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/mutex.h>
  20 #include <linux/slab.h>
  21 #include "ext4.h"
  22
  23 struct ext4_system_zone {
  24         struct rb_node  node;
  25         ext4_fsblk_t    start_blk;
  26         unsigned int    count;
  27 };
  28
  29 static struct kmem_cache *ext4_system_zone_cachep;
  30
  31 int __init ext4_init_system_zone(void)
  32 {
  33         ext4_system_zone_cachep = KMEM_CACHE(ext4_system_zone, 0);
  34         if (ext4_system_zone_cachep == NULL)
  35                 return -ENOMEM;
  36         return 0;
  37 }
  38
  39 void ext4_exit_system_zone(void)
  40 {
  41         kmem_cache_destroy(ext4_system_zone_cachep);
  42 }
  43
  44 static inline int can_merge(struct ext4_system_zone *entry1,
  45                      struct ext4_system_zone *entry2)
  46 {
  47         if ((entry1->start_blk + entry1->count) == entry2->start_blk)
  48                 return 1;
  49         return 0;
  50 }
  51
  52 /*
  53  * Mark a range of blocks as belonging to the "system zone" --- that
  54  * is, filesystem metadata blocks which should never be used by
  55  * inodes.
  56  */
  57 static int add_system_zone(struct ext4_sb_info *sbi,
  58                            ext4_fsblk_t start_blk,
  59                            unsigned int count)
  60 {
  61         struct ext4_system_zone *new_entry = NULL, *entry;
  62         struct rb_node **n = &sbi->system_blks.rb_node, *node;
  63         struct rb_node *parent = NULL, *new_node = NULL;
  64
  65         while (*n) {
  66                 parent = *n;
  67                 entry = rb_entry(parent, struct ext4_system_zone, node);
  68                 if (start_blk < entry->start_blk)
  69                         n = &(*n)->rb_left;
  70                 else if (start_blk >= (entry->start_blk + entry->count))
  71                         n = &(*n)->rb_right;
  72                 else {
  73                         if (start_blk + count > (entry->start_blk +
  74                                                  entry->count))
  75                                 entry->count = (start_blk + count -
  76                                                 entry->start_blk);
  77                         new_node = *n;
  78                         new_entry = rb_entry(new_node, struct ext4_system_zone,
  79                                              node);
  80                         break;
  81                 }
  82         }
  83
  84         if (!new_entry) {
  85                 new_entry = kmem_cache_alloc(ext4_system_zone_cachep,
  86                                              GFP_KERNEL);
  87                 if (!new_entry)
  88                         return -ENOMEM;
  89                 new_entry->start_blk = start_blk;
  90                 new_entry->count = count;
  91                 new_node = &new_entry->node;
  92
  93                 rb_link_node(new_node, parent, n);
  94                 rb_insert_color(new_node, &sbi->system_blks);
  95         }
  96
  97         /* Can we merge to the left? */
  98         node = rb_prev(new_node);
  99         if (node) {
 100                 entry = rb_entry(node, struct ext4_system_zone, node);
 101                 if (can_merge(entry, new_entry)) {
 102                         new_entry->start_blk = entry->start_blk;
 103                         new_entry->count += entry->count;
 104                         rb_erase(node, &sbi->system_blks);
 105                         kmem_cache_free(ext4_system_zone_cachep, entry);
 106                 }
 107         }
 108
 109         /* Can we merge to the right? */
 110         node = rb_next(new_node);
 111         if (node) {
 112                 entry = rb_entry(node, struct ext4_system_zone, node);
 113                 if (can_merge(new_entry, entry)) {
 114                         new_entry->count += entry->count;
 115                         rb_erase(node, &sbi->system_blks);
 116                         kmem_cache_free(ext4_system_zone_cachep, entry);
 117                 }
 118         }
 119         return 0;
 120 }
 121
 122 static void debug_print_tree(struct ext4_sb_info *sbi)
 123 {
 124         struct rb_node *node;
 125         struct ext4_system_zone *entry;
 126         int first = 1;
 127
 128         printk(KERN_INFO "System zones: ");
 129         node = rb_first(&sbi->system_blks);
 130         while (node) {
 131                 entry = rb_entry(node, struct ext4_system_zone, node);
 132                 printk("%s%llu-%llu", first ? "" : ", ",
 133                        entry->start_blk, entry->start_blk + entry->count - 1);
 134                 first = 0;
 135                 node = rb_next(node);
 136         }
 137         printk("\n");
 138 }
 139
 140 int ext4_setup_system_zone(struct super_block *sb)
 141 {
 142         ext4_group_t ngroups = ext4_get_groups_count(sb);
 143         struct ext4_sb_info *sbi = EXT4_SB(sb);
 144         struct ext4_group_desc *gdp;
 145         ext4_group_t i;
 146         int flex_size = ext4_flex_bg_size(sbi);
 147         int ret;
 148
 149         if (!test_opt(sb, BLOCK_VALIDITY)) {
 150                 if (EXT4_SB(sb)->system_blks.rb_node)
 151                         ext4_release_system_zone(sb);
 152                 return 0;
 153         }
 154         if (EXT4_SB(sb)->system_blks.rb_node)
 155                 return 0;
 156
 157         for (i=0; i < ngroups; i++) {
 158                 if (ext4_bg_has_super(sb, i) &&
 159                     ((i < 5) || ((i % flex_size) == 0)))
 160                         add_system_zone(sbi, ext4_group_first_block_no(sb, i),
 161                                         ext4_bg_num_gdb(sb, i) + 1);
 162                 gdp = ext4_get_group_desc(sb, i, NULL);
 163                 ret = add_system_zone(sbi, ext4_block_bitmap(sb, gdp), 1);
 164                 if (ret)
 165                         return ret;
 166                 ret = add_system_zone(sbi, ext4_inode_bitmap(sb, gdp), 1);
 167                 if (ret)
 168                         return ret;
 169                 ret = add_system_zone(sbi, ext4_inode_table(sb, gdp),
 170                                 sbi->s_itb_per_group);
 171                 if (ret)
 172                         return ret;
 173         }
 174
 175         if (test_opt(sb, DEBUG))
 176                 debug_print_tree(EXT4_SB(sb));
 177         return 0;
 178 }
 179
 180 /* Called when the filesystem is unmounted */
 181 void ext4_release_system_zone(struct super_block *sb)
 182 {
 183         struct rb_node  *n = EXT4_SB(sb)->system_blks.rb_node;
 184         struct rb_node  *parent;
 185         struct ext4_system_zone *entry;
 186
 187         while (n) {
 188                 /* Do the node's children first */
 189                 if (n->rb_left) {
 190                         n = n->rb_left;
 191                         continue;
 192                 }
 193                 if (n->rb_right) {
 194                         n = n->rb_right;
 195                         continue;
 196                 }
 197                 /*
 198                  * The node has no children; free it, and then zero
 199                  * out parent's link to it.  Finally go to the
 200                  * beginning of the loop and try to free the parent
 201                  * node.
 202                  */
 203                 parent = rb_parent(n);
 204                 entry = rb_entry(n, struct ext4_system_zone, node);
 205                 kmem_cache_free(ext4_system_zone_cachep, entry);
 206                 if (!parent)
 207                         EXT4_SB(sb)->system_blks = RB_ROOT;
 208                 else if (parent->rb_left == n)
 209                         parent->rb_left = NULL;
 210                 else if (parent->rb_right == n)
 211                         parent->rb_right = NULL;
 212                 n = parent;
 213         }
 214         EXT4_SB(sb)->system_blks = RB_ROOT;
 215 }
 216
 217 /*
 218  * Returns 1 if the passed-in block region (start_blk,
 219  * start_blk+count) is valid; 0 if some part of the block region
 220  * overlaps with filesystem metadata blocks.
 221  */
 222 int ext4_data_block_valid(struct ext4_sb_info *sbi, ext4_fsblk_t start_blk,
 223                           unsigned int count)
 224 {
 225         struct ext4_system_zone *entry;
 226         struct rb_node *n = sbi->system_blks.rb_node;
 227
 228         if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
 229             (start_blk + count < start_blk) ||
 230             (start_blk + count > ext4_blocks_count(sbi->s_es))) {
 231                 sbi->s_es->s_last_error_block = cpu_to_le64(start_blk);
 232                 return 0;
 233         }
 234         while (n) {
 235                 entry = rb_entry(n, struct ext4_system_zone, node);
 236                 if (start_blk + count - 1 < entry->start_blk)
 237                         n = n->rb_left;
 238                 else if (start_blk >= (entry->start_blk + entry->count))
 239                         n = n->rb_right;
 240                 else {
 241                         sbi->s_es->s_last_error_block = cpu_to_le64(start_blk);
 242                         return 0;
 243                 }
 244         }
 245         return 1;
 246 }
 247
 248 int ext4_check_blockref(const char *function, unsigned int line,
 249                         struct inode *inode, __le32 *p, unsigned int max)
 250 {
 251         struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
 252         __le32 *bref = p;
 253         unsigned int blk;
 254
 255         while (bref < p+max) {
 256                 blk = le32_to_cpu(*bref++);
 257                 if (blk &&
 258                     unlikely(!ext4_data_block_valid(EXT4_SB(inode->i_sb),
 259                                                     blk, 1))) {
 260                         es->s_last_error_block = cpu_to_le64(blk);
 261                         ext4_error_inode(inode, function, line, blk,
 262                                          "invalid block");
 263                         return -EIO;
 264                 }
 265         }
 266         return 0;
 267 }
 268