mm/cleancache.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Cleancache frontend
   4  *
   5  * This code provides the generic "frontend" layer to call a matching
   6  * "backend" driver implementation of cleancache.  See
   7  * Documentation/vm/cleancache.rst for more information.
   8  *
   9  * Copyright (C) 2009-2010 Oracle Corp. All rights reserved.
  10  * Author: Dan Magenheimer
  11  */
  12
  13 #include <linux/module.h>
  14 #include <linux/fs.h>
  15 #include <linux/exportfs.h>
  16 #include <linux/mm.h>
  17 #include <linux/debugfs.h>
  18 #include <linux/cleancache.h>
  19
  20 /*
  21  * cleancache_ops is set by cleancache_register_ops to contain the pointers
  22  * to the cleancache "backend" implementation functions.
  23  */
  24 static const struct cleancache_ops *cleancache_ops __read_mostly;
  25
  26 /*
  27  * Counters available via /sys/kernel/debug/cleancache (if debugfs is
  28  * properly configured.  These are for information only so are not protected
  29  * against increment races.
  30  */
  31 static u64 cleancache_succ_gets;
  32 static u64 cleancache_failed_gets;
  33 static u64 cleancache_puts;
  34 static u64 cleancache_invalidates;
  35
  36 static void cleancache_register_ops_sb(struct super_block *sb, void *unused)
  37 {
  38         switch (sb->cleancache_poolid) {
  39         case CLEANCACHE_NO_BACKEND:
  40                 __cleancache_init_fs(sb);
  41                 break;
  42         case CLEANCACHE_NO_BACKEND_SHARED:
  43                 __cleancache_init_shared_fs(sb);
  44                 break;
  45         }
  46 }
  47
  48 /*
  49  * Register operations for cleancache. Returns 0 on success.
  50  */
  51 int cleancache_register_ops(const struct cleancache_ops *ops)
  52 {
  53         if (cmpxchg(&cleancache_ops, NULL, ops))
  54                 return -EBUSY;
  55
  56         /*
  57          * A cleancache backend can be built as a module and hence loaded after
  58          * a cleancache enabled filesystem has called cleancache_init_fs. To
  59          * handle such a scenario, here we call ->init_fs or ->init_shared_fs
  60          * for each active super block. To differentiate between local and
  61          * shared filesystems, we temporarily initialize sb->cleancache_poolid
  62          * to CLEANCACHE_NO_BACKEND or CLEANCACHE_NO_BACKEND_SHARED
  63          * respectively in case there is no backend registered at the time
  64          * cleancache_init_fs or cleancache_init_shared_fs is called.
  65          *
  66          * Since filesystems can be mounted concurrently with cleancache
  67          * backend registration, we have to be careful to guarantee that all
  68          * cleancache enabled filesystems that has been mounted by the time
  69          * cleancache_register_ops is called has got and all mounted later will
  70          * get cleancache_poolid. This is assured by the following statements
  71          * tied together:
  72          *
  73          * a) iterate_supers skips only those super blocks that has started
  74          *    ->kill_sb
  75          *
  76          * b) if iterate_supers encounters a super block that has not finished
  77          *    ->mount yet, it waits until it is finished
  78          *
  79          * c) cleancache_init_fs is called from ->mount and
  80          *    cleancache_invalidate_fs is called from ->kill_sb
  81          *
  82          * d) we call iterate_supers after cleancache_ops has been set
  83          *
  84          * From a) it follows that if iterate_supers skips a super block, then
  85          * either the super block is already dead, in which case we do not need
  86          * to bother initializing cleancache for it, or it was mounted after we
  87          * initiated iterate_supers. In the latter case, it must have seen
  88          * cleancache_ops set according to d) and initialized cleancache from
  89          * ->mount by itself according to c). This proves that we call
  90          * ->init_fs at least once for each active super block.
  91          *
  92          * From b) and c) it follows that if iterate_supers encounters a super
  93          * block that has already started ->init_fs, it will wait until ->mount
  94          * and hence ->init_fs has finished, then check cleancache_poolid, see
  95          * that it has already been set and therefore do nothing. This proves
  96          * that we call ->init_fs no more than once for each super block.
  97          *
  98          * Combined together, the last two paragraphs prove the function
  99          * correctness.
 100          *
 101          * Note that various cleancache callbacks may proceed before this
 102          * function is called or even concurrently with it, but since
 103          * CLEANCACHE_NO_BACKEND is negative, they will all result in a noop
 104          * until the corresponding ->init_fs has been actually called and
 105          * cleancache_ops has been set.
 106          */
 107         iterate_supers(cleancache_register_ops_sb, NULL);
 108         return 0;
 109 }
 110 EXPORT_SYMBOL(cleancache_register_ops);
 111
 112 /* Called by a cleancache-enabled filesystem at time of mount */
 113 void __cleancache_init_fs(struct super_block *sb)
 114 {
 115         int pool_id = CLEANCACHE_NO_BACKEND;
 116
 117         if (cleancache_ops) {
 118                 pool_id = cleancache_ops->init_fs(PAGE_SIZE);
 119                 if (pool_id < 0)
 120                         pool_id = CLEANCACHE_NO_POOL;
 121         }
 122         sb->cleancache_poolid = pool_id;
 123 }
 124 EXPORT_SYMBOL(__cleancache_init_fs);
 125
 126 /* Called by a cleancache-enabled clustered filesystem at time of mount */
 127 void __cleancache_init_shared_fs(struct super_block *sb)
 128 {
 129         int pool_id = CLEANCACHE_NO_BACKEND_SHARED;
 130
 131         if (cleancache_ops) {
 132                 pool_id = cleancache_ops->init_shared_fs(&sb->s_uuid, PAGE_SIZE);
 133                 if (pool_id < 0)
 134                         pool_id = CLEANCACHE_NO_POOL;
 135         }
 136         sb->cleancache_poolid = pool_id;
 137 }
 138 EXPORT_SYMBOL(__cleancache_init_shared_fs);
 139
 140 /*
 141  * If the filesystem uses exportable filehandles, use the filehandle as
 142  * the key, else use the inode number.
 143  */
 144 static int cleancache_get_key(struct inode *inode,
 145                               struct cleancache_filekey *key)
 146 {
 147         int (*fhfn)(struct inode *, __u32 *fh, int *, struct inode *);
 148         int len = 0, maxlen = CLEANCACHE_KEY_MAX;
 149         struct super_block *sb = inode->i_sb;
 150
 151         key->u.ino = inode->i_ino;
 152         if (sb->s_export_op != NULL) {
 153                 fhfn = sb->s_export_op->encode_fh;
 154                 if  (fhfn) {
 155                         len = (*fhfn)(inode, &key->u.fh[0], &maxlen, NULL);
 156                         if (len <= FILEID_ROOT || len == FILEID_INVALID)
 157                                 return -1;
 158                         if (maxlen > CLEANCACHE_KEY_MAX)
 159                                 return -1;
 160                 }
 161         }
 162         return 0;
 163 }
 164
 165 /*
 166  * "Get" data from cleancache associated with the poolid/inode/index
 167  * that were specified when the data was put to cleanache and, if
 168  * successful, use it to fill the specified page with data and return 0.
 169  * The pageframe is unchanged and returns -1 if the get fails.
 170  * Page must be locked by caller.
 171  *
 172  * The function has two checks before any action is taken - whether
 173  * a backend is registered and whether the sb->cleancache_poolid
 174  * is correct.
 175  */
 176 int __cleancache_get_page(struct page *page)
 177 {
 178         int ret = -1;
 179         int pool_id;
 180         struct cleancache_filekey key = { .u.key = { 0 } };
 181
 182         if (!cleancache_ops) {
 183                 cleancache_failed_gets++;
 184                 goto out;
 185         }
 186
 187         VM_BUG_ON_PAGE(!PageLocked(page), page);
 188         pool_id = page->mapping->host->i_sb->cleancache_poolid;
 189         if (pool_id < 0)
 190                 goto out;
 191
 192         if (cleancache_get_key(page->mapping->host, &key) < 0)
 193                 goto out;
 194
 195         ret = cleancache_ops->get_page(pool_id, key, page->index, page);
 196         if (ret == 0)
 197                 cleancache_succ_gets++;
 198         else
 199                 cleancache_failed_gets++;
 200 out:
 201         return ret;
 202 }
 203 EXPORT_SYMBOL(__cleancache_get_page);
 204
 205 /*
 206  * "Put" data from a page to cleancache and associate it with the
 207  * (previously-obtained per-filesystem) poolid and the page's,
 208  * inode and page index.  Page must be locked.  Note that a put_page
 209  * always "succeeds", though a subsequent get_page may succeed or fail.
 210  *
 211  * The function has two checks before any action is taken - whether
 212  * a backend is registered and whether the sb->cleancache_poolid
 213  * is correct.
 214  */
 215 void __cleancache_put_page(struct page *page)
 216 {
 217         int pool_id;
 218         struct cleancache_filekey key = { .u.key = { 0 } };
 219
 220         if (!cleancache_ops) {
 221                 cleancache_puts++;
 222                 return;
 223         }
 224
 225         VM_BUG_ON_PAGE(!PageLocked(page), page);
 226         pool_id = page->mapping->host->i_sb->cleancache_poolid;
 227         if (pool_id >= 0 &&
 228                 cleancache_get_key(page->mapping->host, &key) >= 0) {
 229                 cleancache_ops->put_page(pool_id, key, page->index, page);
 230                 cleancache_puts++;
 231         }
 232 }
 233 EXPORT_SYMBOL(__cleancache_put_page);
 234
 235 /*
 236  * Invalidate any data from cleancache associated with the poolid and the
 237  * page's inode and page index so that a subsequent "get" will fail.
 238  *
 239  * The function has two checks before any action is taken - whether
 240  * a backend is registered and whether the sb->cleancache_poolid
 241  * is correct.
 242  */
 243 void __cleancache_invalidate_page(struct address_space *mapping,
 244                                         struct page *page)
 245 {
 246         /* careful... page->mapping is NULL sometimes when this is called */
 247         int pool_id = mapping->host->i_sb->cleancache_poolid;
 248         struct cleancache_filekey key = { .u.key = { 0 } };
 249
 250         if (!cleancache_ops)
 251                 return;
 252
 253         if (pool_id >= 0) {
 254                 VM_BUG_ON_PAGE(!PageLocked(page), page);
 255                 if (cleancache_get_key(mapping->host, &key) >= 0) {
 256                         cleancache_ops->invalidate_page(pool_id,
 257                                         key, page->index);
 258                         cleancache_invalidates++;
 259                 }
 260         }
 261 }
 262 EXPORT_SYMBOL(__cleancache_invalidate_page);
 263
 264 /*
 265  * Invalidate all data from cleancache associated with the poolid and the
 266  * mappings's inode so that all subsequent gets to this poolid/inode
 267  * will fail.
 268  *
 269  * The function has two checks before any action is taken - whether
 270  * a backend is registered and whether the sb->cleancache_poolid
 271  * is correct.
 272  */
 273 void __cleancache_invalidate_inode(struct address_space *mapping)
 274 {
 275         int pool_id = mapping->host->i_sb->cleancache_poolid;
 276         struct cleancache_filekey key = { .u.key = { 0 } };
 277
 278         if (!cleancache_ops)
 279                 return;
 280
 281         if (pool_id >= 0 && cleancache_get_key(mapping->host, &key) >= 0)
 282                 cleancache_ops->invalidate_inode(pool_id, key);
 283 }
 284 EXPORT_SYMBOL(__cleancache_invalidate_inode);
 285
 286 /*
 287  * Called by any cleancache-enabled filesystem at time of unmount;
 288  * note that pool_id is surrendered and may be returned by a subsequent
 289  * cleancache_init_fs or cleancache_init_shared_fs.
 290  */
 291 void __cleancache_invalidate_fs(struct super_block *sb)
 292 {
 293         int pool_id;
 294
 295         pool_id = sb->cleancache_poolid;
 296         sb->cleancache_poolid = CLEANCACHE_NO_POOL;
 297
 298         if (cleancache_ops && pool_id >= 0)
 299                 cleancache_ops->invalidate_fs(pool_id);
 300 }
 301 EXPORT_SYMBOL(__cleancache_invalidate_fs);
 302
 303 static int __init init_cleancache(void)
 304 {
 305 #ifdef CONFIG_DEBUG_FS
 306         struct dentry *root = debugfs_create_dir("cleancache", NULL);
 307
 308         debugfs_create_u64("succ_gets", 0444, root, &cleancache_succ_gets);
 309         debugfs_create_u64("failed_gets", 0444, root, &cleancache_failed_gets);
 310         debugfs_create_u64("puts", 0444, root, &cleancache_puts);
 311         debugfs_create_u64("invalidates", 0444, root, &cleancache_invalidates);
 312 #endif
 313         return 0;
 314 }
 315 module_init(init_cleancache)