xref: /openbmc/linux/mm/shmem_quota.c (revision c7077f43)
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 
shmem_check_quota_file(struct super_block * sb,int type)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  */
shmem_read_file_info(struct super_block * sb,int type)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(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 
shmem_write_file_info(struct super_block * sb,int type)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  */
shmem_free_file_info(struct super_block * sb,int type)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(entry);
110 	}
111 
112 	kfree(root);
113 	return 0;
114 }
115 
shmem_get_next_id(struct super_block * sb,struct kqid * qid)116 static int shmem_get_next_id(struct super_block *sb, struct kqid *qid)
117 {
118 	struct mem_dqinfo *info = sb_dqinfo(sb, qid->type);
119 	struct rb_node *node;
120 	qid_t id = from_kqid(&init_user_ns, *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, qid->type))
126 		return -ESRCH;
127 
128 	down_read(&dqopt->dqio_sem);
129 	node = ((struct rb_root *)info->dqi_priv)->rb_node;
130 	while (node) {
131 		entry = rb_entry(node, struct quota_id, node);
132 
133 		if (id < entry->id)
134 			node = node->rb_left;
135 		else if (id > entry->id)
136 			node = node->rb_right;
137 		else
138 			goto got_next_id;
139 	}
140 
141 	if (!entry) {
142 		ret = -ENOENT;
143 		goto out_unlock;
144 	}
145 
146 	if (id > entry->id) {
147 		node = rb_next(&entry->node);
148 		if (!node) {
149 			ret = -ENOENT;
150 			goto out_unlock;
151 		}
152 		entry = rb_entry(node, struct quota_id, node);
153 	}
154 
155 got_next_id:
156 	*qid = make_kqid(&init_user_ns, qid->type, entry->id);
157 out_unlock:
158 	up_read(&dqopt->dqio_sem);
159 	return ret;
160 }
161 
162 /*
163  * Load dquot with limits from existing entry, or create the new entry if
164  * it does not exist.
165  */
shmem_acquire_dquot(struct dquot * dquot)166 static int shmem_acquire_dquot(struct dquot *dquot)
167 {
168 	struct mem_dqinfo *info = sb_dqinfo(dquot->dq_sb, dquot->dq_id.type);
169 	struct rb_node **n;
170 	struct shmem_sb_info *sbinfo = dquot->dq_sb->s_fs_info;
171 	struct rb_node *parent = NULL, *new_node = NULL;
172 	struct quota_id *new_entry, *entry;
173 	qid_t id = from_kqid(&init_user_ns, dquot->dq_id);
174 	struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);
175 	int ret = 0;
176 
177 	mutex_lock(&dquot->dq_lock);
178 
179 	down_write(&dqopt->dqio_sem);
180 	n = &((struct rb_root *)info->dqi_priv)->rb_node;
181 
182 	while (*n) {
183 		parent = *n;
184 		entry = rb_entry(parent, struct quota_id, node);
185 
186 		if (id < entry->id)
187 			n = &(*n)->rb_left;
188 		else if (id > entry->id)
189 			n = &(*n)->rb_right;
190 		else
191 			goto found;
192 	}
193 
194 	/* We don't have entry for this id yet, create it */
195 	new_entry = kzalloc(sizeof(struct quota_id), GFP_NOFS);
196 	if (!new_entry) {
197 		ret = -ENOMEM;
198 		goto out_unlock;
199 	}
200 
201 	new_entry->id = id;
202 	if (dquot->dq_id.type == USRQUOTA) {
203 		new_entry->bhardlimit = sbinfo->qlimits.usrquota_bhardlimit;
204 		new_entry->ihardlimit = sbinfo->qlimits.usrquota_ihardlimit;
205 	} else if (dquot->dq_id.type == GRPQUOTA) {
206 		new_entry->bhardlimit = sbinfo->qlimits.grpquota_bhardlimit;
207 		new_entry->ihardlimit = sbinfo->qlimits.grpquota_ihardlimit;
208 	}
209 
210 	new_node = &new_entry->node;
211 	rb_link_node(new_node, parent, n);
212 	rb_insert_color(new_node, (struct rb_root *)info->dqi_priv);
213 	entry = new_entry;
214 
215 found:
216 	/* Load the stored limits from the tree */
217 	spin_lock(&dquot->dq_dqb_lock);
218 	dquot->dq_dqb.dqb_bhardlimit = entry->bhardlimit;
219 	dquot->dq_dqb.dqb_bsoftlimit = entry->bsoftlimit;
220 	dquot->dq_dqb.dqb_ihardlimit = entry->ihardlimit;
221 	dquot->dq_dqb.dqb_isoftlimit = entry->isoftlimit;
222 
223 	if (!dquot->dq_dqb.dqb_bhardlimit &&
224 	    !dquot->dq_dqb.dqb_bsoftlimit &&
225 	    !dquot->dq_dqb.dqb_ihardlimit &&
226 	    !dquot->dq_dqb.dqb_isoftlimit)
227 		set_bit(DQ_FAKE_B, &dquot->dq_flags);
228 	spin_unlock(&dquot->dq_dqb_lock);
229 
230 	/* Make sure flags update is visible after dquot has been filled */
231 	smp_mb__before_atomic();
232 	set_bit(DQ_ACTIVE_B, &dquot->dq_flags);
233 out_unlock:
234 	up_write(&dqopt->dqio_sem);
235 	mutex_unlock(&dquot->dq_lock);
236 	return ret;
237 }
238 
shmem_is_empty_dquot(struct dquot * dquot)239 static bool shmem_is_empty_dquot(struct dquot *dquot)
240 {
241 	struct shmem_sb_info *sbinfo = dquot->dq_sb->s_fs_info;
242 	qsize_t bhardlimit;
243 	qsize_t ihardlimit;
244 
245 	if (dquot->dq_id.type == USRQUOTA) {
246 		bhardlimit = sbinfo->qlimits.usrquota_bhardlimit;
247 		ihardlimit = sbinfo->qlimits.usrquota_ihardlimit;
248 	} else if (dquot->dq_id.type == GRPQUOTA) {
249 		bhardlimit = sbinfo->qlimits.grpquota_bhardlimit;
250 		ihardlimit = sbinfo->qlimits.grpquota_ihardlimit;
251 	}
252 
253 	if (test_bit(DQ_FAKE_B, &dquot->dq_flags) ||
254 		(dquot->dq_dqb.dqb_curspace == 0 &&
255 		 dquot->dq_dqb.dqb_curinodes == 0 &&
256 		 dquot->dq_dqb.dqb_bhardlimit == bhardlimit &&
257 		 dquot->dq_dqb.dqb_ihardlimit == ihardlimit))
258 		return true;
259 
260 	return false;
261 }
262 /*
263  * Store limits from dquot in the tree unless it's fake. If it is fake
264  * remove the id from the tree since there is no useful information in
265  * there.
266  */
shmem_release_dquot(struct dquot * dquot)267 static int shmem_release_dquot(struct dquot *dquot)
268 {
269 	struct mem_dqinfo *info = sb_dqinfo(dquot->dq_sb, dquot->dq_id.type);
270 	struct rb_node *node;
271 	qid_t id = from_kqid(&init_user_ns, dquot->dq_id);
272 	struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);
273 	struct quota_id *entry = NULL;
274 
275 	mutex_lock(&dquot->dq_lock);
276 	/* Check whether we are not racing with some other dqget() */
277 	if (dquot_is_busy(dquot))
278 		goto out_dqlock;
279 
280 	down_write(&dqopt->dqio_sem);
281 	node = ((struct rb_root *)info->dqi_priv)->rb_node;
282 	while (node) {
283 		entry = rb_entry(node, struct quota_id, node);
284 
285 		if (id < entry->id)
286 			node = node->rb_left;
287 		else if (id > entry->id)
288 			node = node->rb_right;
289 		else
290 			goto found;
291 	}
292 
293 	/* We should always find the entry in the rb tree */
294 	WARN_ONCE(1, "quota id %u from dquot %p, not in rb tree!\n", id, dquot);
295 	up_write(&dqopt->dqio_sem);
296 	mutex_unlock(&dquot->dq_lock);
297 	return -ENOENT;
298 
299 found:
300 	if (shmem_is_empty_dquot(dquot)) {
301 		/* Remove entry from the tree */
302 		rb_erase(&entry->node, info->dqi_priv);
303 		kfree(entry);
304 	} else {
305 		/* Store the limits in the tree */
306 		spin_lock(&dquot->dq_dqb_lock);
307 		entry->bhardlimit = dquot->dq_dqb.dqb_bhardlimit;
308 		entry->bsoftlimit = dquot->dq_dqb.dqb_bsoftlimit;
309 		entry->ihardlimit = dquot->dq_dqb.dqb_ihardlimit;
310 		entry->isoftlimit = dquot->dq_dqb.dqb_isoftlimit;
311 		spin_unlock(&dquot->dq_dqb_lock);
312 	}
313 
314 	clear_bit(DQ_ACTIVE_B, &dquot->dq_flags);
315 	up_write(&dqopt->dqio_sem);
316 
317 out_dqlock:
318 	mutex_unlock(&dquot->dq_lock);
319 	return 0;
320 }
321 
shmem_mark_dquot_dirty(struct dquot * dquot)322 static int shmem_mark_dquot_dirty(struct dquot *dquot)
323 {
324 	return 0;
325 }
326 
shmem_dquot_write_info(struct super_block * sb,int type)327 static int shmem_dquot_write_info(struct super_block *sb, int type)
328 {
329 	return 0;
330 }
331 
332 static const struct quota_format_ops shmem_format_ops = {
333 	.check_quota_file	= shmem_check_quota_file,
334 	.read_file_info		= shmem_read_file_info,
335 	.write_file_info	= shmem_write_file_info,
336 	.free_file_info		= shmem_free_file_info,
337 };
338 
339 struct quota_format_type shmem_quota_format = {
340 	.qf_fmt_id = QFMT_SHMEM,
341 	.qf_ops = &shmem_format_ops,
342 	.qf_owner = THIS_MODULE
343 };
344 
345 const struct dquot_operations shmem_quota_operations = {
346 	.acquire_dquot		= shmem_acquire_dquot,
347 	.release_dquot		= shmem_release_dquot,
348 	.alloc_dquot		= dquot_alloc,
349 	.destroy_dquot		= dquot_destroy,
350 	.write_info		= shmem_dquot_write_info,
351 	.mark_dirty		= shmem_mark_dquot_dirty,
352 	.get_next_id		= shmem_get_next_id,
353 };
354 #endif /* CONFIG_TMPFS_QUOTA */
355