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 path path;
  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         ret = kern_path(cache->rootdirname, LOOKUP_DIRECTORY, &path);
 118         if (ret < 0)
 119                 goto error_open_root;
 120
 121         cache->mnt = path.mnt;
 122         root = path.dentry;
 123
 124         /* check parameters */
 125         ret = -EOPNOTSUPP;
 126         if (!root->d_inode ||
 127             !root->d_inode->i_op ||
 128             !root->d_inode->i_op->lookup ||
 129             !root->d_inode->i_op->mkdir ||
 130             !root->d_inode->i_op->setxattr ||
 131             !root->d_inode->i_op->getxattr ||
 132             !root->d_sb ||
 133             !root->d_sb->s_op ||
 134             !root->d_sb->s_op->statfs ||
 135             !root->d_sb->s_op->sync_fs)
 136                 goto error_unsupported;
 137
 138         ret = -EROFS;
 139         if (root->d_sb->s_flags & MS_RDONLY)
 140                 goto error_unsupported;
 141
 142         /* determine the security of the on-disk cache as this governs
 143          * security ID of files we create */
 144         ret = cachefiles_determine_cache_security(cache, root, &saved_cred);
 145         if (ret < 0)
 146                 goto error_unsupported;
 147
 148         /* get the cache size and blocksize */
 149         ret = vfs_statfs(root, &stats);
 150         if (ret < 0)
 151                 goto error_unsupported;
 152
 153         ret = -ERANGE;
 154         if (stats.f_bsize <= 0)
 155                 goto error_unsupported;
 156
 157         ret = -EOPNOTSUPP;
 158         if (stats.f_bsize > PAGE_SIZE)
 159                 goto error_unsupported;
 160
 161         cache->bsize = stats.f_bsize;
 162         cache->bshift = 0;
 163         if (stats.f_bsize < PAGE_SIZE)
 164                 cache->bshift = PAGE_SHIFT - ilog2(stats.f_bsize);
 165
 166         _debug("blksize %u (shift %u)",
 167                cache->bsize, cache->bshift);
 168
 169         _debug("size %llu, avail %llu",
 170                (unsigned long long) stats.f_blocks,
 171                (unsigned long long) stats.f_bavail);
 172
 173         /* set up caching limits */
 174         do_div(stats.f_files, 100);
 175         cache->fstop = stats.f_files * cache->fstop_percent;
 176         cache->fcull = stats.f_files * cache->fcull_percent;
 177         cache->frun  = stats.f_files * cache->frun_percent;
 178
 179         _debug("limits {%llu,%llu,%llu} files",
 180                (unsigned long long) cache->frun,
 181                (unsigned long long) cache->fcull,
 182                (unsigned long long) cache->fstop);
 183
 184         stats.f_blocks >>= cache->bshift;
 185         do_div(stats.f_blocks, 100);
 186         cache->bstop = stats.f_blocks * cache->bstop_percent;
 187         cache->bcull = stats.f_blocks * cache->bcull_percent;
 188         cache->brun  = stats.f_blocks * cache->brun_percent;
 189
 190         _debug("limits {%llu,%llu,%llu} blocks",
 191                (unsigned long long) cache->brun,
 192                (unsigned long long) cache->bcull,
 193                (unsigned long long) cache->bstop);
 194
 195         /* get the cache directory and check its type */
 196         cachedir = cachefiles_get_directory(cache, root, "cache");
 197         if (IS_ERR(cachedir)) {
 198                 ret = PTR_ERR(cachedir);
 199                 goto error_unsupported;
 200         }
 201
 202         fsdef->dentry = cachedir;
 203         fsdef->fscache.cookie = NULL;
 204
 205         ret = cachefiles_check_object_type(fsdef);
 206         if (ret < 0)
 207                 goto error_unsupported;
 208
 209         /* get the graveyard directory */
 210         graveyard = cachefiles_get_directory(cache, root, "graveyard");
 211         if (IS_ERR(graveyard)) {
 212                 ret = PTR_ERR(graveyard);
 213                 goto error_unsupported;
 214         }
 215
 216         cache->graveyard = graveyard;
 217
 218         /* publish the cache */
 219         fscache_init_cache(&cache->cache,
 220                            &cachefiles_cache_ops,
 221                            "%s",
 222                            fsdef->dentry->d_sb->s_id);
 223
 224         fscache_object_init(&fsdef->fscache, NULL, &cache->cache);
 225
 226         ret = fscache_add_cache(&cache->cache, &fsdef->fscache, cache->tag);
 227         if (ret < 0)
 228                 goto error_add_cache;
 229
 230         /* done */
 231         set_bit(CACHEFILES_READY, &cache->flags);
 232         dput(root);
 233
 234         printk(KERN_INFO "CacheFiles:"
 235                " File cache on %s registered\n",
 236                cache->cache.identifier);
 237
 238         /* check how much space the cache has */
 239         cachefiles_has_space(cache, 0, 0);
 240         cachefiles_end_secure(cache, saved_cred);
 241         return 0;
 242
 243 error_add_cache:
 244         dput(cache->graveyard);
 245         cache->graveyard = NULL;
 246 error_unsupported:
 247         mntput(cache->mnt);
 248         cache->mnt = NULL;
 249         dput(fsdef->dentry);
 250         fsdef->dentry = NULL;
 251         dput(root);
 252 error_open_root:
 253         kmem_cache_free(cachefiles_object_jar, fsdef);
 254 error_root_object:
 255         cachefiles_end_secure(cache, saved_cred);
 256         kerror("Failed to register: %d", ret);
 257         return ret;
 258 }
 259
 260 /*
 261  * unbind a cache on fd release
 262  */
 263 void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
 264 {
 265         _enter("");
 266
 267         if (test_bit(CACHEFILES_READY, &cache->flags)) {
 268                 printk(KERN_INFO "CacheFiles:"
 269                        " File cache on %s unregistering\n",
 270                        cache->cache.identifier);
 271
 272                 fscache_withdraw_cache(&cache->cache);
 273         }
 274
 275         dput(cache->graveyard);
 276         mntput(cache->mnt);
 277
 278         kfree(cache->rootdirname);
 279         kfree(cache->secctx);
 280         kfree(cache->tag);
 281
 282         _leave("");
 283 }