fs/ext4/block_validity.c

   1 /*
   2  *  linux/fs/ext4/block_validity.c
   3  *
   4  * Copyright (C) 2009
   5  * Theodore Ts'o (tytso@mit.edu)
   6  *
   7  * Track which blocks in the filesystem are metadata blocks that
   8  * should never be used as data blocks by files or directories.
   9  */
  10
  11 #include <linux/time.h>
  12 #include <linux/fs.h>
  13 #include <linux/namei.h>
  14 #include <linux/quotaops.h>
  15 #include <linux/buffer_head.h>
  16 #include <linux/swap.h>
  17 #include <linux/pagemap.h>
  18 #include <linux/blkdev.h>
  19 #include <linux/slab.h>
  20 #include "ext4.h"
  21
  22 struct ext4_system_zone {
  23         struct rb_node  node;
  24         ext4_fsblk_t    start_blk;
  25         unsigned int    count;
  26 };
  27
  28 static struct kmem_cache *ext4_system_zone_cachep;
  29
  30 int __init ext4_init_system_zone(void)
  31 {
  32         ext4_system_zone_cachep = KMEM_CACHE(ext4_system_zone, 0);
  33         if (ext4_system_zone_cachep == NULL)
  34                 return -ENOMEM;
  35         return 0;
  36 }
  37
  38 void ext4_exit_system_zone(void)
  39 {
  40         kmem_cache_destroy(ext4_system_zone_cachep);
  41 }
  42
  43 static inline int can_merge(struct ext4_system_zone *entry1,
  44                      struct ext4_system_zone *entry2)
  45 {
  46         if ((entry1->start_blk + entry1->count) == entry2->start_blk)
  47                 return 1;
  48         return 0;
  49 }
  50
  51 /*
  52  * Mark a range of blocks as belonging to the "system zone" --- that
  53  * is, filesystem metadata blocks which should never be used by
  54  * inodes.
  55  */
  56 static int add_system_zone(struct ext4_sb_info *sbi,
  57                            ext4_fsblk_t start_blk,
  58                            unsigned int count)
  59 {
  60         struct ext4_system_zone *new_entry = NULL, *entry;
  61         struct rb_node **n = &sbi->system_blks.rb_node, *node;
  62         struct rb_node *parent = NULL, *new_node = NULL;
  63
  64         while (*n) {
  65                 parent = *n;
  66                 entry = rb_entry(parent, struct ext4_system_zone, node);
  67                 if (start_blk < entry->start_blk)
  68                         n = &(*n)->rb_left;
  69                 else if (start_blk >= (entry->start_blk + entry->count))
  70                         n = &(*n)->rb_right;
  71                 else {
  72                         if (start_blk + count > (entry->start_blk +
  73                                                  entry->count))
  74                                 entry->count = (start_blk + count -
  75                                                 entry->start_blk);
  76                         new_node = *n;
  77                         new_entry = rb_entry(new_node, struct ext4_system_zone,
  78                                              node);
  79                         break;
  80                 }
  81         }
  82
  83         if (!new_entry) {
  84                 new_entry = kmem_cache_alloc(ext4_system_zone_cachep,
  85                                              GFP_KERNEL);
  86                 if (!new_entry)
  87                         return -ENOMEM;
  88                 new_entry->start_blk = start_blk;
  89                 new_entry->count = count;
  90                 new_node = &new_entry->node;
  91
  92                 rb_link_node(new_node, parent, n);
  93                 rb_insert_color(new_node, &sbi->system_blks);
  94         }
  95
  96         /* Can we merge to the left? */
  97         node = rb_prev(new_node);
  98         if (node) {
  99                 entry = rb_entry(node, struct ext4_system_zone, node);
 100                 if (can_merge(entry, new_entry)) {
 101                         new_entry->start_blk = entry->start_blk;
 102                         new_entry->count += entry->count;
 103                         rb_erase(node, &sbi->system_blks);
 104                         kmem_cache_free(ext4_system_zone_cachep, entry);
 105                 }
 106         }
 107
 108         /* Can we merge to the right? */
 109         node = rb_next(new_node);
 110         if (node) {
 111                 entry = rb_entry(node, struct ext4_system_zone, node);
 112                 if (can_merge(new_entry, entry)) {
 113                         new_entry->count += entry->count;
 114                         rb_erase(node, &sbi->system_blks);
 115                         kmem_cache_free(ext4_system_zone_cachep, entry);
 116                 }
 117         }
 118         return 0;
 119 }
 120
 121 static void debug_print_tree(struct ext4_sb_info *sbi)
 122 {
 123         struct rb_node *node;
 124         struct ext4_system_zone *entry;
 125         int first = 1;
 126
 127         printk(KERN_INFO "System zones: ");
 128         node = rb_first(&sbi->system_blks);
 129         while (node) {
 130                 entry = rb_entry(node, struct ext4_system_zone, node);
 131                 printk("%s%llu-%llu", first ? "" : ", ",
 132                        entry->start_blk, entry->start_blk + entry->count - 1);
 133                 first = 0;
 134                 node = rb_next(node);
 135         }
 136         printk("\n");
 137 }
 138
 139 int ext4_setup_system_zone(struct super_block *sb)
 140 {
 141         ext4_group_t ngroups = ext4_get_groups_count(sb);
 142         struct ext4_sb_info *sbi = EXT4_SB(sb);
 143         struct ext4_group_desc *gdp;
 144         ext4_group_t i;
 145         int flex_size = ext4_flex_bg_size(sbi);
 146         int ret;
 147
 148         if (!test_opt(sb, BLOCK_VALIDITY)) {
 149                 if (EXT4_SB(sb)->system_blks.rb_node)
 150                         ext4_release_system_zone(sb);
 151                 return 0;
 152         }
 153         if (EXT4_SB(sb)->system_blks.rb_node)
 154                 return 0;
 155
 156         for (i=0; i < ngroups; i++) {
 157                 if (ext4_bg_has_super(sb, i) &&
 158                     ((i < 5) || ((i % flex_size) == 0)))
 159                         add_system_zone(sbi, ext4_group_first_block_no(sb, i),
 160                                         ext4_bg_num_gdb(sb, i) + 1);
 161                 gdp = ext4_get_group_desc(sb, i, NULL);
 162                 ret = add_system_zone(sbi, ext4_block_bitmap(sb, gdp), 1);
 163                 if (ret)
 164                         return ret;
 165                 ret = add_system_zone(sbi, ext4_inode_bitmap(sb, gdp), 1);
 166                 if (ret)
 167                         return ret;
 168                 ret = add_system_zone(sbi, ext4_inode_table(sb, gdp),
 169                                 sbi->s_itb_per_group);
 170                 if (ret)
 171                         return ret;
 172         }
 173
 174         if (test_opt(sb, DEBUG))
 175                 debug_print_tree(EXT4_SB(sb));
 176         return 0;
 177 }
 178
 179 /* Called when the filesystem is unmounted */
 180 void ext4_release_system_zone(struct super_block *sb)
 181 {
 182         struct ext4_system_zone *entry, *n;
 183
 184         rbtree_postorder_for_each_entry_safe(entry, n,
 185                         &EXT4_SB(sb)->system_blks, node)
 186                 kmem_cache_free(ext4_system_zone_cachep, entry);
 187
 188         EXT4_SB(sb)->system_blks = RB_ROOT;
 189 }
 190
 191 /*
 192  * Returns 1 if the passed-in block region (start_blk,
 193  * start_blk+count) is valid; 0 if some part of the block region
 194  * overlaps with filesystem metadata blocks.
 195  */
 196 int ext4_data_block_valid(struct ext4_sb_info *sbi, ext4_fsblk_t start_blk,
 197                           unsigned int count)
 198 {
 199         struct ext4_system_zone *entry;
 200         struct rb_node *n = sbi->system_blks.rb_node;
 201
 202         if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
 203             (start_blk + count < start_blk) ||
 204             (start_blk + count > ext4_blocks_count(sbi->s_es))) {
 205                 sbi->s_es->s_last_error_block = cpu_to_le64(start_blk);
 206                 return 0;
 207         }
 208         while (n) {
 209                 entry = rb_entry(n, struct ext4_system_zone, node);
 210                 if (start_blk + count - 1 < entry->start_blk)
 211                         n = n->rb_left;
 212                 else if (start_blk >= (entry->start_blk + entry->count))
 213                         n = n->rb_right;
 214                 else {
 215                         sbi->s_es->s_last_error_block = cpu_to_le64(start_blk);
 216                         return 0;
 217                 }
 218         }
 219         return 1;
 220 }
 221
 222 int ext4_check_blockref(const char *function, unsigned int line,
 223                         struct inode *inode, __le32 *p, unsigned int max)
 224 {
 225         struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
 226         __le32 *bref = p;
 227         unsigned int blk;
 228
 229         while (bref < p+max) {
 230                 blk = le32_to_cpu(*bref++);
 231                 if (blk &&
 232                     unlikely(!ext4_data_block_valid(EXT4_SB(inode->i_sb),
 233                                                     blk, 1))) {
 234                         es->s_last_error_block = cpu_to_le64(blk);
 235                         ext4_error_inode(inode, function, line, blk,
 236                                          "invalid block");
 237                         return -EFSCORRUPTED;
 238                 }
 239         }
 240         return 0;
 241 }
 242