QUEUE_FLAG_DAX is an indication that a given block device supports
filesystem DAX and should not be set for PMEM namespaces which are in "raw"
mode.  These namespaces lack struct page and are prevented from
participating in filesystem DAX as of commit 569d0365f571 ("dax: require
'struct page' by default for filesystem dax").

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Suggested-by: Mike Snitzer <snitzer@redhat.com>
Fixes: 569d0365f571 ("dax: require 'struct page' by default for filesystem dax")
Cc: stable@vger.kernel.org
Acked-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

This commit:

5fdf8e5ba566 ("libnvdimm: re-enable deep flush for pmem devices via fsync()")

intended to make sure that deep flush was always available even on
platforms which support a power-fail protected CPU cache.  An unintended
side effect of this change was that we also lost the ability to skip
flushing CPU caches on those power-fail protected CPU cache.

Fix this by skipping the low level cache flushing in dax_flush() if we have
CPU caches which are power-fail protected.  The user can still override this
behavior by manually setting the write_cache state of a namespace.  See
libndctl's ndctl_namespace_write_cache_is_enabled(),
ndctl_namespace_enable_write_cache() and
ndctl_namespace_disable_write_cache() functions.

Cc: <stable@vger.kernel.org>
Fixes: 5fdf8e5ba566 ("libnvdimm: re-enable deep flush for pmem devices via fsync()")
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Prior to this commit we would only do a "deep flush" (have nvdimm_flush()
write to each of the flush hints for a region) in response to an
msync/fsync/sync call if the nvdimm_has_cache() returned true at the time
we were setting up the request queue.  This happens due to the write cache
value passed in to blk_queue_write_cache(), which then causes the block
layer to send down BIOs with REQ_FUA and REQ_PREFLUSH set.  We do have a
"write_cache" sysfs entry for namespaces, i.e.:

  /sys/bus/nd/devices/pfn0.1/block/pmem0/dax/write_cache

which can be used to control whether or not the kernel thinks a given
namespace has a write cache, but this didn't modify the deep flush behavior
that we set up when the driver was initialized.  Instead, it only modified
whether or not DAX would flush CPU caches via dax_flush() in response to
*sync calls.

Simplify this by making the *sync deep flush always happen, regardless of
the write cache setting of a namespace.  The DAX CPU cache flushing will
still be controlled the write_cache setting of the namespace.

Cc: <stable@vger.kernel.org>
Fixes: 5fdf8e5ba566 ("libnvdimm: re-enable deep flush for pmem devices via fsync()")
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Complete the move from REQ_FLUSH to REQ_PREFLUSH that apparently started
way back in v4.8.

Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

There is currently a mismatch between the resources that will trigger
the e820_pmem driver to register/load and the resources that will
actually be surfaced as pmem ranges. register_e820_pmem() uses
walk_iomem_res_desc() which includes children and siblings. In contrast,
e820_pmem_probe() only considers top level resources. For example the
following resource tree results in the driver being loaded, but no
resources being registered:

    398000000000-39bfffffffff : PCI Bus 0000:ae
      39be00000000-39bf07ffffff : PCI Bus 0000:af
        39be00000000-39beffffffff : 0000:af:00.0
          39be10000000-39beffffffff : Persistent Memory (legacy)

Fix this up to allow definitions of "legacy" pmem ranges anywhere in
system-physical address space. Not that it is a recommended or safe to
define a pmem range in PCI space, but it is useful for debug /
experimentation, and the restriction on being a top-level resource was
arbitrary.

Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Instrument nvdimm_bus_probe() to emit timestamps for the start and end
of libnvdimm device probing. This is useful for identifying sources of
libnvdimm sub-system initialization latency.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

The pmem driver does not honor a forced read-only setting for very long:
	$ blockdev --setro /dev/pmem0
	$ blockdev --getro /dev/pmem0
	1

followed by various commands like these:
	$ blockdev --rereadpt /dev/pmem0
	or
	$ mkfs.ext4 /dev/pmem0

results in this in the kernel serial log:
	 nd_pmem namespace0.0: region0 read-write, marking pmem0 read-write

with the read-only setting lost:
	$ blockdev --getro /dev/pmem0
	0

That's from bus.c nvdimm_revalidate_disk(), which always applies the
setting from nd_region (which is initially based on the ACPI NFIT
NVDIMM state flags not_armed bit).

In contrast, commit 20bd1d026aac ("scsi: sd: Keep disk read-only when
re-reading partition") fixed this issue for SCSI devices to preserve
the previous setting if it was set to read-only.

This patch modifies bus.c to preserve any previous read-only setting.
It also eliminates the kernel serial log print except for cases where
read-write is changed to read-only, so it doesn't print read-only to
read-only non-changes.

Cc: <stable@vger.kernel.org>
Fixes: 581388209405 ("libnvdimm, nfit: handle unarmed dimms, mark namespaces read-only")
Signed-off-by: Robert Elliott <elliott@hpe.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Use the machine check safe version of copy_to_iter() for the
->copy_to_iter() operation published by the pmem driver.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>