LXR linux/fs/ext4/block

   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
  24struct ext4_system_zone {
  25        struct rb_node  node;
  26        ext4_fsblk_t    start_blk;
  27        unsigned int    count;
  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        kmem_cache_destroy(ext4_system_zone_cachep);
  43}
  44
  45static 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 */
  58static 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
 123static 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
 141int 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 */
 182void 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 */
 223int 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
 249