projects/linux·blob v5.13 · refs

280 lines · 6.9 KiB

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 ([email protected])
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 ret = -EINVAL;
122 if (mnt_user_ns(path.mnt) != &init_user_ns) {
123 pr_warn("File cache on idmapped mounts not supported");
124 goto error_unsupported;
125 }
126
127 /* check parameters */
128 ret = -EOPNOTSUPP;
129 if (d_is_negative(root) ||
130 !d_backing_inode(root)->i_op->lookup ||
131 !d_backing_inode(root)->i_op->mkdir ||
132 !(d_backing_inode(root)->i_opflags & IOP_XATTR) ||
133 !root->d_sb->s_op->statfs ||
134 !root->d_sb->s_op->sync_fs)
135 goto error_unsupported;
136
137 ret = -EROFS;
138 if (sb_rdonly(root->d_sb))
139 goto error_unsupported;
140
141 /* determine the security of the on-disk cache as this governs
142 * security ID of files we create */
143 ret = cachefiles_determine_cache_security(cache, root, &saved_cred);
144 if (ret < 0)
145 goto error_unsupported;
146
147 /* get the cache size and blocksize */
148 ret = vfs_statfs(&path, &stats);
149 if (ret < 0)
150 goto error_unsupported;
151
152 ret = -ERANGE;
153 if (stats.f_bsize <= 0)
154 goto error_unsupported;
155
156 ret = -EOPNOTSUPP;
157 if (stats.f_bsize > PAGE_SIZE)
158 goto error_unsupported;
159
160 cache->bsize = stats.f_bsize;
161 cache->bshift = 0;
162 if (stats.f_bsize < PAGE_SIZE)
163 cache->bshift = PAGE_SHIFT - ilog2(stats.f_bsize);
164
165 _debug("blksize %u (shift %u)",
166 cache->bsize, cache->bshift);
167
168 _debug("size %llu, avail %llu",
169 (unsigned long long) stats.f_blocks,
170 (unsigned long long) stats.f_bavail);
171
172 /* set up caching limits */
173 do_div(stats.f_files, 100);
174 cache->fstop = stats.f_files * cache->fstop_percent;
175 cache->fcull = stats.f_files * cache->fcull_percent;
176 cache->frun = stats.f_files * cache->frun_percent;
177
178 _debug("limits {%llu,%llu,%llu} files",
179 (unsigned long long) cache->frun,
180 (unsigned long long) cache->fcull,
181 (unsigned long long) cache->fstop);
182
183 stats.f_blocks >>= cache->bshift;
184 do_div(stats.f_blocks, 100);
185 cache->bstop = stats.f_blocks * cache->bstop_percent;
186 cache->bcull = stats.f_blocks * cache->bcull_percent;
187 cache->brun = stats.f_blocks * cache->brun_percent;
188
189 _debug("limits {%llu,%llu,%llu} blocks",
190 (unsigned long long) cache->brun,
191 (unsigned long long) cache->bcull,
192 (unsigned long long) cache->bstop);
193
194 /* get the cache directory and check its type */
195 cachedir = cachefiles_get_directory(cache, root, "cache");
196 if (IS_ERR(cachedir)) {
197 ret = PTR_ERR(cachedir);
198 goto error_unsupported;
199 }
200
201 fsdef->dentry = cachedir;
202 fsdef->fscache.cookie = NULL;
203
204 ret = cachefiles_check_object_type(fsdef);
205 if (ret < 0)
206 goto error_unsupported;
207
208 /* get the graveyard directory */
209 graveyard = cachefiles_get_directory(cache, root, "graveyard");
210 if (IS_ERR(graveyard)) {
211 ret = PTR_ERR(graveyard);
212 goto error_unsupported;
213 }
214
215 cache->graveyard = graveyard;
216
217 /* publish the cache */
218 fscache_init_cache(&cache->cache,
219 &cachefiles_cache_ops,
220 "%s",
221 fsdef->dentry->d_sb->s_id);
222
223 fscache_object_init(&fsdef->fscache, &fscache_fsdef_index,
224 &cache->cache);
225
226 ret = fscache_add_cache(&cache->cache, &fsdef->fscache, cache->tag);
227 if (ret < 0)
228 goto error_add_cache;
229
230 /* done */
231 set_bit(CACHEFILES_READY, &cache->flags);
232 dput(root);
233
234 pr_info("File cache on %s registered\n", 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
241error_add_cache:
242 dput(cache->graveyard);
243 cache->graveyard = NULL;
244error_unsupported:
245 mntput(cache->mnt);
246 cache->mnt = NULL;
247 dput(fsdef->dentry);
248 fsdef->dentry = NULL;
249 dput(root);
250error_open_root:
251 kmem_cache_free(cachefiles_object_jar, fsdef);
252error_root_object:
253 cachefiles_end_secure(cache, saved_cred);
254 pr_err("Failed to register: %d\n", ret);
255 return ret;
256}
257
258/*
259 * unbind a cache on fd release
260 */
261void cachefiles_daemon_unbind(struct cachefiles_cache *cache)
262{
263 _enter("");
264
265 if (test_bit(CACHEFILES_READY, &cache->flags)) {
266 pr_info("File cache on %s unregistering\n",
267 cache->cache.identifier);
268
269 fscache_withdraw_cache(&cache->cache);
270 }
271
272 dput(cache->graveyard);
273 mntput(cache->mnt);
274
275 kfree(cache->rootdirname);
276 kfree(cache->secctx);
277 kfree(cache->tag);
278
279 _leave("");
280}