Commit | Line | Data |
---|---|---|
8ed5eec9 AG |
1 | /* |
2 | * Overlayfs NFS export support. | |
3 | * | |
4 | * Amir Goldstein <amir73il@gmail.com> | |
5 | * | |
6 | * Copyright (C) 2017-2018 CTERA Networks. All Rights Reserved. | |
7 | * | |
8 | * This program is free software; you can redistribute it and/or modify it | |
9 | * under the terms of the GNU General Public License version 2 as published by | |
10 | * the Free Software Foundation. | |
11 | */ | |
12 | ||
13 | #include <linux/fs.h> | |
14 | #include <linux/cred.h> | |
15 | #include <linux/mount.h> | |
16 | #include <linux/namei.h> | |
17 | #include <linux/xattr.h> | |
18 | #include <linux/exportfs.h> | |
19 | #include <linux/ratelimit.h> | |
20 | #include "overlayfs.h" | |
21 | ||
2ca3c148 AG |
22 | static int ovl_encode_maybe_copy_up(struct dentry *dentry) |
23 | { | |
24 | int err; | |
25 | ||
26 | if (ovl_dentry_upper(dentry)) | |
27 | return 0; | |
28 | ||
29 | err = ovl_want_write(dentry); | |
30 | if (!err) { | |
31 | err = ovl_copy_up(dentry); | |
32 | ovl_drop_write(dentry); | |
33 | } | |
34 | ||
35 | if (err) { | |
36 | pr_warn_ratelimited("overlayfs: failed to copy up on encode (%pd2, err=%i)\n", | |
37 | dentry, err); | |
38 | } | |
39 | ||
40 | return err; | |
41 | } | |
42 | ||
43 | /* | |
44 | * Before encoding a non-upper directory file handle from real layer N, we need | |
45 | * to check if it will be possible to reconnect an overlay dentry from the real | |
46 | * lower decoded dentry. This is done by following the overlay ancestry up to a | |
47 | * "layer N connected" ancestor and verifying that all parents along the way are | |
48 | * "layer N connectable". If an ancestor that is NOT "layer N connectable" is | |
49 | * found, we need to copy up an ancestor, which is "layer N connectable", thus | |
50 | * making that ancestor "layer N connected". For example: | |
51 | * | |
52 | * layer 1: /a | |
53 | * layer 2: /a/b/c | |
54 | * | |
55 | * The overlay dentry /a is NOT "layer 2 connectable", because if dir /a is | |
56 | * copied up and renamed, upper dir /a will be indexed by lower dir /a from | |
57 | * layer 1. The dir /a from layer 2 will never be indexed, so the algorithm (*) | |
58 | * in ovl_lookup_real_ancestor() will not be able to lookup a connected overlay | |
59 | * dentry from the connected lower dentry /a/b/c. | |
60 | * | |
61 | * To avoid this problem on decode time, we need to copy up an ancestor of | |
62 | * /a/b/c, which is "layer 2 connectable", on encode time. That ancestor is | |
63 | * /a/b. After copy up (and index) of /a/b, it will become "layer 2 connected" | |
64 | * and when the time comes to decode the file handle from lower dentry /a/b/c, | |
65 | * ovl_lookup_real_ancestor() will find the indexed ancestor /a/b and decoding | |
66 | * a connected overlay dentry will be accomplished. | |
67 | * | |
68 | * (*) the algorithm in ovl_lookup_real_ancestor() can be improved to lookup an | |
69 | * entry /a in the lower layers above layer N and find the indexed dir /a from | |
70 | * layer 1. If that improvement is made, then the check for "layer N connected" | |
71 | * will need to verify there are no redirects in lower layers above N. In the | |
72 | * example above, /a will be "layer 2 connectable". However, if layer 2 dir /a | |
73 | * is a target of a layer 1 redirect, then /a will NOT be "layer 2 connectable": | |
74 | * | |
75 | * layer 1: /A (redirect = /a) | |
76 | * layer 2: /a/b/c | |
77 | */ | |
78 | ||
79 | /* Return the lowest layer for encoding a connectable file handle */ | |
80 | static int ovl_connectable_layer(struct dentry *dentry) | |
81 | { | |
82 | struct ovl_entry *oe = OVL_E(dentry); | |
83 | ||
84 | /* We can get overlay root from root of any layer */ | |
85 | if (dentry == dentry->d_sb->s_root) | |
86 | return oe->numlower; | |
87 | ||
88 | /* | |
89 | * If it's an unindexed merge dir, then it's not connectable with any | |
90 | * lower layer | |
91 | */ | |
92 | if (ovl_dentry_upper(dentry) && | |
93 | !ovl_test_flag(OVL_INDEX, d_inode(dentry))) | |
94 | return 0; | |
95 | ||
96 | /* We can get upper/overlay path from indexed/lower dentry */ | |
97 | return oe->lowerstack[0].layer->idx; | |
98 | } | |
99 | ||
100 | /* | |
101 | * @dentry is "connected" if all ancestors up to root or a "connected" ancestor | |
102 | * have the same uppermost lower layer as the origin's layer. We may need to | |
103 | * copy up a "connectable" ancestor to make it "connected". A "connected" dentry | |
104 | * cannot become non "connected", so cache positive result in dentry flags. | |
105 | * | |
106 | * Return the connected origin layer or < 0 on error. | |
107 | */ | |
108 | static int ovl_connect_layer(struct dentry *dentry) | |
109 | { | |
110 | struct dentry *next, *parent = NULL; | |
111 | int origin_layer; | |
112 | int err = 0; | |
113 | ||
114 | if (WARN_ON(dentry == dentry->d_sb->s_root) || | |
115 | WARN_ON(!ovl_dentry_lower(dentry))) | |
116 | return -EIO; | |
117 | ||
118 | origin_layer = OVL_E(dentry)->lowerstack[0].layer->idx; | |
119 | if (ovl_dentry_test_flag(OVL_E_CONNECTED, dentry)) | |
120 | return origin_layer; | |
121 | ||
122 | /* Find the topmost origin layer connectable ancestor of @dentry */ | |
123 | next = dget(dentry); | |
124 | for (;;) { | |
125 | parent = dget_parent(next); | |
126 | if (WARN_ON(parent == next)) { | |
127 | err = -EIO; | |
128 | break; | |
129 | } | |
130 | ||
131 | /* | |
132 | * If @parent is not origin layer connectable, then copy up | |
133 | * @next which is origin layer connectable and we are done. | |
134 | */ | |
135 | if (ovl_connectable_layer(parent) < origin_layer) { | |
136 | err = ovl_encode_maybe_copy_up(next); | |
137 | break; | |
138 | } | |
139 | ||
140 | /* If @parent is connected or indexed we are done */ | |
141 | if (ovl_dentry_test_flag(OVL_E_CONNECTED, parent) || | |
142 | ovl_test_flag(OVL_INDEX, d_inode(parent))) | |
143 | break; | |
144 | ||
145 | dput(next); | |
146 | next = parent; | |
147 | } | |
148 | ||
149 | dput(parent); | |
150 | dput(next); | |
151 | ||
152 | if (!err) | |
153 | ovl_dentry_set_flag(OVL_E_CONNECTED, dentry); | |
154 | ||
155 | return err ?: origin_layer; | |
156 | } | |
157 | ||
b305e844 AG |
158 | /* |
159 | * We only need to encode origin if there is a chance that the same object was | |
160 | * encoded pre copy up and then we need to stay consistent with the same | |
161 | * encoding also after copy up. If non-pure upper is not indexed, then it was | |
162 | * copied up before NFS export was enabled. In that case we don't need to worry | |
163 | * about staying consistent with pre copy up encoding and we encode an upper | |
164 | * file handle. Overlay root dentry is a private case of non-indexed upper. | |
165 | * | |
166 | * The following table summarizes the different file handle encodings used for | |
167 | * different overlay object types: | |
168 | * | |
169 | * Object type | Encoding | |
170 | * -------------------------------- | |
171 | * Pure upper | U | |
172 | * Non-indexed upper | U | |
05e1f118 AG |
173 | * Indexed upper | L (*) |
174 | * Non-upper | L (*) | |
b305e844 AG |
175 | * |
176 | * U = upper file handle | |
177 | * L = lower file handle | |
05e1f118 AG |
178 | * |
179 | * (*) Connecting an overlay dir from real lower dentry is not always | |
2ca3c148 AG |
180 | * possible when there are redirects in lower layers and non-indexed merge dirs. |
181 | * To mitigate those case, we may copy up the lower dir ancestor before encode | |
182 | * a lower dir file handle. | |
183 | * | |
184 | * Return 0 for upper file handle, > 0 for lower file handle or < 0 on error. | |
b305e844 | 185 | */ |
2ca3c148 | 186 | static int ovl_check_encode_origin(struct dentry *dentry) |
b305e844 | 187 | { |
05e1f118 AG |
188 | struct ovl_fs *ofs = dentry->d_sb->s_fs_info; |
189 | ||
2ca3c148 | 190 | /* Upper file handle for pure upper */ |
b305e844 | 191 | if (!ovl_dentry_lower(dentry)) |
2ca3c148 | 192 | return 0; |
b305e844 | 193 | |
05e1f118 | 194 | /* |
2ca3c148 | 195 | * Upper file handle for non-indexed upper. |
05e1f118 | 196 | * |
2ca3c148 AG |
197 | * Root is never indexed, so if there's an upper layer, encode upper for |
198 | * root. | |
05e1f118 | 199 | */ |
b305e844 AG |
200 | if (ovl_dentry_upper(dentry) && |
201 | !ovl_test_flag(OVL_INDEX, d_inode(dentry))) | |
05e1f118 AG |
202 | return 0; |
203 | ||
2ca3c148 AG |
204 | /* |
205 | * Decoding a merge dir, whose origin's ancestor is under a redirected | |
206 | * lower dir or under a non-indexed upper is not always possible. | |
207 | * ovl_connect_layer() will try to make origin's layer "connected" by | |
208 | * copying up a "connectable" ancestor. | |
209 | */ | |
210 | if (d_is_dir(dentry) && ofs->upper_mnt) | |
211 | return ovl_connect_layer(dentry); | |
05e1f118 | 212 | |
2ca3c148 AG |
213 | /* Lower file handle for indexed and non-upper dir/non-dir */ |
214 | return 1; | |
05e1f118 AG |
215 | } |
216 | ||
8ed5eec9 AG |
217 | static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen) |
218 | { | |
8ed5eec9 | 219 | struct ovl_fh *fh = NULL; |
2ca3c148 | 220 | int err, enc_lower; |
8ed5eec9 | 221 | |
05e1f118 | 222 | /* |
2ca3c148 AG |
223 | * Check if we should encode a lower or upper file handle and maybe |
224 | * copy up an ancestor to make lower file handle connectable. | |
05e1f118 | 225 | */ |
2ca3c148 AG |
226 | err = enc_lower = ovl_check_encode_origin(dentry); |
227 | if (enc_lower < 0) | |
228 | goto fail; | |
8ed5eec9 | 229 | |
2ca3c148 AG |
230 | /* Encode an upper or lower file handle */ |
231 | fh = ovl_encode_fh(enc_lower ? ovl_dentry_lower(dentry) : | |
232 | ovl_dentry_upper(dentry), !enc_lower); | |
9b6faee0 AG |
233 | err = PTR_ERR(fh); |
234 | if (IS_ERR(fh)) | |
235 | goto fail; | |
8ed5eec9 AG |
236 | |
237 | err = -EOVERFLOW; | |
238 | if (fh->len > buflen) | |
239 | goto fail; | |
240 | ||
241 | memcpy(buf, (char *)fh, fh->len); | |
242 | err = fh->len; | |
243 | ||
244 | out: | |
245 | kfree(fh); | |
246 | return err; | |
247 | ||
248 | fail: | |
249 | pr_warn_ratelimited("overlayfs: failed to encode file handle (%pd2, err=%i, buflen=%d, len=%d, type=%d)\n", | |
250 | dentry, err, buflen, fh ? (int)fh->len : 0, | |
251 | fh ? fh->type : 0); | |
252 | goto out; | |
253 | } | |
254 | ||
255 | static int ovl_dentry_to_fh(struct dentry *dentry, u32 *fid, int *max_len) | |
256 | { | |
257 | int res, len = *max_len << 2; | |
258 | ||
259 | res = ovl_d_to_fh(dentry, (char *)fid, len); | |
260 | if (res <= 0) | |
261 | return FILEID_INVALID; | |
262 | ||
263 | len = res; | |
264 | ||
265 | /* Round up to dwords */ | |
266 | *max_len = (len + 3) >> 2; | |
267 | return OVL_FILEID; | |
268 | } | |
269 | ||
270 | static int ovl_encode_inode_fh(struct inode *inode, u32 *fid, int *max_len, | |
271 | struct inode *parent) | |
272 | { | |
273 | struct dentry *dentry; | |
274 | int type; | |
275 | ||
276 | /* TODO: encode connectable file handles */ | |
277 | if (parent) | |
278 | return FILEID_INVALID; | |
279 | ||
280 | dentry = d_find_any_alias(inode); | |
281 | if (WARN_ON(!dentry)) | |
282 | return FILEID_INVALID; | |
283 | ||
284 | type = ovl_dentry_to_fh(dentry, fid, max_len); | |
285 | ||
286 | dput(dentry); | |
287 | return type; | |
288 | } | |
289 | ||
8556a420 | 290 | /* |
f71bd9cf | 291 | * Find or instantiate an overlay dentry from real dentries and index. |
8556a420 AG |
292 | */ |
293 | static struct dentry *ovl_obtain_alias(struct super_block *sb, | |
f71bd9cf AG |
294 | struct dentry *upper_alias, |
295 | struct ovl_path *lowerpath, | |
296 | struct dentry *index) | |
8556a420 | 297 | { |
f941866f | 298 | struct dentry *lower = lowerpath ? lowerpath->dentry : NULL; |
f71bd9cf | 299 | struct dentry *upper = upper_alias ?: index; |
8556a420 | 300 | struct dentry *dentry; |
f941866f | 301 | struct inode *inode; |
8556a420 | 302 | struct ovl_entry *oe; |
8556a420 | 303 | |
f71bd9cf AG |
304 | /* We get overlay directory dentries with ovl_lookup_real() */ |
305 | if (d_is_dir(upper ?: lower)) | |
8556a420 AG |
306 | return ERR_PTR(-EIO); |
307 | ||
f71bd9cf | 308 | inode = ovl_get_inode(sb, dget(upper), lower, index, !!lower); |
8556a420 AG |
309 | if (IS_ERR(inode)) { |
310 | dput(upper); | |
311 | return ERR_CAST(inode); | |
312 | } | |
313 | ||
f71bd9cf AG |
314 | if (index) |
315 | ovl_set_flag(OVL_INDEX, inode); | |
316 | ||
8556a420 AG |
317 | dentry = d_find_any_alias(inode); |
318 | if (!dentry) { | |
319 | dentry = d_alloc_anon(inode->i_sb); | |
320 | if (!dentry) | |
321 | goto nomem; | |
f941866f | 322 | oe = ovl_alloc_entry(lower ? 1 : 0); |
8556a420 AG |
323 | if (!oe) |
324 | goto nomem; | |
325 | ||
f941866f AG |
326 | if (lower) { |
327 | oe->lowerstack->dentry = dget(lower); | |
328 | oe->lowerstack->layer = lowerpath->layer; | |
329 | } | |
8556a420 | 330 | dentry->d_fsdata = oe; |
f71bd9cf | 331 | if (upper_alias) |
f941866f | 332 | ovl_dentry_set_upper_alias(dentry); |
8556a420 AG |
333 | } |
334 | ||
335 | return d_instantiate_anon(dentry, inode); | |
336 | ||
337 | nomem: | |
338 | iput(inode); | |
339 | dput(dentry); | |
340 | return ERR_PTR(-ENOMEM); | |
341 | } | |
342 | ||
98892516 AG |
343 | /* Get the upper or lower dentry in stach whose on layer @idx */ |
344 | static struct dentry *ovl_dentry_real_at(struct dentry *dentry, int idx) | |
345 | { | |
346 | struct ovl_entry *oe = dentry->d_fsdata; | |
347 | int i; | |
348 | ||
349 | if (!idx) | |
350 | return ovl_dentry_upper(dentry); | |
351 | ||
352 | for (i = 0; i < oe->numlower; i++) { | |
353 | if (oe->lowerstack[i].layer->idx == idx) | |
354 | return oe->lowerstack[i].dentry; | |
355 | } | |
356 | ||
357 | return NULL; | |
358 | } | |
359 | ||
3985b70a AG |
360 | /* |
361 | * Lookup a child overlay dentry to get a connected overlay dentry whose real | |
362 | * dentry is @real. If @real is on upper layer, we lookup a child overlay | |
363 | * dentry with the same name as the real dentry. Otherwise, we need to consult | |
364 | * index for lookup. | |
365 | */ | |
366 | static struct dentry *ovl_lookup_real_one(struct dentry *connected, | |
367 | struct dentry *real, | |
368 | struct ovl_layer *layer) | |
369 | { | |
370 | struct inode *dir = d_inode(connected); | |
371 | struct dentry *this, *parent = NULL; | |
372 | struct name_snapshot name; | |
373 | int err; | |
374 | ||
3985b70a AG |
375 | /* |
376 | * Lookup child overlay dentry by real name. The dir mutex protects us | |
377 | * from racing with overlay rename. If the overlay dentry that is above | |
378 | * real has already been moved to a parent that is not under the | |
379 | * connected overlay dir, we return -ECHILD and restart the lookup of | |
380 | * connected real path from the top. | |
381 | */ | |
382 | inode_lock_nested(dir, I_MUTEX_PARENT); | |
383 | err = -ECHILD; | |
384 | parent = dget_parent(real); | |
98892516 | 385 | if (ovl_dentry_real_at(connected, layer->idx) != parent) |
3985b70a AG |
386 | goto fail; |
387 | ||
388 | /* | |
389 | * We also need to take a snapshot of real dentry name to protect us | |
390 | * from racing with underlying layer rename. In this case, we don't | |
391 | * care about returning ESTALE, only from dereferencing a free name | |
392 | * pointer because we hold no lock on the real dentry. | |
393 | */ | |
394 | take_dentry_name_snapshot(&name, real); | |
395 | this = lookup_one_len(name.name, connected, strlen(name.name)); | |
396 | err = PTR_ERR(this); | |
397 | if (IS_ERR(this)) { | |
398 | goto fail; | |
399 | } else if (!this || !this->d_inode) { | |
400 | dput(this); | |
401 | err = -ENOENT; | |
402 | goto fail; | |
98892516 | 403 | } else if (ovl_dentry_real_at(this, layer->idx) != real) { |
3985b70a AG |
404 | dput(this); |
405 | err = -ESTALE; | |
406 | goto fail; | |
407 | } | |
408 | ||
409 | out: | |
410 | release_dentry_name_snapshot(&name); | |
411 | dput(parent); | |
412 | inode_unlock(dir); | |
413 | return this; | |
414 | ||
415 | fail: | |
416 | pr_warn_ratelimited("overlayfs: failed to lookup one by real (%pd2, layer=%d, connected=%pd2, err=%i)\n", | |
417 | real, layer->idx, connected, err); | |
418 | this = ERR_PTR(err); | |
419 | goto out; | |
420 | } | |
421 | ||
06170154 AG |
422 | static struct dentry *ovl_lookup_real(struct super_block *sb, |
423 | struct dentry *real, | |
424 | struct ovl_layer *layer); | |
425 | ||
4b91c30a AG |
426 | /* |
427 | * Lookup an indexed or hashed overlay dentry by real inode. | |
428 | */ | |
429 | static struct dentry *ovl_lookup_real_inode(struct super_block *sb, | |
430 | struct dentry *real, | |
431 | struct ovl_layer *layer) | |
432 | { | |
06170154 AG |
433 | struct ovl_fs *ofs = sb->s_fs_info; |
434 | struct ovl_layer upper_layer = { .mnt = ofs->upper_mnt }; | |
435 | struct dentry *index = NULL; | |
4b91c30a AG |
436 | struct dentry *this = NULL; |
437 | struct inode *inode; | |
438 | ||
06170154 AG |
439 | /* |
440 | * Decoding upper dir from index is expensive, so first try to lookup | |
441 | * overlay dentry in inode/dcache. | |
442 | */ | |
4b91c30a AG |
443 | inode = ovl_lookup_inode(sb, real, !layer->idx); |
444 | if (IS_ERR(inode)) | |
445 | return ERR_CAST(inode); | |
446 | if (inode) { | |
447 | this = d_find_any_alias(inode); | |
448 | iput(inode); | |
449 | } | |
450 | ||
06170154 AG |
451 | /* |
452 | * For decoded lower dir file handle, lookup index by origin to check | |
453 | * if lower dir was copied up and and/or removed. | |
454 | */ | |
455 | if (!this && layer->idx && ofs->indexdir && !WARN_ON(!d_is_dir(real))) { | |
456 | index = ovl_lookup_index(ofs, NULL, real, false); | |
457 | if (IS_ERR(index)) | |
458 | return index; | |
459 | } | |
460 | ||
461 | /* Get connected upper overlay dir from index */ | |
462 | if (index) { | |
463 | struct dentry *upper = ovl_index_upper(ofs, index); | |
464 | ||
465 | dput(index); | |
466 | if (IS_ERR_OR_NULL(upper)) | |
467 | return upper; | |
468 | ||
469 | /* | |
470 | * ovl_lookup_real() in lower layer may call recursively once to | |
471 | * ovl_lookup_real() in upper layer. The first level call walks | |
472 | * back lower parents to the topmost indexed parent. The second | |
473 | * recursive call walks back from indexed upper to the topmost | |
474 | * connected/hashed upper parent (or up to root). | |
475 | */ | |
476 | this = ovl_lookup_real(sb, upper, &upper_layer); | |
477 | dput(upper); | |
478 | } | |
479 | ||
7168179f AG |
480 | if (IS_ERR_OR_NULL(this)) |
481 | return this; | |
4b91c30a AG |
482 | |
483 | if (WARN_ON(ovl_dentry_real_at(this, layer->idx) != real)) { | |
484 | dput(this); | |
485 | this = ERR_PTR(-EIO); | |
486 | } | |
487 | ||
488 | return this; | |
489 | } | |
490 | ||
491 | /* | |
492 | * Lookup an indexed or hashed overlay dentry, whose real dentry is an | |
493 | * ancestor of @real. | |
494 | */ | |
495 | static struct dentry *ovl_lookup_real_ancestor(struct super_block *sb, | |
496 | struct dentry *real, | |
497 | struct ovl_layer *layer) | |
498 | { | |
499 | struct dentry *next, *parent = NULL; | |
500 | struct dentry *ancestor = ERR_PTR(-EIO); | |
501 | ||
502 | if (real == layer->mnt->mnt_root) | |
503 | return dget(sb->s_root); | |
504 | ||
505 | /* Find the topmost indexed or hashed ancestor */ | |
506 | next = dget(real); | |
507 | for (;;) { | |
508 | parent = dget_parent(next); | |
509 | ||
510 | /* | |
511 | * Lookup a matching overlay dentry in inode/dentry | |
512 | * cache or in index by real inode. | |
513 | */ | |
514 | ancestor = ovl_lookup_real_inode(sb, next, layer); | |
515 | if (ancestor) | |
516 | break; | |
517 | ||
518 | if (parent == layer->mnt->mnt_root) { | |
519 | ancestor = dget(sb->s_root); | |
520 | break; | |
521 | } | |
522 | ||
523 | /* | |
524 | * If @real has been moved out of the layer root directory, | |
525 | * we will eventully hit the real fs root. This cannot happen | |
526 | * by legit overlay rename, so we return error in that case. | |
527 | */ | |
528 | if (parent == next) { | |
529 | ancestor = ERR_PTR(-EXDEV); | |
530 | break; | |
531 | } | |
532 | ||
533 | dput(next); | |
534 | next = parent; | |
535 | } | |
536 | ||
537 | dput(parent); | |
538 | dput(next); | |
539 | ||
540 | return ancestor; | |
541 | } | |
542 | ||
3985b70a AG |
543 | /* |
544 | * Lookup a connected overlay dentry whose real dentry is @real. | |
545 | * If @real is on upper layer, we lookup a child overlay dentry with the same | |
546 | * path the real dentry. Otherwise, we need to consult index for lookup. | |
547 | */ | |
548 | static struct dentry *ovl_lookup_real(struct super_block *sb, | |
549 | struct dentry *real, | |
550 | struct ovl_layer *layer) | |
551 | { | |
552 | struct dentry *connected; | |
553 | int err = 0; | |
554 | ||
4b91c30a AG |
555 | connected = ovl_lookup_real_ancestor(sb, real, layer); |
556 | if (IS_ERR(connected)) | |
557 | return connected; | |
3985b70a | 558 | |
3985b70a AG |
559 | while (!err) { |
560 | struct dentry *next, *this; | |
561 | struct dentry *parent = NULL; | |
98892516 AG |
562 | struct dentry *real_connected = ovl_dentry_real_at(connected, |
563 | layer->idx); | |
3985b70a AG |
564 | |
565 | if (real_connected == real) | |
566 | break; | |
567 | ||
568 | /* Find the topmost dentry not yet connected */ | |
569 | next = dget(real); | |
570 | for (;;) { | |
571 | parent = dget_parent(next); | |
572 | ||
573 | if (parent == real_connected) | |
574 | break; | |
575 | ||
576 | /* | |
577 | * If real has been moved out of 'real_connected', | |
578 | * we will not find 'real_connected' and hit the layer | |
579 | * root. In that case, we need to restart connecting. | |
580 | * This game can go on forever in the worst case. We | |
581 | * may want to consider taking s_vfs_rename_mutex if | |
582 | * this happens more than once. | |
583 | */ | |
584 | if (parent == layer->mnt->mnt_root) { | |
585 | dput(connected); | |
586 | connected = dget(sb->s_root); | |
587 | break; | |
588 | } | |
589 | ||
590 | /* | |
591 | * If real file has been moved out of the layer root | |
592 | * directory, we will eventully hit the real fs root. | |
593 | * This cannot happen by legit overlay rename, so we | |
594 | * return error in that case. | |
595 | */ | |
596 | if (parent == next) { | |
597 | err = -EXDEV; | |
598 | break; | |
599 | } | |
600 | ||
601 | dput(next); | |
602 | next = parent; | |
603 | } | |
604 | ||
605 | if (!err) { | |
606 | this = ovl_lookup_real_one(connected, next, layer); | |
607 | if (IS_ERR(this)) | |
608 | err = PTR_ERR(this); | |
609 | ||
610 | /* | |
611 | * Lookup of child in overlay can fail when racing with | |
612 | * overlay rename of child away from 'connected' parent. | |
613 | * In this case, we need to restart the lookup from the | |
614 | * top, because we cannot trust that 'real_connected' is | |
4b91c30a AG |
615 | * still an ancestor of 'real'. There is a good chance |
616 | * that the renamed overlay ancestor is now in cache, so | |
617 | * ovl_lookup_real_ancestor() will find it and we can | |
618 | * continue to connect exactly from where lookup failed. | |
3985b70a AG |
619 | */ |
620 | if (err == -ECHILD) { | |
4b91c30a AG |
621 | this = ovl_lookup_real_ancestor(sb, real, |
622 | layer); | |
b5095f24 | 623 | err = PTR_ERR_OR_ZERO(this); |
3985b70a AG |
624 | } |
625 | if (!err) { | |
626 | dput(connected); | |
627 | connected = this; | |
628 | } | |
629 | } | |
630 | ||
631 | dput(parent); | |
632 | dput(next); | |
633 | } | |
634 | ||
635 | if (err) | |
636 | goto fail; | |
637 | ||
638 | return connected; | |
639 | ||
640 | fail: | |
641 | pr_warn_ratelimited("overlayfs: failed to lookup by real (%pd2, layer=%d, connected=%pd2, err=%i)\n", | |
642 | real, layer->idx, connected, err); | |
643 | dput(connected); | |
644 | return ERR_PTR(err); | |
645 | } | |
646 | ||
647 | /* | |
f71bd9cf | 648 | * Get an overlay dentry from upper/lower real dentries and index. |
3985b70a AG |
649 | */ |
650 | static struct dentry *ovl_get_dentry(struct super_block *sb, | |
651 | struct dentry *upper, | |
f71bd9cf AG |
652 | struct ovl_path *lowerpath, |
653 | struct dentry *index) | |
3985b70a AG |
654 | { |
655 | struct ovl_fs *ofs = sb->s_fs_info; | |
656 | struct ovl_layer upper_layer = { .mnt = ofs->upper_mnt }; | |
98892516 | 657 | struct ovl_layer *layer = upper ? &upper_layer : lowerpath->layer; |
f71bd9cf | 658 | struct dentry *real = upper ?: (index ?: lowerpath->dentry); |
3985b70a | 659 | |
f941866f | 660 | /* |
f71bd9cf AG |
661 | * Obtain a disconnected overlay dentry from a non-dir real dentry |
662 | * and index. | |
f941866f | 663 | */ |
f71bd9cf AG |
664 | if (!d_is_dir(real)) |
665 | return ovl_obtain_alias(sb, upper, lowerpath, index); | |
f941866f | 666 | |
3985b70a | 667 | /* Removed empty directory? */ |
98892516 | 668 | if ((real->d_flags & DCACHE_DISCONNECTED) || d_unhashed(real)) |
3985b70a AG |
669 | return ERR_PTR(-ENOENT); |
670 | ||
671 | /* | |
98892516 AG |
672 | * If real dentry is connected and hashed, get a connected overlay |
673 | * dentry whose real dentry is @real. | |
3985b70a | 674 | */ |
98892516 | 675 | return ovl_lookup_real(sb, real, layer); |
3985b70a AG |
676 | } |
677 | ||
8556a420 AG |
678 | static struct dentry *ovl_upper_fh_to_d(struct super_block *sb, |
679 | struct ovl_fh *fh) | |
680 | { | |
681 | struct ovl_fs *ofs = sb->s_fs_info; | |
682 | struct dentry *dentry; | |
683 | struct dentry *upper; | |
684 | ||
685 | if (!ofs->upper_mnt) | |
686 | return ERR_PTR(-EACCES); | |
687 | ||
688 | upper = ovl_decode_fh(fh, ofs->upper_mnt); | |
689 | if (IS_ERR_OR_NULL(upper)) | |
690 | return upper; | |
691 | ||
f71bd9cf | 692 | dentry = ovl_get_dentry(sb, upper, NULL, NULL); |
8556a420 AG |
693 | dput(upper); |
694 | ||
695 | return dentry; | |
696 | } | |
697 | ||
f941866f AG |
698 | static struct dentry *ovl_lower_fh_to_d(struct super_block *sb, |
699 | struct ovl_fh *fh) | |
700 | { | |
701 | struct ovl_fs *ofs = sb->s_fs_info; | |
702 | struct ovl_path origin = { }; | |
703 | struct ovl_path *stack = &origin; | |
704 | struct dentry *dentry = NULL; | |
f71bd9cf | 705 | struct dentry *index = NULL; |
9436a1a3 AG |
706 | struct inode *inode = NULL; |
707 | bool is_deleted = false; | |
f941866f AG |
708 | int err; |
709 | ||
f71bd9cf AG |
710 | /* First lookup indexed upper by fh */ |
711 | if (ofs->indexdir) { | |
712 | index = ovl_get_index_fh(ofs, fh); | |
713 | err = PTR_ERR(index); | |
9436a1a3 AG |
714 | if (IS_ERR(index)) { |
715 | if (err != -ESTALE) | |
716 | return ERR_PTR(err); | |
717 | ||
718 | /* Found a whiteout index - treat as deleted inode */ | |
719 | is_deleted = true; | |
720 | index = NULL; | |
721 | } | |
f71bd9cf AG |
722 | } |
723 | ||
3b0bfc6e AG |
724 | /* Then try to get upper dir by index */ |
725 | if (index && d_is_dir(index)) { | |
726 | struct dentry *upper = ovl_index_upper(ofs, index); | |
727 | ||
728 | err = PTR_ERR(upper); | |
729 | if (IS_ERR_OR_NULL(upper)) | |
730 | goto out_err; | |
731 | ||
732 | dentry = ovl_get_dentry(sb, upper, NULL, NULL); | |
733 | dput(upper); | |
734 | goto out; | |
735 | } | |
736 | ||
f71bd9cf | 737 | /* Then lookup origin by fh */ |
f941866f | 738 | err = ovl_check_origin_fh(ofs, fh, NULL, &stack); |
f71bd9cf AG |
739 | if (err) { |
740 | goto out_err; | |
741 | } else if (index) { | |
742 | err = ovl_verify_origin(index, origin.dentry, false); | |
743 | if (err) | |
744 | goto out_err; | |
9436a1a3 AG |
745 | } else if (is_deleted) { |
746 | /* Lookup deleted non-dir by origin inode */ | |
747 | if (!d_is_dir(origin.dentry)) | |
4b91c30a | 748 | inode = ovl_lookup_inode(sb, origin.dentry, false); |
9436a1a3 AG |
749 | err = -ESTALE; |
750 | if (!inode || atomic_read(&inode->i_count) == 1) | |
751 | goto out_err; | |
752 | ||
753 | /* Deleted but still open? */ | |
754 | index = dget(ovl_i_dentry_upper(inode)); | |
f71bd9cf | 755 | } |
f941866f | 756 | |
f71bd9cf | 757 | dentry = ovl_get_dentry(sb, NULL, &origin, index); |
f941866f | 758 | |
f71bd9cf AG |
759 | out: |
760 | dput(origin.dentry); | |
761 | dput(index); | |
9436a1a3 | 762 | iput(inode); |
f941866f | 763 | return dentry; |
f71bd9cf AG |
764 | |
765 | out_err: | |
766 | dentry = ERR_PTR(err); | |
767 | goto out; | |
f941866f AG |
768 | } |
769 | ||
8556a420 AG |
770 | static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid, |
771 | int fh_len, int fh_type) | |
772 | { | |
773 | struct dentry *dentry = NULL; | |
774 | struct ovl_fh *fh = (struct ovl_fh *) fid; | |
775 | int len = fh_len << 2; | |
776 | unsigned int flags = 0; | |
777 | int err; | |
778 | ||
779 | err = -EINVAL; | |
780 | if (fh_type != OVL_FILEID) | |
781 | goto out_err; | |
782 | ||
783 | err = ovl_check_fh_len(fh, len); | |
784 | if (err) | |
785 | goto out_err; | |
786 | ||
8556a420 | 787 | flags = fh->flags; |
f941866f AG |
788 | dentry = (flags & OVL_FH_FLAG_PATH_UPPER) ? |
789 | ovl_upper_fh_to_d(sb, fh) : | |
790 | ovl_lower_fh_to_d(sb, fh); | |
8556a420 AG |
791 | err = PTR_ERR(dentry); |
792 | if (IS_ERR(dentry) && err != -ESTALE) | |
793 | goto out_err; | |
794 | ||
795 | return dentry; | |
796 | ||
797 | out_err: | |
798 | pr_warn_ratelimited("overlayfs: failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n", | |
799 | len, fh_type, flags, err); | |
800 | return ERR_PTR(err); | |
801 | } | |
802 | ||
3985b70a AG |
803 | static struct dentry *ovl_fh_to_parent(struct super_block *sb, struct fid *fid, |
804 | int fh_len, int fh_type) | |
805 | { | |
806 | pr_warn_ratelimited("overlayfs: connectable file handles not supported; use 'no_subtree_check' exportfs option.\n"); | |
807 | return ERR_PTR(-EACCES); | |
808 | } | |
809 | ||
810 | static int ovl_get_name(struct dentry *parent, char *name, | |
811 | struct dentry *child) | |
812 | { | |
813 | /* | |
814 | * ovl_fh_to_dentry() returns connected dir overlay dentries and | |
815 | * ovl_fh_to_parent() is not implemented, so we should not get here. | |
816 | */ | |
817 | WARN_ON_ONCE(1); | |
818 | return -EIO; | |
819 | } | |
820 | ||
821 | static struct dentry *ovl_get_parent(struct dentry *dentry) | |
822 | { | |
823 | /* | |
824 | * ovl_fh_to_dentry() returns connected dir overlay dentries, so we | |
825 | * should not get here. | |
826 | */ | |
827 | WARN_ON_ONCE(1); | |
828 | return ERR_PTR(-EIO); | |
829 | } | |
830 | ||
8ed5eec9 AG |
831 | const struct export_operations ovl_export_operations = { |
832 | .encode_fh = ovl_encode_inode_fh, | |
8556a420 | 833 | .fh_to_dentry = ovl_fh_to_dentry, |
3985b70a AG |
834 | .fh_to_parent = ovl_fh_to_parent, |
835 | .get_name = ovl_get_name, | |
836 | .get_parent = ovl_get_parent, | |
8ed5eec9 | 837 | }; |