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1// SPDX-License-Identifier: GPL-2.02/*3 * linux/fs/ext4/block_validity.c4 *5 * Copyright (C) 20096 * Theodore Ts'o (tytso@mit.edu)7 *8 * Track which blocks in the filesystem are metadata blocks that9 * should never be used as data blocks by files or directories.10 */11 12#include <linux/time.h>13#include <linux/fs.h>14#include <linux/namei.h>15#include <linux/quotaops.h>16#include <linux/buffer_head.h>17#include <linux/swap.h>18#include <linux/pagemap.h>19#include <linux/blkdev.h>20#include <linux/slab.h>21#include "ext4.h"22 23struct ext4_system_zone {24 struct rb_node node;25 ext4_fsblk_t start_blk;26 unsigned int count;27 u32 ino;28};29 30static struct kmem_cache *ext4_system_zone_cachep;31 32int __init ext4_init_system_zone(void)33{34 ext4_system_zone_cachep = KMEM_CACHE(ext4_system_zone, 0);35 if (ext4_system_zone_cachep == NULL)36 return -ENOMEM;37 return 0;38}39 40void ext4_exit_system_zone(void)41{42 rcu_barrier();43 kmem_cache_destroy(ext4_system_zone_cachep);44}45 46static inline int can_merge(struct ext4_system_zone *entry1,47 struct ext4_system_zone *entry2)48{49 if ((entry1->start_blk + entry1->count) == entry2->start_blk &&50 entry1->ino == entry2->ino)51 return 1;52 return 0;53}54 55static void release_system_zone(struct ext4_system_blocks *system_blks)56{57 struct ext4_system_zone *entry, *n;58 59 rbtree_postorder_for_each_entry_safe(entry, n,60 &system_blks->root, node)61 kmem_cache_free(ext4_system_zone_cachep, entry);62}63 64/*65 * Mark a range of blocks as belonging to the "system zone" --- that66 * is, filesystem metadata blocks which should never be used by67 * inodes.68 */69static int add_system_zone(struct ext4_system_blocks *system_blks,70 ext4_fsblk_t start_blk,71 unsigned int count, u32 ino)72{73 struct ext4_system_zone *new_entry, *entry;74 struct rb_node **n = &system_blks->root.rb_node, *node;75 struct rb_node *parent = NULL, *new_node;76 77 while (*n) {78 parent = *n;79 entry = rb_entry(parent, struct ext4_system_zone, node);80 if (start_blk < entry->start_blk)81 n = &(*n)->rb_left;82 else if (start_blk >= (entry->start_blk + entry->count))83 n = &(*n)->rb_right;84 else /* Unexpected overlap of system zones. */85 return -EFSCORRUPTED;86 }87 88 new_entry = kmem_cache_alloc(ext4_system_zone_cachep,89 GFP_KERNEL);90 if (!new_entry)91 return -ENOMEM;92 new_entry->start_blk = start_blk;93 new_entry->count = count;94 new_entry->ino = ino;95 new_node = &new_entry->node;96 97 rb_link_node(new_node, parent, n);98 rb_insert_color(new_node, &system_blks->root);99 100 /* Can we merge to the left? */101 node = rb_prev(new_node);102 if (node) {103 entry = rb_entry(node, struct ext4_system_zone, node);104 if (can_merge(entry, new_entry)) {105 new_entry->start_blk = entry->start_blk;106 new_entry->count += entry->count;107 rb_erase(node, &system_blks->root);108 kmem_cache_free(ext4_system_zone_cachep, entry);109 }110 }111 112 /* Can we merge to the right? */113 node = rb_next(new_node);114 if (node) {115 entry = rb_entry(node, struct ext4_system_zone, node);116 if (can_merge(new_entry, entry)) {117 new_entry->count += entry->count;118 rb_erase(node, &system_blks->root);119 kmem_cache_free(ext4_system_zone_cachep, entry);120 }121 }122 return 0;123}124 125static void debug_print_tree(struct ext4_sb_info *sbi)126{127 struct rb_node *node;128 struct ext4_system_zone *entry;129 struct ext4_system_blocks *system_blks;130 int first = 1;131 132 printk(KERN_INFO "System zones: ");133 rcu_read_lock();134 system_blks = rcu_dereference(sbi->s_system_blks);135 node = rb_first(&system_blks->root);136 while (node) {137 entry = rb_entry(node, struct ext4_system_zone, node);138 printk(KERN_CONT "%s%llu-%llu", first ? "" : ", ",139 entry->start_blk, entry->start_blk + entry->count - 1);140 first = 0;141 node = rb_next(node);142 }143 rcu_read_unlock();144 printk(KERN_CONT "\n");145}146 147static int ext4_protect_reserved_inode(struct super_block *sb,148 struct ext4_system_blocks *system_blks,149 u32 ino)150{151 struct inode *inode;152 struct ext4_sb_info *sbi = EXT4_SB(sb);153 struct ext4_map_blocks map;154 u32 i = 0, num;155 int err = 0, n;156 157 if ((ino < EXT4_ROOT_INO) ||158 (ino > le32_to_cpu(sbi->s_es->s_inodes_count)))159 return -EINVAL;160 inode = ext4_iget(sb, ino, EXT4_IGET_SPECIAL);161 if (IS_ERR(inode))162 return PTR_ERR(inode);163 num = (inode->i_size + sb->s_blocksize - 1) >> sb->s_blocksize_bits;164 while (i < num) {165 cond_resched();166 map.m_lblk = i;167 map.m_len = num - i;168 n = ext4_map_blocks(NULL, inode, &map, 0);169 if (n < 0) {170 err = n;171 break;172 }173 if (n == 0) {174 i++;175 } else {176 err = add_system_zone(system_blks, map.m_pblk, n, ino);177 if (err < 0) {178 if (err == -EFSCORRUPTED) {179 EXT4_ERROR_INODE_ERR(inode, -err,180 "blocks %llu-%llu from inode overlap system zone",181 map.m_pblk,182 map.m_pblk + map.m_len - 1);183 }184 break;185 }186 i += n;187 }188 }189 iput(inode);190 return err;191}192 193static void ext4_destroy_system_zone(struct rcu_head *rcu)194{195 struct ext4_system_blocks *system_blks;196 197 system_blks = container_of(rcu, struct ext4_system_blocks, rcu);198 release_system_zone(system_blks);199 kfree(system_blks);200}201 202/*203 * Build system zone rbtree which is used for block validity checking.204 *205 * The update of system_blks pointer in this function is protected by206 * sb->s_umount semaphore. However we have to be careful as we can be207 * racing with ext4_inode_block_valid() calls reading system_blks rbtree208 * protected only by RCU. That's why we first build the rbtree and then209 * swap it in place.210 */211int ext4_setup_system_zone(struct super_block *sb)212{213 ext4_group_t ngroups = ext4_get_groups_count(sb);214 struct ext4_sb_info *sbi = EXT4_SB(sb);215 struct ext4_system_blocks *system_blks;216 struct ext4_group_desc *gdp;217 ext4_group_t i;218 int ret;219 220 system_blks = kzalloc(sizeof(*system_blks), GFP_KERNEL);221 if (!system_blks)222 return -ENOMEM;223 224 for (i=0; i < ngroups; i++) {225 unsigned int meta_blks = ext4_num_base_meta_blocks(sb, i);226 227 cond_resched();228 if (meta_blks != 0) {229 ret = add_system_zone(system_blks,230 ext4_group_first_block_no(sb, i),231 meta_blks, 0);232 if (ret)233 goto err;234 }235 gdp = ext4_get_group_desc(sb, i, NULL);236 ret = add_system_zone(system_blks,237 ext4_block_bitmap(sb, gdp), 1, 0);238 if (ret)239 goto err;240 ret = add_system_zone(system_blks,241 ext4_inode_bitmap(sb, gdp), 1, 0);242 if (ret)243 goto err;244 ret = add_system_zone(system_blks,245 ext4_inode_table(sb, gdp),246 sbi->s_itb_per_group, 0);247 if (ret)248 goto err;249 }250 if (ext4_has_feature_journal(sb) && sbi->s_es->s_journal_inum) {251 ret = ext4_protect_reserved_inode(sb, system_blks,252 le32_to_cpu(sbi->s_es->s_journal_inum));253 if (ret)254 goto err;255 }256 257 /*258 * System blks rbtree complete, announce it once to prevent racing259 * with ext4_inode_block_valid() accessing the rbtree at the same260 * time.261 */262 rcu_assign_pointer(sbi->s_system_blks, system_blks);263 264 if (test_opt(sb, DEBUG))265 debug_print_tree(sbi);266 return 0;267err:268 release_system_zone(system_blks);269 kfree(system_blks);270 return ret;271}272 273/*274 * Called when the filesystem is unmounted or when remounting it with275 * noblock_validity specified.276 *277 * The update of system_blks pointer in this function is protected by278 * sb->s_umount semaphore. However we have to be careful as we can be279 * racing with ext4_inode_block_valid() calls reading system_blks rbtree280 * protected only by RCU. So we first clear the system_blks pointer and281 * then free the rbtree only after RCU grace period expires.282 */283void ext4_release_system_zone(struct super_block *sb)284{285 struct ext4_system_blocks *system_blks;286 287 system_blks = rcu_dereference_protected(EXT4_SB(sb)->s_system_blks,288 lockdep_is_held(&sb->s_umount));289 rcu_assign_pointer(EXT4_SB(sb)->s_system_blks, NULL);290 291 if (system_blks)292 call_rcu(&system_blks->rcu, ext4_destroy_system_zone);293}294 295int ext4_sb_block_valid(struct super_block *sb, struct inode *inode,296 ext4_fsblk_t start_blk, unsigned int count)297{298 struct ext4_sb_info *sbi = EXT4_SB(sb);299 struct ext4_system_blocks *system_blks;300 struct ext4_system_zone *entry;301 struct rb_node *n;302 int ret = 1;303 304 if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||305 (start_blk + count < start_blk) ||306 (start_blk + count > ext4_blocks_count(sbi->s_es)))307 return 0;308 309 /*310 * Lock the system zone to prevent it being released concurrently311 * when doing a remount which inverse current "[no]block_validity"312 * mount option.313 */314 rcu_read_lock();315 system_blks = rcu_dereference(sbi->s_system_blks);316 if (system_blks == NULL)317 goto out_rcu;318 319 n = system_blks->root.rb_node;320 while (n) {321 entry = rb_entry(n, struct ext4_system_zone, node);322 if (start_blk + count - 1 < entry->start_blk)323 n = n->rb_left;324 else if (start_blk >= (entry->start_blk + entry->count))325 n = n->rb_right;326 else {327 ret = 0;328 if (inode)329 ret = (entry->ino == inode->i_ino);330 break;331 }332 }333out_rcu:334 rcu_read_unlock();335 return ret;336}337 338/*339 * Returns 1 if the passed-in block region (start_blk,340 * start_blk+count) is valid; 0 if some part of the block region341 * overlaps with some other filesystem metadata blocks.342 */343int ext4_inode_block_valid(struct inode *inode, ext4_fsblk_t start_blk,344 unsigned int count)345{346 return ext4_sb_block_valid(inode->i_sb, inode, start_blk, count);347}348 349int ext4_check_blockref(const char *function, unsigned int line,350 struct inode *inode, __le32 *p, unsigned int max)351{352 __le32 *bref = p;353 unsigned int blk;354 355 if (ext4_has_feature_journal(inode->i_sb) &&356 (inode->i_ino ==357 le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_journal_inum)))358 return 0;359 360 while (bref < p+max) {361 blk = le32_to_cpu(*bref++);362 if (blk &&363 unlikely(!ext4_inode_block_valid(inode, blk, 1))) {364 ext4_error_inode(inode, function, line, blk,365 "invalid block");366 return -EFSCORRUPTED;367 }368 }369 return 0;370}371 372