The /sys/class/dax compatibility option has shipped in the kernel for 4
years now which should be sufficient time for tools to abandon the old
ABI in favor of the /sys/bus/dax device-model. Delete it now and see if
anyone screams.
Since this compatibility option shipped there has been more reports of
users being surprised by the compat ABI than surprised by the "new", so
the compat infrastructure has outlived its usefulness. Recall that
/sys/bus/dax device-model is required for the dax kmem driver which
allows PMEM to be used as "System RAM".
The following projects were known to have a dependency on /sys/class/dax
and have dropped their dependency as of the listed version:
- ndctl (including libndctl, daxctl, and libdaxctl): v64+
- fio: v3.13+
- pmdk: v1.5.2+
As further evidence this option is no longer needed some distributions
have already stopped enabling CONFIG_DEV_DAX_PMEM_COMPAT.
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Reported-by: Vishal Verma <vishal.l.verma@intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Jane Chu <jane.chu@oracle.com>
Link: https://lore.kernel.org/r/163701116195.3784476.726128179293466337.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
On the expectation that some environments may not upgrade libdaxctl
(userspace component that depends on the /sys/class/dax hierarchy),
provide a default / legacy dax_pmem_compat driver. The dax_pmem_compat
driver implements the original /sys/class/dax sysfs layout rather than
/sys/bus/dax. When userspace is upgraded it can blacklist this module
and switch to the dax_pmem driver going forward.
CONFIG_DEV_DAX_PMEM_COMPAT and supporting code will be deleted according
to the dax_pmem entry in Documentation/ABI/obsolete/.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Move the responsibility of calling devm_request_resource() and
devm_memremap_pages() into the common device-dax driver. This is another
preparatory step to allowing an alternate personality driver for a
device-dax range.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Towards eliminating the dax_class, move the dax-device-attribute
enabling to a new bus.c file in the core. The amount of code
thrash of sub-sequent patches is reduced as no logic changes are made,
just pure code movement.
A temporary export of unregister_dex_dax() and dax_attribute_groups is
needed to preserve compilation, but those symbols become static again in
a follow-on patch.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The multi-resource implementation anticipated discontiguous sub-division
support. That has not yet materialized, delete the infrastructure and
related code.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Nothing consumes this attribute of a region and devres otherwise
remembers the value for de-allocation purposes.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
The last step before devm_memremap_pages() returns success is to allocate
a release action, devm_memremap_pages_release(), to tear the entire setup
down. However, the result from devm_add_action() is not checked.
Checking the error from devm_add_action() is not enough. The api
currently relies on the fact that the percpu_ref it is using is killed by
the time the devm_memremap_pages_release() is run. Rather than continue
this awkward situation, offload the responsibility of killing the
percpu_ref to devm_memremap_pages_release() directly. This allows
devm_memremap_pages() to do the right thing relative to init failures and
shutdown.
Without this change we could fail to register the teardown of
devm_memremap_pages(). The likelihood of hitting this failure is tiny as
small memory allocations almost always succeed. However, the impact of
the failure is large given any future reconfiguration, or disable/enable,
of an nvdimm namespace will fail forever as subsequent calls to
devm_memremap_pages() will fail to setup the pgmap_radix since there will
be stale entries for the physical address range.
An argument could be made to require that the ->kill() operation be set in
the @pgmap arg rather than passed in separately. However, it helps code
readability, tracking the lifetime of a given instance, to be able to grep
the kill routine directly at the devm_memremap_pages() call site.
Link: http://lkml.kernel.org/r/154275558526.76910.7535251937849268605.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Fixes: e8d5134833 ("memremap: change devm_memremap_pages interface...")
Reviewed-by: "Jérôme Glisse" <jglisse@redhat.com>
Reported-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
dax_pmem_percpu_exit() waits for dax_pmem_percpu_release() to invoke the
dax_pmem->cmp completion. Unfortunately this approach to cleaning up
the percpu_ref only works after devm_memremap_pages() was successful.
If devm_add_action_or_reset() or devm_memremap_pages() fails,
dax_pmem_percpu_release() is not invoked. Therefore
dax_pmem_percpu_exit() hangs waiting for the completion:
rc = devm_add_action_or_reset(dev, dax_pmem_percpu_exit,
&dax_pmem->ref);
if (rc)
return rc;
dax_pmem->pgmap.ref = &dax_pmem->ref;
addr = devm_memremap_pages(dev, &dax_pmem->pgmap);
Avoid the hang by calling percpu_ref_exit() in the error paths instead
of going through dax_pmem_percpu_exit().
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Use module_nd_driver() instead of having module_init() and
module_exit() callbacks which just call nd_driver_register() and
nd_driver_unregister().
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Dynamic debug can be instructed to add the function name to the debug
output using the +f switch, so there is no need for the dax modules to
do it again. If a user decides to add the +f switch for the dax modules'
dynamic debug this results in double prints of the function name.
Reported-by: Johannes Thumshirn <jthumshirn@suse.de>
Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This new interface is similar to how struct device (and many others)
work. The caller initializes a 'struct dev_pagemap' as required
and calls 'devm_memremap_pages'. This allows the pagemap structure to
be embedded in another structure and thus container_of can be used. In
this way application specific members can be stored in a containing
struct.
This will be used by the P2P infrastructure and HMM could probably
be cleaned up to use it as well (instead of having it's own, similar
'hmm_devmem_pages_create' function).
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Fix warnings of the form...
WARNING: CPU: 10 PID: 4983 at fs/sysfs/dir.c:31 sysfs_warn_dup+0x62/0x80
sysfs: cannot create duplicate filename '/class/dax/dax12.0'
Call Trace:
dump_stack+0x63/0x86
__warn+0xcb/0xf0
warn_slowpath_fmt+0x5a/0x80
? kernfs_path_from_node+0x4f/0x60
sysfs_warn_dup+0x62/0x80
sysfs_do_create_link_sd.isra.2+0x97/0xb0
sysfs_create_link+0x25/0x40
device_add+0x266/0x630
devm_create_dax_dev+0x2cf/0x340 [dax]
dax_pmem_probe+0x1f5/0x26e [dax_pmem]
nvdimm_bus_probe+0x71/0x120
...by reusing the namespace id for the device-dax instance name.
Now that we have decided that there will never by more than one
device-dax instance per libnvdimm-namespace parent device [1], we can
directly reuse the namepace ids. There are some possible follow-on
cleanups, but those are saved for a later patch to simplify the -stable
backport.
[1]: https://lists.01.org/pipermail/linux-nvdimm/2016-December/008266.html
Fixes: 98a29c39dc ("libnvdimm, namespace: allow creation of multiple pmem...")
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: <stable@vger.kernel.org>
Reported-by: Dariusz Dokupil <dariusz.dokupil@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
* 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
...
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>
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>
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>
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>
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>
drivers/dax/dax.c:75:6: warning: symbol 'dax_region_put' was not declared.
drivers/dax/dax.c:95:19: warning: symbol 'alloc_dax_region' was not declared.
drivers/dax/dax.c:173:5: warning: symbol 'devm_create_dax_dev' was not declared.
drivers/dax/pmem.c:27:17: warning: symbol 'to_dax_pmem' was not declared.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
If devm_add_action() fails, we are explicitly calling the cleanup to free
the resources allocated. Use the helper devm_add_action_or_reset()
and return directly in case of error, since the cleanup function
has been already called by the helper if there was any error.
Reported-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Vikas C Sajjan <vikas.cha.sajjan@hpe.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Device DAX is the device-centric analogue of Filesystem DAX
(CONFIG_FS_DAX). It allows memory ranges to be allocated and mapped
without need of an intervening file system. Device DAX is strict,
precise and predictable. Specifically this interface:
1/ Guarantees fault granularity with respect to a given page size (pte,
pmd, or pud) set at configuration time.
2/ Enforces deterministic behavior by being strict about what fault
scenarios are supported.
For example, by forcing MADV_DONTFORK semantics and omitting MAP_PRIVATE
support device-dax guarantees that a mapping always behaves/performs the
same once established. It is the "what you see is what you get" access
mechanism to differentiated memory vs filesystem DAX which has
filesystem specific implementation semantics.
Persistent memory is the first target, but the mechanism is also
targeted for exclusive allocations of performance differentiated memory
ranges.
This commit is limited to the base device driver infrastructure to
associate a dax device with pmem range.
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
