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