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/slab.h>
20#include "ext4.h"
21
22struct ext4_system_zone {
23	struct rb_node	node;
24	ext4_fsblk_t	start_blk;
25	unsigned int	count;
26};
27
28static struct kmem_cache *ext4_system_zone_cachep;
29
30int __init ext4_init_system_zone(void)
31{
32	ext4_system_zone_cachep = KMEM_CACHE(ext4_system_zone, 0);
33	if (ext4_system_zone_cachep == NULL)
34		return -ENOMEM;
35	return 0;
36}
37
38void ext4_exit_system_zone(void)
39{
40	kmem_cache_destroy(ext4_system_zone_cachep);
41}
42
43static inline int can_merge(struct ext4_system_zone *entry1,
44		     struct ext4_system_zone *entry2)
45{
46	if ((entry1->start_blk + entry1->count) == entry2->start_blk)
47		return 1;
48	return 0;
49}
50
51/*
52 * Mark a range of blocks as belonging to the "system zone" --- that
53 * is, filesystem metadata blocks which should never be used by
54 * inodes.
55 */
56static int add_system_zone(struct ext4_sb_info *sbi,
57			   ext4_fsblk_t start_blk,
58			   unsigned int count)
59{
60	struct ext4_system_zone *new_entry = NULL, *entry;
61	struct rb_node **n = &sbi->system_blks.rb_node, *node;
62	struct rb_node *parent = NULL, *new_node = NULL;
63
64	while (*n) {
65		parent = *n;
66		entry = rb_entry(parent, struct ext4_system_zone, node);
67		if (start_blk < entry->start_blk)
68			n = &(*n)->rb_left;
69		else if (start_blk >= (entry->start_blk + entry->count))
70			n = &(*n)->rb_right;
71		else {
72			if (start_blk + count > (entry->start_blk +
73						 entry->count))
74				entry->count = (start_blk + count -
75						entry->start_blk);
76			new_node = *n;
77			new_entry = rb_entry(new_node, struct ext4_system_zone,
78					     node);
79			break;
80		}
81	}
82
83	if (!new_entry) {
84		new_entry = kmem_cache_alloc(ext4_system_zone_cachep,
85					     GFP_KERNEL);
86		if (!new_entry)
87			return -ENOMEM;
88		new_entry->start_blk = start_blk;
89		new_entry->count = count;
90		new_node = &new_entry->node;
91
92		rb_link_node(new_node, parent, n);
93		rb_insert_color(new_node, &sbi->system_blks);
94	}
95
96	/* Can we merge to the left? */
97	node = rb_prev(new_node);
98	if (node) {
99		entry = rb_entry(node, struct ext4_system_zone, node);
100		if (can_merge(entry, new_entry)) {
101			new_entry->start_blk = entry->start_blk;
102			new_entry->count += entry->count;
103			rb_erase(node, &sbi->system_blks);
104			kmem_cache_free(ext4_system_zone_cachep, entry);
105		}
106	}
107
108	/* Can we merge to the right? */
109	node = rb_next(new_node);
110	if (node) {
111		entry = rb_entry(node, struct ext4_system_zone, node);
112		if (can_merge(new_entry, entry)) {
113			new_entry->count += entry->count;
114			rb_erase(node, &sbi->system_blks);
115			kmem_cache_free(ext4_system_zone_cachep, entry);
116		}
117	}
118	return 0;
119}
120
121static void debug_print_tree(struct ext4_sb_info *sbi)
122{
123	struct rb_node *node;
124	struct ext4_system_zone *entry;
125	int first = 1;
126
127	printk(KERN_INFO "System zones: ");
128	node = rb_first(&sbi->system_blks);
129	while (node) {
130		entry = rb_entry(node, struct ext4_system_zone, node);
131		printk("%s%llu-%llu", first ? "" : ", ",
132		       entry->start_blk, entry->start_blk + entry->count - 1);
133		first = 0;
134		node = rb_next(node);
135	}
136	printk("\n");
137}
138
139int ext4_setup_system_zone(struct super_block *sb)
140{
141	ext4_group_t ngroups = ext4_get_groups_count(sb);
142	struct ext4_sb_info *sbi = EXT4_SB(sb);
143	struct ext4_group_desc *gdp;
144	ext4_group_t i;
145	int flex_size = ext4_flex_bg_size(sbi);
146	int ret;
147
148	if (!test_opt(sb, BLOCK_VALIDITY)) {
149		if (EXT4_SB(sb)->system_blks.rb_node)
150			ext4_release_system_zone(sb);
151		return 0;
152	}
153	if (EXT4_SB(sb)->system_blks.rb_node)
154		return 0;
155
156	for (i=0; i < ngroups; i++) {
157		if (ext4_bg_has_super(sb, i) &&
158		    ((i < 5) || ((i % flex_size) == 0)))
159			add_system_zone(sbi, ext4_group_first_block_no(sb, i),
160					ext4_bg_num_gdb(sb, i) + 1);
161		gdp = ext4_get_group_desc(sb, i, NULL);
162		ret = add_system_zone(sbi, ext4_block_bitmap(sb, gdp), 1);
163		if (ret)
164			return ret;
165		ret = add_system_zone(sbi, ext4_inode_bitmap(sb, gdp), 1);
166		if (ret)
167			return ret;
168		ret = add_system_zone(sbi, ext4_inode_table(sb, gdp),
169				sbi->s_itb_per_group);
170		if (ret)
171			return ret;
172	}
173
174	if (test_opt(sb, DEBUG))
175		debug_print_tree(EXT4_SB(sb));
176	return 0;
177}
178
179/* Called when the filesystem is unmounted */
180void ext4_release_system_zone(struct super_block *sb)
181{
182	struct ext4_system_zone	*entry, *n;
183
184	rbtree_postorder_for_each_entry_safe(entry, n,
185			&EXT4_SB(sb)->system_blks, node)
186		kmem_cache_free(ext4_system_zone_cachep, entry);
187
188	EXT4_SB(sb)->system_blks = RB_ROOT;
189}
190
191/*
192 * Returns 1 if the passed-in block region (start_blk,
193 * start_blk+count) is valid; 0 if some part of the block region
194 * overlaps with filesystem metadata blocks.
195 */
196int ext4_data_block_valid(struct ext4_sb_info *sbi, ext4_fsblk_t start_blk,
197			  unsigned int count)
198{
199	struct ext4_system_zone *entry;
200	struct rb_node *n = sbi->system_blks.rb_node;
201
202	if ((start_blk <= le32_to_cpu(sbi->s_es->s_first_data_block)) ||
203	    (start_blk + count < start_blk) ||
204	    (start_blk + count > ext4_blocks_count(sbi->s_es))) {
205		sbi->s_es->s_last_error_block = cpu_to_le64(start_blk);
206		return 0;
207	}
208	while (n) {
209		entry = rb_entry(n, struct ext4_system_zone, node);
210		if (start_blk + count - 1 < entry->start_blk)
211			n = n->rb_left;
212		else if (start_blk >= (entry->start_blk + entry->count))
213			n = n->rb_right;
214		else {
215			sbi->s_es->s_last_error_block = cpu_to_le64(start_blk);
216			return 0;
217		}
218	}
219	return 1;
220}
221
222int ext4_check_blockref(const char *function, unsigned int line,
223			struct inode *inode, __le32 *p, unsigned int max)
224{
225	struct ext4_super_block *es = EXT4_SB(inode->i_sb)->s_es;
226	__le32 *bref = p;
227	unsigned int blk;
228
229	while (bref < p+max) {
230		blk = le32_to_cpu(*bref++);
231		if (blk &&
232		    unlikely(!ext4_data_block_valid(EXT4_SB(inode->i_sb),
233						    blk, 1))) {
234			es->s_last_error_block = cpu_to_le64(blk);
235			ext4_error_inode(inode, function, line, blk,
236					 "invalid block");
237			return -EFSCORRUPTED;
238		}
239	}
240	return 0;
241}
242
243