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 } 245 246