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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 
 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->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 
241 error_add_cache:
242         dput(cache->graveyard);
243         cache->graveyard = NULL;
244 error_unsupported:
245         mntput(cache->mnt);
246         cache->mnt = NULL;
247         dput(fsdef->dentry);
248         fsdef->dentry = NULL;
249         dput(root);
250 error_open_root:
251         kmem_cache_free(cachefiles_object_jar, fsdef);
252 error_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  */
261 void 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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