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