xref: /linux-6.15/fs/cachefiles/cache.c (revision fe2140e2) 
1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Manage high-level VFS aspects of a cache.
3  *
4  * Copyright (C) 2007, 2021 Red Hat, Inc. All Rights Reserved.
5  * Written by David Howells ([email protected])
6  */
7 
8 #include <linux/slab.h>
9 #include <linux/statfs.h>
10 #include <linux/namei.h>
11 #include "internal.h"
12 
13 /*
14  * Bring a cache online.
15  */
16 int cachefiles_add_cache(struct cachefiles_cache *cache)
17 {
18 	struct fscache_cache *cache_cookie;
19 	struct path path;
20 	struct kstatfs stats;
21 	struct dentry *graveyard, *cachedir, *root;
22 	const struct cred *saved_cred;
23 	int ret;
24 
25 	_enter("");
26 
27 	cache_cookie = fscache_acquire_cache(cache->tag);
28 	if (IS_ERR(cache_cookie))
29 		return PTR_ERR(cache_cookie);
30 
31 	/* we want to work under the module's security ID */
32 	ret = cachefiles_get_security_ID(cache);
33 	if (ret < 0)
34 		goto error_getsec;
35 
36 	cachefiles_begin_secure(cache, &saved_cred);
37 
38 	/* look up the directory at the root of the cache */
39 	ret = kern_path(cache->rootdirname, LOOKUP_DIRECTORY, &path);
40 	if (ret < 0)
41 		goto error_open_root;
42 
43 	cache->mnt = path.mnt;
44 	root = path.dentry;
45 
46 	ret = -EINVAL;
47 	if (mnt_user_ns(path.mnt) != &init_user_ns) {
48 		pr_warn("File cache on idmapped mounts not supported");
49 		goto error_unsupported;
50 	}
51 
52 	/* check parameters */
53 	ret = -EOPNOTSUPP;
54 	if (d_is_negative(root) ||
55 	    !d_backing_inode(root)->i_op->lookup ||
56 	    !d_backing_inode(root)->i_op->mkdir ||
57 	    !(d_backing_inode(root)->i_opflags & IOP_XATTR) ||
58 	    !root->d_sb->s_op->statfs ||
59 	    !root->d_sb->s_op->sync_fs ||
60 	    root->d_sb->s_blocksize > PAGE_SIZE)
61 		goto error_unsupported;
62 
63 	ret = -EROFS;
64 	if (sb_rdonly(root->d_sb))
65 		goto error_unsupported;
66 
67 	/* determine the security of the on-disk cache as this governs
68 	 * security ID of files we create */
69 	ret = cachefiles_determine_cache_security(cache, root, &saved_cred);
70 	if (ret < 0)
71 		goto error_unsupported;
72 
73 	/* get the cache size and blocksize */
74 	ret = vfs_statfs(&path, &stats);
75 	if (ret < 0)
76 		goto error_unsupported;
77 
78 	ret = -ERANGE;
79 	if (stats.f_bsize <= 0)
80 		goto error_unsupported;
81 
82 	ret = -EOPNOTSUPP;
83 	if (stats.f_bsize > PAGE_SIZE)
84 		goto error_unsupported;
85 
86 	cache->bsize = stats.f_bsize;
87 	cache->bshift = 0;
88 	if (stats.f_bsize < PAGE_SIZE)
89 		cache->bshift = PAGE_SHIFT - ilog2(stats.f_bsize);
90 
91 	_debug("blksize %u (shift %u)",
92 	       cache->bsize, cache->bshift);
93 
94 	_debug("size %llu, avail %llu",
95 	       (unsigned long long) stats.f_blocks,
96 	       (unsigned long long) stats.f_bavail);
97 
98 	/* set up caching limits */
99 	do_div(stats.f_files, 100);
100 	cache->fstop = stats.f_files * cache->fstop_percent;
101 	cache->fcull = stats.f_files * cache->fcull_percent;
102 	cache->frun  = stats.f_files * cache->frun_percent;
103 
104 	_debug("limits {%llu,%llu,%llu} files",
105 	       (unsigned long long) cache->frun,
106 	       (unsigned long long) cache->fcull,
107 	       (unsigned long long) cache->fstop);
108 
109 	stats.f_blocks >>= cache->bshift;
110 	do_div(stats.f_blocks, 100);
111 	cache->bstop = stats.f_blocks * cache->bstop_percent;
112 	cache->bcull = stats.f_blocks * cache->bcull_percent;
113 	cache->brun  = stats.f_blocks * cache->brun_percent;
114 
115 	_debug("limits {%llu,%llu,%llu} blocks",
116 	       (unsigned long long) cache->brun,
117 	       (unsigned long long) cache->bcull,
118 	       (unsigned long long) cache->bstop);
119 
120 	/* get the cache directory and check its type */
121 	cachedir = cachefiles_get_directory(cache, root, "cache", NULL);
122 	if (IS_ERR(cachedir)) {
123 		ret = PTR_ERR(cachedir);
124 		goto error_unsupported;
125 	}
126 
127 	cache->store = cachedir;
128 
129 	/* get the graveyard directory */
130 	graveyard = cachefiles_get_directory(cache, root, "graveyard", NULL);
131 	if (IS_ERR(graveyard)) {
132 		ret = PTR_ERR(graveyard);
133 		goto error_unsupported;
134 	}
135 
136 	cache->graveyard = graveyard;
137 	cache->cache = cache_cookie;
138 
139 	ret = fscache_add_cache(cache_cookie, &cachefiles_cache_ops, cache);
140 	if (ret < 0)
141 		goto error_add_cache;
142 
143 	/* done */
144 	set_bit(CACHEFILES_READY, &cache->flags);
145 	dput(root);
146 
147 	pr_info("File cache on %s registered\n", cache_cookie->name);
148 
149 	/* check how much space the cache has */
150 	cachefiles_has_space(cache, 0, 0);
151 	cachefiles_end_secure(cache, saved_cred);
152 	_leave(" = 0 [%px]", cache->cache);
153 	return 0;
154 
155 error_add_cache:
156 	cachefiles_put_directory(cache->graveyard);
157 	cache->graveyard = NULL;
158 error_unsupported:
159 	cachefiles_put_directory(cache->store);
160 	cache->store = NULL;
161 	mntput(cache->mnt);
162 	cache->mnt = NULL;
163 	dput(root);
164 error_open_root:
165 	cachefiles_end_secure(cache, saved_cred);
166 error_getsec:
167 	fscache_relinquish_cache(cache_cookie);
168 	cache->cache = NULL;
169 	pr_err("Failed to register: %d\n", ret);
170 	return ret;
171 }
172 
173 /*
174  * See if we have space for a number of pages and/or a number of files in the
175  * cache
176  */
177 int cachefiles_has_space(struct cachefiles_cache *cache,
178 			 unsigned fnr, unsigned bnr)
179 {
180 	struct kstatfs stats;
181 	u64 b_avail, b_writing;
182 	int ret;
183 
184 	struct path path = {
185 		.mnt	= cache->mnt,
186 		.dentry	= cache->mnt->mnt_root,
187 	};
188 
189 	//_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u",
190 	//       (unsigned long long) cache->frun,
191 	//       (unsigned long long) cache->fcull,
192 	//       (unsigned long long) cache->fstop,
193 	//       (unsigned long long) cache->brun,
194 	//       (unsigned long long) cache->bcull,
195 	//       (unsigned long long) cache->bstop,
196 	//       fnr, bnr);
197 
198 	/* find out how many pages of blockdev are available */
199 	memset(&stats, 0, sizeof(stats));
200 
201 	ret = vfs_statfs(&path, &stats);
202 	if (ret < 0) {
203 		trace_cachefiles_vfs_error(NULL, d_inode(path.dentry), ret,
204 					   cachefiles_trace_statfs_error);
205 		if (ret == -EIO)
206 			cachefiles_io_error(cache, "statfs failed");
207 		_leave(" = %d", ret);
208 		return ret;
209 	}
210 
211 	b_avail = stats.f_bavail >> cache->bshift;
212 	b_writing = atomic_long_read(&cache->b_writing);
213 	if (b_avail > b_writing)
214 		b_avail -= b_writing;
215 	else
216 		b_avail = 0;
217 
218 	//_debug("avail %llu,%llu",
219 	//       (unsigned long long)stats.f_ffree,
220 	//       (unsigned long long)b_avail);
221 
222 	/* see if there is sufficient space */
223 	if (stats.f_ffree > fnr)
224 		stats.f_ffree -= fnr;
225 	else
226 		stats.f_ffree = 0;
227 
228 	if (b_avail > bnr)
229 		b_avail -= bnr;
230 	else
231 		b_avail = 0;
232 
233 	ret = -ENOBUFS;
234 	if (stats.f_ffree < cache->fstop ||
235 	    b_avail < cache->bstop)
236 		goto begin_cull;
237 
238 	ret = 0;
239 	if (stats.f_ffree < cache->fcull ||
240 	    b_avail < cache->bcull)
241 		goto begin_cull;
242 
243 	if (test_bit(CACHEFILES_CULLING, &cache->flags) &&
244 	    stats.f_ffree >= cache->frun &&
245 	    b_avail >= cache->brun &&
246 	    test_and_clear_bit(CACHEFILES_CULLING, &cache->flags)
247 	    ) {
248 		_debug("cease culling");
249 		cachefiles_state_changed(cache);
250 	}
251 
252 	//_leave(" = 0");
253 	return 0;
254 
255 begin_cull:
256 	if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
257 		_debug("### CULL CACHE ###");
258 		cachefiles_state_changed(cache);
259 	}
260 
261 	_leave(" = %d", ret);
262 	return ret;
263 }
264 
265 /*
266  * Withdraw volumes.
267  */
268 static void cachefiles_withdraw_volumes(struct cachefiles_cache *cache)
269 {
270 	_enter("");
271 
272 	for (;;) {
273 		struct cachefiles_volume *volume = NULL;
274 
275 		spin_lock(&cache->object_list_lock);
276 		if (!list_empty(&cache->volumes)) {
277 			volume = list_first_entry(&cache->volumes,
278 						  struct cachefiles_volume, cache_link);
279 			list_del_init(&volume->cache_link);
280 		}
281 		spin_unlock(&cache->object_list_lock);
282 		if (!volume)
283 			break;
284 
285 		cachefiles_withdraw_volume(volume);
286 	}
287 
288 	_leave("");
289 }
290 
291 /*
292  * Sync a cache to backing disk.
293  */
294 static void cachefiles_sync_cache(struct cachefiles_cache *cache)
295 {
296 	const struct cred *saved_cred;
297 	int ret;
298 
299 	_enter("%s", cache->cache->name);
300 
301 	/* make sure all pages pinned by operations on behalf of the netfs are
302 	 * written to disc */
303 	cachefiles_begin_secure(cache, &saved_cred);
304 	down_read(&cache->mnt->mnt_sb->s_umount);
305 	ret = sync_filesystem(cache->mnt->mnt_sb);
306 	up_read(&cache->mnt->mnt_sb->s_umount);
307 	cachefiles_end_secure(cache, saved_cred);
308 
309 	if (ret == -EIO)
310 		cachefiles_io_error(cache,
311 				    "Attempt to sync backing fs superblock returned error %d",
312 				    ret);
313 }
314 
315 /*
316  * Withdraw cache objects.
317  */
318 void cachefiles_withdraw_cache(struct cachefiles_cache *cache)
319 {
320 	struct fscache_cache *fscache = cache->cache;
321 
322 	pr_info("File cache on %s unregistering\n", fscache->name);
323 
324 	fscache_withdraw_cache(fscache);
325 
326 	/* we now have to destroy all the active objects pertaining to this
327 	 * cache - which we do by passing them off to thread pool to be
328 	 * disposed of */
329 	// PLACEHOLDER: Withdraw objects
330 	fscache_wait_for_objects(fscache);
331 
332 	cachefiles_withdraw_volumes(cache);
333 	cachefiles_sync_cache(cache);
334 	cache->cache = NULL;
335 	fscache_relinquish_cache(fscache);
336 }
337