1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * In memory quota format relies on quota infrastructure to store dquot |
4 | * information for us. While conventional quota formats for file systems |
5 | * with persistent storage can load quota information into dquot from the |
6 | * storage on-demand and hence quota dquot shrinker can free any dquot |
7 | * that is not currently being used, it must be avoided here. Otherwise we |
8 | * can lose valuable information, user provided limits, because there is |
9 | * no persistent storage to load the information from afterwards. |
10 | * |
11 | * One information that in-memory quota format needs to keep track of is |
12 | * a sorted list of ids for each quota type. This is done by utilizing |
13 | * an rb tree which root is stored in mem_dqinfo->dqi_priv for each quota |
14 | * type. |
15 | * |
16 | * This format can be used to support quota on file system without persistent |
17 | * storage such as tmpfs. |
18 | * |
19 | * Author: Lukas Czerner <lczerner@redhat.com> |
20 | * Carlos Maiolino <cmaiolino@redhat.com> |
21 | * |
22 | * Copyright (C) 2023 Red Hat, Inc. |
23 | */ |
24 | #include <linux/errno.h> |
25 | #include <linux/fs.h> |
26 | #include <linux/mount.h> |
27 | #include <linux/kernel.h> |
28 | #include <linux/init.h> |
29 | #include <linux/module.h> |
30 | #include <linux/slab.h> |
31 | #include <linux/rbtree.h> |
32 | #include <linux/shmem_fs.h> |
33 | |
34 | #include <linux/quotaops.h> |
35 | #include <linux/quota.h> |
36 | |
37 | #ifdef CONFIG_TMPFS_QUOTA |
38 | |
39 | /* |
40 | * The following constants define the amount of time given a user |
41 | * before the soft limits are treated as hard limits (usually resulting |
42 | * in an allocation failure). The timer is started when the user crosses |
43 | * their soft limit, it is reset when they go below their soft limit. |
44 | */ |
45 | #define SHMEM_MAX_IQ_TIME 604800 /* (7*24*60*60) 1 week */ |
46 | #define SHMEM_MAX_DQ_TIME 604800 /* (7*24*60*60) 1 week */ |
47 | |
48 | struct quota_id { |
49 | struct rb_node node; |
50 | qid_t id; |
51 | qsize_t bhardlimit; |
52 | qsize_t bsoftlimit; |
53 | qsize_t ihardlimit; |
54 | qsize_t isoftlimit; |
55 | }; |
56 | |
57 | static int shmem_check_quota_file(struct super_block *sb, int type) |
58 | { |
59 | /* There is no real quota file, nothing to do */ |
60 | return 1; |
61 | } |
62 | |
63 | /* |
64 | * There is no real quota file. Just allocate rb_root for quota ids and |
65 | * set limits |
66 | */ |
67 | static int shmem_read_file_info(struct super_block *sb, int type) |
68 | { |
69 | struct quota_info *dqopt = sb_dqopt(sb); |
70 | struct mem_dqinfo *info = &dqopt->info[type]; |
71 | |
72 | info->dqi_priv = kzalloc(size: sizeof(struct rb_root), GFP_NOFS); |
73 | if (!info->dqi_priv) |
74 | return -ENOMEM; |
75 | |
76 | info->dqi_max_spc_limit = SHMEM_QUOTA_MAX_SPC_LIMIT; |
77 | info->dqi_max_ino_limit = SHMEM_QUOTA_MAX_INO_LIMIT; |
78 | |
79 | info->dqi_bgrace = SHMEM_MAX_DQ_TIME; |
80 | info->dqi_igrace = SHMEM_MAX_IQ_TIME; |
81 | info->dqi_flags = 0; |
82 | |
83 | return 0; |
84 | } |
85 | |
86 | static int shmem_write_file_info(struct super_block *sb, int type) |
87 | { |
88 | /* There is no real quota file, nothing to do */ |
89 | return 0; |
90 | } |
91 | |
92 | /* |
93 | * Free all the quota_id entries in the rb tree and rb_root. |
94 | */ |
95 | static int shmem_free_file_info(struct super_block *sb, int type) |
96 | { |
97 | struct mem_dqinfo *info = &sb_dqopt(sb)->info[type]; |
98 | struct rb_root *root = info->dqi_priv; |
99 | struct quota_id *entry; |
100 | struct rb_node *node; |
101 | |
102 | info->dqi_priv = NULL; |
103 | node = rb_first(root); |
104 | while (node) { |
105 | entry = rb_entry(node, struct quota_id, node); |
106 | node = rb_next(&entry->node); |
107 | |
108 | rb_erase(&entry->node, root); |
109 | kfree(objp: entry); |
110 | } |
111 | |
112 | kfree(objp: root); |
113 | return 0; |
114 | } |
115 | |
116 | static int shmem_get_next_id(struct super_block *sb, struct kqid *qid) |
117 | { |
118 | struct mem_dqinfo *info = sb_dqinfo(sb, type: qid->type); |
119 | struct rb_node *node = ((struct rb_root *)info->dqi_priv)->rb_node; |
120 | qid_t id = from_kqid(to: &init_user_ns, qid: *qid); |
121 | struct quota_info *dqopt = sb_dqopt(sb); |
122 | struct quota_id *entry = NULL; |
123 | int ret = 0; |
124 | |
125 | if (!sb_has_quota_active(sb, type: qid->type)) |
126 | return -ESRCH; |
127 | |
128 | down_read(sem: &dqopt->dqio_sem); |
129 | while (node) { |
130 | entry = rb_entry(node, struct quota_id, node); |
131 | |
132 | if (id < entry->id) |
133 | node = node->rb_left; |
134 | else if (id > entry->id) |
135 | node = node->rb_right; |
136 | else |
137 | goto got_next_id; |
138 | } |
139 | |
140 | if (!entry) { |
141 | ret = -ENOENT; |
142 | goto out_unlock; |
143 | } |
144 | |
145 | if (id > entry->id) { |
146 | node = rb_next(&entry->node); |
147 | if (!node) { |
148 | ret = -ENOENT; |
149 | goto out_unlock; |
150 | } |
151 | entry = rb_entry(node, struct quota_id, node); |
152 | } |
153 | |
154 | got_next_id: |
155 | *qid = make_kqid(from: &init_user_ns, type: qid->type, qid: entry->id); |
156 | out_unlock: |
157 | up_read(sem: &dqopt->dqio_sem); |
158 | return ret; |
159 | } |
160 | |
161 | /* |
162 | * Load dquot with limits from existing entry, or create the new entry if |
163 | * it does not exist. |
164 | */ |
165 | static int shmem_acquire_dquot(struct dquot *dquot) |
166 | { |
167 | struct mem_dqinfo *info = sb_dqinfo(sb: dquot->dq_sb, type: dquot->dq_id.type); |
168 | struct rb_node **n = &((struct rb_root *)info->dqi_priv)->rb_node; |
169 | struct shmem_sb_info *sbinfo = dquot->dq_sb->s_fs_info; |
170 | struct rb_node *parent = NULL, *new_node = NULL; |
171 | struct quota_id *new_entry, *entry; |
172 | qid_t id = from_kqid(to: &init_user_ns, qid: dquot->dq_id); |
173 | struct quota_info *dqopt = sb_dqopt(sb: dquot->dq_sb); |
174 | int ret = 0; |
175 | |
176 | mutex_lock(&dquot->dq_lock); |
177 | |
178 | down_write(sem: &dqopt->dqio_sem); |
179 | while (*n) { |
180 | parent = *n; |
181 | entry = rb_entry(parent, struct quota_id, node); |
182 | |
183 | if (id < entry->id) |
184 | n = &(*n)->rb_left; |
185 | else if (id > entry->id) |
186 | n = &(*n)->rb_right; |
187 | else |
188 | goto found; |
189 | } |
190 | |
191 | /* We don't have entry for this id yet, create it */ |
192 | new_entry = kzalloc(size: sizeof(struct quota_id), GFP_NOFS); |
193 | if (!new_entry) { |
194 | ret = -ENOMEM; |
195 | goto out_unlock; |
196 | } |
197 | |
198 | new_entry->id = id; |
199 | if (dquot->dq_id.type == USRQUOTA) { |
200 | new_entry->bhardlimit = sbinfo->qlimits.usrquota_bhardlimit; |
201 | new_entry->ihardlimit = sbinfo->qlimits.usrquota_ihardlimit; |
202 | } else if (dquot->dq_id.type == GRPQUOTA) { |
203 | new_entry->bhardlimit = sbinfo->qlimits.grpquota_bhardlimit; |
204 | new_entry->ihardlimit = sbinfo->qlimits.grpquota_ihardlimit; |
205 | } |
206 | |
207 | new_node = &new_entry->node; |
208 | rb_link_node(node: new_node, parent, rb_link: n); |
209 | rb_insert_color(new_node, (struct rb_root *)info->dqi_priv); |
210 | entry = new_entry; |
211 | |
212 | found: |
213 | /* Load the stored limits from the tree */ |
214 | spin_lock(lock: &dquot->dq_dqb_lock); |
215 | dquot->dq_dqb.dqb_bhardlimit = entry->bhardlimit; |
216 | dquot->dq_dqb.dqb_bsoftlimit = entry->bsoftlimit; |
217 | dquot->dq_dqb.dqb_ihardlimit = entry->ihardlimit; |
218 | dquot->dq_dqb.dqb_isoftlimit = entry->isoftlimit; |
219 | |
220 | if (!dquot->dq_dqb.dqb_bhardlimit && |
221 | !dquot->dq_dqb.dqb_bsoftlimit && |
222 | !dquot->dq_dqb.dqb_ihardlimit && |
223 | !dquot->dq_dqb.dqb_isoftlimit) |
224 | set_bit(DQ_FAKE_B, addr: &dquot->dq_flags); |
225 | spin_unlock(lock: &dquot->dq_dqb_lock); |
226 | |
227 | /* Make sure flags update is visible after dquot has been filled */ |
228 | smp_mb__before_atomic(); |
229 | set_bit(DQ_ACTIVE_B, addr: &dquot->dq_flags); |
230 | out_unlock: |
231 | up_write(sem: &dqopt->dqio_sem); |
232 | mutex_unlock(lock: &dquot->dq_lock); |
233 | return ret; |
234 | } |
235 | |
236 | static bool shmem_is_empty_dquot(struct dquot *dquot) |
237 | { |
238 | struct shmem_sb_info *sbinfo = dquot->dq_sb->s_fs_info; |
239 | qsize_t bhardlimit; |
240 | qsize_t ihardlimit; |
241 | |
242 | if (dquot->dq_id.type == USRQUOTA) { |
243 | bhardlimit = sbinfo->qlimits.usrquota_bhardlimit; |
244 | ihardlimit = sbinfo->qlimits.usrquota_ihardlimit; |
245 | } else if (dquot->dq_id.type == GRPQUOTA) { |
246 | bhardlimit = sbinfo->qlimits.grpquota_bhardlimit; |
247 | ihardlimit = sbinfo->qlimits.grpquota_ihardlimit; |
248 | } |
249 | |
250 | if (test_bit(DQ_FAKE_B, &dquot->dq_flags) || |
251 | (dquot->dq_dqb.dqb_curspace == 0 && |
252 | dquot->dq_dqb.dqb_curinodes == 0 && |
253 | dquot->dq_dqb.dqb_bhardlimit == bhardlimit && |
254 | dquot->dq_dqb.dqb_ihardlimit == ihardlimit)) |
255 | return true; |
256 | |
257 | return false; |
258 | } |
259 | /* |
260 | * Store limits from dquot in the tree unless it's fake. If it is fake |
261 | * remove the id from the tree since there is no useful information in |
262 | * there. |
263 | */ |
264 | static int shmem_release_dquot(struct dquot *dquot) |
265 | { |
266 | struct mem_dqinfo *info = sb_dqinfo(sb: dquot->dq_sb, type: dquot->dq_id.type); |
267 | struct rb_node *node = ((struct rb_root *)info->dqi_priv)->rb_node; |
268 | qid_t id = from_kqid(to: &init_user_ns, qid: dquot->dq_id); |
269 | struct quota_info *dqopt = sb_dqopt(sb: dquot->dq_sb); |
270 | struct quota_id *entry = NULL; |
271 | |
272 | mutex_lock(&dquot->dq_lock); |
273 | /* Check whether we are not racing with some other dqget() */ |
274 | if (dquot_is_busy(dquot)) |
275 | goto out_dqlock; |
276 | |
277 | down_write(sem: &dqopt->dqio_sem); |
278 | while (node) { |
279 | entry = rb_entry(node, struct quota_id, node); |
280 | |
281 | if (id < entry->id) |
282 | node = node->rb_left; |
283 | else if (id > entry->id) |
284 | node = node->rb_right; |
285 | else |
286 | goto found; |
287 | } |
288 | |
289 | /* We should always find the entry in the rb tree */ |
290 | WARN_ONCE(1, "quota id %u from dquot %p, not in rb tree!\n" , id, dquot); |
291 | up_write(sem: &dqopt->dqio_sem); |
292 | mutex_unlock(lock: &dquot->dq_lock); |
293 | return -ENOENT; |
294 | |
295 | found: |
296 | if (shmem_is_empty_dquot(dquot)) { |
297 | /* Remove entry from the tree */ |
298 | rb_erase(&entry->node, info->dqi_priv); |
299 | kfree(objp: entry); |
300 | } else { |
301 | /* Store the limits in the tree */ |
302 | spin_lock(lock: &dquot->dq_dqb_lock); |
303 | entry->bhardlimit = dquot->dq_dqb.dqb_bhardlimit; |
304 | entry->bsoftlimit = dquot->dq_dqb.dqb_bsoftlimit; |
305 | entry->ihardlimit = dquot->dq_dqb.dqb_ihardlimit; |
306 | entry->isoftlimit = dquot->dq_dqb.dqb_isoftlimit; |
307 | spin_unlock(lock: &dquot->dq_dqb_lock); |
308 | } |
309 | |
310 | clear_bit(DQ_ACTIVE_B, addr: &dquot->dq_flags); |
311 | up_write(sem: &dqopt->dqio_sem); |
312 | |
313 | out_dqlock: |
314 | mutex_unlock(lock: &dquot->dq_lock); |
315 | return 0; |
316 | } |
317 | |
318 | static int shmem_mark_dquot_dirty(struct dquot *dquot) |
319 | { |
320 | return 0; |
321 | } |
322 | |
323 | static int shmem_dquot_write_info(struct super_block *sb, int type) |
324 | { |
325 | return 0; |
326 | } |
327 | |
328 | static const struct quota_format_ops shmem_format_ops = { |
329 | .check_quota_file = shmem_check_quota_file, |
330 | .read_file_info = shmem_read_file_info, |
331 | .write_file_info = shmem_write_file_info, |
332 | .free_file_info = shmem_free_file_info, |
333 | }; |
334 | |
335 | struct quota_format_type shmem_quota_format = { |
336 | .qf_fmt_id = QFMT_SHMEM, |
337 | .qf_ops = &shmem_format_ops, |
338 | .qf_owner = THIS_MODULE |
339 | }; |
340 | |
341 | const struct dquot_operations shmem_quota_operations = { |
342 | .acquire_dquot = shmem_acquire_dquot, |
343 | .release_dquot = shmem_release_dquot, |
344 | .alloc_dquot = dquot_alloc, |
345 | .destroy_dquot = dquot_destroy, |
346 | .write_info = shmem_dquot_write_info, |
347 | .mark_dirty = shmem_mark_dquot_dirty, |
348 | .get_next_id = shmem_get_next_id, |
349 | }; |
350 | #endif /* CONFIG_TMPFS_QUOTA */ |
351 | |