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authorDan Williams <dan.j.williams@intel.com>2017-06-26 21:28:41 -0700
committerDan Williams <dan.j.williams@intel.com>2017-06-29 09:29:50 -0700
commit6e0c90d691cd5d90569f5918ab03eb76c81f9c6e (patch)
tree58a98b00690d31fc0b7552cca10686661acaf51e /drivers/dax
parent9a60c3ef577beb0376704808949f2c1f8fb0672c (diff)
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libnvdimm, pmem, dax: export a cache control attribute
The dax_flush() operation can be turned into a nop on platforms where firmware arranges for cpu caches to be flushed on a power-fail event. The ACPI 6.2 specification defines a mechanism for the platform to indicate this capability so the kernel can select the proper default. However, for other platforms, the administrator must toggle this setting manually. Given this flush setting is a dax-specific mechanism we advertise it through a 'dax' attribute group hanging off a host device. For example, a 'pmem0' block-device gets a 'dax' sysfs-subdirectory with a 'write_cache' attribute to control response to dax cache flush requests. This is similar to the 'queue/write_cache' attribute that appears under block devices. Cc: Jan Kara <jack@suse.cz> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Suggested-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/dax')
-rw-r--r--drivers/dax/super.c79
1 files changed, 79 insertions, 0 deletions
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 8bf71195921b..4827251782a1 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -119,6 +119,8 @@ EXPORT_SYMBOL_GPL(__bdev_dax_supported);
enum dax_device_flags {
/* !alive + rcu grace period == no new operations / mappings */
DAXDEV_ALIVE,
+ /* gate whether dax_flush() calls the low level flush routine */
+ DAXDEV_WRITE_CACHE,
};
/**
@@ -139,6 +141,71 @@ struct dax_device {
const struct dax_operations *ops;
};
+static ssize_t write_cache_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
+ ssize_t rc;
+
+ WARN_ON_ONCE(!dax_dev);
+ if (!dax_dev)
+ return -ENXIO;
+
+ rc = sprintf(buf, "%d\n", !!test_bit(DAXDEV_WRITE_CACHE,
+ &dax_dev->flags));
+ put_dax(dax_dev);
+ return rc;
+}
+
+static ssize_t write_cache_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t len)
+{
+ bool write_cache;
+ int rc = strtobool(buf, &write_cache);
+ struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
+
+ WARN_ON_ONCE(!dax_dev);
+ if (!dax_dev)
+ return -ENXIO;
+
+ if (rc)
+ len = rc;
+ else if (write_cache)
+ set_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
+ else
+ clear_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
+
+ put_dax(dax_dev);
+ return len;
+}
+static DEVICE_ATTR_RW(write_cache);
+
+static umode_t dax_visible(struct kobject *kobj, struct attribute *a, int n)
+{
+ struct device *dev = container_of(kobj, typeof(*dev), kobj);
+ struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
+
+ WARN_ON_ONCE(!dax_dev);
+ if (!dax_dev)
+ return 0;
+
+ if (a == &dev_attr_write_cache.attr && !dax_dev->ops->flush)
+ return 0;
+ return a->mode;
+}
+
+static struct attribute *dax_attributes[] = {
+ &dev_attr_write_cache.attr,
+ NULL,
+};
+
+struct attribute_group dax_attribute_group = {
+ .name = "dax",
+ .attrs = dax_attributes,
+ .is_visible = dax_visible,
+};
+EXPORT_SYMBOL_GPL(dax_attribute_group);
+
/**
* dax_direct_access() - translate a device pgoff to an absolute pfn
* @dax_dev: a dax_device instance representing the logical memory range
@@ -194,11 +261,23 @@ void dax_flush(struct dax_device *dax_dev, pgoff_t pgoff, void *addr,
if (!dax_alive(dax_dev))
return;
+ if (!test_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags))
+ return;
+
if (dax_dev->ops->flush)
dax_dev->ops->flush(dax_dev, pgoff, addr, size);
}
EXPORT_SYMBOL_GPL(dax_flush);
+void dax_write_cache(struct dax_device *dax_dev, bool wc)
+{
+ if (wc)
+ set_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
+ else
+ clear_bit(DAXDEV_WRITE_CACHE, &dax_dev->flags);
+}
+EXPORT_SYMBOL_GPL(dax_write_cache);
+
bool dax_alive(struct dax_device *dax_dev)
{
lockdep_assert_held(&dax_srcu);