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  */
  27 int cleancache_enabled;
  28 EXPORT_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  */
  34 static struct cleancache_ops cleancache_ops;
  35
  36 /* useful stats available in /sys/kernel/mm/cleancache */
  37 static unsigned long cleancache_succ_gets;
  38 static unsigned long cleancache_failed_gets;
  39 static unsigned long cleancache_puts;
  40 static unsigned long cleancache_flushes;
  41
  42 /*
  43  * register operations for cleancache, returning previous thus allowing
  44  * detection of multiple backends and possible nesting
  45  */
  46 struct 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 }
  54 EXPORT_SYMBOL(cleancache_register_ops);
  55
  56 /* Called by a cleancache-enabled filesystem at time of mount */
  57 void __cleancache_init_fs(struct super_block *sb)
  58 {
  59         sb->cleancache_poolid = (*cleancache_ops.init_fs)(PAGE_SIZE);
  60 }
  61 EXPORT_SYMBOL(__cleancache_init_fs);
  62
  63 /* Called by a cleancache-enabled clustered filesystem at time of mount */
  64 void __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 }
  69 EXPORT_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  */
  75 static 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  */
 105 int __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++;
 124 out:
 125         return ret;
 126 }
 127 EXPORT_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  */
 135 void __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 }
 148 EXPORT_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  */
 154 void __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 }
 168 EXPORT_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  */
 175 void __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 }
 183 EXPORT_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  */
 190 void __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 }
 198 EXPORT_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
 215 CLEANCACHE_SYSFS_RO(succ_gets);
 216 CLEANCACHE_SYSFS_RO(failed_gets);
 217 CLEANCACHE_SYSFS_RO(puts);
 218 CLEANCACHE_SYSFS_RO(flushes);
 219
 220 static 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
 228 static struct attribute_group cleancache_attr_group = {
 229         .attrs = cleancache_attrs,
 230         .name = "cleancache",
 231 };
 232
 233 #endif /* CONFIG_SYSFS */
 234
 235 static 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 }
 244 module_init(init_cleancache)