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
 22static int cachefiles_daemon_add_cache(struct cachefiles_cache *caches);
 23
 24/*
 25 * bind a directory as a cache
 26 */
 27int 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 */
 81static 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
235error_add_cache:
236	dput(cache->graveyard);
237	cache->graveyard = NULL;
238error_unsupported:
239	mntput(cache->mnt);
240	cache->mnt = NULL;
241	dput(fsdef->dentry);
242	fsdef->dentry = NULL;
243	dput(root);
244error_open_root:
245	kmem_cache_free(cachefiles_object_jar, fsdef);
246error_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 */
255void 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}