linux/fs/cachefiles/bind.c
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   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
  25static int cachefiles_daemon_add_cache(struct cachefiles_cache *caches);
  26
  27/*
  28 * bind a directory as a cache
  29 */
  30int 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 */
  84static 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->s_op->statfs ||
 133            !root->d_sb->s_op->sync_fs)
 134                goto error_unsupported;
 135
 136        ret = -EROFS;
 137        if (root->d_sb->s_flags & MS_RDONLY)
 138                goto error_unsupported;
 139
 140        /* determine the security of the on-disk cache as this governs
 141         * security ID of files we create */
 142        ret = cachefiles_determine_cache_security(cache, root, &saved_cred);
 143        if (ret < 0)
 144                goto error_unsupported;
 145
 146        /* get the cache size and blocksize */
 147        ret = vfs_statfs(&path, &stats);
 148        if (ret < 0)
 149                goto error_unsupported;
 150
 151        ret = -ERANGE;
 152        if (stats.f_bsize <= 0)
 153                goto error_unsupported;
 154
 155        ret = -EOPNOTSUPP;
 156        if (stats.f_bsize > PAGE_SIZE)
 157                goto error_unsupported;
 158
 159        cache->bsize = stats.f_bsize;
 160        cache->bshift = 0;
 161        if (stats.f_bsize < PAGE_SIZE)
 162                cache->bshift = PAGE_SHIFT - ilog2(stats.f_bsize);
 163
 164        _debug("blksize %u (shift %u)",
 165               cache->bsize, cache->bshift);
 166
 167        _debug("size %llu, avail %llu",
 168               (unsigned long long) stats.f_blocks,
 169               (unsigned long long) stats.f_bavail);
 170
 171        /* set up caching limits */
 172        do_div(stats.f_files, 100);
 173        cache->fstop = stats.f_files * cache->fstop_percent;
 174        cache->fcull = stats.f_files * cache->fcull_percent;
 175        cache->frun  = stats.f_files * cache->frun_percent;
 176
 177        _debug("limits {%llu,%llu,%llu} files",
 178               (unsigned long long) cache->frun,
 179               (unsigned long long) cache->fcull,
 180               (unsigned long long) cache->fstop);
 181
 182        stats.f_blocks >>= cache->bshift;
 183        do_div(stats.f_blocks, 100);
 184        cache->bstop = stats.f_blocks * cache->bstop_percent;
 185        cache->bcull = stats.f_blocks * cache->bcull_percent;
 186        cache->brun  = stats.f_blocks * cache->brun_percent;
 187
 188        _debug("limits {%llu,%llu,%llu} blocks",
 189               (unsigned long long) cache->brun,
 190               (unsigned long long) cache->bcull,
 191               (unsigned long long) cache->bstop);
 192
 193        /* get the cache directory and check its type */
 194        cachedir = cachefiles_get_directory(cache, root, "cache");
 195        if (IS_ERR(cachedir)) {
 196                ret = PTR_ERR(cachedir);
 197                goto error_unsupported;
 198        }
 199
 200        fsdef->dentry = cachedir;
 201        fsdef->fscache.cookie = NULL;
 202
 203        ret = cachefiles_check_object_type(fsdef);
 204        if (ret < 0)
 205                goto error_unsupported;
 206
 207        /* get the graveyard directory */
 208        graveyard = cachefiles_get_directory(cache, root, "graveyard");
 209        if (IS_ERR(graveyard)) {
 210                ret = PTR_ERR(graveyard);
 211                goto error_unsupported;
 212        }
 213
 214        cache->graveyard = graveyard;
 215
 216        /* publish the cache */
 217        fscache_init_cache(&cache->cache,
 218                           &cachefiles_cache_ops,
 219                           "%s",
 220                           fsdef->dentry->d_sb->s_id);
 221
 222        fscache_object_init(&fsdef->fscache, NULL, &cache->cache);
 223
 224        ret = fscache_add_cache(&cache->cache, &fsdef->fscache, cache->tag);
 225        if (ret < 0)
 226                goto error_add_cache;
 227
 228        /* done */
 229        set_bit(CACHEFILES_READY, &cache->flags);
 230        dput(root);
 231
 232        printk(KERN_INFO "CacheFiles:"
 233               " File cache on %s registered\n",
 234               cache->cache.identifier);
 235
 236        /* check how much space the cache has */
 237        cachefiles_has_space(cache, 0, 0);
 238        cachefiles_end_secure(cache, saved_cred);
 239        return 0;
 240
 241error_add_cache:
 242        dput(cache->graveyard);
 243        cache->graveyard = NULL;
 244error_unsupported:
 245        mntput(cache->mnt);
 246        cache->mnt = NULL;
 247        dput(fsdef->dentry);
 248        fsdef->dentry = NULL;
 249        dput(root);
 250error_open_root:
 251        kmem_cache_free(cachefiles_object_jar, fsdef);
 252error_root_object:
 253        cachefiles_end_secure(cache, saved_cred);
 254        kerror("Failed to register: %d", ret);
 255        return ret;
 256}
 257
 258/*
 259 * unbind a cache on fd release
 260 */
 261void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
 262{
 263        _enter("");
 264
 265        if (test_bit(CACHEFILES_READY, &cache->flags)) {
 266                printk(KERN_INFO "CacheFiles:"
 267                       " File cache on %s unregistering\n",
 268                       cache->cache.identifier);
 269
 270                fscache_withdraw_cache(&cache->cache);
 271        }
 272
 273        dput(cache->graveyard);
 274        mntput(cache->mnt);
 275
 276        kfree(cache->rootdirname);
 277        kfree(cache->secctx);
 278        kfree(cache->tag);
 279
 280        _leave("");
 281}
 282
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