FAILED: patch "[PATCH] libnvdimm/namespace: Fix reaping of invalidated" failed to apply to 4.9-stable tree

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2dd2a1740ee19cd2636d247276cf27bfa434b0e2 Mon Sep 17 00:00:00 2001
From: Dan Williams <[email protected]>
Date: Fri, 20 Nov 2020 08:50:07 -0800
Subject: [PATCH] libnvdimm/namespace: Fix reaping of invalidated
block-window-namespace labels

A recent change to ndctl to attempt to reconfigure namespaces in place uncovered a label accounting problem in block-window-type namespaces. The ndctl "create.sh" test is able to trigger this signature:

 WARNING: CPU: 34 PID: 9167 at drivers/nvdimm/label.c:1100 __blk_label_update+0x9a3/0xbc0 [libnvdimm]
 [..]
 RIP: 0010:__blk_label_update+0x9a3/0xbc0 [libnvdimm]
 [..]
 Call Trace:
  uuid_store+0x21b/0x2f0 [libnvdimm]
  kernfs_fop_write+0xcf/0x1c0
  vfs_write+0xcc/0x380
  ksys_write+0x68/0xe0

When allocated capacity for a namespace is renamed (new UUID) the labels with the old UUID need to be deleted. The ndctl behavior to always destroy namespaces on reconfiguration hid this problem.

The immediate impact of this bug is limited since block-window-type namespaces only seem to exist in the specification and not in any shipping products. However, the label handling code is being reused for other technologies like CXL region labels, so there is a benefit to making sure both vertical labels sets (block-window) and horizontal label sets (pmem) have a functional reference implementation in libnvdimm.

index 47a4828b8b31..6f2be7a34598 100644
@@ -980,6 +980,15 @@ static int __blk_label_update(struct nd_region *nd_region,
 		}
 	}
 
+	/* release slots associated with any invalidated UUIDs */
+	mutex_lock(&nd_mapping->lock);
+	list_for_each_entry_safe(label_ent, e, &nd_mapping->labels, list)
+		if (test_and_clear_bit(ND_LABEL_REAP, &label_ent->flags)) {
+			reap_victim(nd_mapping, label_ent);
+			list_move(&label_ent->list, &list);
+		}
+	mutex_unlock(&nd_mapping->lock);
+
 	/*
 	 * Find the resource associated with the first label in the set
 	 * per the v1.2 namespace specification.