libnvdimm: Export max available extent

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 unallocated space that may be allocated
to create a new namespace.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
index c30d5af02cc2..fa37afcd43ff 100644
--- a/drivers/nvdimm/region_devs.c
+++ b/drivers/nvdimm/region_devs.c
@@ -434,6 +434,21 @@ 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_allocatable_dpa(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)
 {
@@ -585,6 +600,7 @@ 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,