1/*
  2 * Cleancache frontend
  3 *
  4 * This code provides the generic "frontend" layer to call a matching
  5 * "backend" driver implementation of cleancache.  See
  6 * Documentation/vm/cleancache.txt for more information.
  7 *
  8 * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
  9 * Author: Dan Magenheimer
 10 *
 11 * This work is licensed under the terms of the GNU GPL, version 2.
 12 */
 13
 14#include <linux/module.h>
 15#include <linux/fs.h>
 16#include <linux/exportfs.h>
 17#include <linux/mm.h>
 18#include <linux/cleancache.h>
 19
 20/*
 21 * This global enablement flag may be read thousands of times per second
 22 * by cleancache_get/put/flush even on systems where cleancache_ops
 23 * is not claimed (e.g. cleancache is config'ed on but remains
 24 * disabled), so is preferred to the slower alternative: a function
 25 * call that checks a non-global.
 26 */
 27int cleancache_enabled;
 28EXPORT_SYMBOL(cleancache_enabled);
 29
 30/*
 31 * cleancache_ops is set by cleancache_ops_register to contain the pointers
 32 * to the cleancache "backend" implementation functions.
 33 */
 34static struct cleancache_ops cleancache_ops;
 35
 36/* useful stats available in /sys/kernel/mm/cleancache */
 37static unsigned long cleancache_succ_gets;
 38static unsigned long cleancache_failed_gets;
 39static unsigned long cleancache_puts;
 40static unsigned long cleancache_flushes;
 41
 42/*
 43 * register operations for cleancache, returning previous thus allowing
 44 * detection of multiple backends and possible nesting
 45 */
 46struct cleancache_ops cleancache_register_ops(struct cleancache_ops *ops)
 47{
 48	struct cleancache_ops old = cleancache_ops;
 49
 50	cleancache_ops = *ops;
 51	cleancache_enabled = 1;
 52	return old;
 53}
 54EXPORT_SYMBOL(cleancache_register_ops);
 55
 56/* Called by a cleancache-enabled filesystem at time of mount */
 57void __cleancache_init_fs(struct super_block *sb)
 58{
 59	sb->cleancache_poolid = (*cleancache_ops.init_fs)(PAGE_SIZE);
 60}
 61EXPORT_SYMBOL(__cleancache_init_fs);
 62
 63/* Called by a cleancache-enabled clustered filesystem at time of mount */
 64void __cleancache_init_shared_fs(char *uuid, struct super_block *sb)
 65{
 66	sb->cleancache_poolid =
 67		(*cleancache_ops.init_shared_fs)(uuid, PAGE_SIZE);
 68}
 69EXPORT_SYMBOL(__cleancache_init_shared_fs);
 70
 71/*
 72 * If the filesystem uses exportable filehandles, use the filehandle as
 73 * the key, else use the inode number.
 74 */
 75static int cleancache_get_key(struct inode *inode,
 76			      struct cleancache_filekey *key)
 77{
 78	int (*fhfn)(struct dentry *, __u32 *fh, int *, int);
 79	int len = 0, maxlen = CLEANCACHE_KEY_MAX;
 80	struct super_block *sb = inode->i_sb;
 81
 82	key->u.ino = inode->i_ino;
 83	if (sb->s_export_op != NULL) {
 84		fhfn = sb->s_export_op->encode_fh;
 85		if  (fhfn) {
 86			struct dentry d;
 87			d.d_inode = inode;
 88			len = (*fhfn)(&d, &key->u.fh[0], &maxlen, 0);
 89			if (len <= 0 || len == 255)
 90				return -1;
 91			if (maxlen > CLEANCACHE_KEY_MAX)
 92				return -1;
 93		}
 94	}
 95	return 0;
 96}
 97
 98/*
 99 * "Get" data from cleancache associated with the poolid/inode/index
100 * that were specified when the data was put to cleanache and, if
101 * successful, use it to fill the specified page with data and return 0.
102 * The pageframe is unchanged and returns -1 if the get fails.
103 * Page must be locked by caller.
104 */
105int __cleancache_get_page(struct page *page)
106{
107	int ret = -1;
108	int pool_id;
109	struct cleancache_filekey key = { .u.key = { 0 } };
110
111	VM_BUG_ON(!PageLocked(page));
112	pool_id = page->mapping->host->i_sb->cleancache_poolid;
113	if (pool_id < 0)
114		goto out;
115
116	if (cleancache_get_key(page->mapping->host, &key) < 0)
117		goto out;
118
119	ret = (*cleancache_ops.get_page)(pool_id, key, page->index, page);
120	if (ret == 0)
121		cleancache_succ_gets++;
122	else
123		cleancache_failed_gets++;
124out:
125	return ret;
126}
127EXPORT_SYMBOL(__cleancache_get_page);
128
129/*
130 * "Put" data from a page to cleancache and associate it with the
131 * (previously-obtained per-filesystem) poolid and the page's,
132 * inode and page index.  Page must be locked.  Note that a put_page
133 * always "succeeds", though a subsequent get_page may succeed or fail.
134 */
135void __cleancache_put_page(struct page *page)
136{
137	int pool_id;
138	struct cleancache_filekey key = { .u.key = { 0 } };
139
140	VM_BUG_ON(!PageLocked(page));
141	pool_id = page->mapping->host->i_sb->cleancache_poolid;
142	if (pool_id >= 0 &&
143	      cleancache_get_key(page->mapping->host, &key) >= 0) {
144		(*cleancache_ops.put_page)(pool_id, key, page->index, page);
145		cleancache_puts++;
146	}
147}
148EXPORT_SYMBOL(__cleancache_put_page);
149
150/*
151 * Flush any data from cleancache associated with the poolid and the
152 * page's inode and page index so that a subsequent "get" will fail.
153 */
154void __cleancache_flush_page(struct address_space *mapping, struct page *page)
155{
156	/* careful... page->mapping is NULL sometimes when this is called */
157	int pool_id = mapping->host->i_sb->cleancache_poolid;
158	struct cleancache_filekey key = { .u.key = { 0 } };
159
160	if (pool_id >= 0) {
161		VM_BUG_ON(!PageLocked(page));
162		if (cleancache_get_key(mapping->host, &key) >= 0) {
163			(*cleancache_ops.flush_page)(pool_id, key, page->index);
164			cleancache_flushes++;
165		}
166	}
167}
168EXPORT_SYMBOL(__cleancache_flush_page);
169
170/*
171 * Flush all data from cleancache associated with the poolid and the
172 * mappings's inode so that all subsequent gets to this poolid/inode
173 * will fail.
174 */
175void __cleancache_flush_inode(struct address_space *mapping)
176{
177	int pool_id = mapping->host->i_sb->cleancache_poolid;
178	struct cleancache_filekey key = { .u.key = { 0 } };
179
180	if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
181		(*cleancache_ops.flush_inode)(pool_id, key);
182}
183EXPORT_SYMBOL(__cleancache_flush_inode);
184
185/*
186 * Called by any cleancache-enabled filesystem at time of unmount;
187 * note that pool_id is surrendered and may be reutrned by a subsequent
188 * cleancache_init_fs or cleancache_init_shared_fs
189 */
190void __cleancache_flush_fs(struct super_block *sb)
191{
192	if (sb->cleancache_poolid >= 0) {
193		int old_poolid = sb->cleancache_poolid;
194		sb->cleancache_poolid = -1;
195		(*cleancache_ops.flush_fs)(old_poolid);
196	}
197}
198EXPORT_SYMBOL(__cleancache_flush_fs);
199
200#ifdef CONFIG_SYSFS
201
202/* see Documentation/ABI/xxx/sysfs-kernel-mm-cleancache */
203
204#define CLEANCACHE_SYSFS_RO(_name) \
205	static ssize_t cleancache_##_name##_show(struct kobject *kobj, \
206				struct kobj_attribute *attr, char *buf) \
207	{ \
208		return sprintf(buf, "%lu\n", cleancache_##_name); \
209	} \
210	static struct kobj_attribute cleancache_##_name##_attr = { \
211		.attr = { .name = __stringify(_name), .mode = 0444 }, \
212		.show = cleancache_##_name##_show, \
213	}
214
215CLEANCACHE_SYSFS_RO(succ_gets);
216CLEANCACHE_SYSFS_RO(failed_gets);
217CLEANCACHE_SYSFS_RO(puts);
218CLEANCACHE_SYSFS_RO(flushes);
219
220static struct attribute *cleancache_attrs[] = {
221	&cleancache_succ_gets_attr.attr,
222	&cleancache_failed_gets_attr.attr,
223	&cleancache_puts_attr.attr,
224	&cleancache_flushes_attr.attr,
225	NULL,
226};
227
228static struct attribute_group cleancache_attr_group = {
229	.attrs = cleancache_attrs,
230	.name = "cleancache",
231};
232
233#endif /* CONFIG_SYSFS */
234
235static int __init init_cleancache(void)
236{
237#ifdef CONFIG_SYSFS
238	int err;
239
240	err = sysfs_create_group(mm_kobj, &cleancache_attr_group);
241#endif /* CONFIG_SYSFS */
242	return 0;
243}
244module_init(init_cleancache)