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356 lines · 9.5 KiB

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 <[email protected]>
20 * Carlos Maiolino <[email protected]>
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#include <linux/magic.h>
34
35#include <linux/quotaops.h>
36#include <linux/quota.h>
37
38/*
39 * The following constants define the amount of time given a user
40 * before the soft limits are treated as hard limits (usually resulting
41 * in an allocation failure). The timer is started when the user crosses
42 * their soft limit, it is reset when they go below their soft limit.
43 */
44#define SHMEM_MAX_IQ_TIME 604800 /* (7*24*60*60) 1 week */
45#define SHMEM_MAX_DQ_TIME 604800 /* (7*24*60*60) 1 week */
46
47struct quota_id {
48 struct rb_node node;
49 qid_t id;
50 qsize_t bhardlimit;
51 qsize_t bsoftlimit;
52 qsize_t ihardlimit;
53 qsize_t isoftlimit;
54};
55
56static int shmem_check_quota_file(struct super_block *sb, int type)
57{
58 /* Verify enabling happens on tmpfs superblock */
59 if (sb->s_magic != TMPFS_MAGIC)
60 return 0;
61
62 /* There is no real quota file, nothing to do */
63 return 1;
64}
65
66/*
67 * There is no real quota file. Just allocate rb_root for quota ids and
68 * set limits
69 */
70static int shmem_read_file_info(struct super_block *sb, int type)
71{
72 struct quota_info *dqopt = sb_dqopt(sb);
73 struct mem_dqinfo *info = &dqopt->info[type];
74
75 info->dqi_priv = kzalloc_obj(struct rb_root, GFP_NOFS);
76 if (!info->dqi_priv)
77 return -ENOMEM;
78
79 info->dqi_max_spc_limit = SHMEM_QUOTA_MAX_SPC_LIMIT;
80 info->dqi_max_ino_limit = SHMEM_QUOTA_MAX_INO_LIMIT;
81
82 info->dqi_bgrace = SHMEM_MAX_DQ_TIME;
83 info->dqi_igrace = SHMEM_MAX_IQ_TIME;
84 info->dqi_flags = 0;
85
86 return 0;
87}
88
89static int shmem_write_file_info(struct super_block *sb, int type)
90{
91 /* There is no real quota file, nothing to do */
92 return 0;
93}
94
95/*
96 * Free all the quota_id entries in the rb tree and rb_root.
97 */
98static int shmem_free_file_info(struct super_block *sb, int type)
99{
100 struct mem_dqinfo *info = &sb_dqopt(sb)->info[type];
101 struct rb_root *root = info->dqi_priv;
102 struct quota_id *entry;
103 struct rb_node *node;
104
105 info->dqi_priv = NULL;
106 node = rb_first(root);
107 while (node) {
108 entry = rb_entry(node, struct quota_id, node);
109 node = rb_next(&entry->node);
110
111 rb_erase(&entry->node, root);
112 kfree(entry);
113 }
114
115 kfree(root);
116 return 0;
117}
118
119static int shmem_get_next_id(struct super_block *sb, struct kqid *qid)
120{
121 struct mem_dqinfo *info = sb_dqinfo(sb, qid->type);
122 struct rb_node *node;
123 qid_t id = from_kqid(&init_user_ns, *qid);
124 struct quota_info *dqopt = sb_dqopt(sb);
125 struct quota_id *entry = NULL;
126 int ret = 0;
127
128 if (!sb_has_quota_active(sb, qid->type))
129 return -ESRCH;
130
131 down_read(&dqopt->dqio_sem);
132 node = ((struct rb_root *)info->dqi_priv)->rb_node;
133 while (node) {
134 entry = rb_entry(node, struct quota_id, node);
135
136 if (id < entry->id)
137 node = node->rb_left;
138 else if (id > entry->id)
139 node = node->rb_right;
140 else
141 goto got_next_id;
142 }
143
144 if (!entry) {
145 ret = -ENOENT;
146 goto out_unlock;
147 }
148
149 if (id > entry->id) {
150 node = rb_next(&entry->node);
151 if (!node) {
152 ret = -ENOENT;
153 goto out_unlock;
154 }
155 entry = rb_entry(node, struct quota_id, node);
156 }
157
158got_next_id:
159 *qid = make_kqid(&init_user_ns, qid->type, entry->id);
160out_unlock:
161 up_read(&dqopt->dqio_sem);
162 return ret;
163}
164
165/*
166 * Load dquot with limits from existing entry, or create the new entry if
167 * it does not exist.
168 */
169static int shmem_acquire_dquot(struct dquot *dquot)
170{
171 struct mem_dqinfo *info = sb_dqinfo(dquot->dq_sb, dquot->dq_id.type);
172 struct rb_node **n;
173 struct shmem_sb_info *sbinfo = dquot->dq_sb->s_fs_info;
174 struct rb_node *parent = NULL, *new_node = NULL;
175 struct quota_id *new_entry, *entry;
176 qid_t id = from_kqid(&init_user_ns, dquot->dq_id);
177 struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);
178 int ret = 0;
179
180 mutex_lock(&dquot->dq_lock);
181
182 down_write(&dqopt->dqio_sem);
183 n = &((struct rb_root *)info->dqi_priv)->rb_node;
184
185 while (*n) {
186 parent = *n;
187 entry = rb_entry(parent, struct quota_id, node);
188
189 if (id < entry->id)
190 n = &(*n)->rb_left;
191 else if (id > entry->id)
192 n = &(*n)->rb_right;
193 else
194 goto found;
195 }
196
197 /* We don't have entry for this id yet, create it */
198 new_entry = kzalloc_obj(struct quota_id, GFP_NOFS);
199 if (!new_entry) {
200 ret = -ENOMEM;
201 goto out_unlock;
202 }
203
204 new_entry->id = id;
205 if (dquot->dq_id.type == USRQUOTA) {
206 new_entry->bhardlimit = sbinfo->qlimits.usrquota_bhardlimit;
207 new_entry->ihardlimit = sbinfo->qlimits.usrquota_ihardlimit;
208 } else if (dquot->dq_id.type == GRPQUOTA) {
209 new_entry->bhardlimit = sbinfo->qlimits.grpquota_bhardlimit;
210 new_entry->ihardlimit = sbinfo->qlimits.grpquota_ihardlimit;
211 }
212
213 new_node = &new_entry->node;
214 rb_link_node(new_node, parent, n);
215 rb_insert_color(new_node, (struct rb_root *)info->dqi_priv);
216 entry = new_entry;
217
218found:
219 /* Load the stored limits from the tree */
220 spin_lock(&dquot->dq_dqb_lock);
221 dquot->dq_dqb.dqb_bhardlimit = entry->bhardlimit;
222 dquot->dq_dqb.dqb_bsoftlimit = entry->bsoftlimit;
223 dquot->dq_dqb.dqb_ihardlimit = entry->ihardlimit;
224 dquot->dq_dqb.dqb_isoftlimit = entry->isoftlimit;
225
226 if (!dquot->dq_dqb.dqb_bhardlimit &&
227 !dquot->dq_dqb.dqb_bsoftlimit &&
228 !dquot->dq_dqb.dqb_ihardlimit &&
229 !dquot->dq_dqb.dqb_isoftlimit)
230 set_bit(DQ_FAKE_B, &dquot->dq_flags);
231 spin_unlock(&dquot->dq_dqb_lock);
232
233 /* Make sure flags update is visible after dquot has been filled */
234 smp_mb__before_atomic();
235 set_bit(DQ_ACTIVE_B, &dquot->dq_flags);
236out_unlock:
237 up_write(&dqopt->dqio_sem);
238 mutex_unlock(&dquot->dq_lock);
239 return ret;
240}
241
242static bool shmem_is_empty_dquot(struct dquot *dquot)
243{
244 struct shmem_sb_info *sbinfo = dquot->dq_sb->s_fs_info;
245 qsize_t bhardlimit;
246 qsize_t ihardlimit;
247
248 if (dquot->dq_id.type == USRQUOTA) {
249 bhardlimit = sbinfo->qlimits.usrquota_bhardlimit;
250 ihardlimit = sbinfo->qlimits.usrquota_ihardlimit;
251 } else if (dquot->dq_id.type == GRPQUOTA) {
252 bhardlimit = sbinfo->qlimits.grpquota_bhardlimit;
253 ihardlimit = sbinfo->qlimits.grpquota_ihardlimit;
254 }
255
256 if (test_bit(DQ_FAKE_B, &dquot->dq_flags) ||
257 (dquot->dq_dqb.dqb_curspace == 0 &&
258 dquot->dq_dqb.dqb_curinodes == 0 &&
259 dquot->dq_dqb.dqb_bhardlimit == bhardlimit &&
260 dquot->dq_dqb.dqb_ihardlimit == ihardlimit))
261 return true;
262
263 return false;
264}
265/*
266 * Store limits from dquot in the tree unless it's fake. If it is fake
267 * remove the id from the tree since there is no useful information in
268 * there.
269 */
270static int shmem_release_dquot(struct dquot *dquot)
271{
272 struct mem_dqinfo *info = sb_dqinfo(dquot->dq_sb, dquot->dq_id.type);
273 struct rb_node *node;
274 qid_t id = from_kqid(&init_user_ns, dquot->dq_id);
275 struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);
276 struct quota_id *entry = NULL;
277
278 mutex_lock(&dquot->dq_lock);
279 /* Check whether we are not racing with some other dqget() */
280 if (dquot_is_busy(dquot))
281 goto out_dqlock;
282
283 down_write(&dqopt->dqio_sem);
284 node = ((struct rb_root *)info->dqi_priv)->rb_node;
285 while (node) {
286 entry = rb_entry(node, struct quota_id, node);
287
288 if (id < entry->id)
289 node = node->rb_left;
290 else if (id > entry->id)
291 node = node->rb_right;
292 else
293 goto found;
294 }
295
296 /* We should always find the entry in the rb tree */
297 WARN_ONCE(1, "quota id %u from dquot %p, not in rb tree!\n", id, dquot);
298 up_write(&dqopt->dqio_sem);
299 mutex_unlock(&dquot->dq_lock);
300 return -ENOENT;
301
302found:
303 if (shmem_is_empty_dquot(dquot)) {
304 /* Remove entry from the tree */
305 rb_erase(&entry->node, info->dqi_priv);
306 kfree(entry);
307 } else {
308 /* Store the limits in the tree */
309 spin_lock(&dquot->dq_dqb_lock);
310 entry->bhardlimit = dquot->dq_dqb.dqb_bhardlimit;
311 entry->bsoftlimit = dquot->dq_dqb.dqb_bsoftlimit;
312 entry->ihardlimit = dquot->dq_dqb.dqb_ihardlimit;
313 entry->isoftlimit = dquot->dq_dqb.dqb_isoftlimit;
314 spin_unlock(&dquot->dq_dqb_lock);
315 }
316
317 clear_bit(DQ_ACTIVE_B, &dquot->dq_flags);
318 up_write(&dqopt->dqio_sem);
319
320out_dqlock:
321 mutex_unlock(&dquot->dq_lock);
322 return 0;
323}
324
325static int shmem_mark_dquot_dirty(struct dquot *dquot)
326{
327 return 0;
328}
329
330static int shmem_dquot_write_info(struct super_block *sb, int type)
331{
332 return 0;
333}
334
335static const struct quota_format_ops shmem_format_ops = {
336 .check_quota_file = shmem_check_quota_file,
337 .read_file_info = shmem_read_file_info,
338 .write_file_info = shmem_write_file_info,
339 .free_file_info = shmem_free_file_info,
340};
341
342struct quota_format_type shmem_quota_format = {
343 .qf_fmt_id = QFMT_SHMEM,
344 .qf_ops = &shmem_format_ops,
345 .qf_owner = THIS_MODULE
346};
347
348const struct dquot_operations shmem_quota_operations = {
349 .acquire_dquot = shmem_acquire_dquot,
350 .release_dquot = shmem_release_dquot,
351 .alloc_dquot = dquot_alloc,
352 .destroy_dquot = dquot_destroy,
353 .write_info = shmem_dquot_write_info,
354 .mark_dirty = shmem_mark_dquot_dirty,
355 .get_next_id = shmem_get_next_id,
356};