the number of affected deployments is hopefully low.

  The clashing status bits could lead to a confusing in-memory state of
  the whole-filesystem operations if used with the quota override sysfs
  knob"

* 'for-4.14-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  Btrfs: fix overlap of fs_info::flags values
  btrfs: avoid overflow when sector_t is 32 bit

Pull ceph fixes from Ilya Dryomov:
 "Two fixups for CephFS snapshot-handling patches in -rc1"

* tag 'ceph-for-4.14-rc4' of git://github.com/ceph/ceph-client:
  ceph: fix __choose_mds() for LSSNAP request
  ceph: properly queue cap snap for newly created snap realm

DW ethernet controller on HSDK hangs sometimes after SW reset, so
add reset node to make possible to reset DW ethernet controller HW.
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>