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 (dhowells@redhat.com) |
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(name: cache->tag); |
28 | if (IS_ERR(ptr: cache_cookie)) |
29 | return PTR_ERR(ptr: 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: &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 (is_idmapped_mnt(mnt: path.mnt)) { |
48 | pr_warn("File cache on idmapped mounts not supported" ); |
49 | goto error_unsupported; |
50 | } |
51 | |
52 | /* Check features of the backing filesystem: |
53 | * - Directories must support looking up and directory creation |
54 | * - We create tmpfiles to handle invalidation |
55 | * - We use xattrs to store metadata |
56 | * - We need to be able to query the amount of space available |
57 | * - We want to be able to sync the filesystem when stopping the cache |
58 | * - We use DIO to/from pages, so the blocksize mustn't be too big. |
59 | */ |
60 | ret = -EOPNOTSUPP; |
61 | if (d_is_negative(dentry: root) || |
62 | !d_backing_inode(upper: root)->i_op->lookup || |
63 | !d_backing_inode(upper: root)->i_op->mkdir || |
64 | !d_backing_inode(upper: root)->i_op->tmpfile || |
65 | !(d_backing_inode(upper: root)->i_opflags & IOP_XATTR) || |
66 | !root->d_sb->s_op->statfs || |
67 | !root->d_sb->s_op->sync_fs || |
68 | root->d_sb->s_blocksize > PAGE_SIZE) |
69 | goto error_unsupported; |
70 | |
71 | ret = -EROFS; |
72 | if (sb_rdonly(sb: root->d_sb)) |
73 | goto error_unsupported; |
74 | |
75 | /* determine the security of the on-disk cache as this governs |
76 | * security ID of files we create */ |
77 | ret = cachefiles_determine_cache_security(cache, root, saved_cred: &saved_cred); |
78 | if (ret < 0) |
79 | goto error_unsupported; |
80 | |
81 | /* get the cache size and blocksize */ |
82 | ret = vfs_statfs(&path, &stats); |
83 | if (ret < 0) |
84 | goto error_unsupported; |
85 | |
86 | ret = -ERANGE; |
87 | if (stats.f_bsize <= 0) |
88 | goto error_unsupported; |
89 | |
90 | ret = -EOPNOTSUPP; |
91 | if (stats.f_bsize > PAGE_SIZE) |
92 | goto error_unsupported; |
93 | |
94 | cache->bsize = stats.f_bsize; |
95 | cache->bshift = ilog2(stats.f_bsize); |
96 | |
97 | _debug("blksize %u (shift %u)" , |
98 | cache->bsize, cache->bshift); |
99 | |
100 | _debug("size %llu, avail %llu" , |
101 | (unsigned long long) stats.f_blocks, |
102 | (unsigned long long) stats.f_bavail); |
103 | |
104 | /* set up caching limits */ |
105 | do_div(stats.f_files, 100); |
106 | cache->fstop = stats.f_files * cache->fstop_percent; |
107 | cache->fcull = stats.f_files * cache->fcull_percent; |
108 | cache->frun = stats.f_files * cache->frun_percent; |
109 | |
110 | _debug("limits {%llu,%llu,%llu} files" , |
111 | (unsigned long long) cache->frun, |
112 | (unsigned long long) cache->fcull, |
113 | (unsigned long long) cache->fstop); |
114 | |
115 | do_div(stats.f_blocks, 100); |
116 | cache->bstop = stats.f_blocks * cache->bstop_percent; |
117 | cache->bcull = stats.f_blocks * cache->bcull_percent; |
118 | cache->brun = stats.f_blocks * cache->brun_percent; |
119 | |
120 | _debug("limits {%llu,%llu,%llu} blocks" , |
121 | (unsigned long long) cache->brun, |
122 | (unsigned long long) cache->bcull, |
123 | (unsigned long long) cache->bstop); |
124 | |
125 | /* get the cache directory and check its type */ |
126 | cachedir = cachefiles_get_directory(cache, dir: root, name: "cache" , NULL); |
127 | if (IS_ERR(ptr: cachedir)) { |
128 | ret = PTR_ERR(ptr: cachedir); |
129 | goto error_unsupported; |
130 | } |
131 | |
132 | cache->store = cachedir; |
133 | |
134 | /* get the graveyard directory */ |
135 | graveyard = cachefiles_get_directory(cache, dir: root, name: "graveyard" , NULL); |
136 | if (IS_ERR(ptr: graveyard)) { |
137 | ret = PTR_ERR(ptr: graveyard); |
138 | goto error_unsupported; |
139 | } |
140 | |
141 | cache->graveyard = graveyard; |
142 | cache->cache = cache_cookie; |
143 | |
144 | ret = fscache_add_cache(cache: cache_cookie, ops: &cachefiles_cache_ops, cache_priv: cache); |
145 | if (ret < 0) |
146 | goto error_add_cache; |
147 | |
148 | /* done */ |
149 | set_bit(CACHEFILES_READY, addr: &cache->flags); |
150 | dput(root); |
151 | |
152 | pr_info("File cache on %s registered\n" , cache_cookie->name); |
153 | |
154 | /* check how much space the cache has */ |
155 | cachefiles_has_space(cache, fnr: 0, bnr: 0, reason: cachefiles_has_space_check); |
156 | cachefiles_end_secure(cache, saved_cred); |
157 | _leave(" = 0 [%px]" , cache->cache); |
158 | return 0; |
159 | |
160 | error_add_cache: |
161 | cachefiles_put_directory(dir: cache->graveyard); |
162 | cache->graveyard = NULL; |
163 | error_unsupported: |
164 | cachefiles_put_directory(dir: cache->store); |
165 | cache->store = NULL; |
166 | mntput(mnt: cache->mnt); |
167 | cache->mnt = NULL; |
168 | dput(root); |
169 | error_open_root: |
170 | cachefiles_end_secure(cache, saved_cred); |
171 | error_getsec: |
172 | fscache_relinquish_cache(cache: cache_cookie); |
173 | cache->cache = NULL; |
174 | pr_err("Failed to register: %d\n" , ret); |
175 | return ret; |
176 | } |
177 | |
178 | /* |
179 | * See if we have space for a number of pages and/or a number of files in the |
180 | * cache |
181 | */ |
182 | int cachefiles_has_space(struct cachefiles_cache *cache, |
183 | unsigned fnr, unsigned bnr, |
184 | enum cachefiles_has_space_for reason) |
185 | { |
186 | struct kstatfs stats; |
187 | u64 b_avail, b_writing; |
188 | int ret; |
189 | |
190 | struct path path = { |
191 | .mnt = cache->mnt, |
192 | .dentry = cache->mnt->mnt_root, |
193 | }; |
194 | |
195 | //_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u", |
196 | // (unsigned long long) cache->frun, |
197 | // (unsigned long long) cache->fcull, |
198 | // (unsigned long long) cache->fstop, |
199 | // (unsigned long long) cache->brun, |
200 | // (unsigned long long) cache->bcull, |
201 | // (unsigned long long) cache->bstop, |
202 | // fnr, bnr); |
203 | |
204 | /* find out how many pages of blockdev are available */ |
205 | memset(&stats, 0, sizeof(stats)); |
206 | |
207 | ret = vfs_statfs(&path, &stats); |
208 | if (ret < 0) { |
209 | trace_cachefiles_vfs_error(NULL, backer: d_inode(dentry: path.dentry), error: ret, |
210 | where: cachefiles_trace_statfs_error); |
211 | if (ret == -EIO) |
212 | cachefiles_io_error(cache, "statfs failed" ); |
213 | _leave(" = %d" , ret); |
214 | return ret; |
215 | } |
216 | |
217 | b_avail = stats.f_bavail; |
218 | b_writing = atomic_long_read(v: &cache->b_writing); |
219 | if (b_avail > b_writing) |
220 | b_avail -= b_writing; |
221 | else |
222 | b_avail = 0; |
223 | |
224 | //_debug("avail %llu,%llu", |
225 | // (unsigned long long)stats.f_ffree, |
226 | // (unsigned long long)b_avail); |
227 | |
228 | /* see if there is sufficient space */ |
229 | if (stats.f_ffree > fnr) |
230 | stats.f_ffree -= fnr; |
231 | else |
232 | stats.f_ffree = 0; |
233 | |
234 | if (b_avail > bnr) |
235 | b_avail -= bnr; |
236 | else |
237 | b_avail = 0; |
238 | |
239 | ret = -ENOBUFS; |
240 | if (stats.f_ffree < cache->fstop || |
241 | b_avail < cache->bstop) |
242 | goto stop_and_begin_cull; |
243 | |
244 | ret = 0; |
245 | if (stats.f_ffree < cache->fcull || |
246 | b_avail < cache->bcull) |
247 | goto begin_cull; |
248 | |
249 | if (test_bit(CACHEFILES_CULLING, &cache->flags) && |
250 | stats.f_ffree >= cache->frun && |
251 | b_avail >= cache->brun && |
252 | test_and_clear_bit(CACHEFILES_CULLING, addr: &cache->flags) |
253 | ) { |
254 | _debug("cease culling" ); |
255 | cachefiles_state_changed(cache); |
256 | } |
257 | |
258 | //_leave(" = 0"); |
259 | return 0; |
260 | |
261 | stop_and_begin_cull: |
262 | switch (reason) { |
263 | case cachefiles_has_space_for_write: |
264 | fscache_count_no_write_space(); |
265 | break; |
266 | case cachefiles_has_space_for_create: |
267 | fscache_count_no_create_space(); |
268 | break; |
269 | default: |
270 | break; |
271 | } |
272 | begin_cull: |
273 | if (!test_and_set_bit(CACHEFILES_CULLING, addr: &cache->flags)) { |
274 | _debug("### CULL CACHE ###" ); |
275 | cachefiles_state_changed(cache); |
276 | } |
277 | |
278 | _leave(" = %d" , ret); |
279 | return ret; |
280 | } |
281 | |
282 | /* |
283 | * Mark all the objects as being out of service and queue them all for cleanup. |
284 | */ |
285 | static void cachefiles_withdraw_objects(struct cachefiles_cache *cache) |
286 | { |
287 | struct cachefiles_object *object; |
288 | unsigned int count = 0; |
289 | |
290 | _enter("" ); |
291 | |
292 | spin_lock(lock: &cache->object_list_lock); |
293 | |
294 | while (!list_empty(head: &cache->object_list)) { |
295 | object = list_first_entry(&cache->object_list, |
296 | struct cachefiles_object, cache_link); |
297 | cachefiles_see_object(object, why: cachefiles_obj_see_withdrawal); |
298 | list_del_init(entry: &object->cache_link); |
299 | fscache_withdraw_cookie(cookie: object->cookie); |
300 | count++; |
301 | if ((count & 63) == 0) { |
302 | spin_unlock(lock: &cache->object_list_lock); |
303 | cond_resched(); |
304 | spin_lock(lock: &cache->object_list_lock); |
305 | } |
306 | } |
307 | |
308 | spin_unlock(lock: &cache->object_list_lock); |
309 | _leave(" [%u objs]" , count); |
310 | } |
311 | |
312 | /* |
313 | * Withdraw volumes. |
314 | */ |
315 | static void cachefiles_withdraw_volumes(struct cachefiles_cache *cache) |
316 | { |
317 | _enter("" ); |
318 | |
319 | for (;;) { |
320 | struct cachefiles_volume *volume = NULL; |
321 | |
322 | spin_lock(lock: &cache->object_list_lock); |
323 | if (!list_empty(head: &cache->volumes)) { |
324 | volume = list_first_entry(&cache->volumes, |
325 | struct cachefiles_volume, cache_link); |
326 | list_del_init(entry: &volume->cache_link); |
327 | } |
328 | spin_unlock(lock: &cache->object_list_lock); |
329 | if (!volume) |
330 | break; |
331 | |
332 | cachefiles_withdraw_volume(volume); |
333 | } |
334 | |
335 | _leave("" ); |
336 | } |
337 | |
338 | /* |
339 | * Sync a cache to backing disk. |
340 | */ |
341 | static void cachefiles_sync_cache(struct cachefiles_cache *cache) |
342 | { |
343 | const struct cred *saved_cred; |
344 | int ret; |
345 | |
346 | _enter("%s" , cache->cache->name); |
347 | |
348 | /* make sure all pages pinned by operations on behalf of the netfs are |
349 | * written to disc */ |
350 | cachefiles_begin_secure(cache, saved_cred: &saved_cred); |
351 | down_read(sem: &cache->mnt->mnt_sb->s_umount); |
352 | ret = sync_filesystem(cache->mnt->mnt_sb); |
353 | up_read(sem: &cache->mnt->mnt_sb->s_umount); |
354 | cachefiles_end_secure(cache, saved_cred); |
355 | |
356 | if (ret == -EIO) |
357 | cachefiles_io_error(cache, |
358 | "Attempt to sync backing fs superblock returned error %d" , |
359 | ret); |
360 | } |
361 | |
362 | /* |
363 | * Withdraw cache objects. |
364 | */ |
365 | void cachefiles_withdraw_cache(struct cachefiles_cache *cache) |
366 | { |
367 | struct fscache_cache *fscache = cache->cache; |
368 | |
369 | pr_info("File cache on %s unregistering\n" , fscache->name); |
370 | |
371 | fscache_withdraw_cache(cache: fscache); |
372 | |
373 | /* we now have to destroy all the active objects pertaining to this |
374 | * cache - which we do by passing them off to thread pool to be |
375 | * disposed of */ |
376 | cachefiles_withdraw_objects(cache); |
377 | fscache_wait_for_objects(cache: fscache); |
378 | |
379 | cachefiles_withdraw_volumes(cache); |
380 | cachefiles_sync_cache(cache); |
381 | cache->cache = NULL; |
382 | fscache_relinquish_cache(cache: fscache); |
383 | } |
384 | |