fs/cachefiles/bind.c

   1 /* Bind and unbind a cache from the filesystem backing it
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/sched.h>
  15 #include <linux/completion.h>
  16 #include <linux/slab.h>
  17 #include <linux/fs.h>
  18 #include <linux/file.h>
  19 #include <linux/namei.h>
  20 #include <linux/mount.h>
  21 #include <linux/statfs.h>
  22 #include <linux/ctype.h>
  23 #include "internal.h"
  24
  25 static int cachefiles_daemon_add_cache(struct cachefiles_cache *caches);
  26
  27 /*
  28  * bind a directory as a cache
  29  */
  30 int cachefiles_daemon_bind(struct cachefiles_cache *cache, char *args)
  31 {
  32         _enter("{%u,%u,%u,%u,%u,%u},%s",
  33                cache->frun_percent,
  34                cache->fcull_percent,
  35                cache->fstop_percent,
  36                cache->brun_percent,
  37                cache->bcull_percent,
  38                cache->bstop_percent,
  39                args);
  40
  41         /* start by checking things over */
  42         ASSERT(cache->fstop_percent >= 0 &&
  43                cache->fstop_percent < cache->fcull_percent &&
  44                cache->fcull_percent < cache->frun_percent &&
  45                cache->frun_percent  < 100);
  46
  47         ASSERT(cache->bstop_percent >= 0 &&
  48                cache->bstop_percent < cache->bcull_percent &&
  49                cache->bcull_percent < cache->brun_percent &&
  50                cache->brun_percent  < 100);
  51
  52         if (*args) {
  53                 kerror("'bind' command doesn't take an argument");
  54                 return -EINVAL;
  55         }
  56
  57         if (!cache->rootdirname) {
  58                 kerror("No cache directory specified");
  59                 return -EINVAL;
  60         }
  61
  62         /* don't permit already bound caches to be re-bound */
  63         if (test_bit(CACHEFILES_READY, &cache->flags)) {
  64                 kerror("Cache already bound");
  65                 return -EBUSY;
  66         }
  67
  68         /* make sure we have copies of the tag and dirname strings */
  69         if (!cache->tag) {
  70                 /* the tag string is released by the fops->release()
  71                  * function, so we don't release it on error here */
  72                 cache->tag = kstrdup("CacheFiles", GFP_KERNEL);
  73                 if (!cache->tag)
  74                         return -ENOMEM;
  75         }
  76
  77         /* add the cache */
  78         return cachefiles_daemon_add_cache(cache);
  79 }
  80
  81 /*
  82  * add a cache
  83  */
  84 static int cachefiles_daemon_add_cache(struct cachefiles_cache *cache)
  85 {
  86         struct cachefiles_object *fsdef;
  87         struct nameidata nd;
  88         struct kstatfs stats;
  89         struct dentry *graveyard, *cachedir, *root;
  90         const struct cred *saved_cred;
  91         int ret;
  92
  93         _enter("");
  94
  95         /* we want to work under the module's security ID */
  96         ret = cachefiles_get_security_ID(cache);
  97         if (ret < 0)
  98                 return ret;
  99
 100         cachefiles_begin_secure(cache, &saved_cred);
 101
 102         /* allocate the root index object */
 103         ret = -ENOMEM;
 104
 105         fsdef = kmem_cache_alloc(cachefiles_object_jar, GFP_KERNEL);
 106         if (!fsdef)
 107                 goto error_root_object;
 108
 109         ASSERTCMP(fsdef->backer, ==, NULL);
 110
 111         atomic_set(&fsdef->usage, 1);
 112         fsdef->type = FSCACHE_COOKIE_TYPE_INDEX;
 113
 114         _debug("- fsdef %p", fsdef);
 115
 116         /* look up the directory at the root of the cache */
 117         memset(&nd, 0, sizeof(nd));
 118
 119         ret = path_lookup(cache->rootdirname, LOOKUP_DIRECTORY, &nd);
 120         if (ret < 0)
 121                 goto error_open_root;
 122
 123         cache->mnt = mntget(nd.path.mnt);
 124         root = dget(nd.path.dentry);
 125         path_put(&nd.path);
 126
 127         /* check parameters */
 128         ret = -EOPNOTSUPP;
 129         if (!root->d_inode ||
 130             !root->d_inode->i_op ||
 131             !root->d_inode->i_op->lookup ||
 132             !root->d_inode->i_op->mkdir ||
 133             !root->d_inode->i_op->setxattr ||
 134             !root->d_inode->i_op->getxattr ||
 135             !root->d_sb ||
 136             !root->d_sb->s_op ||
 137             !root->d_sb->s_op->statfs ||
 138             !root->d_sb->s_op->sync_fs)
 139                 goto error_unsupported;
 140
 141         ret = -EROFS;
 142         if (root->d_sb->s_flags & MS_RDONLY)
 143                 goto error_unsupported;
 144
 145         /* determine the security of the on-disk cache as this governs
 146          * security ID of files we create */
 147         ret = cachefiles_determine_cache_security(cache, root, &saved_cred);
 148         if (ret < 0)
 149                 goto error_unsupported;
 150
 151         /* get the cache size and blocksize */
 152         ret = vfs_statfs(root, &stats);
 153         if (ret < 0)
 154                 goto error_unsupported;
 155
 156         ret = -ERANGE;
 157         if (stats.f_bsize <= 0)
 158                 goto error_unsupported;
 159
 160         ret = -EOPNOTSUPP;
 161         if (stats.f_bsize > PAGE_SIZE)
 162                 goto error_unsupported;
 163
 164         cache->bsize = stats.f_bsize;
 165         cache->bshift = 0;
 166         if (stats.f_bsize < PAGE_SIZE)
 167                 cache->bshift = PAGE_SHIFT - ilog2(stats.f_bsize);
 168
 169         _debug("blksize %u (shift %u)",
 170                cache->bsize, cache->bshift);
 171
 172         _debug("size %llu, avail %llu",
 173                (unsigned long long) stats.f_blocks,
 174                (unsigned long long) stats.f_bavail);
 175
 176         /* set up caching limits */
 177         do_div(stats.f_files, 100);
 178         cache->fstop = stats.f_files * cache->fstop_percent;
 179         cache->fcull = stats.f_files * cache->fcull_percent;
 180         cache->frun  = stats.f_files * cache->frun_percent;
 181
 182         _debug("limits {%llu,%llu,%llu} files",
 183                (unsigned long long) cache->frun,
 184                (unsigned long long) cache->fcull,
 185                (unsigned long long) cache->fstop);
 186
 187         stats.f_blocks >>= cache->bshift;
 188         do_div(stats.f_blocks, 100);
 189         cache->bstop = stats.f_blocks * cache->bstop_percent;
 190         cache->bcull = stats.f_blocks * cache->bcull_percent;
 191         cache->brun  = stats.f_blocks * cache->brun_percent;
 192
 193         _debug("limits {%llu,%llu,%llu} blocks",
 194                (unsigned long long) cache->brun,
 195                (unsigned long long) cache->bcull,
 196                (unsigned long long) cache->bstop);
 197
 198         /* get the cache directory and check its type */
 199         cachedir = cachefiles_get_directory(cache, root, "cache");
 200         if (IS_ERR(cachedir)) {
 201                 ret = PTR_ERR(cachedir);
 202                 goto error_unsupported;
 203         }
 204
 205         fsdef->dentry = cachedir;
 206         fsdef->fscache.cookie = NULL;
 207
 208         ret = cachefiles_check_object_type(fsdef);
 209         if (ret < 0)
 210                 goto error_unsupported;
 211
 212         /* get the graveyard directory */
 213         graveyard = cachefiles_get_directory(cache, root, "graveyard");
 214         if (IS_ERR(graveyard)) {
 215                 ret = PTR_ERR(graveyard);
 216                 goto error_unsupported;
 217         }
 218
 219         cache->graveyard = graveyard;
 220
 221         /* publish the cache */
 222         fscache_init_cache(&cache->cache,
 223                            &cachefiles_cache_ops,
 224                            "%s",
 225                            fsdef->dentry->d_sb->s_id);
 226
 227         fscache_object_init(&fsdef->fscache, NULL, &cache->cache);
 228
 229         ret = fscache_add_cache(&cache->cache, &fsdef->fscache, cache->tag);
 230         if (ret < 0)
 231                 goto error_add_cache;
 232
 233         /* done */
 234         set_bit(CACHEFILES_READY, &cache->flags);
 235         dput(root);
 236
 237         printk(KERN_INFO "CacheFiles:"
 238                " File cache on %s registered\n",
 239                cache->cache.identifier);
 240
 241         /* check how much space the cache has */
 242         cachefiles_has_space(cache, 0, 0);
 243         cachefiles_end_secure(cache, saved_cred);
 244         return 0;
 245
 246 error_add_cache:
 247         dput(cache->graveyard);
 248         cache->graveyard = NULL;
 249 error_unsupported:
 250         mntput(cache->mnt);
 251         cache->mnt = NULL;
 252         dput(fsdef->dentry);
 253         fsdef->dentry = NULL;
 254         dput(root);
 255 error_open_root:
 256         kmem_cache_free(cachefiles_object_jar, fsdef);
 257 error_root_object:
 258         cachefiles_end_secure(cache, saved_cred);
 259         kerror("Failed to register: %d", ret);
 260         return ret;
 261 }
 262
 263 /*
 264  * unbind a cache on fd release
 265  */
 266 void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
 267 {
 268         _enter("");
 269
 270         if (test_bit(CACHEFILES_READY, &cache->flags)) {
 271                 printk(KERN_INFO "CacheFiles:"
 272                        " File cache on %s unregistering\n",
 273                        cache->cache.identifier);
 274
 275                 fscache_withdraw_cache(&cache->cache);
 276         }
 277
 278         dput(cache->graveyard);
 279         mntput(cache->mnt);
 280
 281         kfree(cache->rootdirname);
 282         kfree(cache->secctx);
 283         kfree(cache->tag);
 284
 285         _leave("");
 286 }