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 <linux/xattr.h>
  24 #include "internal.h"
  25
  26 static int cachefiles_daemon_add_cache(struct cachefiles_cache *caches);
  27
  28 /*
  29  * bind a directory as a cache
  30  */
  31 int cachefiles_daemon_bind(struct cachefiles_cache *cache, char *args)
  32 {
  33         _enter("{%u,%u,%u,%u,%u,%u},%s",
  34                cache->frun_percent,
  35                cache->fcull_percent,
  36                cache->fstop_percent,
  37                cache->brun_percent,
  38                cache->bcull_percent,
  39                cache->bstop_percent,
  40                args);
  41
  42         /* start by checking things over */
  43         ASSERT(cache->fstop_percent >= 0 &&
  44                cache->fstop_percent < cache->fcull_percent &&
  45                cache->fcull_percent < cache->frun_percent &&
  46                cache->frun_percent  < 100);
  47
  48         ASSERT(cache->bstop_percent >= 0 &&
  49                cache->bstop_percent < cache->bcull_percent &&
  50                cache->bcull_percent < cache->brun_percent &&
  51                cache->brun_percent  < 100);
  52
  53         if (*args) {
  54                 pr_err("'bind' command doesn't take an argument\n");
  55                 return -EINVAL;
  56         }
  57
  58         if (!cache->rootdirname) {
  59                 pr_err("No cache directory specified\n");
  60                 return -EINVAL;
  61         }
  62
  63         /* don't permit already bound caches to be re-bound */
  64         if (test_bit(CACHEFILES_READY, &cache->flags)) {
  65                 pr_err("Cache already bound\n");
  66                 return -EBUSY;
  67         }
  68
  69         /* make sure we have copies of the tag and dirname strings */
  70         if (!cache->tag) {
  71                 /* the tag string is released by the fops->release()
  72                  * function, so we don't release it on error here */
  73                 cache->tag = kstrdup("CacheFiles", GFP_KERNEL);
  74                 if (!cache->tag)
  75                         return -ENOMEM;
  76         }
  77
  78         /* add the cache */
  79         return cachefiles_daemon_add_cache(cache);
  80 }
  81
  82 /*
  83  * add a cache
  84  */
  85 static int cachefiles_daemon_add_cache(struct cachefiles_cache *cache)
  86 {
  87         struct cachefiles_object *fsdef;
  88         struct path path;
  89         struct kstatfs stats;
  90         struct dentry *graveyard, *cachedir, *root;
  91         const struct cred *saved_cred;
  92         int ret;
  93
  94         _enter("");
  95
  96         /* we want to work under the module's security ID */
  97         ret = cachefiles_get_security_ID(cache);
  98         if (ret < 0)
  99                 return ret;
 100
 101         cachefiles_begin_secure(cache, &saved_cred);
 102
 103         /* allocate the root index object */
 104         ret = -ENOMEM;
 105
 106         fsdef = kmem_cache_alloc(cachefiles_object_jar, GFP_KERNEL);
 107         if (!fsdef)
 108                 goto error_root_object;
 109
 110         ASSERTCMP(fsdef->backer, ==, NULL);
 111
 112         atomic_set(&fsdef->usage, 1);
 113         fsdef->type = FSCACHE_COOKIE_TYPE_INDEX;
 114
 115         _debug("- fsdef %p", fsdef);
 116
 117         /* look up the directory at the root of the cache */
 118         ret = kern_path(cache->rootdirname, LOOKUP_DIRECTORY, &path);
 119         if (ret < 0)
 120                 goto error_open_root;
 121
 122         cache->mnt = path.mnt;
 123         root = path.dentry;
 124
 125         /* check parameters */
 126         ret = -EOPNOTSUPP;
 127         if (d_is_negative(root) ||
 128             !d_backing_inode(root)->i_op->lookup ||
 129             !d_backing_inode(root)->i_op->mkdir ||
 130             !(d_backing_inode(root)->i_opflags & IOP_XATTR) ||
 131             !root->d_sb->s_op->statfs ||
 132             !root->d_sb->s_op->sync_fs)
 133                 goto error_unsupported;
 134
 135         ret = -EROFS;
 136         if (sb_rdonly(root->d_sb))
 137                 goto error_unsupported;
 138
 139         /* determine the security of the on-disk cache as this governs
 140          * security ID of files we create */
 141         ret = cachefiles_determine_cache_security(cache, root, &saved_cred);
 142         if (ret < 0)
 143                 goto error_unsupported;
 144
 145         /* get the cache size and blocksize */
 146         ret = vfs_statfs(&path, &stats);
 147         if (ret < 0)
 148                 goto error_unsupported;
 149
 150         ret = -ERANGE;
 151         if (stats.f_bsize <= 0)
 152                 goto error_unsupported;
 153
 154         ret = -EOPNOTSUPP;
 155         if (stats.f_bsize > PAGE_SIZE)
 156                 goto error_unsupported;
 157
 158         cache->bsize = stats.f_bsize;
 159         cache->bshift = 0;
 160         if (stats.f_bsize < PAGE_SIZE)
 161                 cache->bshift = PAGE_SHIFT - ilog2(stats.f_bsize);
 162
 163         _debug("blksize %u (shift %u)",
 164                cache->bsize, cache->bshift);
 165
 166         _debug("size %llu, avail %llu",
 167                (unsigned long long) stats.f_blocks,
 168                (unsigned long long) stats.f_bavail);
 169
 170         /* set up caching limits */
 171         do_div(stats.f_files, 100);
 172         cache->fstop = stats.f_files * cache->fstop_percent;
 173         cache->fcull = stats.f_files * cache->fcull_percent;
 174         cache->frun  = stats.f_files * cache->frun_percent;
 175
 176         _debug("limits {%llu,%llu,%llu} files",
 177                (unsigned long long) cache->frun,
 178                (unsigned long long) cache->fcull,
 179                (unsigned long long) cache->fstop);
 180
 181         stats.f_blocks >>= cache->bshift;
 182         do_div(stats.f_blocks, 100);
 183         cache->bstop = stats.f_blocks * cache->bstop_percent;
 184         cache->bcull = stats.f_blocks * cache->bcull_percent;
 185         cache->brun  = stats.f_blocks * cache->brun_percent;
 186
 187         _debug("limits {%llu,%llu,%llu} blocks",
 188                (unsigned long long) cache->brun,
 189                (unsigned long long) cache->bcull,
 190                (unsigned long long) cache->bstop);
 191
 192         /* get the cache directory and check its type */
 193         cachedir = cachefiles_get_directory(cache, root, "cache");
 194         if (IS_ERR(cachedir)) {
 195                 ret = PTR_ERR(cachedir);
 196                 goto error_unsupported;
 197         }
 198
 199         fsdef->dentry = cachedir;
 200         fsdef->fscache.cookie = NULL;
 201
 202         ret = cachefiles_check_object_type(fsdef);
 203         if (ret < 0)
 204                 goto error_unsupported;
 205
 206         /* get the graveyard directory */
 207         graveyard = cachefiles_get_directory(cache, root, "graveyard");
 208         if (IS_ERR(graveyard)) {
 209                 ret = PTR_ERR(graveyard);
 210                 goto error_unsupported;
 211         }
 212
 213         cache->graveyard = graveyard;
 214
 215         /* publish the cache */
 216         fscache_init_cache(&cache->cache,
 217                            &cachefiles_cache_ops,
 218                            "%s",
 219                            fsdef->dentry->d_sb->s_id);
 220
 221         fscache_object_init(&fsdef->fscache, &fscache_fsdef_index,
 222                             &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         pr_info("File cache on %s registered\n", cache->cache.identifier);
 233
 234         /* check how much space the cache has */
 235         cachefiles_has_space(cache, 0, 0);
 236         cachefiles_end_secure(cache, saved_cred);
 237         return 0;
 238
 239 error_add_cache:
 240         dput(cache->graveyard);
 241         cache->graveyard = NULL;
 242 error_unsupported:
 243         mntput(cache->mnt);
 244         cache->mnt = NULL;
 245         dput(fsdef->dentry);
 246         fsdef->dentry = NULL;
 247         dput(root);
 248 error_open_root:
 249         kmem_cache_free(cachefiles_object_jar, fsdef);
 250 error_root_object:
 251         cachefiles_end_secure(cache, saved_cred);
 252         pr_err("Failed to register: %d\n", ret);
 253         return ret;
 254 }
 255
 256 /*
 257  * unbind a cache on fd release
 258  */
 259 void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
 260 {
 261         _enter("");
 262
 263         if (test_bit(CACHEFILES_READY, &cache->flags)) {
 264                 pr_info("File cache on %s unregistering\n",
 265                         cache->cache.identifier);
 266
 267                 fscache_withdraw_cache(&cache->cache);
 268         }
 269
 270         dput(cache->graveyard);
 271         mntput(cache->mnt);
 272
 273         kfree(cache->rootdirname);
 274         kfree(cache->secctx);
 275         kfree(cache->tag);
 276
 277         _leave("");
 278 }