mm/shmem_quota.c

   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(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(entry);
 110         }
 111
 112         kfree(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, 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  */
 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
 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  */
 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
 322 static int shmem_mark_dquot_dirty(struct dquot *dquot)
 323 {
 324         return 0;
 325 }
 326
 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 */