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  */
cachefiles_daemon_bind(struct cachefiles_cache * cache,char * args)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  */
cachefiles_daemon_add_cache(struct cachefiles_cache * cache)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  */
cachefiles_daemon_unbind(struct cachefiles_cache * cache)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 }
275