[PATCH] device-dax: Fix range release

[Dan Williams]

There are multiple locations that open-code the release of the last
range in a device-dax instance. Consolidate this into a new
dev_dax_trim_range() helper.

This also addresses a kmemleak report:

# cat /sys/kernel/debug/kmemleak
[..]
unreferenced object 0xffff976bd46f6240 (size 64):
   comm "ndctl", pid 23556, jiffies 4299514316 (age 5406.733s)
   hex dump (first 32 bytes):
     00 00 00 00 00 00 00 00 00 00 20 c3 37 00 00 00  .......... .7...
     ff ff ff 7f 38 00 00 00 00 00 00 00 00 00 00 00  ....8...........
   backtrace:
     [<00000000064003cf>] __kmalloc_track_caller+0x136/0x379
     [<00000000d85e3c52>] krealloc+0x67/0x92
     [<00000000d7d3ba8a>] __alloc_dev_dax_range+0x73/0x25c
     [<0000000027d58626>] devm_create_dev_dax+0x27d/0x416
     [<00000000434abd43>] __dax_pmem_probe+0x1c9/0x1000 [dax_pmem_core]
     [<0000000083726c1c>] dax_pmem_probe+0x10/0x1f [dax_pmem]
     [<00000000b5f2319c>] nvdimm_bus_probe+0x9d/0x340 [libnvdimm]
     [<00000000c055e544>] really_probe+0x230/0x48d
     [<000000006cabd38e>] driver_probe_device+0x122/0x13b
     [<0000000029c7b95a>] device_driver_attach+0x5b/0x60
     [<0000000053e5659b>] bind_store+0xb7/0xc3
     [<00000000d3bdaadc>] drv_attr_store+0x27/0x31
     [<00000000949069c5>] sysfs_kf_write+0x4a/0x57
     [<000000004a8b5adf>] kernfs_fop_write+0x150/0x1e5
     [<00000000bded60f0>] __vfs_write+0x1b/0x34
     [<00000000b92900f0>] vfs_write+0xd8/0x1d1

Reported-by: Jane Chu <jane.chu@xxxxxxxxxx>
Cc: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 drivers/dax/bus.c |   44 +++++++++++++++++++++-----------------------
 1 file changed, 21 insertions(+), 23 deletions(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 9761cb40d4bb..720cd140209f 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -367,19 +367,28 @@ void kill_dev_dax(struct dev_dax *dev_dax)
 }
 EXPORT_SYMBOL_GPL(kill_dev_dax);
 
-static void free_dev_dax_ranges(struct dev_dax *dev_dax)
+static void trim_dev_dax_range(struct dev_dax *dev_dax)
 {
+	int i = dev_dax->nr_range - 1;
+	struct range *range = &dev_dax->ranges[i].range;
 	struct dax_region *dax_region = dev_dax->region;
-	int i;
 
 	device_lock_assert(dax_region->dev);
-	for (i = 0; i < dev_dax->nr_range; i++) {
-		struct range *range = &dev_dax->ranges[i].range;
-
-		__release_region(&dax_region->res, range->start,
-				range_len(range));
+	dev_dbg(&dev_dax->dev, "delete range[%d]: %#llx:%#llx\n", i,
+		(unsigned long long)range->start,
+		(unsigned long long)range->end);
+
+	__release_region(&dax_region->res, range->start, range_len(range));
+	if (--dev_dax->nr_range == 0) {
+		kfree(dev_dax->ranges);
+		dev_dax->ranges = NULL;
 	}
-	dev_dax->nr_range = 0;
+}
+
+static void free_dev_dax_ranges(struct dev_dax *dev_dax)
+{
+	while (dev_dax->nr_range)
+		trim_dev_dax_range(dev_dax);
 }
 
 static void unregister_dev_dax(void *dev)
@@ -804,15 +813,10 @@ static int alloc_dev_dax_range(struct dev_dax *dev_dax, u64 start,
 		return 0;
 
 	rc = devm_register_dax_mapping(dev_dax, dev_dax->nr_range - 1);
-	if (rc) {
-		dev_dbg(dev, "delete range[%d]: %pa:%pa\n", dev_dax->nr_range - 1,
-				&alloc->start, &alloc->end);
-		dev_dax->nr_range--;
-		__release_region(res, alloc->start, resource_size(alloc));
-		return rc;
-	}
+	if (rc)
+		trim_dev_dax_range(dev_dax);
 
-	return 0;
+	return rc;
 }
 
 static int adjust_dev_dax_range(struct dev_dax *dev_dax, struct resource *res, resource_size_t size)
@@ -885,12 +889,7 @@ static int dev_dax_shrink(struct dev_dax *dev_dax, resource_size_t size)
 		if (shrink >= range_len(range)) {
 			devm_release_action(dax_region->dev,
 					unregister_dax_mapping, &mapping->dev);
-			__release_region(&dax_region->res, range->start,
-					range_len(range));
-			dev_dax->nr_range--;
-			dev_dbg(dev, "delete range[%d]: %#llx:%#llx\n", i,
-					(unsigned long long) range->start,
-					(unsigned long long) range->end);
+			trim_dev_dax_range(dev_dax);
 			to_shrink -= shrink;
 			if (!to_shrink)
 				break;
@@ -1267,7 +1266,6 @@ static void dev_dax_release(struct device *dev)
 	put_dax(dax_dev);
 	free_dev_dax_id(dev_dax);
 	dax_region_put(dax_region);
-	kfree(dev_dax->ranges);
 	kfree(dev_dax->pgmap);
 	kfree(dev_dax);
 }