linux/mm/cleancache.c
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   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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