1 /*
2 * extent.c --- ext2 extent abstraction
3 *
4 * This abstraction is used to provide a compact way of representing a
5 * translation table, for moving multiple contiguous ranges (extents)
6 * of blocks or inodes.
7 *
8 * Copyright (C) 1997, 1998 by Theodore Ts'o and
9 * PowerQuest, Inc.
10 *
11 * Copyright (C) 1999, 2000 by Theodore Ts'o
12 *
13 * %Begin-Header%
14 * This file may be redistributed under the terms of the GNU Public
15 * License.
16 * %End-Header%
17 */
18
19 #include "config.h"
20 #include "resize2fs.h"
21
22 struct ext2_extent_entry {
23 __u64 old_loc, new_loc;
24 __u64 size;
25 };
26
27 struct _ext2_extent {
28 struct ext2_extent_entry *list;
29 __u64 cursor;
30 __u64 size;
31 __u64 num;
32 __u64 sorted;
33 };
34
35 /*
36 * Create an extent table
37 */
ext2fs_create_extent_table(ext2_extent * ret_extent,__u64 size)38 errcode_t ext2fs_create_extent_table(ext2_extent *ret_extent, __u64 size)
39 {
40 ext2_extent extent;
41 errcode_t retval;
42
43 retval = ext2fs_get_mem(sizeof(struct _ext2_extent), &extent);
44 if (retval)
45 return retval;
46 memset(extent, 0, sizeof(struct _ext2_extent));
47
48 extent->size = size ? size : 50;
49 extent->cursor = 0;
50 extent->num = 0;
51 extent->sorted = 1;
52
53 retval = ext2fs_get_array(sizeof(struct ext2_extent_entry),
54 extent->size, &extent->list);
55 if (retval) {
56 ext2fs_free_mem(&extent);
57 return retval;
58 }
59 memset(extent->list, 0,
60 sizeof(struct ext2_extent_entry) * extent->size);
61 *ret_extent = extent;
62 return 0;
63 }
64
65 /*
66 * Free an extent table
67 */
ext2fs_free_extent_table(ext2_extent extent)68 void ext2fs_free_extent_table(ext2_extent extent)
69 {
70 if (extent->list)
71 ext2fs_free_mem(&extent->list);
72 extent->list = 0;
73 extent->size = 0;
74 extent->num = 0;
75 ext2fs_free_mem(&extent);
76 }
77
78 /*
79 * Add an entry to the extent table
80 */
ext2fs_add_extent_entry(ext2_extent extent,__u64 old_loc,__u64 new_loc)81 errcode_t ext2fs_add_extent_entry(ext2_extent extent, __u64 old_loc, __u64 new_loc)
82 {
83 struct ext2_extent_entry *ent;
84 errcode_t retval;
85 __u64 newsize;
86 __u64 curr;
87
88 if (extent->num >= extent->size) {
89 newsize = extent->size + 100;
90 retval = ext2fs_resize_mem(sizeof(struct ext2_extent_entry) *
91 extent->size,
92 sizeof(struct ext2_extent_entry) *
93 newsize, &extent->list);
94 if (retval)
95 return retval;
96 extent->size = newsize;
97 }
98 curr = extent->num;
99 ent = extent->list + curr;
100 if (curr) {
101 /*
102 * Check to see if this can be coalesced with the last
103 * extent
104 */
105 ent--;
106 if ((ent->old_loc + ent->size == old_loc) &&
107 (ent->new_loc + ent->size == new_loc)) {
108 ent->size++;
109 return 0;
110 }
111 /*
112 * Now see if we're going to ruin the sorting
113 */
114 if (ent->old_loc + ent->size > old_loc)
115 extent->sorted = 0;
116 ent++;
117 }
118 ent->old_loc = old_loc;
119 ent->new_loc = new_loc;
120 ent->size = 1;
121 extent->num++;
122 return 0;
123 }
124
125 /*
126 * Helper function for qsort
127 */
extent_cmp(const void * a,const void * b)128 static EXT2_QSORT_TYPE extent_cmp(const void *a, const void *b)
129 {
130 const struct ext2_extent_entry *db_a;
131 const struct ext2_extent_entry *db_b;
132
133 db_a = (const struct ext2_extent_entry *) a;
134 db_b = (const struct ext2_extent_entry *) b;
135
136 return (db_a->old_loc - db_b->old_loc);
137 }
138
139 /*
140 * Given an inode map and inode number, look up the old inode number
141 * and return the new inode number.
142 */
ext2fs_extent_translate(ext2_extent extent,__u64 old_loc)143 __u64 ext2fs_extent_translate(ext2_extent extent, __u64 old_loc)
144 {
145 __s64 low, high, mid;
146 __u64 lowval, highval;
147 float range;
148
149 if (!extent->sorted) {
150 qsort(extent->list, extent->num,
151 sizeof(struct ext2_extent_entry), extent_cmp);
152 extent->sorted = 1;
153 }
154 low = 0;
155 high = extent->num-1;
156 while (low <= high) {
157 #if 0
158 mid = (low+high)/2;
159 #else
160 if (low == high)
161 mid = low;
162 else {
163 /* Interpolate for efficiency */
164 lowval = extent->list[low].old_loc;
165 highval = extent->list[high].old_loc;
166
167 if (old_loc < lowval)
168 range = 0;
169 else if (old_loc > highval)
170 range = 1;
171 else {
172 range = ((float) (old_loc - lowval)) /
173 (highval - lowval);
174 if (range > 0.9)
175 range = 0.9;
176 if (range < 0.1)
177 range = 0.1;
178 }
179 mid = low + ((__u64) (range * (high-low)));
180 }
181 #endif
182 if ((old_loc >= extent->list[mid].old_loc) &&
183 (old_loc < extent->list[mid].old_loc + extent->list[mid].size))
184 return (extent->list[mid].new_loc +
185 (old_loc - extent->list[mid].old_loc));
186 if (old_loc < extent->list[mid].old_loc)
187 high = mid-1;
188 else
189 low = mid+1;
190 }
191 return 0;
192 }
193
194 /*
195 * For debugging only
196 */
ext2fs_extent_dump(ext2_extent extent,FILE * out)197 void ext2fs_extent_dump(ext2_extent extent, FILE *out)
198 {
199 __u64 i;
200 struct ext2_extent_entry *ent;
201
202 fputs(_("# Extent dump:\n"), out);
203 fprintf(out, _("#\tNum=%llu, Size=%llu, Cursor=%llu, Sorted=%llu\n"),
204 extent->num, extent->size, extent->cursor, extent->sorted);
205 for (i=0, ent=extent->list; i < extent->num; i++, ent++) {
206 fprintf(out, "#\t\t %llu -> %llu (%llu)\n", ent->old_loc,
207 ent->new_loc, ent->size);
208 }
209 }
210
211 /*
212 * Iterate over the contents of the extent table
213 */
ext2fs_iterate_extent(ext2_extent extent,__u64 * old_loc,__u64 * new_loc,__u64 * size)214 errcode_t ext2fs_iterate_extent(ext2_extent extent, __u64 *old_loc,
215 __u64 *new_loc, __u64 *size)
216 {
217 struct ext2_extent_entry *ent;
218
219 if (!old_loc) {
220 extent->cursor = 0;
221 return 0;
222 }
223
224 if (extent->cursor >= extent->num) {
225 *old_loc = 0;
226 *new_loc = 0;
227 *size = 0;
228 return 0;
229 }
230
231 ent = extent->list + extent->cursor++;
232
233 *old_loc = ent->old_loc;
234 *new_loc = ent->new_loc;
235 *size = ent->size;
236 return 0;
237 }
238
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