Root/mm/cleancache.c

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)
245

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