fs/cachefiles/bind.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Bind and unbind a cache from the filesystem backing it
   3  *
   4  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/init.h>
  10 #include <linux/sched.h>
  11 #include <linux/completion.h>
  12 #include <linux/slab.h>
  13 #include <linux/fs.h>
  14 #include <linux/file.h>
  15 #include <linux/namei.h>
  16 #include <linux/mount.h>
  17 #include <linux/statfs.h>
  18 #include <linux/ctype.h>
  19 #include <linux/xattr.h>
  20 #include "internal.h"
  21
  22 static int cachefiles_daemon_add_cache(struct cachefiles_cache *caches);
  23
  24 /*
  25  * bind a directory as a cache
  26  */
  27 int cachefiles_daemon_bind(struct cachefiles_cache *cache, char *args)
  28 {
  29         _enter("{%u,%u,%u,%u,%u,%u},%s",
  30                cache->frun_percent,
  31                cache->fcull_percent,
  32                cache->fstop_percent,
  33                cache->brun_percent,
  34                cache->bcull_percent,
  35                cache->bstop_percent,
  36                args);
  37
  38         /* start by checking things over */
  39         ASSERT(cache->fstop_percent >= 0 &&
  40                cache->fstop_percent < cache->fcull_percent &&
  41                cache->fcull_percent < cache->frun_percent &&
  42                cache->frun_percent  < 100);
  43
  44         ASSERT(cache->bstop_percent >= 0 &&
  45                cache->bstop_percent < cache->bcull_percent &&
  46                cache->bcull_percent < cache->brun_percent &&
  47                cache->brun_percent  < 100);
  48
  49         if (*args) {
  50                 pr_err("'bind' command doesn't take an argument\n");
  51                 return -EINVAL;
  52         }
  53
  54         if (!cache->rootdirname) {
  55                 pr_err("No cache directory specified\n");
  56                 return -EINVAL;
  57         }
  58
  59         /* don't permit already bound caches to be re-bound */
  60         if (test_bit(CACHEFILES_READY, &cache->flags)) {
  61                 pr_err("Cache already bound\n");
  62                 return -EBUSY;
  63         }
  64
  65         /* make sure we have copies of the tag and dirname strings */
  66         if (!cache->tag) {
  67                 /* the tag string is released by the fops->release()
  68                  * function, so we don't release it on error here */
  69                 cache->tag = kstrdup("CacheFiles", GFP_KERNEL);
  70                 if (!cache->tag)
  71                         return -ENOMEM;
  72         }
  73
  74         /* add the cache */
  75         return cachefiles_daemon_add_cache(cache);
  76 }
  77
  78 /*
  79  * add a cache
  80  */
  81 static int cachefiles_daemon_add_cache(struct cachefiles_cache *cache)
  82 {
  83         struct cachefiles_object *fsdef;
  84         struct path path;
  85         struct kstatfs stats;
  86         struct dentry *graveyard, *cachedir, *root;
  87         const struct cred *saved_cred;
  88         int ret;
  89
  90         _enter("");
  91
  92         /* we want to work under the module's security ID */
  93         ret = cachefiles_get_security_ID(cache);
  94         if (ret < 0)
  95                 return ret;
  96
  97         cachefiles_begin_secure(cache, &saved_cred);
  98
  99         /* allocate the root index object */
 100         ret = -ENOMEM;
 101
 102         fsdef = kmem_cache_alloc(cachefiles_object_jar, GFP_KERNEL);
 103         if (!fsdef)
 104                 goto error_root_object;
 105
 106         ASSERTCMP(fsdef->backer, ==, NULL);
 107
 108         atomic_set(&fsdef->usage, 1);
 109         fsdef->type = FSCACHE_COOKIE_TYPE_INDEX;
 110
 111         _debug("- fsdef %p", fsdef);
 112
 113         /* look up the directory at the root of the cache */
 114         ret = kern_path(cache->rootdirname, LOOKUP_DIRECTORY, &path);
 115         if (ret < 0)
 116                 goto error_open_root;
 117
 118         cache->mnt = path.mnt;
 119         root = path.dentry;
 120
 121         /* check parameters */
 122         ret = -EOPNOTSUPP;
 123         if (d_is_negative(root) ||
 124             !d_backing_inode(root)->i_op->lookup ||
 125             !d_backing_inode(root)->i_op->mkdir ||
 126             !(d_backing_inode(root)->i_opflags & IOP_XATTR) ||
 127             !root->d_sb->s_op->statfs ||
 128             !root->d_sb->s_op->sync_fs)
 129                 goto error_unsupported;
 130
 131         ret = -EROFS;
 132         if (sb_rdonly(root->d_sb))
 133                 goto error_unsupported;
 134
 135         /* determine the security of the on-disk cache as this governs
 136          * security ID of files we create */
 137         ret = cachefiles_determine_cache_security(cache, root, &saved_cred);
 138         if (ret < 0)
 139                 goto error_unsupported;
 140
 141         /* get the cache size and blocksize */
 142         ret = vfs_statfs(&path, &stats);
 143         if (ret < 0)
 144                 goto error_unsupported;
 145
 146         ret = -ERANGE;
 147         if (stats.f_bsize <= 0)
 148                 goto error_unsupported;
 149
 150         ret = -EOPNOTSUPP;
 151         if (stats.f_bsize > PAGE_SIZE)
 152                 goto error_unsupported;
 153
 154         cache->bsize = stats.f_bsize;
 155         cache->bshift = 0;
 156         if (stats.f_bsize < PAGE_SIZE)
 157                 cache->bshift = PAGE_SHIFT - ilog2(stats.f_bsize);
 158
 159         _debug("blksize %u (shift %u)",
 160                cache->bsize, cache->bshift);
 161
 162         _debug("size %llu, avail %llu",
 163                (unsigned long long) stats.f_blocks,
 164                (unsigned long long) stats.f_bavail);
 165
 166         /* set up caching limits */
 167         do_div(stats.f_files, 100);
 168         cache->fstop = stats.f_files * cache->fstop_percent;
 169         cache->fcull = stats.f_files * cache->fcull_percent;
 170         cache->frun  = stats.f_files * cache->frun_percent;
 171
 172         _debug("limits {%llu,%llu,%llu} files",
 173                (unsigned long long) cache->frun,
 174                (unsigned long long) cache->fcull,
 175                (unsigned long long) cache->fstop);
 176
 177         stats.f_blocks >>= cache->bshift;
 178         do_div(stats.f_blocks, 100);
 179         cache->bstop = stats.f_blocks * cache->bstop_percent;
 180         cache->bcull = stats.f_blocks * cache->bcull_percent;
 181         cache->brun  = stats.f_blocks * cache->brun_percent;
 182
 183         _debug("limits {%llu,%llu,%llu} blocks",
 184                (unsigned long long) cache->brun,
 185                (unsigned long long) cache->bcull,
 186                (unsigned long long) cache->bstop);
 187
 188         /* get the cache directory and check its type */
 189         cachedir = cachefiles_get_directory(cache, root, "cache");
 190         if (IS_ERR(cachedir)) {
 191                 ret = PTR_ERR(cachedir);
 192                 goto error_unsupported;
 193         }
 194
 195         fsdef->dentry = cachedir;
 196         fsdef->fscache.cookie = NULL;
 197
 198         ret = cachefiles_check_object_type(fsdef);
 199         if (ret < 0)
 200                 goto error_unsupported;
 201
 202         /* get the graveyard directory */
 203         graveyard = cachefiles_get_directory(cache, root, "graveyard");
 204         if (IS_ERR(graveyard)) {
 205                 ret = PTR_ERR(graveyard);
 206                 goto error_unsupported;
 207         }
 208
 209         cache->graveyard = graveyard;
 210
 211         /* publish the cache */
 212         fscache_init_cache(&cache->cache,
 213                            &cachefiles_cache_ops,
 214                            "%s",
 215                            fsdef->dentry->d_sb->s_id);
 216
 217         fscache_object_init(&fsdef->fscache, &fscache_fsdef_index,
 218                             &cache->cache);
 219
 220         ret = fscache_add_cache(&cache->cache, &fsdef->fscache, cache->tag);
 221         if (ret < 0)
 222                 goto error_add_cache;
 223
 224         /* done */
 225         set_bit(CACHEFILES_READY, &cache->flags);
 226         dput(root);
 227
 228         pr_info("File cache on %s registered\n", cache->cache.identifier);
 229
 230         /* check how much space the cache has */
 231         cachefiles_has_space(cache, 0, 0);
 232         cachefiles_end_secure(cache, saved_cred);
 233         return 0;
 234
 235 error_add_cache:
 236         dput(cache->graveyard);
 237         cache->graveyard = NULL;
 238 error_unsupported:
 239         mntput(cache->mnt);
 240         cache->mnt = NULL;
 241         dput(fsdef->dentry);
 242         fsdef->dentry = NULL;
 243         dput(root);
 244 error_open_root:
 245         kmem_cache_free(cachefiles_object_jar, fsdef);
 246 error_root_object:
 247         cachefiles_end_secure(cache, saved_cred);
 248         pr_err("Failed to register: %d\n", ret);
 249         return ret;
 250 }
 251
 252 /*
 253  * unbind a cache on fd release
 254  */
 255 void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
 256 {
 257         _enter("");
 258
 259         if (test_bit(CACHEFILES_READY, &cache->flags)) {
 260                 pr_info("File cache on %s unregistering\n",
 261                         cache->cache.identifier);
 262
 263                 fscache_withdraw_cache(&cache->cache);
 264         }
 265
 266         dput(cache->graveyard);
 267         mntput(cache->mnt);
 268
 269         kfree(cache->rootdirname);
 270         kfree(cache->secctx);
 271         kfree(cache->tag);
 272
 273         _leave("");
 274 }