commit 0b277961f4484fb3f142caaa1dd1748cb0b2cbee
author Dan Williams <dan.j.williams@intel.com> Fri Jun 09 09:46:50 2017 -0700
committer Dan Williams <dan.j.williams@intel.com> Thu Jun 29 09:29:50 2017 -0700
tree c3ba6190530a8732a64df8e2dba2c6028d36a2eb
parent 6e0c90d691cd5d90569f5918ab03eb76c81f9c6e

libnvdimm, pmem: disable dax flushing when pmem is fronting a volatile region

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 dax_write_cache() 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/region_devs.c

diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index 53a64a1..0c3b089 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -1060,6 +1060,12 @@ 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);