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 <trace/events/fscache.h> |
12 | #include "internal.h" |
13 | |
14 | /* |
15 | * Bring a cache online. |
16 | */ |
17 | int cachefiles_add_cache(struct cachefiles_cache *cache) |
18 | { |
19 | struct fscache_cache *cache_cookie; |
20 | struct path path; |
21 | struct kstatfs stats; |
22 | struct dentry *graveyard, *cachedir, *root; |
23 | const struct cred *saved_cred; |
24 | int ret; |
25 | |
26 | _enter("" ); |
27 | |
28 | cache_cookie = fscache_acquire_cache(name: cache->tag); |
29 | if (IS_ERR(ptr: cache_cookie)) |
30 | return PTR_ERR(ptr: cache_cookie); |
31 | |
32 | /* we want to work under the module's security ID */ |
33 | ret = cachefiles_get_security_ID(cache); |
34 | if (ret < 0) |
35 | goto error_getsec; |
36 | |
37 | cachefiles_begin_secure(cache, saved_cred: &saved_cred); |
38 | |
39 | /* look up the directory at the root of the cache */ |
40 | ret = kern_path(cache->rootdirname, LOOKUP_DIRECTORY, &path); |
41 | if (ret < 0) |
42 | goto error_open_root; |
43 | |
44 | cache->mnt = path.mnt; |
45 | root = path.dentry; |
46 | |
47 | ret = -EINVAL; |
48 | if (is_idmapped_mnt(mnt: path.mnt)) { |
49 | pr_warn("File cache on idmapped mounts not supported" ); |
50 | goto error_unsupported; |
51 | } |
52 | |
53 | /* Check features of the backing filesystem: |
54 | * - Directories must support looking up and directory creation |
55 | * - We create tmpfiles to handle invalidation |
56 | * - We use xattrs to store metadata |
57 | * - We need to be able to query the amount of space available |
58 | * - We want to be able to sync the filesystem when stopping the cache |
59 | * - We use DIO to/from pages, so the blocksize mustn't be too big. |
60 | */ |
61 | ret = -EOPNOTSUPP; |
62 | if (d_is_negative(dentry: root) || |
63 | !d_backing_inode(upper: root)->i_op->lookup || |
64 | !d_backing_inode(upper: root)->i_op->mkdir || |
65 | !d_backing_inode(upper: root)->i_op->tmpfile || |
66 | !(d_backing_inode(upper: root)->i_opflags & IOP_XATTR) || |
67 | !root->d_sb->s_op->statfs || |
68 | !root->d_sb->s_op->sync_fs || |
69 | root->d_sb->s_blocksize > PAGE_SIZE) |
70 | goto error_unsupported; |
71 | |
72 | ret = -EROFS; |
73 | if (sb_rdonly(sb: root->d_sb)) |
74 | goto error_unsupported; |
75 | |
76 | /* determine the security of the on-disk cache as this governs |
77 | * security ID of files we create */ |
78 | ret = cachefiles_determine_cache_security(cache, root, saved_cred: &saved_cred); |
79 | if (ret < 0) |
80 | goto error_unsupported; |
81 | |
82 | /* get the cache size and blocksize */ |
83 | ret = vfs_statfs(&path, &stats); |
84 | if (ret < 0) |
85 | goto error_unsupported; |
86 | |
87 | ret = -ERANGE; |
88 | if (stats.f_bsize <= 0) |
89 | goto error_unsupported; |
90 | |
91 | ret = -EOPNOTSUPP; |
92 | if (stats.f_bsize > PAGE_SIZE) |
93 | goto error_unsupported; |
94 | |
95 | cache->bsize = stats.f_bsize; |
96 | cache->bshift = ilog2(stats.f_bsize); |
97 | |
98 | _debug("blksize %u (shift %u)" , |
99 | cache->bsize, cache->bshift); |
100 | |
101 | _debug("size %llu, avail %llu" , |
102 | (unsigned long long) stats.f_blocks, |
103 | (unsigned long long) stats.f_bavail); |
104 | |
105 | /* set up caching limits */ |
106 | do_div(stats.f_files, 100); |
107 | cache->fstop = stats.f_files * cache->fstop_percent; |
108 | cache->fcull = stats.f_files * cache->fcull_percent; |
109 | cache->frun = stats.f_files * cache->frun_percent; |
110 | |
111 | _debug("limits {%llu,%llu,%llu} files" , |
112 | (unsigned long long) cache->frun, |
113 | (unsigned long long) cache->fcull, |
114 | (unsigned long long) cache->fstop); |
115 | |
116 | do_div(stats.f_blocks, 100); |
117 | cache->bstop = stats.f_blocks * cache->bstop_percent; |
118 | cache->bcull = stats.f_blocks * cache->bcull_percent; |
119 | cache->brun = stats.f_blocks * cache->brun_percent; |
120 | |
121 | _debug("limits {%llu,%llu,%llu} blocks" , |
122 | (unsigned long long) cache->brun, |
123 | (unsigned long long) cache->bcull, |
124 | (unsigned long long) cache->bstop); |
125 | |
126 | /* get the cache directory and check its type */ |
127 | cachedir = cachefiles_get_directory(cache, dir: root, name: "cache" , NULL); |
128 | if (IS_ERR(ptr: cachedir)) { |
129 | ret = PTR_ERR(ptr: cachedir); |
130 | goto error_unsupported; |
131 | } |
132 | |
133 | cache->store = cachedir; |
134 | |
135 | /* get the graveyard directory */ |
136 | graveyard = cachefiles_get_directory(cache, dir: root, name: "graveyard" , NULL); |
137 | if (IS_ERR(ptr: graveyard)) { |
138 | ret = PTR_ERR(ptr: graveyard); |
139 | goto error_unsupported; |
140 | } |
141 | |
142 | cache->graveyard = graveyard; |
143 | cache->cache = cache_cookie; |
144 | |
145 | ret = fscache_add_cache(cache: cache_cookie, ops: &cachefiles_cache_ops, cache_priv: cache); |
146 | if (ret < 0) |
147 | goto error_add_cache; |
148 | |
149 | /* done */ |
150 | set_bit(CACHEFILES_READY, addr: &cache->flags); |
151 | dput(root); |
152 | |
153 | pr_info("File cache on %s registered\n" , cache_cookie->name); |
154 | |
155 | /* check how much space the cache has */ |
156 | cachefiles_has_space(cache, fnr: 0, bnr: 0, reason: cachefiles_has_space_check); |
157 | cachefiles_end_secure(cache, saved_cred); |
158 | _leave(" = 0 [%px]" , cache->cache); |
159 | return 0; |
160 | |
161 | error_add_cache: |
162 | cachefiles_put_directory(dir: cache->graveyard); |
163 | cache->graveyard = NULL; |
164 | error_unsupported: |
165 | cachefiles_put_directory(dir: cache->store); |
166 | cache->store = NULL; |
167 | mntput(mnt: cache->mnt); |
168 | cache->mnt = NULL; |
169 | dput(root); |
170 | error_open_root: |
171 | cachefiles_end_secure(cache, saved_cred); |
172 | put_cred(cred: cache->cache_cred); |
173 | cache->cache_cred = NULL; |
174 | error_getsec: |
175 | fscache_relinquish_cache(cache: cache_cookie); |
176 | cache->cache = NULL; |
177 | pr_err("Failed to register: %d\n" , ret); |
178 | return ret; |
179 | } |
180 | |
181 | /* |
182 | * See if we have space for a number of pages and/or a number of files in the |
183 | * cache |
184 | */ |
185 | int cachefiles_has_space(struct cachefiles_cache *cache, |
186 | unsigned fnr, unsigned bnr, |
187 | enum cachefiles_has_space_for reason) |
188 | { |
189 | struct kstatfs stats; |
190 | u64 b_avail, b_writing; |
191 | int ret; |
192 | |
193 | struct path path = { |
194 | .mnt = cache->mnt, |
195 | .dentry = cache->mnt->mnt_root, |
196 | }; |
197 | |
198 | //_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u", |
199 | // (unsigned long long) cache->frun, |
200 | // (unsigned long long) cache->fcull, |
201 | // (unsigned long long) cache->fstop, |
202 | // (unsigned long long) cache->brun, |
203 | // (unsigned long long) cache->bcull, |
204 | // (unsigned long long) cache->bstop, |
205 | // fnr, bnr); |
206 | |
207 | /* find out how many pages of blockdev are available */ |
208 | memset(&stats, 0, sizeof(stats)); |
209 | |
210 | ret = vfs_statfs(&path, &stats); |
211 | if (ret < 0) { |
212 | trace_cachefiles_vfs_error(NULL, backer: d_inode(dentry: path.dentry), error: ret, |
213 | where: cachefiles_trace_statfs_error); |
214 | if (ret == -EIO) |
215 | cachefiles_io_error(cache, "statfs failed" ); |
216 | _leave(" = %d" , ret); |
217 | return ret; |
218 | } |
219 | |
220 | b_avail = stats.f_bavail; |
221 | b_writing = atomic_long_read(v: &cache->b_writing); |
222 | if (b_avail > b_writing) |
223 | b_avail -= b_writing; |
224 | else |
225 | b_avail = 0; |
226 | |
227 | //_debug("avail %llu,%llu", |
228 | // (unsigned long long)stats.f_ffree, |
229 | // (unsigned long long)b_avail); |
230 | |
231 | /* see if there is sufficient space */ |
232 | if (stats.f_ffree > fnr) |
233 | stats.f_ffree -= fnr; |
234 | else |
235 | stats.f_ffree = 0; |
236 | |
237 | if (b_avail > bnr) |
238 | b_avail -= bnr; |
239 | else |
240 | b_avail = 0; |
241 | |
242 | ret = -ENOBUFS; |
243 | if (stats.f_ffree < cache->fstop || |
244 | b_avail < cache->bstop) |
245 | goto stop_and_begin_cull; |
246 | |
247 | ret = 0; |
248 | if (stats.f_ffree < cache->fcull || |
249 | b_avail < cache->bcull) |
250 | goto begin_cull; |
251 | |
252 | if (test_bit(CACHEFILES_CULLING, &cache->flags) && |
253 | stats.f_ffree >= cache->frun && |
254 | b_avail >= cache->brun && |
255 | test_and_clear_bit(CACHEFILES_CULLING, addr: &cache->flags) |
256 | ) { |
257 | _debug("cease culling" ); |
258 | cachefiles_state_changed(cache); |
259 | } |
260 | |
261 | //_leave(" = 0"); |
262 | return 0; |
263 | |
264 | stop_and_begin_cull: |
265 | switch (reason) { |
266 | case cachefiles_has_space_for_write: |
267 | fscache_count_no_write_space(); |
268 | break; |
269 | case cachefiles_has_space_for_create: |
270 | fscache_count_no_create_space(); |
271 | break; |
272 | default: |
273 | break; |
274 | } |
275 | begin_cull: |
276 | if (!test_and_set_bit(CACHEFILES_CULLING, addr: &cache->flags)) { |
277 | _debug("### CULL CACHE ###" ); |
278 | cachefiles_state_changed(cache); |
279 | } |
280 | |
281 | _leave(" = %d" , ret); |
282 | return ret; |
283 | } |
284 | |
285 | /* |
286 | * Mark all the objects as being out of service and queue them all for cleanup. |
287 | */ |
288 | static void cachefiles_withdraw_objects(struct cachefiles_cache *cache) |
289 | { |
290 | struct cachefiles_object *object; |
291 | unsigned int count = 0; |
292 | |
293 | _enter("" ); |
294 | |
295 | spin_lock(lock: &cache->object_list_lock); |
296 | |
297 | while (!list_empty(head: &cache->object_list)) { |
298 | object = list_first_entry(&cache->object_list, |
299 | struct cachefiles_object, cache_link); |
300 | cachefiles_see_object(object, why: cachefiles_obj_see_withdrawal); |
301 | list_del_init(entry: &object->cache_link); |
302 | fscache_withdraw_cookie(cookie: object->cookie); |
303 | count++; |
304 | if ((count & 63) == 0) { |
305 | spin_unlock(lock: &cache->object_list_lock); |
306 | cond_resched(); |
307 | spin_lock(lock: &cache->object_list_lock); |
308 | } |
309 | } |
310 | |
311 | spin_unlock(lock: &cache->object_list_lock); |
312 | _leave(" [%u objs]" , count); |
313 | } |
314 | |
315 | /* |
316 | * Withdraw fscache volumes. |
317 | */ |
318 | static void cachefiles_withdraw_fscache_volumes(struct cachefiles_cache *cache) |
319 | { |
320 | struct list_head *cur; |
321 | struct cachefiles_volume *volume; |
322 | struct fscache_volume *vcookie; |
323 | |
324 | _enter("" ); |
325 | retry: |
326 | spin_lock(lock: &cache->object_list_lock); |
327 | list_for_each(cur, &cache->volumes) { |
328 | volume = list_entry(cur, struct cachefiles_volume, cache_link); |
329 | |
330 | if (atomic_read(v: &volume->vcookie->n_accesses) == 0) |
331 | continue; |
332 | |
333 | vcookie = fscache_try_get_volume(volume: volume->vcookie, |
334 | where: fscache_volume_get_withdraw); |
335 | if (vcookie) { |
336 | spin_unlock(lock: &cache->object_list_lock); |
337 | fscache_withdraw_volume(volume: vcookie); |
338 | fscache_put_volume(volume: vcookie, where: fscache_volume_put_withdraw); |
339 | goto retry; |
340 | } |
341 | } |
342 | spin_unlock(lock: &cache->object_list_lock); |
343 | |
344 | _leave("" ); |
345 | } |
346 | |
347 | /* |
348 | * Withdraw cachefiles volumes. |
349 | */ |
350 | static void cachefiles_withdraw_volumes(struct cachefiles_cache *cache) |
351 | { |
352 | _enter("" ); |
353 | |
354 | for (;;) { |
355 | struct fscache_volume *vcookie = NULL; |
356 | struct cachefiles_volume *volume = NULL; |
357 | |
358 | spin_lock(lock: &cache->object_list_lock); |
359 | if (!list_empty(head: &cache->volumes)) { |
360 | volume = list_first_entry(&cache->volumes, |
361 | struct cachefiles_volume, cache_link); |
362 | vcookie = fscache_try_get_volume(volume: volume->vcookie, |
363 | where: fscache_volume_get_withdraw); |
364 | if (!vcookie) { |
365 | spin_unlock(lock: &cache->object_list_lock); |
366 | cpu_relax(); |
367 | continue; |
368 | } |
369 | list_del_init(entry: &volume->cache_link); |
370 | } |
371 | spin_unlock(lock: &cache->object_list_lock); |
372 | if (!volume) |
373 | break; |
374 | |
375 | cachefiles_withdraw_volume(volume); |
376 | fscache_put_volume(volume: vcookie, where: fscache_volume_put_withdraw); |
377 | } |
378 | |
379 | _leave("" ); |
380 | } |
381 | |
382 | /* |
383 | * Sync a cache to backing disk. |
384 | */ |
385 | static void cachefiles_sync_cache(struct cachefiles_cache *cache) |
386 | { |
387 | const struct cred *saved_cred; |
388 | int ret; |
389 | |
390 | _enter("%s" , cache->cache->name); |
391 | |
392 | /* make sure all pages pinned by operations on behalf of the netfs are |
393 | * written to disc */ |
394 | cachefiles_begin_secure(cache, saved_cred: &saved_cred); |
395 | down_read(sem: &cache->mnt->mnt_sb->s_umount); |
396 | ret = sync_filesystem(cache->mnt->mnt_sb); |
397 | up_read(sem: &cache->mnt->mnt_sb->s_umount); |
398 | cachefiles_end_secure(cache, saved_cred); |
399 | |
400 | if (ret == -EIO) |
401 | cachefiles_io_error(cache, |
402 | "Attempt to sync backing fs superblock returned error %d" , |
403 | ret); |
404 | } |
405 | |
406 | /* |
407 | * Withdraw cache objects. |
408 | */ |
409 | void cachefiles_withdraw_cache(struct cachefiles_cache *cache) |
410 | { |
411 | struct fscache_cache *fscache = cache->cache; |
412 | |
413 | pr_info("File cache on %s unregistering\n" , fscache->name); |
414 | |
415 | fscache_withdraw_cache(cache: fscache); |
416 | cachefiles_withdraw_fscache_volumes(cache); |
417 | |
418 | /* we now have to destroy all the active objects pertaining to this |
419 | * cache - which we do by passing them off to thread pool to be |
420 | * disposed of */ |
421 | cachefiles_withdraw_objects(cache); |
422 | fscache_wait_for_objects(cache: fscache); |
423 | |
424 | cachefiles_withdraw_volumes(cache); |
425 | cachefiles_sync_cache(cache); |
426 | cache->cache = NULL; |
427 | fscache_relinquish_cache(cache: fscache); |
428 | } |
429 | |