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,
  35                                              SLAB_RECLAIM_ACCOUNT);
  36         if (ext4_system_zone_cachep == NULL)
  37                 return -ENOMEM;
  38         return 0;
  39 }
  40
  41 void exit_ext4_system_zone(void)
  42 {
  43         kmem_cache_destroy(ext4_system_zone_cachep);
  44 }
  45
  46 static 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                 return 1;
  51         return 0;
  52 }
  53
  54 /*
  55  * Mark a range of blocks as belonging to the "system zone" --- that
  56  * is, filesystem metadata blocks which should never be used by
  57  * inodes.
  58  */
  59 static int add_system_zone(struct ext4_sb_info *sbi,
  60                            ext4_fsblk_t start_blk,
  61                            unsigned int count)
  62 {
  63         struct ext4_system_zone *new_entry = NULL, *entry;
  64         struct rb_node **n = &sbi->system_blks.rb_node, *node;
  65         struct rb_node *parent = NULL, *new_node = NULL;
  66
  67         while (*n) {
  68                 parent = *n;
  69                 entry = rb_entry(parent, struct ext4_system_zone, node);
  70                 if (start_blk < entry->start_blk)
  71                         n = &(*n)->rb_left;
  72                 else if (start_blk >= (entry->start_blk + entry->count))
  73                         n = &(*n)->rb_right;
  74                 else {
  75                         if (start_blk + count > (entry->start_blk +
  76                                                  entry->count))
  77                                 entry->count = (start_blk + count -
  78                                                 entry->start_blk);
  79                         new_node = *n;
  80                         new_entry = rb_entry(new_node, struct ext4_system_zone,
  81                                              node);
  82                         break;
  83                 }
  84         }
  85
  86         if (!new_entry) {
  87                 new_entry = kmem_cache_alloc(ext4_system_zone_cachep,
  88                                              GFP_KERNEL);
  89                 if (!new_entry)
  90                         return -ENOMEM;
  91                 new_entry->start_blk = start_blk;
  92                 new_entry->count = count;
  93                 new_node = &new_entry->node;
  94
  95                 rb_link_node(new_node, parent, n);
  96                 rb_insert_color(new_node, &sbi->system_blks);
  97         }
  98
  99         /* Can we merge to the left? */
 100         node = rb_prev(new_node);
 101         if (node) {
 102                 entry = rb_entry(node, struct ext4_system_zone, node);
 103                 if (can_merge(entry, new_entry)) {
 104                         new_entry->start_blk = entry->start_blk;
 105                         new_entry->count += entry->count;
 106                         rb_erase(node, &sbi->system_blks);
 107                         kmem_cache_free(ext4_system_zone_cachep, entry);
 108                 }
 109         }
 110
 111         /* Can we merge to the right? */
 112         node = rb_next(new_node);
 113         if (node) {
 114                 entry = rb_entry(node, struct ext4_system_zone, node);
 115                 if (can_merge(new_entry, entry)) {
 116                         new_entry->count += entry->count;
 117                         rb_erase(node, &sbi->system_blks);
 118                         kmem_cache_free(ext4_system_zone_cachep, entry);
 119                 }
 120         }
 121         return 0;
 122 }
 123
 124 static void debug_print_tree(struct ext4_sb_info *sbi)
 125 {
 126         struct rb_node *node;
 127         struct ext4_system_zone *entry;
 128         int first = 1;
 129
 130         printk(KERN_INFO "System zones: ");
 131         node = rb_first(&sbi->system_blks);
 132         while (node) {
 133                 entry = rb_entry(node, struct ext4_system_zone, node);
 134                 printk("%s%llu-%llu", first ? "" : ", ",
 135                        entry->start_blk, entry->start_blk + entry->count - 1);
 136                 first = 0;
 137                 node = rb_next(node);
 138         }
 139         printk("\n");
 140 }
 141
 142 int ext4_setup_system_zone(struct super_block *sb)
 143 {
 144         ext4_group_t ngroups = ext4_get_groups_count(sb);
 145         struct ext4_sb_info *sbi = EXT4_SB(sb);
 146         struct ext4_group_desc *gdp;
 147         ext4_group_t i;
 148         int flex_size = ext4_flex_bg_size(sbi);
 149         int ret;
 150
 151         if (!test_opt(sb, BLOCK_VALIDITY)) {
 152                 if (EXT4_SB(sb)->system_blks.rb_node)
 153                         ext4_release_system_zone(sb);
 154                 return 0;
 155         }
 156         if (EXT4_SB(sb)->system_blks.rb_node)
 157                 return 0;
 158
 159         for (i=0; i < ngroups; i++) {
 160                 if (ext4_bg_has_super(sb, i) &&
 161                     ((i < 5) || ((i % flex_size) == 0)))
 162                         add_system_zone(sbi, ext4_group_first_block_no(sb, i),
 163                                         ext4_bg_num_gdb(sb, i) + 1);
 164                 gdp = ext4_get_group_desc(sb, i, NULL);
 165                 ret = add_system_zone(sbi, ext4_block_bitmap(sb, gdp), 1);
 166                 if (ret)
 167                         return ret;
 168                 ret = add_system_zone(sbi, ext4_inode_bitmap(sb, gdp), 1);
 169                 if (ret)
 170                         return ret;
 171                 ret = add_system_zone(sbi, ext4_inode_table(sb, gdp),
 172                                 sbi->s_itb_per_group);
 173                 if (ret)
 174                         return ret;
 175         }
 176
 177         if (test_opt(sb, DEBUG))
 178                 debug_print_tree(EXT4_SB(sb));
 179         return 0;
 180 }
 181
 182 /* Called when the filesystem is unmounted */
 183 void ext4_release_system_zone(struct super_block *sb)
 184 {
 185         struct rb_node  *n = EXT4_SB(sb)->system_blks.rb_node;
 186         struct rb_node  *parent;
 187         struct ext4_system_zone *entry;
 188
 189         while (n) {
 190                 /* Do the node's children first */
 191                 if (n->rb_left) {
 192                         n = n->rb_left;
 193                         continue;
 194                 }
 195                 if (n->rb_right) {
 196                         n = n->rb_right;
 197                         continue;
 198                 }
 199                 /*
 200                  * The node has no children; free it, and then zero
 201                  * out parent's link to it.  Finally go to the
 202                  * beginning of the loop and try to free the parent
 203                  * node.
 204                  */
 205                 parent = rb_parent(n);
 206                 entry = rb_entry(n, struct ext4_system_zone, node);
 207                 kmem_cache_free(ext4_system_zone_cachep, entry);
 208                 if (!parent)
 209                         EXT4_SB(sb)->system_blks = RB_ROOT;
 210                 else if (parent->rb_left == n)
 211                         parent->rb_left = NULL;
 212                 else if (parent->rb_right == n)
 213                         parent->rb_right = NULL;
 214                 n = parent;
 215         }
 216         EXT4_SB(sb)->system_blks = RB_ROOT;
 217 }
 218
 219 /*
 220  * Returns 1 if the passed-in block region (start_blk,
 221  * start_blk+count) is valid; 0 if some part of the block region
 222  * overlaps with filesystem metadata blocks.
 223  */
 224 int ext4_data_block_valid(struct ext4_sb_info *sbi, ext4_fsblk_t start_blk,
 225                           unsigned int count)
 226 {
 227         struct ext4_system_zone *entry;
 228         struct rb_node *n = sbi->system_blks.rb_node;
 229
 230         if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
 231             (start_blk + count < start_blk) ||
 232             (start_blk + count > ext4_blocks_count(sbi->s_es)))
 233                 return 0;
 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                         return 0;
 242         }
 243         return 1;
 244 }
 245