v4.19.13 snapshot.
diff --git a/net/9p/util.c b/net/9p/util.c
new file mode 100644
index 0000000..55ad982
--- /dev/null
+++ b/net/9p/util.c
@@ -0,0 +1,140 @@
+/*
+ * net/9p/util.c
+ *
+ * This file contains some helper functions
+ *
+ * Copyright (C) 2007 by Latchesar Ionkov <lucho@ionkov.net>
+ * Copyright (C) 2004 by Eric Van Hensbergen <ericvh@gmail.com>
+ * Copyright (C) 2002 by Ron Minnich <rminnich@lanl.gov>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to:
+ * Free Software Foundation
+ * 51 Franklin Street, Fifth Floor
+ * Boston, MA 02111-1301 USA
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/sched.h>
+#include <linux/parser.h>
+#include <linux/idr.h>
+#include <linux/slab.h>
+#include <net/9p/9p.h>
+
+/**
+ * struct p9_idpool - per-connection accounting for tag idpool
+ * @lock: protects the pool
+ * @pool: idr to allocate tag id from
+ *
+ */
+
+struct p9_idpool {
+ spinlock_t lock;
+ struct idr pool;
+};
+
+/**
+ * p9_idpool_create - create a new per-connection id pool
+ *
+ */
+
+struct p9_idpool *p9_idpool_create(void)
+{
+ struct p9_idpool *p;
+
+ p = kmalloc(sizeof(struct p9_idpool), GFP_KERNEL);
+ if (!p)
+ return ERR_PTR(-ENOMEM);
+
+ spin_lock_init(&p->lock);
+ idr_init(&p->pool);
+
+ return p;
+}
+EXPORT_SYMBOL(p9_idpool_create);
+
+/**
+ * p9_idpool_destroy - create a new per-connection id pool
+ * @p: idpool to destroy
+ */
+
+void p9_idpool_destroy(struct p9_idpool *p)
+{
+ idr_destroy(&p->pool);
+ kfree(p);
+}
+EXPORT_SYMBOL(p9_idpool_destroy);
+
+/**
+ * p9_idpool_get - allocate numeric id from pool
+ * @p: pool to allocate from
+ *
+ * Bugs: This seems to be an awful generic function, should it be in idr.c with
+ * the lock included in struct idr?
+ */
+
+int p9_idpool_get(struct p9_idpool *p)
+{
+ int i;
+ unsigned long flags;
+
+ idr_preload(GFP_NOFS);
+ spin_lock_irqsave(&p->lock, flags);
+
+ /* no need to store exactly p, we just need something non-null */
+ i = idr_alloc(&p->pool, p, 0, 0, GFP_NOWAIT);
+
+ spin_unlock_irqrestore(&p->lock, flags);
+ idr_preload_end();
+ if (i < 0)
+ return -1;
+
+ p9_debug(P9_DEBUG_MUX, " id %d pool %p\n", i, p);
+ return i;
+}
+EXPORT_SYMBOL(p9_idpool_get);
+
+/**
+ * p9_idpool_put - release numeric id from pool
+ * @id: numeric id which is being released
+ * @p: pool to release id into
+ *
+ * Bugs: This seems to be an awful generic function, should it be in idr.c with
+ * the lock included in struct idr?
+ */
+
+void p9_idpool_put(int id, struct p9_idpool *p)
+{
+ unsigned long flags;
+
+ p9_debug(P9_DEBUG_MUX, " id %d pool %p\n", id, p);
+
+ spin_lock_irqsave(&p->lock, flags);
+ idr_remove(&p->pool, id);
+ spin_unlock_irqrestore(&p->lock, flags);
+}
+EXPORT_SYMBOL(p9_idpool_put);
+
+/**
+ * p9_idpool_check - check if the specified id is available
+ * @id: id to check
+ * @p: pool to check
+ */
+
+int p9_idpool_check(int id, struct p9_idpool *p)
+{
+ return idr_find(&p->pool, id) != NULL;
+}
+EXPORT_SYMBOL(p9_idpool_check);