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		pr_err("'bind' command doesn't take an argument\n");
 54		return -EINVAL;
 55	}
 56
 57	if (!cache->rootdirname) {
 58		pr_err("No cache directory specified\n");
 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		pr_err("Cache already bound\n");
 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 (d_is_negative(root) ||
127	    !d_backing_inode(root)->i_op->lookup ||
128	    !d_backing_inode(root)->i_op->mkdir ||
129	    !d_backing_inode(root)->i_op->setxattr ||
130	    !d_backing_inode(root)->i_op->getxattr ||
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 (root->d_sb->s_flags & MS_RDONLY)
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, NULL, &cache->cache);
222
223	ret = fscache_add_cache(&cache->cache, &fsdef->fscache, cache->tag);
224	if (ret < 0)
225		goto error_add_cache;
226
227	/* done */
228	set_bit(CACHEFILES_READY, &cache->flags);
229	dput(root);
230
231	pr_info("File cache on %s registered\n", cache->cache.identifier);
232
233	/* check how much space the cache has */
234	cachefiles_has_space(cache, 0, 0);
235	cachefiles_end_secure(cache, saved_cred);
236	return 0;
237
238error_add_cache:
239	dput(cache->graveyard);
240	cache->graveyard = NULL;
241error_unsupported:
242	mntput(cache->mnt);
243	cache->mnt = NULL;
244	dput(fsdef->dentry);
245	fsdef->dentry = NULL;
246	dput(root);
247error_open_root:
248	kmem_cache_free(cachefiles_object_jar, fsdef);
249error_root_object:
250	cachefiles_end_secure(cache, saved_cred);
251	pr_err("Failed to register: %d\n", ret);
252	return ret;
253}
254
255/*
256 * unbind a cache on fd release
257 */
258void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
259{
260	_enter("");
261
262	if (test_bit(CACHEFILES_READY, &cache->flags)) {
263		pr_info("File cache on %s unregistering\n",
264			cache->cache.identifier);
265
266		fscache_withdraw_cache(&cache->cache);
267	}
268
269	dput(cache->graveyard);
270	mntput(cache->mnt);
271
272	kfree(cache->rootdirname);
273	kfree(cache->secctx);
274	kfree(cache->tag);
275
276	_leave("");
277}