[PATCH 4.9 03/60] libnvdimm, namespace: do not delete namespace-id 0

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Williams <dan.j.williams@xxxxxxxxx>

commit 9d032f4201d39e5cf43a8709a047e481f5723fdc upstream.

Given that the naming of pmem devices changes from the pmemX form to the
pmemX.Y form when namespace id is greater than 0, arrange for namespaces
with id-0 to be exempt from deletion. Otherwise a simple reconfiguration
of an existing namespace to a new mode results in a name change of the
resulting block device:

    # ndctl list --namespace=namespace1.0
    {
      "dev":"namespace1.0",
      "mode":"raw",
      "size":2147483648,
      "uuid":"3dadf3dc-89b9-4b24-b20e-abc8a4707ce3",
      "blockdev":"pmem1"
    }

    # ndctl create-namespace --reconfig=namespace1.0 --mode=memory --force
    {
      "dev":"namespace1.1",
      "mode":"memory",
      "size":2111832064,
      "uuid":"7b4a6341-7318-4219-a02c-fb57c0bbf613",
      "blockdev":"pmem1.1"
    }

This change does require tooling changes to explicitly look for
namespaceX.0 if the seed has already advanced to another namespace.

Fixes: 98a29c39dc68 ("libnvdimm, namespace: allow creation of multiple pmem-namespaces per region")
Reviewed-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/nvdimm/namespace_devs.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/drivers/nvdimm/namespace_devs.c
+++ b/drivers/nvdimm/namespace_devs.c
@@ -962,8 +962,8 @@ static ssize_t __size_store(struct devic
 	struct nvdimm_drvdata *ndd;
 	struct nd_label_id label_id;
 	u32 flags = 0, remainder;
+	int rc, i, id = -1;
 	u8 *uuid = NULL;
-	int rc, i;
 
 	if (dev->driver || ndns->claim)
 		return -EBUSY;
@@ -972,11 +972,13 @@ static ssize_t __size_store(struct devic
 		struct nd_namespace_pmem *nspm = to_nd_namespace_pmem(dev);
 
 		uuid = nspm->uuid;
+		id = nspm->id;
 	} else if (is_namespace_blk(dev)) {
 		struct nd_namespace_blk *nsblk = to_nd_namespace_blk(dev);
 
 		uuid = nsblk->uuid;
 		flags = NSLABEL_FLAG_LOCAL;
+		id = nsblk->id;
 	}
 
 	/*
@@ -1039,10 +1041,11 @@ static ssize_t __size_store(struct devic
 
 	/*
 	 * Try to delete the namespace if we deleted all of its
-	 * allocation, this is not the seed device for the region, and
-	 * it is not actively claimed by a btt instance.
+	 * allocation, this is not the seed or 0th device for the
+	 * region, and it is not actively claimed by a btt, pfn, or dax
+	 * instance.
 	 */
-	if (val == 0 && nd_region->ns_seed != dev && !ndns->claim)
+	if (val == 0 && id != 0 && nd_region->ns_seed != dev && !ndns->claim)
 		nd_device_unregister(dev, ND_ASYNC);
 
 	return rc;