6fe3c941b565142a2b6956bfaab6c78b085e602f
[releases.git] / block_validity.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *  linux/fs/ext4/block_validity.c
4  *
5  * Copyright (C) 2009
6  * Theodore Ts'o (tytso@mit.edu)
7  *
8  * Track which blocks in the filesystem are metadata blocks that
9  * should never be used as data blocks by files or directories.
10  */
11
12 #include <linux/time.h>
13 #include <linux/fs.h>
14 #include <linux/namei.h>
15 #include <linux/quotaops.h>
16 #include <linux/buffer_head.h>
17 #include <linux/swap.h>
18 #include <linux/pagemap.h>
19 #include <linux/blkdev.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         u32             ino;
28 };
29
30 static struct kmem_cache *ext4_system_zone_cachep;
31
32 int __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
40 void ext4_exit_system_zone(void)
41 {
42         rcu_barrier();
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             entry1->ino == entry2->ino)
51                 return 1;
52         return 0;
53 }
54
55 static void release_system_zone(struct ext4_system_blocks *system_blks)
56 {
57         struct ext4_system_zone *entry, *n;
58
59         rbtree_postorder_for_each_entry_safe(entry, n,
60                                 &system_blks->root, node)
61                 kmem_cache_free(ext4_system_zone_cachep, entry);
62 }
63
64 /*
65  * Mark a range of blocks as belonging to the "system zone" --- that
66  * is, filesystem metadata blocks which should never be used by
67  * inodes.
68  */
69 static int add_system_zone(struct ext4_system_blocks *system_blks,
70                            ext4_fsblk_t start_blk,
71                            unsigned int count, u32 ino)
72 {
73         struct ext4_system_zone *new_entry, *entry;
74         struct rb_node **n = &system_blks->root.rb_node, *node;
75         struct rb_node *parent = NULL, *new_node = NULL;
76
77         while (*n) {
78                 parent = *n;
79                 entry = rb_entry(parent, struct ext4_system_zone, node);
80                 if (start_blk < entry->start_blk)
81                         n = &(*n)->rb_left;
82                 else if (start_blk >= (entry->start_blk + entry->count))
83                         n = &(*n)->rb_right;
84                 else    /* Unexpected overlap of system zones. */
85                         return -EFSCORRUPTED;
86         }
87
88         new_entry = kmem_cache_alloc(ext4_system_zone_cachep,
89                                      GFP_KERNEL);
90         if (!new_entry)
91                 return -ENOMEM;
92         new_entry->start_blk = start_blk;
93         new_entry->count = count;
94         new_entry->ino = ino;
95         new_node = &new_entry->node;
96
97         rb_link_node(new_node, parent, n);
98         rb_insert_color(new_node, &system_blks->root);
99
100         /* Can we merge to the left? */
101         node = rb_prev(new_node);
102         if (node) {
103                 entry = rb_entry(node, struct ext4_system_zone, node);
104                 if (can_merge(entry, new_entry)) {
105                         new_entry->start_blk = entry->start_blk;
106                         new_entry->count += entry->count;
107                         rb_erase(node, &system_blks->root);
108                         kmem_cache_free(ext4_system_zone_cachep, entry);
109                 }
110         }
111
112         /* Can we merge to the right? */
113         node = rb_next(new_node);
114         if (node) {
115                 entry = rb_entry(node, struct ext4_system_zone, node);
116                 if (can_merge(new_entry, entry)) {
117                         new_entry->count += entry->count;
118                         rb_erase(node, &system_blks->root);
119                         kmem_cache_free(ext4_system_zone_cachep, entry);
120                 }
121         }
122         return 0;
123 }
124
125 static void debug_print_tree(struct ext4_sb_info *sbi)
126 {
127         struct rb_node *node;
128         struct ext4_system_zone *entry;
129         struct ext4_system_blocks *system_blks;
130         int first = 1;
131
132         printk(KERN_INFO "System zones: ");
133         rcu_read_lock();
134         system_blks = rcu_dereference(sbi->s_system_blks);
135         node = rb_first(&system_blks->root);
136         while (node) {
137                 entry = rb_entry(node, struct ext4_system_zone, node);
138                 printk(KERN_CONT "%s%llu-%llu", first ? "" : ", ",
139                        entry->start_blk, entry->start_blk + entry->count - 1);
140                 first = 0;
141                 node = rb_next(node);
142         }
143         rcu_read_unlock();
144         printk(KERN_CONT "\n");
145 }
146
147 static int ext4_protect_reserved_inode(struct super_block *sb,
148                                        struct ext4_system_blocks *system_blks,
149                                        u32 ino)
150 {
151         struct inode *inode;
152         struct ext4_sb_info *sbi = EXT4_SB(sb);
153         struct ext4_map_blocks map;
154         u32 i = 0, num;
155         int err = 0, n;
156
157         if ((ino < EXT4_ROOT_INO) ||
158             (ino > le32_to_cpu(sbi->s_es->s_inodes_count)))
159                 return -EINVAL;
160         inode = ext4_iget(sb, ino, EXT4_IGET_SPECIAL);
161         if (IS_ERR(inode))
162                 return PTR_ERR(inode);
163         num = (inode->i_size + sb->s_blocksize - 1) >> sb->s_blocksize_bits;
164         while (i < num) {
165                 cond_resched();
166                 map.m_lblk = i;
167                 map.m_len = num - i;
168                 n = ext4_map_blocks(NULL, inode, &map, 0);
169                 if (n < 0) {
170                         err = n;
171                         break;
172                 }
173                 if (n == 0) {
174                         i++;
175                 } else {
176                         err = add_system_zone(system_blks, map.m_pblk, n, ino);
177                         if (err < 0) {
178                                 if (err == -EFSCORRUPTED) {
179                                         EXT4_ERROR_INODE_ERR(inode, -err,
180                                                 "blocks %llu-%llu from inode overlap system zone",
181                                                 map.m_pblk,
182                                                 map.m_pblk + map.m_len - 1);
183                                 }
184                                 break;
185                         }
186                         i += n;
187                 }
188         }
189         iput(inode);
190         return err;
191 }
192
193 static void ext4_destroy_system_zone(struct rcu_head *rcu)
194 {
195         struct ext4_system_blocks *system_blks;
196
197         system_blks = container_of(rcu, struct ext4_system_blocks, rcu);
198         release_system_zone(system_blks);
199         kfree(system_blks);
200 }
201
202 /*
203  * Build system zone rbtree which is used for block validity checking.
204  *
205  * The update of system_blks pointer in this function is protected by
206  * sb->s_umount semaphore. However we have to be careful as we can be
207  * racing with ext4_inode_block_valid() calls reading system_blks rbtree
208  * protected only by RCU. That's why we first build the rbtree and then
209  * swap it in place.
210  */
211 int ext4_setup_system_zone(struct super_block *sb)
212 {
213         ext4_group_t ngroups = ext4_get_groups_count(sb);
214         struct ext4_sb_info *sbi = EXT4_SB(sb);
215         struct ext4_system_blocks *system_blks;
216         struct ext4_group_desc *gdp;
217         ext4_group_t i;
218         int ret;
219
220         system_blks = kzalloc(sizeof(*system_blks), GFP_KERNEL);
221         if (!system_blks)
222                 return -ENOMEM;
223
224         for (i=0; i < ngroups; i++) {
225                 unsigned int meta_blks = ext4_num_base_meta_blocks(sb, i);
226
227                 cond_resched();
228                 if (meta_blks != 0) {
229                         ret = add_system_zone(system_blks,
230                                         ext4_group_first_block_no(sb, i),
231                                         meta_blks, 0);
232                         if (ret)
233                                 goto err;
234                 }
235                 gdp = ext4_get_group_desc(sb, i, NULL);
236                 ret = add_system_zone(system_blks,
237                                 ext4_block_bitmap(sb, gdp), 1, 0);
238                 if (ret)
239                         goto err;
240                 ret = add_system_zone(system_blks,
241                                 ext4_inode_bitmap(sb, gdp), 1, 0);
242                 if (ret)
243                         goto err;
244                 ret = add_system_zone(system_blks,
245                                 ext4_inode_table(sb, gdp),
246                                 sbi->s_itb_per_group, 0);
247                 if (ret)
248                         goto err;
249         }
250         if (ext4_has_feature_journal(sb) && sbi->s_es->s_journal_inum) {
251                 ret = ext4_protect_reserved_inode(sb, system_blks,
252                                 le32_to_cpu(sbi->s_es->s_journal_inum));
253                 if (ret)
254                         goto err;
255         }
256
257         /*
258          * System blks rbtree complete, announce it once to prevent racing
259          * with ext4_inode_block_valid() accessing the rbtree at the same
260          * time.
261          */
262         rcu_assign_pointer(sbi->s_system_blks, system_blks);
263
264         if (test_opt(sb, DEBUG))
265                 debug_print_tree(sbi);
266         return 0;
267 err:
268         release_system_zone(system_blks);
269         kfree(system_blks);
270         return ret;
271 }
272
273 /*
274  * Called when the filesystem is unmounted or when remounting it with
275  * noblock_validity specified.
276  *
277  * The update of system_blks pointer in this function is protected by
278  * sb->s_umount semaphore. However we have to be careful as we can be
279  * racing with ext4_inode_block_valid() calls reading system_blks rbtree
280  * protected only by RCU. So we first clear the system_blks pointer and
281  * then free the rbtree only after RCU grace period expires.
282  */
283 void ext4_release_system_zone(struct super_block *sb)
284 {
285         struct ext4_system_blocks *system_blks;
286
287         system_blks = rcu_dereference_protected(EXT4_SB(sb)->s_system_blks,
288                                         lockdep_is_held(&sb->s_umount));
289         rcu_assign_pointer(EXT4_SB(sb)->s_system_blks, NULL);
290
291         if (system_blks)
292                 call_rcu(&system_blks->rcu, ext4_destroy_system_zone);
293 }
294
295 int ext4_sb_block_valid(struct super_block *sb, struct inode *inode,
296                                 ext4_fsblk_t start_blk, unsigned int count)
297 {
298         struct ext4_sb_info *sbi = EXT4_SB(sb);
299         struct ext4_system_blocks *system_blks;
300         struct ext4_system_zone *entry;
301         struct rb_node *n;
302         int ret = 1;
303
304         if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
305             (start_blk + count < start_blk) ||
306             (start_blk + count > ext4_blocks_count(sbi->s_es)))
307                 return 0;
308
309         /*
310          * Lock the system zone to prevent it being released concurrently
311          * when doing a remount which inverse current "[no]block_validity"
312          * mount option.
313          */
314         rcu_read_lock();
315         system_blks = rcu_dereference(sbi->s_system_blks);
316         if (system_blks == NULL)
317                 goto out_rcu;
318
319         n = system_blks->root.rb_node;
320         while (n) {
321                 entry = rb_entry(n, struct ext4_system_zone, node);
322                 if (start_blk + count - 1 < entry->start_blk)
323                         n = n->rb_left;
324                 else if (start_blk >= (entry->start_blk + entry->count))
325                         n = n->rb_right;
326                 else {
327                         ret = 0;
328                         if (inode)
329                                 ret = (entry->ino == inode->i_ino);
330                         break;
331                 }
332         }
333 out_rcu:
334         rcu_read_unlock();
335         return ret;
336 }
337
338 /*
339  * Returns 1 if the passed-in block region (start_blk,
340  * start_blk+count) is valid; 0 if some part of the block region
341  * overlaps with some other filesystem metadata blocks.
342  */
343 int ext4_inode_block_valid(struct inode *inode, ext4_fsblk_t start_blk,
344                           unsigned int count)
345 {
346         return ext4_sb_block_valid(inode->i_sb, inode, start_blk, count);
347 }
348
349 int ext4_check_blockref(const char *function, unsigned int line,
350                         struct inode *inode, __le32 *p, unsigned int max)
351 {
352         __le32 *bref = p;
353         unsigned int blk;
354
355         if (ext4_has_feature_journal(inode->i_sb) &&
356             (inode->i_ino ==
357              le32_to_cpu(EXT4_SB(inode->i_sb)->s_es->s_journal_inum)))
358                 return 0;
359
360         while (bref < p+max) {
361                 blk = le32_to_cpu(*bref++);
362                 if (blk &&
363                     unlikely(!ext4_inode_block_valid(inode, blk, 1))) {
364                         ext4_error_inode(inode, function, line, blk,
365                                          "invalid block");
366                         return -EFSCORRUPTED;
367                 }
368         }
369         return 0;
370 }
371