FS-Cache: Provide a slab for cookie allocation

Provide a slab from which can be allocated the FS-Cache cookies that will be
presented to the netfs.

Also provide a slab constructor and a function to recursively discard a cookie
and its ancestor chain.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Steve Dickson <steved@redhat.com>
Acked-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Daire Byrne <Daire.Byrne@framestore.com>

fs/fscache/Makefile

@@ -4,6 +4,7 @@
 
 fscache-y := \
 	cache.o \
+	cookie.o \
 	fsdef.o \
 	main.o
 

fs/fscache/cookie.c

@@ -0,0 +1,56 @@
+/* netfs cookie management
+ *
+ * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#define FSCACHE_DEBUG_LEVEL COOKIE
+#include <linux/module.h>
+#include <linux/slab.h>
+#include "internal.h"
+
+struct kmem_cache *fscache_cookie_jar;
+
+/*
+ * initialise an cookie jar slab element prior to any use
+ */
+void fscache_cookie_init_once(void *_cookie)
+{
+	struct fscache_cookie *cookie = _cookie;
+
+	memset(cookie, 0, sizeof(*cookie));
+	spin_lock_init(&cookie->lock);
+	INIT_HLIST_HEAD(&cookie->backing_objects);
+}
+
+/*
+ * destroy a cookie
+ */
+void __fscache_cookie_put(struct fscache_cookie *cookie)
+{
+	struct fscache_cookie *parent;
+
+	_enter("%p", cookie);
+
+	for (;;) {
+		_debug("FREE COOKIE %p", cookie);
+		parent = cookie->parent;
+		BUG_ON(!hlist_empty(&cookie->backing_objects));
+		kmem_cache_free(fscache_cookie_jar, cookie);
+
+		if (!parent)
+			break;
+
+		cookie = parent;
+		BUG_ON(atomic_read(&cookie->usage) <= 0);
+		if (!atomic_dec_and_test(&cookie->usage))
+			break;
+	}
+
+	_leave("");
+}

fs/fscache/internal.h

@@ -36,6 +36,14 @@ extern struct rw_semaphore fscache_addremove_sem;
 extern struct fscache_cache *fscache_select_cache_for_object(
 	struct fscache_cookie *);
 
+/*
+ * fsc-cookie.c
+ */
+extern struct kmem_cache *fscache_cookie_jar;
+
+extern void fscache_cookie_init_once(void *);
+extern void __fscache_cookie_put(struct fscache_cookie *);
+
 /*
  * fsc-fsdef.c
  */

fs/fscache/main.c

@@ -56,6 +56,18 @@ static int __init fscache_init(void)
 	if (ret < 0)
 		goto error_proc;
 
+	fscache_cookie_jar = kmem_cache_create("fscache_cookie_jar",
+					       sizeof(struct fscache_cookie),
+					       0,
+					       0,
+					       fscache_cookie_init_once);
+	if (!fscache_cookie_jar) {
+		printk(KERN_NOTICE
+		       "FS-Cache: Failed to allocate a cookie jar\n");
+		ret = -ENOMEM;
+		goto error_cookie_jar;
+	}
+
 	fscache_root = kobject_create_and_add("fscache", kernel_kobj);
 	if (!fscache_root)
 		goto error_kobj;
@@ -64,6 +76,8 @@ static int __init fscache_init(void)
 	return 0;
 
 error_kobj:
+	kmem_cache_destroy(fscache_cookie_jar);
+error_cookie_jar:
 	fscache_proc_cleanup();
 error_proc:
 	slow_work_unregister_user();
@@ -81,6 +95,7 @@ static void __exit fscache_exit(void)
 	_enter("");
 
 	kobject_put(fscache_root);
+	kmem_cache_destroy(fscache_cookie_jar);
 	fscache_proc_cleanup();
 	slow_work_unregister_user();
 	printk(KERN_NOTICE "FS-Cache: Unloaded\n");