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 = ((struct rb_root *)info->dqi_priv)->rb_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         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(&init_user_ns, qid->type, entry->id);
 156 out_unlock:
 157         up_read(&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(dquot->dq_sb, 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(&init_user_ns, dquot->dq_id);
 173         struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);
 174         int ret = 0;
 175
 176         mutex_lock(&dquot->dq_lock);
 177
 178         down_write(&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(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(new_node, parent, 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(&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, &dquot->dq_flags);
 225         spin_unlock(&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, &dquot->dq_flags);
 230 out_unlock:
 231         up_write(&dqopt->dqio_sem);
 232         mutex_unlock(&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(dquot->dq_sb, dquot->dq_id.type);
 267         struct rb_node *node = ((struct rb_root *)info->dqi_priv)->rb_node;
 268         qid_t id = from_kqid(&init_user_ns, dquot->dq_id);
 269         struct quota_info *dqopt = sb_dqopt(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(&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(&dqopt->dqio_sem);
 292         mutex_unlock(&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(entry);
 300         } else {
 301                 /* Store the limits in the tree */
 302                 spin_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(&dquot->dq_dqb_lock);
 308         }
 309
 310         clear_bit(DQ_ACTIVE_B, &dquot->dq_flags);
 311         up_write(&dqopt->dqio_sem);
 312
 313 out_dqlock:
 314         mutex_unlock(&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 */