* Region media error reporting: A libnvdimm region device is the parent
to one or more namespaces. To date, media errors have been reported via
the "badblocks" attribute attached to pmem block devices for namespaces
in "raw" or "memory" mode. Given that namespaces can be in "device-dax"
or "btt-sector" mode this new interface reports media errors
generically, i.e. independent of namespace modes or state. This
subsequently allows userspace tooling to craft "ACPI 6.1 Section
9.20.7.6 Function Index 4 - Clear Uncorrectable Error" requests and
submit them via the ioctl path for NVDIMM root bus devices.
* Introduce 'struct dax_device' and 'struct dax_operations': Prompted by
a request from Linus and feedback from Christoph this allows for dax
capable drivers to publish their own custom dax operations. This fixes
the broken assumption that all dax operations are related to a
persistent memory device, and makes it easier for other architectures
and platforms to add customized persistent memory support.
* 'libnvdimm' core updates: A new "deep_flush" sysfs attribute is
available for storage appliance applications to manually trigger memory
controllers to drain write-pending buffers that would otherwise be
flushed automatically by the platform ADR (asynchronous-DRAM-refresh)
mechanism at a power loss event. Support for "locked" DIMMs is included
to prevent namespaces from surfacing when the namespace label data area
is locked. Finally, fixes for various reported deadlocks and crashes,
also tagged for -stable.
* ACPI / nfit driver updates: General updates of the nfit driver to add
DSM command overrides, ACPI 6.1 health state flags support, DSM payload
debug available by default, and various fixes.
Acknowledgements that came after the branch was pushed:
commmit 565851c972 "device-dax: fix sysfs attribute deadlock"
Tested-by: Yi Zhang <yizhan@redhat.com>
commit 23f4984483 "libnvdimm: rework region badblocks clearing"
Tested-by: Toshi Kani <toshi.kani@hpe.com>
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Merge tag 'libnvdimm-for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm
Pull libnvdimm updates from Dan Williams:
"The bulk of this has been in multiple -next releases. There were a few
late breaking fixes and small features that got added in the last
couple days, but the whole set has received a build success
notification from the kbuild robot.
Change summary:
- Region media error reporting: A libnvdimm region device is the
parent to one or more namespaces. To date, media errors have been
reported via the "badblocks" attribute attached to pmem block
devices for namespaces in "raw" or "memory" mode. Given that
namespaces can be in "device-dax" or "btt-sector" mode this new
interface reports media errors generically, i.e. independent of
namespace modes or state.
This subsequently allows userspace tooling to craft "ACPI 6.1
Section 9.20.7.6 Function Index 4 - Clear Uncorrectable Error"
requests and submit them via the ioctl path for NVDIMM root bus
devices.
- Introduce 'struct dax_device' and 'struct dax_operations': Prompted
by a request from Linus and feedback from Christoph this allows for
dax capable drivers to publish their own custom dax operations.
This fixes the broken assumption that all dax operations are
related to a persistent memory device, and makes it easier for
other architectures and platforms to add customized persistent
memory support.
- 'libnvdimm' core updates: A new "deep_flush" sysfs attribute is
available for storage appliance applications to manually trigger
memory controllers to drain write-pending buffers that would
otherwise be flushed automatically by the platform ADR
(asynchronous-DRAM-refresh) mechanism at a power loss event.
Support for "locked" DIMMs is included to prevent namespaces from
surfacing when the namespace label data area is locked. Finally,
fixes for various reported deadlocks and crashes, also tagged for
-stable.
- ACPI / nfit driver updates: General updates of the nfit driver to
add DSM command overrides, ACPI 6.1 health state flags support, DSM
payload debug available by default, and various fixes.
Acknowledgements that came after the branch was pushed:
- commmit 565851c972 "device-dax: fix sysfs attribute deadlock":
Tested-by: Yi Zhang <yizhan@redhat.com>
- commit 23f4984483 "libnvdimm: rework region badblocks clearing"
Tested-by: Toshi Kani <toshi.kani@hpe.com>"
* tag 'libnvdimm-for-4.12' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm: (52 commits)
libnvdimm, pfn: fix 'npfns' vs section alignment
libnvdimm: handle locked label storage areas
libnvdimm: convert NDD_ flags to use bitops, introduce NDD_LOCKED
brd: fix uninitialized use of brd->dax_dev
block, dax: use correct format string in bdev_dax_supported
device-dax: fix sysfs attribute deadlock
libnvdimm: restore "libnvdimm: band aid btt vs clear poison locking"
libnvdimm: fix nvdimm_bus_lock() vs device_lock() ordering
libnvdimm: rework region badblocks clearing
acpi, nfit: kill ACPI_NFIT_DEBUG
libnvdimm: fix clear length of nvdimm_forget_poison()
libnvdimm, pmem: fix a NULL pointer BUG in nd_pmem_notify
libnvdimm, region: sysfs trigger for nvdimm_flush()
libnvdimm: fix phys_addr for nvdimm_clear_poison
x86, dax, pmem: remove indirection around memcpy_from_pmem()
block: remove block_device_operations ->direct_access()
block, dax: convert bdev_dax_supported() to dax_direct_access()
filesystem-dax: convert to dax_direct_access()
Revert "block: use DAX for partition table reads"
ext2, ext4, xfs: retrieve dax_device for iomap operations
...
Here is the big set of new char/misc driver drivers and features for
4.12-rc1.
There's lots of new drivers added this time around, new firmware drivers
from Google, more auxdisplay drivers, extcon drivers, fpga drivers, and
a bunch of other driver updates. Nothing major, except if you happen to
have the hardware for these drivers, and then you will be happy :)
All of these have been in linux-next for a while with no reported
issues.
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Merge tag 'char-misc-4.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc
Pull char/misc driver updates from Greg KH:
"Here is the big set of new char/misc driver drivers and features for
4.12-rc1.
There's lots of new drivers added this time around, new firmware
drivers from Google, more auxdisplay drivers, extcon drivers, fpga
drivers, and a bunch of other driver updates. Nothing major, except if
you happen to have the hardware for these drivers, and then you will
be happy :)
All of these have been in linux-next for a while with no reported
issues"
* tag 'char-misc-4.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc: (136 commits)
firmware: google memconsole: Fix return value check in platform_memconsole_init()
firmware: Google VPD: Fix return value check in vpd_platform_init()
goldfish_pipe: fix build warning about using too much stack.
goldfish_pipe: An implementation of more parallel pipe
fpga fr br: update supported version numbers
fpga: region: release FPGA region reference in error path
fpga altera-hps2fpga: disable/unprepare clock on error in alt_fpga_bridge_probe()
mei: drop the TODO from samples
firmware: Google VPD sysfs driver
firmware: Google VPD: import lib_vpd source files
misc: lkdtm: Add volatile to intentional NULL pointer reference
eeprom: idt_89hpesx: Add OF device ID table
misc: ds1682: Add OF device ID table
misc: tsl2550: Add OF device ID table
w1: Remove unneeded use of assert() and remove w1_log.h
w1: Use kernel common min() implementation
uio_mf624: Align memory regions to page size and set correct offsets
uio_mf624: Refactor memory info initialization
uio: Allow handling of non page-aligned memory regions
hangcheck-timer: Fix typo in comment
...
Pull x86 mm updates from Ingo Molnar:
"The main x86 MM changes in this cycle were:
- continued native kernel PCID support preparation patches to the TLB
flushing code (Andy Lutomirski)
- various fixes related to 32-bit compat syscall returning address
over 4Gb in applications, launched from 64-bit binaries - motivated
by C/R frameworks such as Virtuozzo. (Dmitry Safonov)
- continued Intel 5-level paging enablement: in particular the
conversion of x86 GUP to the generic GUP code. (Kirill A. Shutemov)
- x86/mpx ABI corner case fixes/enhancements (Joerg Roedel)
- ... plus misc updates, fixes and cleanups"
* 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (62 commits)
mm, zone_device: Replace {get, put}_zone_device_page() with a single reference to fix pmem crash
x86/mm: Fix flush_tlb_page() on Xen
x86/mm: Make flush_tlb_mm_range() more predictable
x86/mm: Remove flush_tlb() and flush_tlb_current_task()
x86/vm86/32: Switch to flush_tlb_mm_range() in mark_screen_rdonly()
x86/mm/64: Fix crash in remove_pagetable()
Revert "x86/mm/gup: Switch GUP to the generic get_user_page_fast() implementation"
x86/boot/e820: Remove a redundant self assignment
x86/mm: Fix dump pagetables for 4 levels of page tables
x86/mpx, selftests: Only check bounds-vs-shadow when we keep shadow
x86/mpx: Correctly report do_mpx_bt_fault() failures to user-space
Revert "x86/mm/numa: Remove numa_nodemask_from_meminfo()"
x86/espfix: Add support for 5-level paging
x86/kasan: Extend KASAN to support 5-level paging
x86/mm: Add basic defines/helpers for CONFIG_X86_5LEVEL=y
x86/paravirt: Add 5-level support to the paravirt code
x86/mm: Define virtual memory map for 5-level paging
x86/asm: Remove __VIRTUAL_MASK_SHIFT==47 assert
x86/boot: Detect 5-level paging support
x86/mm/numa: Remove numa_nodemask_from_meminfo()
...
Usage of device_lock() for dax_region attributes is unnecessary and
deadlock prone. It's unnecessary because the order of registration /
un-registration guarantees that drvdata is always valid. It's deadlock
prone because it sets up this situation:
ndctl D 0 2170 2082 0x00000000
Call Trace:
__schedule+0x31f/0x980
schedule+0x3d/0x90
schedule_preempt_disabled+0x15/0x20
__mutex_lock+0x402/0x980
? __mutex_lock+0x158/0x980
? align_show+0x2b/0x80 [dax]
? kernfs_seq_start+0x2f/0x90
mutex_lock_nested+0x1b/0x20
align_show+0x2b/0x80 [dax]
dev_attr_show+0x20/0x50
ndctl D 0 2186 2079 0x00000000
Call Trace:
__schedule+0x31f/0x980
schedule+0x3d/0x90
__kernfs_remove+0x1f6/0x340
? kernfs_remove_by_name_ns+0x45/0xa0
? remove_wait_queue+0x70/0x70
kernfs_remove_by_name_ns+0x45/0xa0
remove_files.isra.1+0x35/0x70
sysfs_remove_group+0x44/0x90
sysfs_remove_groups+0x2e/0x50
dax_region_unregister+0x25/0x40 [dax]
devm_action_release+0xf/0x20
release_nodes+0x16d/0x2b0
devres_release_all+0x3c/0x60
device_release_driver_internal+0x17d/0x220
device_release_driver+0x12/0x20
unbind_store+0x112/0x160
ndctl/2170 is trying to acquire the device_lock() to read an attribute,
and ndctl/2186 is holding the device_lock() while trying to drain all
active attribute readers.
Thanks to Yi Zhang for the reproduction script.
Fixes: d7fe1a67f6 ("dax: add region 'id', 'size', and 'align' attributes")
Cc: <stable@vger.kernel.org>
Reported-by: Yi Zhang <yizhan@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The x86 conversion to the generic GUP code included a small change which causes
crashes and data corruption in the pmem code - not good.
The root cause is that the /dev/pmem driver code implicitly relies on the x86
get_user_pages() implementation doing a get_page() on the page refcount, because
get_page() does a get_zone_device_page() which properly refcounts pmem's separate
page struct arrays that are not present in the regular page struct structures.
(The pmem driver does this because it can cover huge memory areas.)
But the x86 conversion to the generic GUP code changed the get_page() to
page_cache_get_speculative() which is faster but doesn't do the
get_zone_device_page() call the pmem code relies on.
One way to solve the regression would be to change the generic GUP code to use
get_page(), but that would slow things down a bit and punish other generic-GUP
using architectures for an x86-ism they did not care about. (Arguably the pmem
driver was probably not working reliably for them: but nvdimm is an Intel
feature, so non-x86 exposure is probably still limited.)
So restructure the pmem code's interface with the MM instead: get rid of the
get/put_zone_device_page() distinction, integrate put_zone_device_page() into
__put_page() and and restructure the pmem completion-wait and teardown machinery:
Kirill points out that the calls to {get,put}_dev_pagemap() can be
removed from the mm fast path if we take a single get_dev_pagemap()
reference to signify that the page is alive and use the final put of the
page to drop that reference.
This does require some care to make sure that any waits for the
percpu_ref to drop to zero occur *after* devm_memremap_page_release(),
since it now maintains its own elevated reference.
This speeds up things while also making the pmem refcounting more robust going
forward.
Suggested-by: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Kirill Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/149339998297.24933.1129582806028305912.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Replace bdev_direct_access() with dax_direct_access() that uses
dax_device and dax_operations instead of a block_device and
block_device_operations for dax. Once all consumers of the old api have
been converted bdev_direct_access() will be deleted.
Given that block device partitioning decisions can cause dax page
alignment constraints to be violated this also introduces the
bdev_dax_pgoff() helper. It handles calculating a logical pgoff relative
to the dax_device and also checks for page alignment.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Setup a dax_device to have the same lifetime as the pmem block device
and add a ->direct_access() method that is equivalent to
pmem_direct_access(). Once fs/dax.c has been converted to use
dax_operations the old pmem_direct_access() will be removed.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Track a set of dax_operations per dax_device that can be set at
alloc_dax() time. These operations will be used to stop the abuse of
block_device_operations for communicating dax capabilities to
filesystems. It will also be used to replace the "pmem api" and move
pmem-specific cache maintenance, and other dax-driver-specific
filesystem-dax operations, to dax device methods. In particular this
allows us to stop abusing __copy_user_nocache(), via memcpy_to_pmem(),
with a driver specific replacement.
This is a standalone introduction of the operations. Follow on patches
convert each dax-driver and teach fs/dax.c to use ->direct_access() from
dax_operations instead of block_device_operations.
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
For the current block_device based filesystem-dax path, we need a way
for it to lookup the dax_device associated with a block_device. Add a
'host' property of a dax_device that can be used for this purpose. It is
a free form string, but for a dax_device associated with a block device
it is the bdev name.
This is a stop-gap until filesystems are able to mount on a dax-inode
directly.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
We want dax capable drivers to be able to publish a set of dax
operations [1]. However, we do not want to further abuse block_devices
to advertise these operations. Instead we will attach these operations
to a dax device and add a lookup mechanism to go from block device path
to a dax device. A dax capable driver like pmem or brd is responsible
for registering a dax device, alongside a block device, and then a dax
capable filesystem is responsible for retrieving the dax device by path
name if it wants to call dax_operations.
For now, we refactor the dax pseudo-fs to be a generic facility, rather
than an implementation detail, of the device-dax use case. Where a "dax
device" is just an inode + dax infrastructure, and "Device DAX" is a
mapping service layered on top of that base 'struct dax_device'.
"Filesystem DAX" is then a mapping service that layers a filesystem on
top of that same base device. Filesystem DAX is associated with a
block_device for now, but perhaps directly to a dax device in the
future, or for new pmem-only filesystems.
[1]: https://lkml.org/lkml/2017/1/19/880
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
In preparation for introducing a struct dax_device type to the kernel
global type namespace, rename dax_dev to dev_dax. A 'dax_device'
instance will be a generic device-driver object for any provider of dax
functionality. A 'dev_dax' object is a device-dax-driver local /
internal instance.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
A couple of minor improvements to the debug output in the fault handlers:
a) Print the region alignment and fault size when we sent a SIGBUS
because the region alignment is greater than the fault size.
b) Fix the message in the PFN_{DEV|MAP} check.
c) Additionally print the fault size enum value in the huge fault handler.
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The default case for dax_dev_huge_fault() fault size handling mistakenly
returns when it should unlock. This is not a problem in practice since
the only three possible fault sizes are handled. Going forward, if the
core mm adds a new fault size beyond pte, pmd, or pud device-dax should
abort VM_FAULT_SIGBUS requests not VM_FAULT_FALLBACK since device-dax
guarantees a configured fault granularity for all faults.
Signed-off-by: Pushkar Jambhlekar <pushkar.iit@gmail.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Provide a replacement pgoff_to_phys() that translates an nfit_test
resource (allocated by vmalloc()) to a pfn.
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The following warning triggers with a new unit test that stresses the
device-dax interface.
===============================
[ ERR: suspicious RCU usage. ]
4.11.0-rc4+ #1049 Tainted: G O
-------------------------------
./include/linux/rcupdate.h:521 Illegal context switch in RCU read-side critical section!
other info that might help us debug this:
rcu_scheduler_active = 2, debug_locks = 0
2 locks held by fio/9070:
#0: (&mm->mmap_sem){++++++}, at: [<ffffffff8d0739d7>] __do_page_fault+0x167/0x4f0
#1: (rcu_read_lock){......}, at: [<ffffffffc03fbd02>] dax_dev_huge_fault+0x32/0x620 [dax]
Call Trace:
dump_stack+0x86/0xc3
lockdep_rcu_suspicious+0xd7/0x110
___might_sleep+0xac/0x250
__might_sleep+0x4a/0x80
__alloc_pages_nodemask+0x23a/0x360
alloc_pages_current+0xa1/0x1f0
pte_alloc_one+0x17/0x80
__pte_alloc+0x1e/0x120
__get_locked_pte+0x1bf/0x1d0
insert_pfn.isra.70+0x3a/0x100
? lookup_memtype+0xa6/0xd0
vm_insert_mixed+0x64/0x90
dax_dev_huge_fault+0x520/0x620 [dax]
? dax_dev_huge_fault+0x32/0x620 [dax]
dax_dev_fault+0x10/0x20 [dax]
__do_fault+0x1e/0x140
__handle_mm_fault+0x9af/0x10d0
handle_mm_fault+0x16d/0x370
? handle_mm_fault+0x47/0x370
__do_page_fault+0x28c/0x4f0
trace_do_page_fault+0x58/0x2a0
do_async_page_fault+0x1a/0xa0
async_page_fault+0x28/0x30
Inserting a page table entry may trigger an allocation while we are
holding a read lock to keep the device instance alive for the duration
of the fault. Use srcu for this keep-alive protection.
Fixes: dee4107924 ("/dev/dax, core: file operations and dax-mmap")
Cc: <stable@vger.kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Replace the open coded registration of the cdev and dev with the
new device_add_cdev() helper. The helper replaces a common pattern by
taking the proper reference against the parent device and adding both
the cdev and the device.
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
If device_add() fails, cleanup the cdev. Otherwise, we leak a kobj_map()
with a stale device number.
As Jason points out, there is a small possibility that userspace has
opened and mapped the device in the time between cdev_add() and the
device_add() failure. We need a new kill_dax_dev() helper to invalidate
any established mappings.
Fixes: ba09c01d2f ("dax: convert to the cdev api")
Cc: <stable@vger.kernel.org>
Reported-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The debug output for return the return data of pgoff_to_phys() in the
fault handlers has 'phys' and 'pgoff' incorrectly swapped.
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Jeff Moyer reports:
With a device dax alignment of 4KB or 2MB, I get sigbus when running
the attached fio job file for the current kernel (4.11.0-rc1+). If
I specify an alignment of 1GB, it works.
I turned on debug output, and saw that it was failing in the huge
fault code.
dax dax1.0: dax_open
dax dax1.0: dax_mmap
dax dax1.0: dax_dev_huge_fault: fio: write (0x7f08f0a00000 -
dax dax1.0: __dax_dev_pud_fault: phys_to_pgoff(0xffffffffcf60)
dax dax1.0: dax_release
fio config for reproduce:
[global]
ioengine=dev-dax
direct=0
filename=/dev/dax0.0
bs=2m
[write]
rw=write
[read]
stonewall
rw=read
The driver fails to fallback when taking a fault that is larger than
the device alignment, or handling a larger fault when a smaller
mapping is already established. While we could support larger
mappings for a device with a smaller alignment, that change is
too large for the immediate fix. The simplest change is to force
fallback until the fault size matches the alignment.
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Jeff Moyer reports:
With a device dax alignment of 4KB or 2MB, I get sigbus when running
the attached fio job file for the current kernel (4.11.0-rc1+). If
I specify an alignment of 1GB, it works.
I turned on debug output, and saw that it was failing in the huge
fault code.
dax dax1.0: dax_open
dax dax1.0: dax_mmap
dax dax1.0: dax_dev_huge_fault: fio: write (0x7f08f0a00000 -
dax dax1.0: __dax_dev_pud_fault: phys_to_pgoff(0xffffffffcf60
dax dax1.0: dax_release
fio config for reproduce:
[global]
ioengine=dev-dax
direct=0
filename=/dev/dax0.0
bs=2m
[write]
rw=write
[read]
stonewall
rw=read
The driver fails to fallback when taking a fault that is larger than
the device alignment, or handling a larger fault when a smaller
mapping is already established. While we could support larger
mappings for a device with a smaller alignment, that change is
too large for the immediate fix. The simplest change is to force
fallback until the fault size matches the alignment.
Fixes: dee4107924 ("/dev/dax, core: file operations and dax-mmap")
Cc: <stable@vger.kernel.org>
Reported-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Update files that depend on the magic.h inclusion.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Since the introduction of FAULT_FLAG_SIZE to the vm_fault flag, it has
been somewhat painful with getting the flags set and removed at the
correct locations. More than one kernel oops was introduced due to
difficulties of getting the placement correctly.
Remove the flag values and introduce an input parameter to huge_fault
that indicates the size of the page entry. This makes the code easier
to trace and should avoid the issues we see with the fault flags where
removal of the flag was necessary in the fallback paths.
Link: http://lkml.kernel.org/r/148615748258.43180.1690152053774975329.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Tested-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add transparent huge PUD pages support for device DAX by adding a
pud_fault handler.
Link: http://lkml.kernel.org/r/148545060002.17912.6765687780007547551.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Patch series "1G transparent hugepage support for device dax", v2.
The following series implements support for 1G trasparent hugepage on
x86 for device dax. The bulk of the code was written by Mathew Wilcox a
while back supporting transparent 1G hugepage for fs DAX. I have
forward ported the relevant bits to 4.10-rc. The current submission has
only the necessary code to support device DAX.
Comments from Dan Williams: So the motivation and intended user of this
functionality mirrors the motivation and users of 1GB page support in
hugetlbfs. Given expected capacities of persistent memory devices an
in-memory database may want to reduce tlb pressure beyond what they can
already achieve with 2MB mappings of a device-dax file. We have
customer feedback to that effect as Willy mentioned in his previous
version of these patches [1].
[1]: https://lkml.org/lkml/2016/1/31/52
Comments from Nilesh @ Oracle:
There are applications which have a process model; and if you assume
10,000 processes attempting to mmap all the 6TB memory available on a
server; we are looking at the following:
processes : 10,000
memory : 6TB
pte @ 4k page size: 8 bytes / 4K of memory * #processes = 6TB / 4k * 8 * 10000 = 1.5GB * 80000 = 120,000GB
pmd @ 2M page size: 120,000 / 512 = ~240GB
pud @ 1G page size: 240GB / 512 = ~480MB
As you can see with 2M pages, this system will use up an exorbitant
amount of DRAM to hold the page tables; but the 1G pages finally brings
it down to a reasonable level. Memory sizes will keep increasing; so
this number will keep increasing.
An argument can be made to convert the applications from process model
to thread model, but in the real world that may not be always practical.
Hopefully this helps explain the use case where this is valuable.
This patch (of 3):
In preparation for adding the ability to handle PUD pages, convert
vm_operations_struct.pmd_fault to vm_operations_struct.huge_fault. The
vm_fault structure is extended to include a union of the different page
table pointers that may be needed, and three flag bits are reserved to
indicate which type of pointer is in the union.
[ross.zwisler@linux.intel.com: remove unused function ext4_dax_huge_fault()]
Link: http://lkml.kernel.org/r/1485813172-7284-1-git-send-email-ross.zwisler@linux.intel.com
[dave.jiang@intel.com: clear PMD or PUD size flags when in fall through path]
Link: http://lkml.kernel.org/r/148589842696.5820.16078080610311444794.stgit@djiang5-desk3.ch.intel.com
Link: http://lkml.kernel.org/r/148545058784.17912.6353162518188733642.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Nilesh Choudhury <nilesh.choudhury@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
->fault(), ->page_mkwrite(), and ->pfn_mkwrite() calls do not need to
take a vma and vmf parameter when the vma already resides in vmf.
Remove the vma parameter to simplify things.
[arnd@arndb.de: fix ARM build]
Link: http://lkml.kernel.org/r/20170125223558.1451224-1-arnd@arndb.de
Link: http://lkml.kernel.org/r/148521301778.19116.10840599906674778980.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jan Kara <jack@suse.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
pmd_fault() and related functions really only need the vmf parameter since
the additional parameters are all included in the vmf struct. Remove the
additional parameter and simplify pmd_fault() and friends.
Link: http://lkml.kernel.org/r/1484085142-2297-8-git-send-email-ross.zwisler@linux.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Instead of passing in multiple parameters in the pmd_fault() handler,
a vmf can be passed in just like a fault() handler. This will simplify
code and remove the need for the actual pmd fault handlers to allocate a
vmf. Related functions are also modified to do the same.
[dave.jiang@intel.com: fix issue with xfs_tests stall when DAX option is off]
Link: http://lkml.kernel.org/r/148469861071.195597.3619476895250028518.stgit@djiang5-desk3.ch.intel.com
Link: http://lkml.kernel.org/r/1484085142-2297-7-git-send-email-ross.zwisler@linux.intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Dynamic label support: To date namespace label support has been
limited to disambiguating cases where PMEM (direct load/store) and BLK
(mmio aperture) accessed-capacity alias on the same DIMM. Since 4.9 added
support for multiple namespaces per PMEM-region there is value to
support namespace labels even in the non-aliasing case. The presence of
a valid namespace index block force-enables label support when the
kernel would otherwise rely on region boundaries, and permits the region
to be sub-divided.
* Handle media errors in namespace metadata: Complement the error
handling for media errors in namespace data areas with support for
clearing errors on writes, and downgrading potential machine-check
exceptions to simple i/o errors on read.
* Device-DAX region attributes: Add 'align', 'id', and 'size' as
attributes for device-dax regions. In particular this enables userspace
tooling to generically size memory mapping and i/o operations. Prevent
userspace from growing assumptions / dependencies about the parent
device topology for a dax region. A libnvdimm namespace may not always
be the parent device of a dax region.
* Various cleanups and small fixes.
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Merge tag 'libnvdimm-for-4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm
Pull libnvdimm updates from Dan Williams:
"The libnvdimm pull request is relatively small this time around due to
some development topics being deferred to 4.11.
As for this pull request the bulk of it has been in -next for several
releases leading to one late fix being added (commit 868f036fee
("libnvdimm: fix mishandled nvdimm_clear_poison() return value")). It
has received a build success notification from the 0day-kbuild robot
and passes the latest libnvdimm unit tests.
Summary:
- Dynamic label support: To date namespace label support has been
limited to disambiguating cases where PMEM (direct load/store) and
BLK (mmio aperture) accessed-capacity alias on the same DIMM. Since
4.9 added support for multiple namespaces per PMEM-region there is
value to support namespace labels even in the non-aliasing case.
The presence of a valid namespace index block force-enables label
support when the kernel would otherwise rely on region boundaries,
and permits the region to be sub-divided.
- Handle media errors in namespace metadata: Complement the error
handling for media errors in namespace data areas with support for
clearing errors on writes, and downgrading potential machine-check
exceptions to simple i/o errors on read.
- Device-DAX region attributes: Add 'align', 'id', and 'size' as
attributes for device-dax regions. In particular this enables
userspace tooling to generically size memory mapping and i/o
operations. Prevent userspace from growing assumptions /
dependencies about the parent device topology for a dax region. A
libnvdimm namespace may not always be the parent device of a dax
region.
- Various cleanups and small fixes"
* tag 'libnvdimm-for-4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
dax: add region 'id', 'size', and 'align' attributes
libnvdimm: fix mishandled nvdimm_clear_poison() return value
libnvdimm: replace mutex_is_locked() warnings with lockdep_assert_held
libnvdimm, pfn: fix align attribute
libnvdimm, e820: use module_platform_driver
libnvdimm, namespace: use octal for permissions
libnvdimm, namespace: avoid multiple sector calculations
libnvdimm: remove else after return in nsio_rw_bytes()
libnvdimm, namespace: fix the type of name variable
libnvdimm: use consistent naming for request_mem_region()
nvdimm: use the right length of "pmem"
libnvdimm: check and clear poison before writing to pmem
tools/testing/nvdimm: dynamic label support
libnvdimm: allow a platform to force enable label support
libnvdimm: use generic iostat interfaces
While this information is available by looking at the nvdimm parent
device that may not always be the case when/if we add support for other
memory regions. Tooling should not depend on walking a given ancestor
topology that is not guaranteed by the device's class. For example, a
device-dax instance will always have a dax_region parent, but it may not
always have a libnvdimm "dax" device as a grandparent.
Reported-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Every single user of vmf->virtual_address typed that entry to unsigned
long before doing anything with it so the type of virtual_address does
not really provide us any additional safety. Just use masked
vmf->address which already has the appropriate type.
Link: http://lkml.kernel.org/r/1479460644-25076-3-git-send-email-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Hugh notes in response to commit 4cb19355ea "device-dax: fail all
private mapping attempts":
"I think that is more restrictive than you intended: haven't tried, but I
believe it rejects a PROT_READ, MAP_SHARED, O_RDONLY fd mmap, leaving no
way to mmap /dev/dax without write permission to it."
Indeed it does restrict read-only mappings, switch to checking
VM_MAYSHARE, not VM_SHARED.
Cc: <stable@vger.kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Pawel Lebioda <pawel.lebioda@intel.com>
Fixes: 4cb19355ea ("device-dax: fail all private mapping attempts")
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Here is an example /proc/iomem listing for a system with 2 namespaces,
one in "sector" mode and one in "memory" mode:
1fc000000-2fbffffff : Persistent Memory (legacy)
1fc000000-2fbffffff : namespace1.0
340000000-34fffffff : Persistent Memory
340000000-34fffffff : btt0.1
Here is the corresponding ndctl listing:
# ndctl list
[
{
"dev":"namespace1.0",
"mode":"memory",
"size":4294967296,
"blockdev":"pmem1"
},
{
"dev":"namespace0.0",
"mode":"sector",
"size":267091968,
"uuid":"f7594f86-badb-4592-875f-ded577da2eaf",
"sector_size":4096,
"blockdev":"pmem0s"
}
]
Notice that the ndctl listing is purely in terms of namespace devices,
while the iomem listing leaks the internal "btt0.1" implementation
detail. Given that ndctl requires the namespace device name to change
the mode, for example:
# ndctl create-namespace --reconfig=namespace0.0 --mode=raw --force
...use the namespace name in the iomem listing to keep the claiming
device name consistent across different mode settings.
Cc: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The device-dax implementation originally tried to be tricky and allow
private read-only mappings, but in the process allowed writable
MAP_PRIVATE + MAP_NORESERVE mappings. For simplicity and predictability
just fail all private mapping attempts since device-dax memory is
statically allocated and will never support overcommit.
Cc: <stable@vger.kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Fixes: dee4107924 ("/dev/dax, core: file operations and dax-mmap")
Reported-by: Pawel Lebioda <pawel.lebioda@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
If the dax_pmem driver is passed a resource that is already busy the
driver probe attempt should fail with a message like the following:
dax_pmem dax0.1: could not reserve region [mem 0x100000000-0x11fffffff]
However, if we do not catch the error we crash for the obvious reason of
accessing memory that is not mapped.
BUG: unable to handle kernel paging request at ffffc90020001000
IP: [<ffffffff81496712>] __memcpy+0x12/0x20
[..]
Call Trace:
[<ffffffff815c4960>] ? nsio_rw_bytes+0x60/0x180
[<ffffffff815c6045>] nd_pfn_validate+0x75/0x320
[<ffffffff815c63a9>] nvdimm_setup_pfn+0xb9/0x5d0
[<ffffffff815c48ef>] ? devm_nsio_enable+0xff/0x110
[<ffffffff815cb699>] dax_pmem_probe+0x59/0x260
Cc: <stable@vger.kernel.org>
Fixes: ab68f26221 ("/dev/dax, pmem: direct access to persistent memory")
Reported-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
We need to wait until the percpu_ref is released before exit. Otherwise,
we sometimes lose the race and trigger this new warning that was added
in v4.9 (commit a67823c1ed "percpu-refcount: init ->confirm_switch
member properly"):
WARNING: CPU: 0 PID: 3629 at lib/percpu-refcount.c:107 percpu_ref_exit+0x51/0x60
[..]
Call Trace:
[<ffffffff814bf093>] dump_stack+0x85/0xc2
[<ffffffff810b15db>] __warn+0xcb/0xf0
[<ffffffff810b170d>] warn_slowpath_null+0x1d/0x20
[<ffffffff814d70c1>] percpu_ref_exit+0x51/0x60
[<ffffffffa005706a>] dax_pmem_percpu_exit+0x1a/0x50 [dax_pmem]
[<ffffffff81615f1f>] devm_action_release+0xf/0x20
Cc: <stable@vger.kernel.org>
Fixes: ab68f26221 ("/dev/dax, pmem: direct access to persistent memory")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
A bugfix just tried to address a randconfig build problem and introduced
a variant of the same problem: with CONFIG_LIBNVDIMM=y and
CONFIG_NVDIMM_DAX=m, the nvdimm module now fails to link:
drivers/nvdimm/built-in.o: In function `to_nd_device_type':
bus.c:(.text+0x1b5d): undefined reference to `is_nd_dax'
drivers/nvdimm/built-in.o: In function `nd_region_notify_driver_action.constprop.2':
region_devs.c:(.text+0x6b6c): undefined reference to `is_nd_dax'
region_devs.c:(.text+0x6b8c): undefined reference to `to_nd_dax'
drivers/nvdimm/built-in.o: In function `nd_region_probe':
region.c:(.text+0x70f3): undefined reference to `nd_dax_create'
drivers/nvdimm/built-in.o: In function `mode_show':
namespace_devs.c:(.text+0xa196): undefined reference to `is_nd_dax'
drivers/nvdimm/built-in.o: In function `nvdimm_namespace_common_probe':
(.text+0xa55f): undefined reference to `is_nd_dax'
drivers/nvdimm/built-in.o: In function `nvdimm_namespace_common_probe':
(.text+0xa56e): undefined reference to `to_nd_dax'
This reverts the earlier fix, making NVDIMM_DAX a 'bool' option again
as it should be (it gets linked into the libnvdimm module). To fix
the original problem, I'm adding a dependency on LIBNVDIMM to
DEV_DAX_PMEM, which ensures we can't have that one built-in if the
rest is a module.
Fixes: 4e65e9381c ("/dev/dax: fix Kconfig dependency build breakage")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The dev_t variable in devm_create_dax_dev() is used before it's
first set:
drivers/dax/dax.c: In function 'devm_create_dax_dev':
drivers/dax/dax.c:205:39: error: 'dev_t' may be used uninitialized in this function [-Werror=maybe-uninitialized]
inode = iget5_locked(dax_superblock, hash_32(devt + DAXFS_MAGIC, 31),
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/dax/dax.c:688:8: note: 'dev_t' was declared here
This reorders the code to how it looks correct to me.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 3bc52c45ba ("dax: define a unified inode/address_space for device-dax mappings")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
pgoff_to_phys() validates that both the starting address and the length
of the mapping against the resource list. We need to check for a
mapping size of PMD_SIZE not PAGE_SIZE in the pmd fault path.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The data offset for a dax region needs to account for a reservation in
the resource range. Otherwise, device-dax is allowing mappings directly
into the memmap or device-info-block area with crash signatures like the
following:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: get_zone_device_page+0x11/0x30
Call Trace:
follow_devmap_pmd+0x298/0x2c0
follow_page_mask+0x275/0x530
__get_user_pages+0xe3/0x750
__gfn_to_pfn_memslot+0x1b2/0x450 [kvm]
tdp_page_fault+0x130/0x280 [kvm]
kvm_mmu_page_fault+0x5f/0xf0 [kvm]
handle_ept_violation+0x94/0x180 [kvm_intel]
vmx_handle_exit+0x1d3/0x1440 [kvm_intel]
kvm_arch_vcpu_ioctl_run+0x81d/0x16a0 [kvm]
kvm_vcpu_ioctl+0x33c/0x620 [kvm]
do_vfs_ioctl+0xa2/0x5d0
SyS_ioctl+0x79/0x90
entry_SYSCALL_64_fastpath+0x1a/0xa4
Fixes: ab68f26221 ("/dev/dax, pmem: direct access to persistent memory")
Link: http://lkml.kernel.org/r/147205536732.1606.8994275381938837346.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reported-by: Abhilash Kumar Mulumudi <m.abhilash-kumar@hpe.com>
Reported-by: Toshi Kani <toshi.kani@hpe.com>
Tested-by: Toshi Kani <toshi.kani@hpe.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
All the extents of a dax-device must match the alignment of the region.
Otherwise, we are unable to guarantee fault semantics of a given page
size. The region must be self-consistent itself as well.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
In support of enabling resize / truncate of device-dax instances, define
a pseudo-fs to provide a unified inode/address space for vm operations.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
A goal of the device-DAX interface is to be able to support many
exclusive allocations (partitions) of performance / feature
differentiated memory. This count may exceed the default minors limit
of 256.
As a result of switching to an embedded cdev the inode-to-dax_dev
conversion is simplified, as well as reference counting which can switch
to the cdev kobject lifetime.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The kref in dax_dev can be made redundant if the final put_device() on
the device associated with the dax_dev frees the dax_dev. This can be
accomplished by embedding a struct device in struct dax_dev, open coding
device_create() and specifying a custom release method.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Linus Torvalds
Dan Williams
Oliver O'Halloran
Pushkar Jambhlekar
Dave Jiang
Greg Kroah-Hartman
Logan Gunthorpe
Ingo Molnar
Jan Kara
Arnd Bergmann