[PATCHv2 2/2] libnvdimm: Export max available extent

[Keith Busch <keith.busch@intel.com>]

The 'available_size' attribute showing the combined total of all
unallocated space isn't always useful to know how large of a namespace
a user may be able to allocate if the region is fragmented. This patch
will export the largest extent of contiguous unallocated space that may
be allocated to create a new namespace.

Signed-off-by: Keith Busch <keith.busch@intel.com>
---
 drivers/nvdimm/region_devs.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index 8af483d7ef57..82aaf7d6488d 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -433,6 +433,21 @@ static ssize_t available_size_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(available_size);
 
+static ssize_t max_available_extent_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct nd_region *nd_region = to_nd_region(dev);
+	unsigned long long available = 0;
+
+	nvdimm_bus_lock(dev);
+	wait_nvdimm_bus_probe_idle(dev);
+	available = nd_region_contiguous_max(nd_region);
+	nvdimm_bus_unlock(dev);
+
+	return sprintf(buf, "%llu\n", available);
+}
+static DEVICE_ATTR_RO(max_available_extent);
+
 static ssize_t init_namespaces_show(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
@@ -584,6 +599,7 @@ static struct attribute *nd_region_attributes[] = {
 	&dev_attr_read_only.attr,
 	&dev_attr_set_cookie.attr,
 	&dev_attr_available_size.attr,
+	&dev_attr_max_available_extent.attr,
 	&dev_attr_namespace_seed.attr,
 	&dev_attr_init_namespaces.attr,
 	&dev_attr_badblocks.attr,
-- 
2.14.3

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