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[PATCH v2 33/33] libnvdimm, pmem: disable dax flushing when pmem is fronting a volatile region

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The pmem driver attaches to both persistent and volatile memory ranges
advertised by the ACPI NFIT. When the region is volatile it is redundant
to spend cycles flushing caches at fsync(). Check if the hosting region
is volatile and do not set QUEUE_FLAG_WC if it is.

Cc: Jan Kara <jack@suse.cz>
Cc: Jeff Moyer <jmoyer@redhat.com>
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        |    9 +++++++--
 drivers/nvdimm/region_devs.c |    6 ++++++
 include/linux/libnvdimm.h    |    1 +
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index b000c6db5731..42876a75dab8 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -275,6 +275,7 @@ static int pmem_attach_disk(struct device *dev,
 	struct vmem_altmap __altmap, *altmap = NULL;
 	struct resource *res = &nsio->res;
 	struct nd_pfn *nd_pfn = NULL;
+	int has_flush, fua = 0, wbc;
 	struct dax_device *dax_dev;
 	int nid = dev_to_node(dev);
 	struct nd_pfn_sb *pfn_sb;
@@ -302,8 +303,12 @@ static int pmem_attach_disk(struct device *dev,
 	dev_set_drvdata(dev, pmem);
 	pmem->phys_addr = res->start;
 	pmem->size = resource_size(res);
-	if (nvdimm_has_flush(nd_region) < 0)
+	has_flush = nvdimm_has_flush(nd_region);
+	if (has_flush < 0)
 		dev_warn(dev, "unable to guarantee persistence of writes\n");
+	else
+		fua = has_flush;
+	wbc = nvdimm_has_cache(nd_region);
 
 	if (!devm_request_mem_region(dev, res->start, resource_size(res),
 				dev_name(&ndns->dev))) {
@@ -344,7 +349,7 @@ static int pmem_attach_disk(struct device *dev,
 		return PTR_ERR(addr);
 	pmem->virt_addr = addr;
 
-	blk_queue_write_cache(q, true, true);
+	blk_queue_write_cache(q, wbc, fua);
 	blk_queue_make_request(q, pmem_make_request);
 	blk_queue_physical_block_size(q, PAGE_SIZE);
 	blk_queue_max_hw_sectors(q, UINT_MAX);
diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index 2df259010720..a085f7094b76 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -989,6 +989,12 @@ int nvdimm_has_flush(struct nd_region *nd_region)
 }
 EXPORT_SYMBOL_GPL(nvdimm_has_flush);
 
+int nvdimm_has_cache(struct nd_region *nd_region)
+{
+	return is_nd_pmem(&nd_region->dev);
+}
+EXPORT_SYMBOL_GPL(nvdimm_has_cache);
+
 void __exit nd_region_devs_exit(void)
 {
 	ida_destroy(&region_ida);
diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
index a98004745768..b733030107bb 100644
--- a/include/linux/libnvdimm.h
+++ b/include/linux/libnvdimm.h
@@ -162,6 +162,7 @@ void nd_region_release_lane(struct nd_region *nd_region, unsigned int lane);
 u64 nd_fletcher64(void *addr, size_t len, bool le);
 void nvdimm_flush(struct nd_region *nd_region);
 int nvdimm_has_flush(struct nd_region *nd_region);
+int nvdimm_has_cache(struct nd_region *nd_region);
 #ifdef CONFIG_ARCH_HAS_PMEM_API
 void arch_memcpy_to_pmem(void *dst, void *src, unsigned size);
 #define ARCH_MEMREMAP_PMEM MEMREMAP_WB

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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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