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/module.h>
  17 #include <linux/swap.h>
  18 #include <linux/pagemap.h>
  19 #include <linux/blkdev.h>
  20 #include <linux/mutex.h>
  21 #include <linux/slab.h>
  22 #include "ext4.h"
  23
  24 struct ext4_system_zone {
  25         struct rb_node  node;
  26         ext4_fsblk_t    start_blk;
  27         unsigned int    count;
  28 };
  29
  30 static struct kmem_cache *ext4_system_zone_cachep;
  31
  32 int __init init_ext4_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
  40 void exit_ext4_system_zone(void)
  41 {
  42         kmem_cache_destroy(ext4_system_zone_cachep);
  43 }
  44
  45 static inline int can_merge(struct ext4_system_zone *entry1,
  46                      struct ext4_system_zone *entry2)
  47 {
  48         if ((entry1->start_blk + entry1->count) == entry2->start_blk)
  49                 return 1;
  50         return 0;
  51 }
  52
  53 /*
  54  * Mark a range of blocks as belonging to the "system zone" --- that
  55  * is, filesystem metadata blocks which should never be used by
  56  * inodes.
  57  */
  58 static int add_system_zone(struct ext4_sb_info *sbi,
  59                            ext4_fsblk_t start_blk,
  60                            unsigned int count)
  61 {
  62         struct ext4_system_zone *new_entry = NULL, *entry;
  63         struct rb_node **n = &sbi->system_blks.rb_node, *node;
  64         struct rb_node *parent = NULL, *new_node = NULL;
  65
  66         while (*n) {
  67                 parent = *n;
  68                 entry = rb_entry(parent, struct ext4_system_zone, node);
  69                 if (start_blk < entry->start_blk)
  70                         n = &(*n)->rb_left;
  71                 else if (start_blk >= (entry->start_blk + entry->count))
  72                         n = &(*n)->rb_right;
  73                 else {
  74                         if (start_blk + count > (entry->start_blk +
  75                                                  entry->count))
  76                                 entry->count = (start_blk + count -
  77                                                 entry->start_blk);
  78                         new_node = *n;
  79                         new_entry = rb_entry(new_node, struct ext4_system_zone,
  80                                              node);
  81                         break;
  82                 }
  83         }
  84
  85         if (!new_entry) {
  86                 new_entry = kmem_cache_alloc(ext4_system_zone_cachep,
  87                                              GFP_KERNEL);
  88                 if (!new_entry)
  89                         return -ENOMEM;
  90                 new_entry->start_blk = start_blk;
  91                 new_entry->count = count;
  92                 new_node = &new_entry->node;
  93
  94                 rb_link_node(new_node, parent, n);
  95                 rb_insert_color(new_node, &sbi->system_blks);
  96         }
  97
  98         /* Can we merge to the left? */
  99         node = rb_prev(new_node);
 100         if (node) {
 101                 entry = rb_entry(node, struct ext4_system_zone, node);
 102                 if (can_merge(entry, new_entry)) {
 103                         new_entry->start_blk = entry->start_blk;
 104                         new_entry->count += entry->count;
 105                         rb_erase(node, &sbi->system_blks);
 106                         kmem_cache_free(ext4_system_zone_cachep, entry);
 107                 }
 108         }
 109
 110         /* Can we merge to the right? */
 111         node = rb_next(new_node);
 112         if (node) {
 113                 entry = rb_entry(node, struct ext4_system_zone, node);
 114                 if (can_merge(new_entry, entry)) {
 115                         new_entry->count += entry->count;
 116                         rb_erase(node, &sbi->system_blks);
 117                         kmem_cache_free(ext4_system_zone_cachep, entry);
 118                 }
 119         }
 120         return 0;
 121 }
 122
 123 static void debug_print_tree(struct ext4_sb_info *sbi)
 124 {
 125         struct rb_node *node;
 126         struct ext4_system_zone *entry;
 127         int first = 1;
 128
 129         printk(KERN_INFO "System zones: ");
 130         node = rb_first(&sbi->system_blks);
 131         while (node) {
 132                 entry = rb_entry(node, struct ext4_system_zone, node);
 133                 printk("%s%llu-%llu", first ? "" : ", ",
 134                        entry->start_blk, entry->start_blk + entry->count - 1);
 135                 first = 0;
 136                 node = rb_next(node);
 137         }
 138         printk("\n");
 139 }
 140
 141 int ext4_setup_system_zone(struct super_block *sb)
 142 {
 143         ext4_group_t ngroups = ext4_get_groups_count(sb);
 144         struct ext4_sb_info *sbi = EXT4_SB(sb);
 145         struct ext4_group_desc *gdp;
 146         ext4_group_t i;
 147         int flex_size = ext4_flex_bg_size(sbi);
 148         int ret;
 149
 150         if (!test_opt(sb, BLOCK_VALIDITY)) {
 151                 if (EXT4_SB(sb)->system_blks.rb_node)
 152                         ext4_release_system_zone(sb);
 153                 return 0;
 154         }
 155         if (EXT4_SB(sb)->system_blks.rb_node)
 156                 return 0;
 157
 158         for (i=0; i < ngroups; i++) {
 159                 if (ext4_bg_has_super(sb, i) &&
 160                     ((i < 5) || ((i % flex_size) == 0)))
 161                         add_system_zone(sbi, ext4_group_first_block_no(sb, i),
 162                                         ext4_bg_num_gdb(sb, i) + 1);
 163                 gdp = ext4_get_group_desc(sb, i, NULL);
 164                 ret = add_system_zone(sbi, ext4_block_bitmap(sb, gdp), 1);
 165                 if (ret)
 166                         return ret;
 167                 ret = add_system_zone(sbi, ext4_inode_bitmap(sb, gdp), 1);
 168                 if (ret)
 169                         return ret;
 170                 ret = add_system_zone(sbi, ext4_inode_table(sb, gdp),
 171                                 sbi->s_itb_per_group);
 172                 if (ret)
 173                         return ret;
 174         }
 175
 176         if (test_opt(sb, DEBUG))
 177                 debug_print_tree(EXT4_SB(sb));
 178         return 0;
 179 }
 180
 181 /* Called when the filesystem is unmounted */
 182 void ext4_release_system_zone(struct super_block *sb)
 183 {
 184         struct rb_node  *n = EXT4_SB(sb)->system_blks.rb_node;
 185         struct rb_node  *parent;
 186         struct ext4_system_zone *entry;
 187
 188         while (n) {
 189                 /* Do the node's children first */
 190                 if (n->rb_left) {
 191                         n = n->rb_left;
 192                         continue;
 193                 }
 194                 if (n->rb_right) {
 195                         n = n->rb_right;
 196                         continue;
 197                 }
 198                 /*
 199                  * The node has no children; free it, and then zero
 200                  * out parent's link to it.  Finally go to the
 201                  * beginning of the loop and try to free the parent
 202                  * node.
 203                  */
 204                 parent = rb_parent(n);
 205                 entry = rb_entry(n, struct ext4_system_zone, node);
 206                 kmem_cache_free(ext4_system_zone_cachep, entry);
 207                 if (!parent)
 208                         EXT4_SB(sb)->system_blks = RB_ROOT;
 209                 else if (parent->rb_left == n)
 210                         parent->rb_left = NULL;
 211                 else if (parent->rb_right == n)
 212                         parent->rb_right = NULL;
 213                 n = parent;
 214         }
 215         EXT4_SB(sb)->system_blks = RB_ROOT;
 216 }
 217
 218 /*
 219  * Returns 1 if the passed-in block region (start_blk,
 220  * start_blk+count) is valid; 0 if some part of the block region
 221  * overlaps with filesystem metadata blocks.
 222  */
 223 int ext4_data_block_valid(struct ext4_sb_info *sbi, ext4_fsblk_t start_blk,
 224                           unsigned int count)
 225 {
 226         struct ext4_system_zone *entry;
 227         struct rb_node *n = sbi->system_blks.rb_node;
 228
 229         if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
 230             (start_blk + count < start_blk) ||
 231             (start_blk + count > ext4_blocks_count(sbi->s_es))) {
 232                 sbi->s_es->s_last_error_block = cpu_to_le64(start_blk);
 233                 return 0;
 234         }
 235         while (n) {
 236                 entry = rb_entry(n, struct ext4_system_zone, node);
 237                 if (start_blk + count - 1 < entry->start_blk)
 238                         n = n->rb_left;
 239                 else if (start_blk >= (entry->start_blk + entry->count))
 240                         n = n->rb_right;
 241                 else {
 242                         sbi->s_es->s_last_error_block = cpu_to_le64(start_blk);
 243                         return 0;
 244                 }
 245         }
 246         return 1;
 247 }
 248