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[PATCH v2 22/33] dax, pmem: introduce an optional 'flush' dax_operation

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Filesystem-DAX flushes caches whenever it writes to the address returned
through dax_direct_access() and when writing back dirty radix entries.
That flushing is only required in the pmem case, so add a dax operation
to allow pmem to take this extra action, but skip it for other dax
capable devices that do not provide a flush routine.

An example for this differentiation might be a volatile ram disk where
there is no expectation of persistence. In fact the pmem driver itself might
front such an address range specified by the NFIT. So, this "no flush"
property might be something passed down by the bus / libnvdimm.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/nvdimm/pmem.c |   11 +++++++++++
 include/linux/dax.h   |    2 ++
 2 files changed, 13 insertions(+)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index e501df4ab4b4..822b85fb3365 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -276,9 +276,20 @@ static long pmem_dax_direct_access(struct dax_device *dax_dev,
 	return __pmem_direct_access(pmem, pgoff, nr_pages, kaddr, pfn);
 }
 
+static void pmem_dax_flush(struct dax_device *dax_dev, pgoff_t pgoff,
+		void *addr, size_t size)
+{
+	/*
+	 * TODO: move arch specific cache management into the driver
+	 * directly.
+	 */
+	wb_cache_pmem(addr, size);
+}
+
 static const struct dax_operations pmem_dax_ops = {
 	.direct_access = pmem_dax_direct_access,
 	.copy_from_iter = pmem_copy_from_iter,
+	.flush = pmem_dax_flush,
 };
 
 static void pmem_release_queue(void *q)
diff --git a/include/linux/dax.h b/include/linux/dax.h
index cd8561bb21f3..c88bbcba26d9 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -19,6 +19,8 @@ struct dax_operations {
 	/* copy_from_iter: dax-driver override for default copy_from_iter */
 	size_t (*copy_from_iter)(struct dax_device *, pgoff_t, void *, size_t,
 			struct iov_iter *);
+	/* flush: optional driver-specific cache management after writes */
+	void (*flush)(struct dax_device *, pgoff_t, void *, size_t);
 };
 
 int dax_read_lock(void);

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[PATCH v2 00/33] dax: introduce dax_operations Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:40 +0200
  [PATCH v2 11/33] dm: add dax_device and dax_operations support Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
    Re: [PATCH v2 11/33] dm: add dax_device and dax_operations support Dan Williams <dan.j.williams@intel.com> - 2017-04-15 17:20 +0200
  [PATCH v2 26/33] x86, dax,  libnvdimm: move wb_cache_pmem() to libnvdimm Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 13/33] ext2, ext4,  xfs: retrieve dax_device for iomap operations Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 32/33] filesystem-dax: gate calls to dax_flush() on  QUEUE_FLAG_WC Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 22/33] dax,  pmem: introduce an optional 'flush' dax_operation Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 20/33] dm: add ->copy_from_iter() dax operation support Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 21/33] filesystem-dax: convert to dax_copy_from_iter() Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 24/33] filesystem-dax: convert to dax_flush() Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 30/33] libnvdimm, pmem: fix persistence warning Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 23/33] dm: add ->flush() dax operation support Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 15/33] filesystem-dax: convert to dax_direct_access() Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 18/33] x86, dax,  pmem: remove indirection around memcpy_from_pmem() Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 29/33] uio, libnvdimm,  pmem: implement cache bypass for all copy_from_iter() operations Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
    Re: [PATCH v2 29/33] uio, libnvdimm, pmem: implement cache bypass  for all copy_from_iter() operations Jan Kara <jack@suse.cz> - 2017-04-24 17:10 +0200
  [PATCH v2 10/33] dax: introduce dax_direct_access() Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 28/33] x86, libnvdimm,  dax: stop abusing __copy_user_nocache Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 25/33] x86,  dax: replace clear_pmem() with open coded memset + dax_ops->flush Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 14/33] Revert "block: use DAX for partition table reads" Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 27/33] x86, libnvdimm,  pmem: move arch_invalidate_pmem() to libnvdimm Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 17/33] block: remove block_device_operations  ->direct_access() Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 33/33] libnvdimm,  pmem: disable dax flushing when pmem is fronting a volatile region Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 16/33] block,  dax: convert bdev_dax_supported() to dax_direct_access() Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 19/33] dax, pmem: introduce 'copy_from_iter' dax operation Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 12/33] dm: teach dm-targets to use a dax_device +  dax_operations Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 31/33] libnvdimm, nfit: enable support for volatile ranges Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200
  [PATCH v2 02/33] dax: refactor dax-fs into a generic provider of  'struct dax_device' instances Dan Williams <dan.j.williams@intel.com> - 2017-04-15 04:50 +0200

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