xref: /linux/fs/bcachefs/namei.c (revision 037ada7a3181300218e4fd78bef6a741cfa7f808)
1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include "bcachefs.h"
4 #include "acl.h"
5 #include "btree_update.h"
6 #include "dirent.h"
7 #include "inode.h"
8 #include "namei.h"
9 #include "subvolume.h"
10 #include "xattr.h"
11 
12 #include <linux/posix_acl.h>
13 
14 static inline int is_subdir_for_nlink(struct bch_inode_unpacked *inode)
15 {
16 	return S_ISDIR(inode->bi_mode) && !inode->bi_subvol;
17 }
18 
19 int bch2_create_trans(struct btree_trans *trans,
20 		      subvol_inum dir,
21 		      struct bch_inode_unpacked *dir_u,
22 		      struct bch_inode_unpacked *new_inode,
23 		      const struct qstr *name,
24 		      uid_t uid, gid_t gid, umode_t mode, dev_t rdev,
25 		      struct posix_acl *default_acl,
26 		      struct posix_acl *acl,
27 		      subvol_inum snapshot_src,
28 		      unsigned flags)
29 {
30 	struct bch_fs *c = trans->c;
31 	struct btree_iter dir_iter = {};
32 	struct btree_iter inode_iter = {};
33 	subvol_inum new_inum = dir;
34 	u64 now = bch2_current_time(c);
35 	u64 cpu = raw_smp_processor_id();
36 	u64 dir_target;
37 	u32 snapshot;
38 	unsigned dir_type = mode_to_type(mode);
39 	int ret;
40 
41 	ret = bch2_subvolume_get_snapshot(trans, dir.subvol, &snapshot);
42 	if (ret)
43 		goto err;
44 
45 	ret = bch2_inode_peek(trans, &dir_iter, dir_u, dir,
46 			      BTREE_ITER_intent|BTREE_ITER_with_updates);
47 	if (ret)
48 		goto err;
49 
50 	if (!(flags & BCH_CREATE_SNAPSHOT)) {
51 		/* Normal create path - allocate a new inode: */
52 		bch2_inode_init_late(new_inode, now, uid, gid, mode, rdev, dir_u);
53 
54 		if (flags & BCH_CREATE_TMPFILE)
55 			new_inode->bi_flags |= BCH_INODE_unlinked;
56 
57 		ret = bch2_inode_create(trans, &inode_iter, new_inode, snapshot, cpu);
58 		if (ret)
59 			goto err;
60 
61 		snapshot_src = (subvol_inum) { 0 };
62 	} else {
63 		/*
64 		 * Creating a snapshot - we're not allocating a new inode, but
65 		 * we do have to lookup the root inode of the subvolume we're
66 		 * snapshotting and update it (in the new snapshot):
67 		 */
68 
69 		if (!snapshot_src.inum) {
70 			/* Inode wasn't specified, just snapshot: */
71 			struct bch_subvolume s;
72 			ret = bch2_subvolume_get(trans, snapshot_src.subvol, true, &s);
73 			if (ret)
74 				goto err;
75 
76 			snapshot_src.inum = le64_to_cpu(s.inode);
77 		}
78 
79 		ret = bch2_inode_peek(trans, &inode_iter, new_inode, snapshot_src,
80 				      BTREE_ITER_intent);
81 		if (ret)
82 			goto err;
83 
84 		if (new_inode->bi_subvol != snapshot_src.subvol) {
85 			/* Not a subvolume root: */
86 			ret = -EINVAL;
87 			goto err;
88 		}
89 
90 		/*
91 		 * If we're not root, we have to own the subvolume being
92 		 * snapshotted:
93 		 */
94 		if (uid && new_inode->bi_uid != uid) {
95 			ret = -EPERM;
96 			goto err;
97 		}
98 
99 		flags |= BCH_CREATE_SUBVOL;
100 	}
101 
102 	new_inum.inum	= new_inode->bi_inum;
103 	dir_target	= new_inode->bi_inum;
104 
105 	if (flags & BCH_CREATE_SUBVOL) {
106 		u32 new_subvol, dir_snapshot;
107 
108 		ret = bch2_subvolume_create(trans, new_inode->bi_inum,
109 					    dir.subvol,
110 					    snapshot_src.subvol,
111 					    &new_subvol, &snapshot,
112 					    (flags & BCH_CREATE_SNAPSHOT_RO) != 0);
113 		if (ret)
114 			goto err;
115 
116 		new_inode->bi_parent_subvol	= dir.subvol;
117 		new_inode->bi_subvol		= new_subvol;
118 		new_inum.subvol			= new_subvol;
119 		dir_target			= new_subvol;
120 		dir_type			= DT_SUBVOL;
121 
122 		ret = bch2_subvolume_get_snapshot(trans, dir.subvol, &dir_snapshot);
123 		if (ret)
124 			goto err;
125 
126 		bch2_btree_iter_set_snapshot(trans, &dir_iter, dir_snapshot);
127 		ret = bch2_btree_iter_traverse(trans, &dir_iter);
128 		if (ret)
129 			goto err;
130 	}
131 
132 	if (!(flags & BCH_CREATE_SNAPSHOT)) {
133 		if (default_acl) {
134 			ret = bch2_set_acl_trans(trans, new_inum, new_inode,
135 						 default_acl, ACL_TYPE_DEFAULT);
136 			if (ret)
137 				goto err;
138 		}
139 
140 		if (acl) {
141 			ret = bch2_set_acl_trans(trans, new_inum, new_inode,
142 						 acl, ACL_TYPE_ACCESS);
143 			if (ret)
144 				goto err;
145 		}
146 	}
147 
148 	if (!(flags & BCH_CREATE_TMPFILE)) {
149 		struct bch_hash_info dir_hash = bch2_hash_info_init(c, dir_u);
150 		u64 dir_offset;
151 
152 		if (is_subdir_for_nlink(new_inode))
153 			dir_u->bi_nlink++;
154 		dir_u->bi_mtime = dir_u->bi_ctime = now;
155 
156 		ret =   bch2_dirent_create(trans, dir, &dir_hash,
157 					   dir_type,
158 					   name,
159 					   dir_target,
160 					   &dir_offset,
161 					   &dir_u->bi_size,
162 					   STR_HASH_must_create|BTREE_ITER_with_updates) ?:
163 			bch2_inode_write(trans, &dir_iter, dir_u);
164 		if (ret)
165 			goto err;
166 
167 		new_inode->bi_dir		= dir_u->bi_inum;
168 		new_inode->bi_dir_offset	= dir_offset;
169 	}
170 
171 	if (S_ISDIR(mode) &&
172 	    !new_inode->bi_subvol)
173 		new_inode->bi_depth = dir_u->bi_depth + 1;
174 
175 	inode_iter.flags &= ~BTREE_ITER_all_snapshots;
176 	bch2_btree_iter_set_snapshot(trans, &inode_iter, snapshot);
177 
178 	ret   = bch2_btree_iter_traverse(trans, &inode_iter) ?:
179 		bch2_inode_write(trans, &inode_iter, new_inode);
180 err:
181 	bch2_trans_iter_exit(trans, &inode_iter);
182 	bch2_trans_iter_exit(trans, &dir_iter);
183 	return ret;
184 }
185 
186 int bch2_link_trans(struct btree_trans *trans,
187 		    subvol_inum dir,  struct bch_inode_unpacked *dir_u,
188 		    subvol_inum inum, struct bch_inode_unpacked *inode_u,
189 		    const struct qstr *name)
190 {
191 	struct bch_fs *c = trans->c;
192 	struct btree_iter dir_iter = {};
193 	struct btree_iter inode_iter = {};
194 	struct bch_hash_info dir_hash;
195 	u64 now = bch2_current_time(c);
196 	u64 dir_offset = 0;
197 	int ret;
198 
199 	if (dir.subvol != inum.subvol)
200 		return -EXDEV;
201 
202 	ret = bch2_inode_peek(trans, &inode_iter, inode_u, inum, BTREE_ITER_intent);
203 	if (ret)
204 		return ret;
205 
206 	inode_u->bi_ctime = now;
207 	ret = bch2_inode_nlink_inc(inode_u);
208 	if (ret)
209 		goto err;
210 
211 	ret = bch2_inode_peek(trans, &dir_iter, dir_u, dir, BTREE_ITER_intent);
212 	if (ret)
213 		goto err;
214 
215 	if (bch2_reinherit_attrs(inode_u, dir_u)) {
216 		ret = -EXDEV;
217 		goto err;
218 	}
219 
220 	dir_u->bi_mtime = dir_u->bi_ctime = now;
221 
222 	dir_hash = bch2_hash_info_init(c, dir_u);
223 
224 	ret = bch2_dirent_create(trans, dir, &dir_hash,
225 				 mode_to_type(inode_u->bi_mode),
226 				 name, inum.inum,
227 				 &dir_offset,
228 				 &dir_u->bi_size,
229 				 STR_HASH_must_create);
230 	if (ret)
231 		goto err;
232 
233 	inode_u->bi_dir		= dir.inum;
234 	inode_u->bi_dir_offset	= dir_offset;
235 
236 	ret =   bch2_inode_write(trans, &dir_iter, dir_u) ?:
237 		bch2_inode_write(trans, &inode_iter, inode_u);
238 err:
239 	bch2_trans_iter_exit(trans, &dir_iter);
240 	bch2_trans_iter_exit(trans, &inode_iter);
241 	return ret;
242 }
243 
244 int bch2_unlink_trans(struct btree_trans *trans,
245 		      subvol_inum dir,
246 		      struct bch_inode_unpacked *dir_u,
247 		      struct bch_inode_unpacked *inode_u,
248 		      const struct qstr *name,
249 		      bool deleting_subvol)
250 {
251 	struct bch_fs *c = trans->c;
252 	struct btree_iter dir_iter = {};
253 	struct btree_iter dirent_iter = {};
254 	struct btree_iter inode_iter = {};
255 	struct bch_hash_info dir_hash;
256 	subvol_inum inum;
257 	u64 now = bch2_current_time(c);
258 	struct bkey_s_c k;
259 	int ret;
260 
261 	ret = bch2_inode_peek(trans, &dir_iter, dir_u, dir, BTREE_ITER_intent);
262 	if (ret)
263 		goto err;
264 
265 	dir_hash = bch2_hash_info_init(c, dir_u);
266 
267 	ret = bch2_dirent_lookup_trans(trans, &dirent_iter, dir, &dir_hash,
268 				       name, &inum, BTREE_ITER_intent);
269 	if (ret)
270 		goto err;
271 
272 	ret = bch2_inode_peek(trans, &inode_iter, inode_u, inum,
273 			      BTREE_ITER_intent);
274 	if (ret)
275 		goto err;
276 
277 	if (!deleting_subvol && S_ISDIR(inode_u->bi_mode)) {
278 		ret = bch2_empty_dir_trans(trans, inum);
279 		if (ret)
280 			goto err;
281 	}
282 
283 	if (deleting_subvol && !inode_u->bi_subvol) {
284 		ret = -BCH_ERR_ENOENT_not_subvol;
285 		goto err;
286 	}
287 
288 	if (inode_u->bi_subvol) {
289 		/* Recursive subvolume destroy not allowed (yet?) */
290 		ret = bch2_subvol_has_children(trans, inode_u->bi_subvol);
291 		if (ret)
292 			goto err;
293 	}
294 
295 	if (deleting_subvol || inode_u->bi_subvol) {
296 		ret = bch2_subvolume_unlink(trans, inode_u->bi_subvol);
297 		if (ret)
298 			goto err;
299 
300 		k = bch2_btree_iter_peek_slot(trans, &dirent_iter);
301 		ret = bkey_err(k);
302 		if (ret)
303 			goto err;
304 
305 		/*
306 		 * If we're deleting a subvolume, we need to really delete the
307 		 * dirent, not just emit a whiteout in the current snapshot:
308 		 */
309 		bch2_btree_iter_set_snapshot(trans, &dirent_iter, k.k->p.snapshot);
310 		ret = bch2_btree_iter_traverse(trans, &dirent_iter);
311 		if (ret)
312 			goto err;
313 	} else {
314 		bch2_inode_nlink_dec(trans, inode_u);
315 	}
316 
317 	if (inode_u->bi_dir		== dirent_iter.pos.inode &&
318 	    inode_u->bi_dir_offset	== dirent_iter.pos.offset) {
319 		inode_u->bi_dir		= 0;
320 		inode_u->bi_dir_offset	= 0;
321 	}
322 
323 	dir_u->bi_mtime = dir_u->bi_ctime = inode_u->bi_ctime = now;
324 	dir_u->bi_nlink -= is_subdir_for_nlink(inode_u);
325 
326 	ret =   bch2_hash_delete_at(trans, bch2_dirent_hash_desc,
327 				    &dir_hash, &dirent_iter,
328 				    BTREE_UPDATE_internal_snapshot_node) ?:
329 		bch2_inode_write(trans, &dir_iter, dir_u) ?:
330 		bch2_inode_write(trans, &inode_iter, inode_u);
331 err:
332 	bch2_trans_iter_exit(trans, &inode_iter);
333 	bch2_trans_iter_exit(trans, &dirent_iter);
334 	bch2_trans_iter_exit(trans, &dir_iter);
335 	return ret;
336 }
337 
338 bool bch2_reinherit_attrs(struct bch_inode_unpacked *dst_u,
339 			  struct bch_inode_unpacked *src_u)
340 {
341 	u64 src, dst;
342 	unsigned id;
343 	bool ret = false;
344 
345 	for (id = 0; id < Inode_opt_nr; id++) {
346 		/* Skip attributes that were explicitly set on this inode */
347 		if (dst_u->bi_fields_set & (1 << id))
348 			continue;
349 
350 		src = bch2_inode_opt_get(src_u, id);
351 		dst = bch2_inode_opt_get(dst_u, id);
352 
353 		if (src == dst)
354 			continue;
355 
356 		bch2_inode_opt_set(dst_u, id, src);
357 		ret = true;
358 	}
359 
360 	return ret;
361 }
362 
363 static int subvol_update_parent(struct btree_trans *trans, u32 subvol, u32 new_parent)
364 {
365 	struct btree_iter iter;
366 	struct bkey_i_subvolume *s =
367 		bch2_bkey_get_mut_typed(trans, &iter,
368 			BTREE_ID_subvolumes, POS(0, subvol),
369 			BTREE_ITER_cached, subvolume);
370 	int ret = PTR_ERR_OR_ZERO(s);
371 	if (ret)
372 		return ret;
373 
374 	s->v.fs_path_parent = cpu_to_le32(new_parent);
375 	bch2_trans_iter_exit(trans, &iter);
376 	return 0;
377 }
378 
379 int bch2_rename_trans(struct btree_trans *trans,
380 		      subvol_inum src_dir, struct bch_inode_unpacked *src_dir_u,
381 		      subvol_inum dst_dir, struct bch_inode_unpacked *dst_dir_u,
382 		      struct bch_inode_unpacked *src_inode_u,
383 		      struct bch_inode_unpacked *dst_inode_u,
384 		      const struct qstr *src_name,
385 		      const struct qstr *dst_name,
386 		      enum bch_rename_mode mode)
387 {
388 	struct bch_fs *c = trans->c;
389 	struct btree_iter src_dir_iter = {};
390 	struct btree_iter dst_dir_iter = {};
391 	struct btree_iter src_inode_iter = {};
392 	struct btree_iter dst_inode_iter = {};
393 	struct bch_hash_info src_hash, dst_hash;
394 	subvol_inum src_inum, dst_inum;
395 	u64 src_offset, dst_offset;
396 	u64 now = bch2_current_time(c);
397 	int ret;
398 
399 	ret = bch2_inode_peek(trans, &src_dir_iter, src_dir_u, src_dir,
400 			      BTREE_ITER_intent);
401 	if (ret)
402 		goto err;
403 
404 	src_hash = bch2_hash_info_init(c, src_dir_u);
405 
406 	if (dst_dir.inum	!= src_dir.inum ||
407 	    dst_dir.subvol	!= src_dir.subvol) {
408 		ret = bch2_inode_peek(trans, &dst_dir_iter, dst_dir_u, dst_dir,
409 				      BTREE_ITER_intent);
410 		if (ret)
411 			goto err;
412 
413 		dst_hash = bch2_hash_info_init(c, dst_dir_u);
414 	} else {
415 		dst_dir_u = src_dir_u;
416 		dst_hash = src_hash;
417 	}
418 
419 	ret = bch2_dirent_rename(trans,
420 				 src_dir, &src_hash, &src_dir_u->bi_size,
421 				 dst_dir, &dst_hash, &dst_dir_u->bi_size,
422 				 src_name, &src_inum, &src_offset,
423 				 dst_name, &dst_inum, &dst_offset,
424 				 mode);
425 	if (ret)
426 		goto err;
427 
428 	ret = bch2_inode_peek(trans, &src_inode_iter, src_inode_u, src_inum,
429 			      BTREE_ITER_intent);
430 	if (ret)
431 		goto err;
432 
433 	if (dst_inum.inum) {
434 		ret = bch2_inode_peek(trans, &dst_inode_iter, dst_inode_u, dst_inum,
435 				      BTREE_ITER_intent);
436 		if (ret)
437 			goto err;
438 	}
439 
440 	if (src_inode_u->bi_subvol &&
441 	    dst_dir.subvol != src_inode_u->bi_parent_subvol) {
442 		ret = subvol_update_parent(trans, src_inode_u->bi_subvol, dst_dir.subvol);
443 		if (ret)
444 			goto err;
445 	}
446 
447 	if (mode == BCH_RENAME_EXCHANGE &&
448 	    dst_inode_u->bi_subvol &&
449 	    src_dir.subvol != dst_inode_u->bi_parent_subvol) {
450 		ret = subvol_update_parent(trans, dst_inode_u->bi_subvol, src_dir.subvol);
451 		if (ret)
452 			goto err;
453 	}
454 
455 	/* Can't move across subvolumes, unless it's a subvolume root: */
456 	if (src_dir.subvol != dst_dir.subvol &&
457 	    (!src_inode_u->bi_subvol ||
458 	     (dst_inum.inum && !dst_inode_u->bi_subvol))) {
459 		ret = -EXDEV;
460 		goto err;
461 	}
462 
463 	if (src_inode_u->bi_parent_subvol)
464 		src_inode_u->bi_parent_subvol = dst_dir.subvol;
465 
466 	if ((mode == BCH_RENAME_EXCHANGE) &&
467 	    dst_inode_u->bi_parent_subvol)
468 		dst_inode_u->bi_parent_subvol = src_dir.subvol;
469 
470 	src_inode_u->bi_dir		= dst_dir_u->bi_inum;
471 	src_inode_u->bi_dir_offset	= dst_offset;
472 
473 	if (mode == BCH_RENAME_EXCHANGE) {
474 		dst_inode_u->bi_dir		= src_dir_u->bi_inum;
475 		dst_inode_u->bi_dir_offset	= src_offset;
476 	}
477 
478 	if (mode == BCH_RENAME_OVERWRITE &&
479 	    dst_inode_u->bi_dir		== dst_dir_u->bi_inum &&
480 	    dst_inode_u->bi_dir_offset	== src_offset) {
481 		dst_inode_u->bi_dir		= 0;
482 		dst_inode_u->bi_dir_offset	= 0;
483 	}
484 
485 	if (mode == BCH_RENAME_OVERWRITE) {
486 		if (S_ISDIR(src_inode_u->bi_mode) !=
487 		    S_ISDIR(dst_inode_u->bi_mode)) {
488 			ret = -ENOTDIR;
489 			goto err;
490 		}
491 
492 		if (S_ISDIR(dst_inode_u->bi_mode)) {
493 			ret = bch2_empty_dir_trans(trans, dst_inum);
494 			if (ret)
495 				goto err;
496 		}
497 	}
498 
499 	if (bch2_reinherit_attrs(src_inode_u, dst_dir_u) &&
500 	    S_ISDIR(src_inode_u->bi_mode)) {
501 		ret = -EXDEV;
502 		goto err;
503 	}
504 
505 	if (mode == BCH_RENAME_EXCHANGE &&
506 	    bch2_reinherit_attrs(dst_inode_u, src_dir_u) &&
507 	    S_ISDIR(dst_inode_u->bi_mode)) {
508 		ret = -EXDEV;
509 		goto err;
510 	}
511 
512 	if (is_subdir_for_nlink(src_inode_u)) {
513 		src_dir_u->bi_nlink--;
514 		dst_dir_u->bi_nlink++;
515 	}
516 
517 	if (S_ISDIR(src_inode_u->bi_mode) &&
518 	    !src_inode_u->bi_subvol)
519 		src_inode_u->bi_depth = dst_dir_u->bi_depth + 1;
520 
521 	if (mode == BCH_RENAME_EXCHANGE &&
522 	    S_ISDIR(dst_inode_u->bi_mode) &&
523 	    !dst_inode_u->bi_subvol)
524 		dst_inode_u->bi_depth = src_dir_u->bi_depth + 1;
525 
526 	if (dst_inum.inum && is_subdir_for_nlink(dst_inode_u)) {
527 		dst_dir_u->bi_nlink--;
528 		src_dir_u->bi_nlink += mode == BCH_RENAME_EXCHANGE;
529 	}
530 
531 	if (mode == BCH_RENAME_OVERWRITE)
532 		bch2_inode_nlink_dec(trans, dst_inode_u);
533 
534 	src_dir_u->bi_mtime		= now;
535 	src_dir_u->bi_ctime		= now;
536 
537 	if (src_dir.inum != dst_dir.inum) {
538 		dst_dir_u->bi_mtime	= now;
539 		dst_dir_u->bi_ctime	= now;
540 	}
541 
542 	src_inode_u->bi_ctime		= now;
543 
544 	if (dst_inum.inum)
545 		dst_inode_u->bi_ctime	= now;
546 
547 	ret =   bch2_inode_write(trans, &src_dir_iter, src_dir_u) ?:
548 		(src_dir.inum != dst_dir.inum
549 		 ? bch2_inode_write(trans, &dst_dir_iter, dst_dir_u)
550 		 : 0) ?:
551 		bch2_inode_write(trans, &src_inode_iter, src_inode_u) ?:
552 		(dst_inum.inum
553 		 ? bch2_inode_write(trans, &dst_inode_iter, dst_inode_u)
554 		 : 0);
555 err:
556 	bch2_trans_iter_exit(trans, &dst_inode_iter);
557 	bch2_trans_iter_exit(trans, &src_inode_iter);
558 	bch2_trans_iter_exit(trans, &dst_dir_iter);
559 	bch2_trans_iter_exit(trans, &src_dir_iter);
560 	return ret;
561 }
562 
563 /* inum_to_path */
564 
565 static inline void prt_bytes_reversed(struct printbuf *out, const void *b, unsigned n)
566 {
567 	bch2_printbuf_make_room(out, n);
568 
569 	unsigned can_print = min(n, printbuf_remaining(out));
570 
571 	b += n;
572 
573 	for (unsigned i = 0; i < can_print; i++)
574 		out->buf[out->pos++] = *((char *) --b);
575 
576 	printbuf_nul_terminate(out);
577 }
578 
579 static inline void prt_str_reversed(struct printbuf *out, const char *s)
580 {
581 	prt_bytes_reversed(out, s, strlen(s));
582 }
583 
584 static inline void reverse_bytes(void *b, size_t n)
585 {
586 	char *e = b + n, *s = b;
587 
588 	while (s < e) {
589 		--e;
590 		swap(*s, *e);
591 		s++;
592 	}
593 }
594 
595 /* XXX: we don't yet attempt to print paths when we don't know the subvol */
596 int bch2_inum_to_path(struct btree_trans *trans, subvol_inum inum, struct printbuf *path)
597 {
598 	unsigned orig_pos = path->pos;
599 	int ret = 0;
600 
601 	while (!(inum.subvol == BCACHEFS_ROOT_SUBVOL &&
602 		 inum.inum   == BCACHEFS_ROOT_INO)) {
603 		struct bch_inode_unpacked inode;
604 		ret = bch2_inode_find_by_inum_trans(trans, inum, &inode);
605 		if (ret)
606 			goto disconnected;
607 
608 		if (!inode.bi_dir && !inode.bi_dir_offset) {
609 			ret = -BCH_ERR_ENOENT_inode_no_backpointer;
610 			goto disconnected;
611 		}
612 
613 		inum.subvol	= inode.bi_parent_subvol ?: inum.subvol;
614 		inum.inum	= inode.bi_dir;
615 
616 		u32 snapshot;
617 		ret = bch2_subvolume_get_snapshot(trans, inum.subvol, &snapshot);
618 		if (ret)
619 			goto disconnected;
620 
621 		struct btree_iter d_iter;
622 		struct bkey_s_c_dirent d = bch2_bkey_get_iter_typed(trans, &d_iter,
623 				BTREE_ID_dirents, SPOS(inode.bi_dir, inode.bi_dir_offset, snapshot),
624 				0, dirent);
625 		ret = bkey_err(d.s_c);
626 		if (ret)
627 			goto disconnected;
628 
629 		struct qstr dirent_name = bch2_dirent_get_name(d);
630 		prt_bytes_reversed(path, dirent_name.name, dirent_name.len);
631 
632 		prt_char(path, '/');
633 
634 		bch2_trans_iter_exit(trans, &d_iter);
635 	}
636 
637 	if (orig_pos == path->pos)
638 		prt_char(path, '/');
639 out:
640 	ret = path->allocation_failure ? -ENOMEM : 0;
641 	if (ret)
642 		goto err;
643 
644 	reverse_bytes(path->buf + orig_pos, path->pos - orig_pos);
645 	return 0;
646 err:
647 	return ret;
648 disconnected:
649 	if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
650 		goto err;
651 
652 	prt_str_reversed(path, "(disconnected)");
653 	goto out;
654 }
655 
656 /* fsck */
657 
658 static int bch2_check_dirent_inode_dirent(struct btree_trans *trans,
659 					  struct bkey_s_c_dirent d,
660 					  struct bch_inode_unpacked *target,
661 					  bool in_fsck)
662 {
663 	struct bch_fs *c = trans->c;
664 	struct printbuf buf = PRINTBUF;
665 	struct btree_iter bp_iter = {};
666 	int ret = 0;
667 
668 	if (inode_points_to_dirent(target, d))
669 		return 0;
670 
671 	if (!target->bi_dir &&
672 	    !target->bi_dir_offset) {
673 		fsck_err_on(S_ISDIR(target->bi_mode),
674 			    trans, inode_dir_missing_backpointer,
675 			    "directory with missing backpointer\n%s",
676 			    (printbuf_reset(&buf),
677 			     bch2_bkey_val_to_text(&buf, c, d.s_c),
678 			     prt_printf(&buf, "\n"),
679 			     bch2_inode_unpacked_to_text(&buf, target),
680 			     buf.buf));
681 
682 		fsck_err_on(target->bi_flags & BCH_INODE_unlinked,
683 			    trans, inode_unlinked_but_has_dirent,
684 			    "inode unlinked but has dirent\n%s",
685 			    (printbuf_reset(&buf),
686 			     bch2_bkey_val_to_text(&buf, c, d.s_c),
687 			     prt_printf(&buf, "\n"),
688 			     bch2_inode_unpacked_to_text(&buf, target),
689 			     buf.buf));
690 
691 		target->bi_flags &= ~BCH_INODE_unlinked;
692 		target->bi_dir		= d.k->p.inode;
693 		target->bi_dir_offset	= d.k->p.offset;
694 		return __bch2_fsck_write_inode(trans, target);
695 	}
696 
697 	if (bch2_inode_should_have_single_bp(target) &&
698 	    !fsck_err(trans, inode_wrong_backpointer,
699 		      "dirent points to inode that does not point back:\n%s",
700 		      (bch2_bkey_val_to_text(&buf, c, d.s_c),
701 		       prt_newline(&buf),
702 		       bch2_inode_unpacked_to_text(&buf, target),
703 		       buf.buf)))
704 		goto err;
705 
706 	struct bkey_s_c_dirent bp_dirent =
707 		bch2_bkey_get_iter_typed(trans, &bp_iter, BTREE_ID_dirents,
708 			      SPOS(target->bi_dir, target->bi_dir_offset, target->bi_snapshot),
709 			      0, dirent);
710 	ret = bkey_err(bp_dirent);
711 	if (ret && !bch2_err_matches(ret, ENOENT))
712 		goto err;
713 
714 	bool backpointer_exists = !ret;
715 	ret = 0;
716 
717 	if (!backpointer_exists) {
718 		if (fsck_err(trans, inode_wrong_backpointer,
719 			     "inode %llu:%u has wrong backpointer:\n"
720 			     "got       %llu:%llu\n"
721 			     "should be %llu:%llu",
722 			     target->bi_inum, target->bi_snapshot,
723 			     target->bi_dir,
724 			     target->bi_dir_offset,
725 			     d.k->p.inode,
726 			     d.k->p.offset)) {
727 			target->bi_dir		= d.k->p.inode;
728 			target->bi_dir_offset	= d.k->p.offset;
729 			ret = __bch2_fsck_write_inode(trans, target);
730 		}
731 	} else {
732 		bch2_bkey_val_to_text(&buf, c, d.s_c);
733 		prt_newline(&buf);
734 		bch2_bkey_val_to_text(&buf, c, bp_dirent.s_c);
735 
736 		if (S_ISDIR(target->bi_mode) || target->bi_subvol) {
737 			/*
738 			 * XXX: verify connectivity of the other dirent
739 			 * up to the root before removing this one
740 			 *
741 			 * Additionally, bch2_lookup would need to cope with the
742 			 * dirent it found being removed - or should we remove
743 			 * the other one, even though the inode points to it?
744 			 */
745 			if (in_fsck) {
746 				if (fsck_err(trans, inode_dir_multiple_links,
747 					     "%s %llu:%u with multiple links\n%s",
748 					     S_ISDIR(target->bi_mode) ? "directory" : "subvolume",
749 					     target->bi_inum, target->bi_snapshot, buf.buf))
750 					ret = bch2_fsck_remove_dirent(trans, d.k->p);
751 			} else {
752 				bch2_fs_inconsistent(c,
753 						"%s %llu:%u with multiple links\n%s",
754 						S_ISDIR(target->bi_mode) ? "directory" : "subvolume",
755 						target->bi_inum, target->bi_snapshot, buf.buf);
756 			}
757 
758 			goto out;
759 		} else {
760 			/*
761 			 * hardlinked file with nlink 0:
762 			 * We're just adjusting nlink here so check_nlinks() will pick
763 			 * it up, it ignores inodes with nlink 0
764 			 */
765 			if (fsck_err_on(!target->bi_nlink,
766 					trans, inode_multiple_links_but_nlink_0,
767 					"inode %llu:%u type %s has multiple links but i_nlink 0\n%s",
768 					target->bi_inum, target->bi_snapshot, bch2_d_types[d.v->d_type], buf.buf)) {
769 				target->bi_nlink++;
770 				target->bi_flags &= ~BCH_INODE_unlinked;
771 				ret = __bch2_fsck_write_inode(trans, target);
772 				if (ret)
773 					goto err;
774 			}
775 		}
776 	}
777 out:
778 err:
779 fsck_err:
780 	bch2_trans_iter_exit(trans, &bp_iter);
781 	printbuf_exit(&buf);
782 	bch_err_fn(c, ret);
783 	return ret;
784 }
785 
786 int __bch2_check_dirent_target(struct btree_trans *trans,
787 			       struct btree_iter *dirent_iter,
788 			       struct bkey_s_c_dirent d,
789 			       struct bch_inode_unpacked *target,
790 			       bool in_fsck)
791 {
792 	struct bch_fs *c = trans->c;
793 	struct printbuf buf = PRINTBUF;
794 	int ret = 0;
795 
796 	ret = bch2_check_dirent_inode_dirent(trans, d, target, in_fsck);
797 	if (ret)
798 		goto err;
799 
800 	if (fsck_err_on(d.v->d_type != inode_d_type(target),
801 			trans, dirent_d_type_wrong,
802 			"incorrect d_type: got %s, should be %s:\n%s",
803 			bch2_d_type_str(d.v->d_type),
804 			bch2_d_type_str(inode_d_type(target)),
805 			(printbuf_reset(&buf),
806 			 bch2_bkey_val_to_text(&buf, c, d.s_c), buf.buf))) {
807 		struct bkey_i_dirent *n = bch2_trans_kmalloc(trans, bkey_bytes(d.k));
808 		ret = PTR_ERR_OR_ZERO(n);
809 		if (ret)
810 			goto err;
811 
812 		bkey_reassemble(&n->k_i, d.s_c);
813 		n->v.d_type = inode_d_type(target);
814 		if (n->v.d_type == DT_SUBVOL) {
815 			n->v.d_parent_subvol = cpu_to_le32(target->bi_parent_subvol);
816 			n->v.d_child_subvol = cpu_to_le32(target->bi_subvol);
817 		} else {
818 			n->v.d_inum = cpu_to_le64(target->bi_inum);
819 		}
820 
821 		ret = bch2_trans_update(trans, dirent_iter, &n->k_i, 0);
822 		if (ret)
823 			goto err;
824 	}
825 err:
826 fsck_err:
827 	printbuf_exit(&buf);
828 	bch_err_fn(c, ret);
829 	return ret;
830 }
831