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 /*
  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 };