Update Linux to v5.4.148

Sourced from [1]

[1] https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.4.148.tar.gz

Change-Id: Ib3d26c5ba9b022e2e03533005c4fed4d7c30b61b
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/fs/afs/dynroot.c b/fs/afs/dynroot.c
index 4150280..f07e53a 100644
--- a/fs/afs/dynroot.c
+++ b/fs/afs/dynroot.c
@@ -136,6 +136,9 @@
 
 	ASSERTCMP(d_inode(dentry), ==, NULL);
 
+	if (flags & LOOKUP_CREATE)
+		return ERR_PTR(-EOPNOTSUPP);
+
 	if (dentry->d_name.len >= AFSNAMEMAX) {
 		_leave(" = -ENAMETOOLONG");
 		return ERR_PTR(-ENAMETOOLONG);
@@ -286,15 +289,17 @@
 		net->dynroot_sb = NULL;
 	mutex_unlock(&net->proc_cells_lock);
 
-	inode_lock(root->d_inode);
+	if (root) {
+		inode_lock(root->d_inode);
 
-	/* Remove all the pins for dirs created for manually added cells */
-	list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
-		if (subdir->d_fsdata) {
-			subdir->d_fsdata = NULL;
-			dput(subdir);
+		/* Remove all the pins for dirs created for manually added cells */
+		list_for_each_entry_safe(subdir, tmp, &root->d_subdirs, d_child) {
+			if (subdir->d_fsdata) {
+				subdir->d_fsdata = NULL;
+				dput(subdir);
+			}
 		}
-	}
 
-	inode_unlock(root->d_inode);
+		inode_unlock(root->d_inode);
+	}
 }