1// SPDX-License-Identifier: GPL-2.0
2/*
3 *  linux/fs/sysv/itree.c
4 *
5 *  Handling of indirect blocks' trees.
6 *  AV, Sep--Dec 2000
7 */
8
9#include <linux/buffer_head.h>
10#include <linux/mount.h>
11#include <linux/mpage.h>
12#include <linux/string.h>
13#include "sysv.h"
14
15enum {DIRECT = 10, DEPTH = 4};	/* Have triple indirect */
16
17static inline void dirty_indirect(struct buffer_head *bh, struct inode *inode)
18{
19	mark_buffer_dirty_inode(bh, inode);
20	if (IS_SYNC(inode))
21		sync_dirty_buffer(bh);
22}
23
24static int block_to_path(struct inode *inode, long block, int offsets[DEPTH])
25{
26	struct super_block *sb = inode->i_sb;
27	struct sysv_sb_info *sbi = SYSV_SB(sb);
28	int ptrs_bits = sbi->s_ind_per_block_bits;
29	unsigned long	indirect_blocks = sbi->s_ind_per_block,
30			double_blocks = sbi->s_ind_per_block_2;
31	int n = 0;
32
33	if (block < 0) {
34		printk("sysv_block_map: block < 0\n");
35	} else if (block < DIRECT) {
36		offsets[n++] = block;
37	} else if ( (block -= DIRECT) < indirect_blocks) {
38		offsets[n++] = DIRECT;
39		offsets[n++] = block;
40	} else if ((block -= indirect_blocks) < double_blocks) {
41		offsets[n++] = DIRECT+1;
42		offsets[n++] = block >> ptrs_bits;
43		offsets[n++] = block & (indirect_blocks - 1);
44	} else if (((block -= double_blocks) >> (ptrs_bits * 2)) < indirect_blocks) {
45		offsets[n++] = DIRECT+2;
46		offsets[n++] = block >> (ptrs_bits * 2);
47		offsets[n++] = (block >> ptrs_bits) & (indirect_blocks - 1);
48		offsets[n++] = block & (indirect_blocks - 1);
49	} else {
50		/* nothing */;
51	}
52	return n;
53}
54
55static inline int block_to_cpu(struct sysv_sb_info *sbi, sysv_zone_t nr)
56{
57	return sbi->s_block_base + fs32_to_cpu(sbi, nr);
58}
59
60typedef struct {
61	sysv_zone_t     *p;
62	sysv_zone_t     key;
63	struct buffer_head *bh;
64} Indirect;
65
66static DEFINE_RWLOCK(pointers_lock);
67
68static inline void add_chain(Indirect *p, struct buffer_head *bh, sysv_zone_t *v)
69{
70	p->key = *(p->p = v);
71	p->bh = bh;
72}
73
74static inline int verify_chain(Indirect *from, Indirect *to)
75{
76	while (from <= to && from->key == *from->p)
77		from++;
78	return (from > to);
79}
80
81static inline sysv_zone_t *block_end(struct buffer_head *bh)
82{
83	return (sysv_zone_t*)((char*)bh->b_data + bh->b_size);
84}
85
86static Indirect *get_branch(struct inode *inode,
87			    int depth,
88			    int offsets[],
89			    Indirect chain[],
90			    int *err)
91{
92	struct super_block *sb = inode->i_sb;
93	Indirect *p = chain;
94	struct buffer_head *bh;
95
96	*err = 0;
97	add_chain(chain, NULL, SYSV_I(inode)->i_data + *offsets);
98	if (!p->key)
99		goto no_block;
100	while (--depth) {
101		int block = block_to_cpu(SYSV_SB(sb), p->key);
102		bh = sb_bread(sb, block);
103		if (!bh)
104			goto failure;
105		read_lock(&pointers_lock);
106		if (!verify_chain(chain, p))
107			goto changed;
108		add_chain(++p, bh, (sysv_zone_t*)bh->b_data + *++offsets);
109		read_unlock(&pointers_lock);
110		if (!p->key)
111			goto no_block;
112	}
113	return NULL;
114
115changed:
116	read_unlock(&pointers_lock);
117	brelse(bh);
118	*err = -EAGAIN;
119	goto no_block;
120failure:
121	*err = -EIO;
122no_block:
123	return p;
124}
125
126static int alloc_branch(struct inode *inode,
127			int num,
128			int *offsets,
129			Indirect *branch)
130{
131	int blocksize = inode->i_sb->s_blocksize;
132	int n = 0;
133	int i;
134
135	branch[0].key = sysv_new_block(inode->i_sb);
136	if (branch[0].key) for (n = 1; n < num; n++) {
137		struct buffer_head *bh;
138		int parent;
139		/* Allocate the next block */
140		branch[n].key = sysv_new_block(inode->i_sb);
141		if (!branch[n].key)
142			break;
143		/*
144		 * Get buffer_head for parent block, zero it out and set
145		 * the pointer to new one, then send parent to disk.
146		 */
147		parent = block_to_cpu(SYSV_SB(inode->i_sb), branch[n-1].key);
148		bh = sb_getblk(inode->i_sb, parent);
149		if (!bh) {
150			sysv_free_block(inode->i_sb, branch[n].key);
151			break;
152		}
153		lock_buffer(bh);
154		memset(bh->b_data, 0, blocksize);
155		branch[n].bh = bh;
156		branch[n].p = (sysv_zone_t*) bh->b_data + offsets[n];
157		*branch[n].p = branch[n].key;
158		set_buffer_uptodate(bh);
159		unlock_buffer(bh);
160		dirty_indirect(bh, inode);
161	}
162	if (n == num)
163		return 0;
164
165	/* Allocation failed, free what we already allocated */
166	for (i = 1; i < n; i++)
167		bforget(branch[i].bh);
168	for (i = 0; i < n; i++)
169		sysv_free_block(inode->i_sb, branch[i].key);
170	return -ENOSPC;
171}
172
173static inline int splice_branch(struct inode *inode,
174				Indirect chain[],
175				Indirect *where,
176				int num)
177{
178	int i;
179
180	/* Verify that place we are splicing to is still there and vacant */
181	write_lock(&pointers_lock);
182	if (!verify_chain(chain, where-1) || *where->p)
183		goto changed;
184	*where->p = where->key;
185	write_unlock(&pointers_lock);
186
187	inode_set_ctime_current(inode);
188
189	/* had we spliced it onto indirect block? */
190	if (where->bh)
191		dirty_indirect(where->bh, inode);
192
193	if (IS_SYNC(inode))
194		sysv_sync_inode(inode);
195	else
196		mark_inode_dirty(inode);
197	return 0;
198
199changed:
200	write_unlock(&pointers_lock);
201	for (i = 1; i < num; i++)
202		bforget(where[i].bh);
203	for (i = 0; i < num; i++)
204		sysv_free_block(inode->i_sb, where[i].key);
205	return -EAGAIN;
206}
207
208static int get_block(struct inode *inode, sector_t iblock, struct buffer_head *bh_result, int create)
209{
210	int err = -EIO;
211	int offsets[DEPTH];
212	Indirect chain[DEPTH];
213	struct super_block *sb = inode->i_sb;
214	Indirect *partial;
215	int left;
216	int depth = block_to_path(inode, iblock, offsets);
217
218	if (depth == 0)
219		goto out;
220
221reread:
222	partial = get_branch(inode, depth, offsets, chain, &err);
223
224	/* Simplest case - block found, no allocation needed */
225	if (!partial) {
226got_it:
227		map_bh(bh_result, sb, block_to_cpu(SYSV_SB(sb),
228					chain[depth-1].key));
229		/* Clean up and exit */
230		partial = chain+depth-1; /* the whole chain */
231		goto cleanup;
232	}
233
234	/* Next simple case - plain lookup or failed read of indirect block */
235	if (!create || err == -EIO) {
236cleanup:
237		while (partial > chain) {
238			brelse(partial->bh);
239			partial--;
240		}
241out:
242		return err;
243	}
244
245	/*
246	 * Indirect block might be removed by truncate while we were
247	 * reading it. Handling of that case (forget what we've got and
248	 * reread) is taken out of the main path.
249	 */
250	if (err == -EAGAIN)
251		goto changed;
252
253	left = (chain + depth) - partial;
254	err = alloc_branch(inode, left, offsets+(partial-chain), partial);
255	if (err)
256		goto cleanup;
257
258	if (splice_branch(inode, chain, partial, left) < 0)
259		goto changed;
260
261	set_buffer_new(bh_result);
262	goto got_it;
263
264changed:
265	while (partial > chain) {
266		brelse(partial->bh);
267		partial--;
268	}
269	goto reread;
270}
271
272static inline int all_zeroes(sysv_zone_t *p, sysv_zone_t *q)
273{
274	while (p < q)
275		if (*p++)
276			return 0;
277	return 1;
278}
279
280static Indirect *find_shared(struct inode *inode,
281				int depth,
282				int offsets[],
283				Indirect chain[],
284				sysv_zone_t *top)
285{
286	Indirect *partial, *p;
287	int k, err;
288
289	*top = 0;
290	for (k = depth; k > 1 && !offsets[k-1]; k--)
291		;
292	partial = get_branch(inode, k, offsets, chain, &err);
293
294	write_lock(&pointers_lock);
295	if (!partial)
296		partial = chain + k-1;
297	/*
298	 * If the branch acquired continuation since we've looked at it -
299	 * fine, it should all survive and (new) top doesn't belong to us.
300	 */
301	if (!partial->key && *partial->p) {
302		write_unlock(&pointers_lock);
303		goto no_top;
304	}
305	for (p=partial; p>chain && all_zeroes((sysv_zone_t*)p->bh->b_data,p->p); p--)
306		;
307	/*
308	 * OK, we've found the last block that must survive. The rest of our
309	 * branch should be detached before unlocking. However, if that rest
310	 * of branch is all ours and does not grow immediately from the inode
311	 * it's easier to cheat and just decrement partial->p.
312	 */
313	if (p == chain + k - 1 && p > chain) {
314		p->p--;
315	} else {
316		*top = *p->p;
317		*p->p = 0;
318	}
319	write_unlock(&pointers_lock);
320
321	while (partial > p) {
322		brelse(partial->bh);
323		partial--;
324	}
325no_top:
326	return partial;
327}
328
329static inline void free_data(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q)
330{
331	for ( ; p < q ; p++) {
332		sysv_zone_t nr = *p;
333		if (nr) {
334			*p = 0;
335			sysv_free_block(inode->i_sb, nr);
336			mark_inode_dirty(inode);
337		}
338	}
339}
340
341static void free_branches(struct inode *inode, sysv_zone_t *p, sysv_zone_t *q, int depth)
342{
343	struct buffer_head * bh;
344	struct super_block *sb = inode->i_sb;
345
346	if (depth--) {
347		for ( ; p < q ; p++) {
348			int block;
349			sysv_zone_t nr = *p;
350			if (!nr)
351				continue;
352			*p = 0;
353			block = block_to_cpu(SYSV_SB(sb), nr);
354			bh = sb_bread(sb, block);
355			if (!bh)
356				continue;
357			free_branches(inode, (sysv_zone_t*)bh->b_data,
358					block_end(bh), depth);
359			bforget(bh);
360			sysv_free_block(sb, nr);
361			mark_inode_dirty(inode);
362		}
363	} else
364		free_data(inode, p, q);
365}
366
367void sysv_truncate (struct inode * inode)
368{
369	sysv_zone_t *i_data = SYSV_I(inode)->i_data;
370	int offsets[DEPTH];
371	Indirect chain[DEPTH];
372	Indirect *partial;
373	sysv_zone_t nr = 0;
374	int n;
375	long iblock;
376	unsigned blocksize;
377
378	if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
379	    S_ISLNK(inode->i_mode)))
380		return;
381
382	blocksize = inode->i_sb->s_blocksize;
383	iblock = (inode->i_size + blocksize-1)
384					>> inode->i_sb->s_blocksize_bits;
385
386	block_truncate_page(inode->i_mapping, inode->i_size, get_block);
387
388	n = block_to_path(inode, iblock, offsets);
389	if (n == 0)
390		return;
391
392	if (n == 1) {
393		free_data(inode, i_data+offsets[0], i_data + DIRECT);
394		goto do_indirects;
395	}
396
397	partial = find_shared(inode, n, offsets, chain, &nr);
398	/* Kill the top of shared branch (already detached) */
399	if (nr) {
400		if (partial == chain)
401			mark_inode_dirty(inode);
402		else
403			dirty_indirect(partial->bh, inode);
404		free_branches(inode, &nr, &nr+1, (chain+n-1) - partial);
405	}
406	/* Clear the ends of indirect blocks on the shared branch */
407	while (partial > chain) {
408		free_branches(inode, partial->p + 1, block_end(partial->bh),
409				(chain+n-1) - partial);
410		dirty_indirect(partial->bh, inode);
411		brelse (partial->bh);
412		partial--;
413	}
414do_indirects:
415	/* Kill the remaining (whole) subtrees (== subtrees deeper than...) */
416	while (n < DEPTH) {
417		nr = i_data[DIRECT + n - 1];
418		if (nr) {
419			i_data[DIRECT + n - 1] = 0;
420			mark_inode_dirty(inode);
421			free_branches(inode, &nr, &nr+1, n);
422		}
423		n++;
424	}
425	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
426	if (IS_SYNC(inode))
427		sysv_sync_inode (inode);
428	else
429		mark_inode_dirty(inode);
430}
431
432static unsigned sysv_nblocks(struct super_block *s, loff_t size)
433{
434	struct sysv_sb_info *sbi = SYSV_SB(s);
435	int ptrs_bits = sbi->s_ind_per_block_bits;
436	unsigned blocks, res, direct = DIRECT, i = DEPTH;
437	blocks = (size + s->s_blocksize - 1) >> s->s_blocksize_bits;
438	res = blocks;
439	while (--i && blocks > direct) {
440		blocks = ((blocks - direct - 1) >> ptrs_bits) + 1;
441		res += blocks;
442		direct = 1;
443	}
444	return res;
445}
446
447int sysv_getattr(struct mnt_idmap *idmap, const struct path *path,
448		 struct kstat *stat, u32 request_mask, unsigned int flags)
449{
450	struct super_block *s = path->dentry->d_sb;
451	generic_fillattr(&nop_mnt_idmap, request_mask, d_inode(path->dentry),
452			 stat);
453	stat->blocks = (s->s_blocksize / 512) * sysv_nblocks(s, stat->size);
454	stat->blksize = s->s_blocksize;
455	return 0;
456}
457
458static int sysv_writepages(struct address_space *mapping,
459		struct writeback_control *wbc)
460{
461	return mpage_writepages(mapping, wbc, get_block);
462}
463
464static int sysv_read_folio(struct file *file, struct folio *folio)
465{
466	return block_read_full_folio(folio, get_block);
467}
468
469int sysv_prepare_chunk(struct page *page, loff_t pos, unsigned len)
470{
471	return __block_write_begin(page, pos, len, get_block);
472}
473
474static void sysv_write_failed(struct address_space *mapping, loff_t to)
475{
476	struct inode *inode = mapping->host;
477
478	if (to > inode->i_size) {
479		truncate_pagecache(inode, inode->i_size);
480		sysv_truncate(inode);
481	}
482}
483
484static int sysv_write_begin(struct file *file, struct address_space *mapping,
485			loff_t pos, unsigned len,
486			struct page **pagep, void **fsdata)
487{
488	int ret;
489
490	ret = block_write_begin(mapping, pos, len, pagep, get_block);
491	if (unlikely(ret))
492		sysv_write_failed(mapping, pos + len);
493
494	return ret;
495}
496
497static sector_t sysv_bmap(struct address_space *mapping, sector_t block)
498{
499	return generic_block_bmap(mapping,block,get_block);
500}
501
502const struct address_space_operations sysv_aops = {
503	.dirty_folio = block_dirty_folio,
504	.invalidate_folio = block_invalidate_folio,
505	.read_folio = sysv_read_folio,
506	.writepages = sysv_writepages,
507	.write_begin = sysv_write_begin,
508	.write_end = generic_write_end,
509	.migrate_folio = buffer_migrate_folio,
510	.bmap = sysv_bmap
511};
512