summaryrefslogtreecommitdiff
path: root/fs/minix/itree_common.c
blob: 043c3fdbc8e7ebe5b0d8cf8d078322c4936b2581 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
// SPDX-License-Identifier: GPL-2.0
/* Generic part */

typedef struct {
	block_t	*p;
	block_t	key;
	struct buffer_head *bh;
} Indirect;

static DEFINE_RWLOCK(pointers_lock);

static inline void add_chain(Indirect *p, struct buffer_head *bh, block_t *v)
{
	p->key = *(p->p = v);
	p->bh = bh;
}

static inline int verify_chain(Indirect *from, Indirect *to)
{
	while (from <= to && from->key == *from->p)
		from++;
	return (from > to);
}

static inline block_t *block_end(struct buffer_head *bh)
{
	return (block_t *)((char*)bh->b_data + bh->b_size);
}

static inline Indirect *get_branch(struct inode *inode,
					int depth,
					int *offsets,
					Indirect chain[DEPTH],
					int *err)
{
	struct super_block *sb = inode->i_sb;
	Indirect *p = chain;
	struct buffer_head *bh;

	*err = 0;
	/* i_data is not going away, no lock needed */
	add_chain (chain, NULL, i_data(inode) + *offsets);
	if (!p->key)
		goto no_block;
	while (--depth) {
		bh = sb_bread(sb, block_to_cpu(p->key));
		if (!bh)
			goto failure;
		read_lock(&pointers_lock);
		if (!verify_chain(chain, p))
			goto changed;
		add_chain(++p, bh, (block_t *)bh->b_data + *++offsets);
		read_unlock(&pointers_lock);
		if (!p->key)
			goto no_block;
	}
	return NULL;

changed:
	read_unlock(&pointers_lock);
	brelse(bh);
	*err = -EAGAIN;
	goto no_block;
failure:
	*err = -EIO;
no_block:
	return p;
}

static int alloc_branch(struct inode *inode,
			     int num,
			     int *offsets,
			     Indirect *branch)
{
	int n = 0;
	int i;
	int parent = minix_new_block(inode);

	branch[0].key = cpu_to_block(parent);
	if (parent) for (n = 1; n < num; n++) {
		struct buffer_head *bh;
		/* Allocate the next block */
		int nr = minix_new_block(inode);
		if (!nr)
			break;
		branch[n].key = cpu_to_block(nr);
		bh = sb_getblk(inode->i_sb, parent);
		lock_buffer(bh);
		memset(bh->b_data, 0, bh->b_size);
		branch[n].bh = bh;
		branch[n].p = (block_t*) bh->b_data + offsets[n];
		*branch[n].p = branch[n].key;
		set_buffer_uptodate(bh);
		unlock_buffer(bh);
		mark_buffer_dirty_inode(bh, inode);
		parent = nr;
	}
	if (n == num)
		return 0;

	/* Allocation failed, free what we already allocated */
	for (i = 1; i < n; i++)
		bforget(branch[i].bh);
	for (i = 0; i < n; i++)
		minix_free_block(inode, block_to_cpu(branch[i].key));
	return -ENOSPC;
}

static inline int splice_branch(struct inode *inode,
				     Indirect chain[DEPTH],
				     Indirect *where,
				     int num)
{
	int i;

	write_lock(&pointers_lock);

	/* Verify that place we are splicing to is still there and vacant */
	if (!verify_chain(chain, where-1) || *where->p)
		goto changed;

	*where->p = where->key;

	write_unlock(&pointers_lock);

	/* We are done with atomic stuff, now do the rest of housekeeping */

	inode->i_ctime = current_time(inode);

	/* had we spliced it onto indirect block? */
	if (where->bh)
		mark_buffer_dirty_inode(where->bh, inode);

	mark_inode_dirty(inode);
	return 0;

changed:
	write_unlock(&pointers_lock);
	for (i = 1; i < num; i++)
		bforget(where[i].bh);
	for (i = 0; i < num; i++)
		minix_free_block(inode, block_to_cpu(where[i].key));
	return -EAGAIN;
}

static int get_block(struct inode * inode, sector_t block,
			struct buffer_head *bh, int create)
{
	int err = -EIO;
	int offsets[DEPTH];
	Indirect chain[DEPTH];
	Indirect *partial;
	int left;
	int depth = block_to_path(inode, block, offsets);

	if (depth == 0)
		goto out;

reread:
	partial = get_branch(inode, depth, offsets, chain, &err);

	/* Simplest case - block found, no allocation needed */
	if (!partial) {
got_it:
		map_bh(bh, inode->i_sb, block_to_cpu(chain[depth-1].key));
		/* Clean up and exit */
		partial = chain+depth-1; /* the whole chain */
		goto cleanup;
	}

	/* Next simple case - plain lookup or failed read of indirect block */
	if (!create || err == -EIO) {
cleanup:
		while (partial > chain) {
			brelse(partial->bh);
			partial--;
		}
out:
		return err;
	}

	/*
	 * Indirect block might be removed by truncate while we were
	 * reading it. Handling of that case (forget what we've got and
	 * reread) is taken out of the main path.
	 */
	if (err == -EAGAIN)
		goto changed;

	left = (chain + depth) - partial;
	err = alloc_branch(inode, left, offsets+(partial-chain), partial);
	if (err)
		goto cleanup;

	if (splice_branch(inode, chain, partial, left) < 0)
		goto changed;

	set_buffer_new(bh);
	goto got_it;

changed:
	while (partial > chain) {
		brelse(partial->bh);
		partial--;
	}
	goto reread;
}

static inline int all_zeroes(block_t *p, block_t *q)
{
	while (p < q)
		if (*p++)
			return 0;
	return 1;
}

static Indirect *find_shared(struct inode *inode,
				int depth,
				int offsets[DEPTH],
				Indirect chain[DEPTH],
				block_t *top)
{
	Indirect *partial, *p;
	int k, err;

	*top = 0;
	for (k = depth; k > 1 && !offsets[k-1]; k--)
		;
	partial = get_branch(inode, k, offsets, chain, &err);

	write_lock(&pointers_lock);
	if (!partial)
		partial = chain + k-1;
	if (!partial->key && *partial->p) {
		write_unlock(&pointers_lock);
		goto no_top;
	}
	for (p=partial;p>chain && all_zeroes((block_t*)p->bh->b_data,p->p);p--)
		;
	if (p == chain + k - 1 && p > chain) {
		p->p--;
	} else {
		*top = *p->p;
		*p->p = 0;
	}
	write_unlock(&pointers_lock);

	while(partial > p)
	{
		brelse(partial->bh);
		partial--;
	}
no_top:
	return partial;
}

static inline void free_data(struct inode *inode, block_t *p, block_t *q)
{
	unsigned long nr;

	for ( ; p < q ; p++) {
		nr = block_to_cpu(*p);
		if (nr) {
			*p = 0;
			minix_free_block(inode, nr);
		}
	}
}

static void free_branches(struct inode *inode, block_t *p, block_t *q, int depth)
{
	struct buffer_head * bh;
	unsigned long nr;

	if (depth--) {
		for ( ; p < q ; p++) {
			nr = block_to_cpu(*p);
			if (!nr)
				continue;
			*p = 0;
			bh = sb_bread(inode->i_sb, nr);
			if (!bh)
				continue;
			free_branches(inode, (block_t*)bh->b_data,
				      block_end(bh), depth);
			bforget(bh);
			minix_free_block(inode, nr);
			mark_inode_dirty(inode);
		}
	} else
		free_data(inode, p, q);
}

static inline void truncate (struct inode * inode)
{
	struct super_block *sb = inode->i_sb;
	block_t *idata = i_data(inode);
	int offsets[DEPTH];
	Indirect chain[DEPTH];
	Indirect *partial;
	block_t nr = 0;
	int n;
	int first_whole;
	long iblock;

	iblock = (inode->i_size + sb->s_blocksize -1) >> sb->s_blocksize_bits;
	block_truncate_page(inode->i_mapping, inode->i_size, get_block);

	n = block_to_path(inode, iblock, offsets);
	if (!n)
		return;

	if (n == 1) {
		free_data(inode, idata+offsets[0], idata + DIRECT);
		first_whole = 0;
		goto do_indirects;
	}

	first_whole = offsets[0] + 1 - DIRECT;
	partial = find_shared(inode, n, offsets, chain, &nr);
	if (nr) {
		if (partial == chain)
			mark_inode_dirty(inode);
		else
			mark_buffer_dirty_inode(partial->bh, inode);
		free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
	}
	/* Clear the ends of indirect blocks on the shared branch */
	while (partial > chain) {
		free_branches(inode, partial->p + 1, block_end(partial->bh),
				(chain+n-1) - partial);
		mark_buffer_dirty_inode(partial->bh, inode);
		brelse (partial->bh);
		partial--;
	}
do_indirects:
	/* Kill the remaining (whole) subtrees */
	while (first_whole < DEPTH-1) {
		nr = idata[DIRECT+first_whole];
		if (nr) {
			idata[DIRECT+first_whole] = 0;
			mark_inode_dirty(inode);
			free_branches(inode, &nr, &nr+1, first_whole+1);
		}
		first_whole++;
	}
	inode->i_mtime = inode->i_ctime = current_time(inode);
	mark_inode_dirty(inode);
}

static inline unsigned nblocks(loff_t size, struct super_block *sb)
{
	int k = sb->s_blocksize_bits - 10;
	unsigned blocks, res, direct = DIRECT, i = DEPTH;
	blocks = (size + sb->s_blocksize - 1) >> (BLOCK_SIZE_BITS + k);
	res = blocks;
	while (--i && blocks > direct) {
		blocks -= direct;
		blocks += sb->s_blocksize/sizeof(block_t) - 1;
		blocks /= sb->s_blocksize/sizeof(block_t);
		res += blocks;
		direct = 1;
	}
	return res;
}