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Linux/fs/ext4/block_validity.c

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  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 
269 

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