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1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2017-2023 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <djwong@kernel.org>
5 */
6#include "xfs.h"
7#include "xfs_fs.h"
8#include "xfs_shared.h"
9#include "xfs_format.h"
10#include "xfs_trans_resv.h"
11#include "xfs_mount.h"
12#include "xfs_log_format.h"
13#include "xfs_trans.h"
14#include "xfs_inode.h"
15#include "xfs_quota.h"
16#include "xfs_qm.h"
17#include "xfs_scrub.h"
18#include "scrub/scrub.h"
19#include "scrub/common.h"
20#include "scrub/trace.h"
21#include "scrub/repair.h"
22#include "scrub/health.h"
23#include "scrub/stats.h"
24#include "scrub/xfile.h"
25
26/*
27 * Online Scrub and Repair
28 *
29 * Traditionally, XFS (the kernel driver) did not know how to check or
30 * repair on-disk data structures. That task was left to the xfs_check
31 * and xfs_repair tools, both of which require taking the filesystem
32 * offline for a thorough but time consuming examination. Online
33 * scrub & repair, on the other hand, enables us to check the metadata
34 * for obvious errors while carefully stepping around the filesystem's
35 * ongoing operations, locking rules, etc.
36 *
37 * Given that most XFS metadata consist of records stored in a btree,
38 * most of the checking functions iterate the btree blocks themselves
39 * looking for irregularities. When a record block is encountered, each
40 * record can be checked for obviously bad values. Record values can
41 * also be cross-referenced against other btrees to look for potential
42 * misunderstandings between pieces of metadata.
43 *
44 * It is expected that the checkers responsible for per-AG metadata
45 * structures will lock the AG headers (AGI, AGF, AGFL), iterate the
46 * metadata structure, and perform any relevant cross-referencing before
47 * unlocking the AG and returning the results to userspace. These
48 * scrubbers must not keep an AG locked for too long to avoid tying up
49 * the block and inode allocators.
50 *
51 * Block maps and b-trees rooted in an inode present a special challenge
52 * because they can involve extents from any AG. The general scrubber
53 * structure of lock -> check -> xref -> unlock still holds, but AG
54 * locking order rules /must/ be obeyed to avoid deadlocks. The
55 * ordering rule, of course, is that we must lock in increasing AG
56 * order. Helper functions are provided to track which AG headers we've
57 * already locked. If we detect an imminent locking order violation, we
58 * can signal a potential deadlock, in which case the scrubber can jump
59 * out to the top level, lock all the AGs in order, and retry the scrub.
60 *
61 * For file data (directories, extended attributes, symlinks) scrub, we
62 * can simply lock the inode and walk the data. For btree data
63 * (directories and attributes) we follow the same btree-scrubbing
64 * strategy outlined previously to check the records.
65 *
66 * We use a bit of trickery with transactions to avoid buffer deadlocks
67 * if there is a cycle in the metadata. The basic problem is that
68 * travelling down a btree involves locking the current buffer at each
69 * tree level. If a pointer should somehow point back to a buffer that
70 * we've already examined, we will deadlock due to the second buffer
71 * locking attempt. Note however that grabbing a buffer in transaction
72 * context links the locked buffer to the transaction. If we try to
73 * re-grab the buffer in the context of the same transaction, we avoid
74 * the second lock attempt and continue. Between the verifier and the
75 * scrubber, something will notice that something is amiss and report
76 * the corruption. Therefore, each scrubber will allocate an empty
77 * transaction, attach buffers to it, and cancel the transaction at the
78 * end of the scrub run. Cancelling a non-dirty transaction simply
79 * unlocks the buffers.
80 *
81 * There are four pieces of data that scrub can communicate to
82 * userspace. The first is the error code (errno), which can be used to
83 * communicate operational errors in performing the scrub. There are
84 * also three flags that can be set in the scrub context. If the data
85 * structure itself is corrupt, the CORRUPT flag will be set. If
86 * the metadata is correct but otherwise suboptimal, the PREEN flag
87 * will be set.
88 *
89 * We perform secondary validation of filesystem metadata by
90 * cross-referencing every record with all other available metadata.
91 * For example, for block mapping extents, we verify that there are no
92 * records in the free space and inode btrees corresponding to that
93 * space extent and that there is a corresponding entry in the reverse
94 * mapping btree. Inconsistent metadata is noted by setting the
95 * XCORRUPT flag; btree query function errors are noted by setting the
96 * XFAIL flag and deleting the cursor to prevent further attempts to
97 * cross-reference with a defective btree.
98 *
99 * If a piece of metadata proves corrupt or suboptimal, the userspace
100 * program can ask the kernel to apply some tender loving care (TLC) to
101 * the metadata object by setting the REPAIR flag and re-calling the
102 * scrub ioctl. "Corruption" is defined by metadata violating the
103 * on-disk specification; operations cannot continue if the violation is
104 * left untreated. It is possible for XFS to continue if an object is
105 * "suboptimal", however performance may be degraded. Repairs are
106 * usually performed by rebuilding the metadata entirely out of
107 * redundant metadata. Optimizing, on the other hand, can sometimes be
108 * done without rebuilding entire structures.
109 *
110 * Generally speaking, the repair code has the following code structure:
111 * Lock -> scrub -> repair -> commit -> re-lock -> re-scrub -> unlock.
112 * The first check helps us figure out if we need to rebuild or simply
113 * optimize the structure so that the rebuild knows what to do. The
114 * second check evaluates the completeness of the repair; that is what
115 * is reported to userspace.
116 *
117 * A quick note on symbol prefixes:
118 * - "xfs_" are general XFS symbols.
119 * - "xchk_" are symbols related to metadata checking.
120 * - "xrep_" are symbols related to metadata repair.
121 * - "xfs_scrub_" are symbols that tie online fsck to the rest of XFS.
122 */
123
124/*
125 * Scrub probe -- userspace uses this to probe if we're willing to scrub
126 * or repair a given mountpoint. This will be used by xfs_scrub to
127 * probe the kernel's abilities to scrub (and repair) the metadata. We
128 * do this by validating the ioctl inputs from userspace, preparing the
129 * filesystem for a scrub (or a repair) operation, and immediately
130 * returning to userspace. Userspace can use the returned errno and
131 * structure state to decide (in broad terms) if scrub/repair are
132 * supported by the running kernel.
133 */
134static int
135xchk_probe(
136 struct xfs_scrub *sc)
137{
138 int error = 0;
139
140 if (xchk_should_terminate(sc, &error))
141 return error;
142
143 return 0;
144}
145
146/* Scrub setup and teardown */
147
148static inline void
149xchk_fsgates_disable(
150 struct xfs_scrub *sc)
151{
152 if (!(sc->flags & XCHK_FSGATES_ALL))
153 return;
154
155 trace_xchk_fsgates_disable(sc, sc->flags & XCHK_FSGATES_ALL);
156
157 if (sc->flags & XCHK_FSGATES_DRAIN)
158 xfs_drain_wait_disable();
159
160 sc->flags &= ~XCHK_FSGATES_ALL;
161}
162
163/* Free all the resources and finish the transactions. */
164STATIC int
165xchk_teardown(
166 struct xfs_scrub *sc,
167 int error)
168{
169 xchk_ag_free(sc, &sc->sa);
170 if (sc->tp) {
171 if (error == 0 && (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR))
172 error = xfs_trans_commit(sc->tp);
173 else
174 xfs_trans_cancel(sc->tp);
175 sc->tp = NULL;
176 }
177 if (sc->ip) {
178 if (sc->ilock_flags)
179 xchk_iunlock(sc, sc->ilock_flags);
180 xchk_irele(sc, sc->ip);
181 sc->ip = NULL;
182 }
183 if (sc->flags & XCHK_HAVE_FREEZE_PROT) {
184 sc->flags &= ~XCHK_HAVE_FREEZE_PROT;
185 mnt_drop_write_file(sc->file);
186 }
187 if (sc->xfile) {
188 xfile_destroy(sc->xfile);
189 sc->xfile = NULL;
190 }
191 if (sc->buf) {
192 if (sc->buf_cleanup)
193 sc->buf_cleanup(sc->buf);
194 kvfree(sc->buf);
195 sc->buf_cleanup = NULL;
196 sc->buf = NULL;
197 }
198
199 xchk_fsgates_disable(sc);
200 return error;
201}
202
203/* Scrubbing dispatch. */
204
205static const struct xchk_meta_ops meta_scrub_ops[] = {
206 [XFS_SCRUB_TYPE_PROBE] = { /* ioctl presence test */
207 .type = ST_NONE,
208 .setup = xchk_setup_fs,
209 .scrub = xchk_probe,
210 .repair = xrep_probe,
211 },
212 [XFS_SCRUB_TYPE_SB] = { /* superblock */
213 .type = ST_PERAG,
214 .setup = xchk_setup_agheader,
215 .scrub = xchk_superblock,
216 .repair = xrep_superblock,
217 },
218 [XFS_SCRUB_TYPE_AGF] = { /* agf */
219 .type = ST_PERAG,
220 .setup = xchk_setup_agheader,
221 .scrub = xchk_agf,
222 .repair = xrep_agf,
223 },
224 [XFS_SCRUB_TYPE_AGFL]= { /* agfl */
225 .type = ST_PERAG,
226 .setup = xchk_setup_agheader,
227 .scrub = xchk_agfl,
228 .repair = xrep_agfl,
229 },
230 [XFS_SCRUB_TYPE_AGI] = { /* agi */
231 .type = ST_PERAG,
232 .setup = xchk_setup_agheader,
233 .scrub = xchk_agi,
234 .repair = xrep_agi,
235 },
236 [XFS_SCRUB_TYPE_BNOBT] = { /* bnobt */
237 .type = ST_PERAG,
238 .setup = xchk_setup_ag_allocbt,
239 .scrub = xchk_allocbt,
240 .repair = xrep_allocbt,
241 .repair_eval = xrep_revalidate_allocbt,
242 },
243 [XFS_SCRUB_TYPE_CNTBT] = { /* cntbt */
244 .type = ST_PERAG,
245 .setup = xchk_setup_ag_allocbt,
246 .scrub = xchk_allocbt,
247 .repair = xrep_allocbt,
248 .repair_eval = xrep_revalidate_allocbt,
249 },
250 [XFS_SCRUB_TYPE_INOBT] = { /* inobt */
251 .type = ST_PERAG,
252 .setup = xchk_setup_ag_iallocbt,
253 .scrub = xchk_iallocbt,
254 .repair = xrep_iallocbt,
255 .repair_eval = xrep_revalidate_iallocbt,
256 },
257 [XFS_SCRUB_TYPE_FINOBT] = { /* finobt */
258 .type = ST_PERAG,
259 .setup = xchk_setup_ag_iallocbt,
260 .scrub = xchk_iallocbt,
261 .has = xfs_has_finobt,
262 .repair = xrep_iallocbt,
263 .repair_eval = xrep_revalidate_iallocbt,
264 },
265 [XFS_SCRUB_TYPE_RMAPBT] = { /* rmapbt */
266 .type = ST_PERAG,
267 .setup = xchk_setup_ag_rmapbt,
268 .scrub = xchk_rmapbt,
269 .has = xfs_has_rmapbt,
270 .repair = xrep_notsupported,
271 },
272 [XFS_SCRUB_TYPE_REFCNTBT] = { /* refcountbt */
273 .type = ST_PERAG,
274 .setup = xchk_setup_ag_refcountbt,
275 .scrub = xchk_refcountbt,
276 .has = xfs_has_reflink,
277 .repair = xrep_refcountbt,
278 },
279 [XFS_SCRUB_TYPE_INODE] = { /* inode record */
280 .type = ST_INODE,
281 .setup = xchk_setup_inode,
282 .scrub = xchk_inode,
283 .repair = xrep_inode,
284 },
285 [XFS_SCRUB_TYPE_BMBTD] = { /* inode data fork */
286 .type = ST_INODE,
287 .setup = xchk_setup_inode_bmap,
288 .scrub = xchk_bmap_data,
289 .repair = xrep_bmap_data,
290 },
291 [XFS_SCRUB_TYPE_BMBTA] = { /* inode attr fork */
292 .type = ST_INODE,
293 .setup = xchk_setup_inode_bmap,
294 .scrub = xchk_bmap_attr,
295 .repair = xrep_bmap_attr,
296 },
297 [XFS_SCRUB_TYPE_BMBTC] = { /* inode CoW fork */
298 .type = ST_INODE,
299 .setup = xchk_setup_inode_bmap,
300 .scrub = xchk_bmap_cow,
301 .repair = xrep_bmap_cow,
302 },
303 [XFS_SCRUB_TYPE_DIR] = { /* directory */
304 .type = ST_INODE,
305 .setup = xchk_setup_directory,
306 .scrub = xchk_directory,
307 .repair = xrep_notsupported,
308 },
309 [XFS_SCRUB_TYPE_XATTR] = { /* extended attributes */
310 .type = ST_INODE,
311 .setup = xchk_setup_xattr,
312 .scrub = xchk_xattr,
313 .repair = xrep_notsupported,
314 },
315 [XFS_SCRUB_TYPE_SYMLINK] = { /* symbolic link */
316 .type = ST_INODE,
317 .setup = xchk_setup_symlink,
318 .scrub = xchk_symlink,
319 .repair = xrep_notsupported,
320 },
321 [XFS_SCRUB_TYPE_PARENT] = { /* parent pointers */
322 .type = ST_INODE,
323 .setup = xchk_setup_parent,
324 .scrub = xchk_parent,
325 .repair = xrep_notsupported,
326 },
327 [XFS_SCRUB_TYPE_RTBITMAP] = { /* realtime bitmap */
328 .type = ST_FS,
329 .setup = xchk_setup_rtbitmap,
330 .scrub = xchk_rtbitmap,
331 .repair = xrep_rtbitmap,
332 },
333 [XFS_SCRUB_TYPE_RTSUM] = { /* realtime summary */
334 .type = ST_FS,
335 .setup = xchk_setup_rtsummary,
336 .scrub = xchk_rtsummary,
337 .repair = xrep_notsupported,
338 },
339 [XFS_SCRUB_TYPE_UQUOTA] = { /* user quota */
340 .type = ST_FS,
341 .setup = xchk_setup_quota,
342 .scrub = xchk_quota,
343 .repair = xrep_quota,
344 },
345 [XFS_SCRUB_TYPE_GQUOTA] = { /* group quota */
346 .type = ST_FS,
347 .setup = xchk_setup_quota,
348 .scrub = xchk_quota,
349 .repair = xrep_quota,
350 },
351 [XFS_SCRUB_TYPE_PQUOTA] = { /* project quota */
352 .type = ST_FS,
353 .setup = xchk_setup_quota,
354 .scrub = xchk_quota,
355 .repair = xrep_quota,
356 },
357 [XFS_SCRUB_TYPE_FSCOUNTERS] = { /* fs summary counters */
358 .type = ST_FS,
359 .setup = xchk_setup_fscounters,
360 .scrub = xchk_fscounters,
361 .repair = xrep_notsupported,
362 },
363};
364
365static int
366xchk_validate_inputs(
367 struct xfs_mount *mp,
368 struct xfs_scrub_metadata *sm)
369{
370 int error;
371 const struct xchk_meta_ops *ops;
372
373 error = -EINVAL;
374 /* Check our inputs. */
375 sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
376 if (sm->sm_flags & ~XFS_SCRUB_FLAGS_IN)
377 goto out;
378 /* sm_reserved[] must be zero */
379 if (memchr_inv(sm->sm_reserved, 0, sizeof(sm->sm_reserved)))
380 goto out;
381
382 error = -ENOENT;
383 /* Do we know about this type of metadata? */
384 if (sm->sm_type >= XFS_SCRUB_TYPE_NR)
385 goto out;
386 ops = &meta_scrub_ops[sm->sm_type];
387 if (ops->setup == NULL || ops->scrub == NULL)
388 goto out;
389 /* Does this fs even support this type of metadata? */
390 if (ops->has && !ops->has(mp))
391 goto out;
392
393 error = -EINVAL;
394 /* restricting fields must be appropriate for type */
395 switch (ops->type) {
396 case ST_NONE:
397 case ST_FS:
398 if (sm->sm_ino || sm->sm_gen || sm->sm_agno)
399 goto out;
400 break;
401 case ST_PERAG:
402 if (sm->sm_ino || sm->sm_gen ||
403 sm->sm_agno >= mp->m_sb.sb_agcount)
404 goto out;
405 break;
406 case ST_INODE:
407 if (sm->sm_agno || (sm->sm_gen && !sm->sm_ino))
408 goto out;
409 break;
410 default:
411 goto out;
412 }
413
414 /* No rebuild without repair. */
415 if ((sm->sm_flags & XFS_SCRUB_IFLAG_FORCE_REBUILD) &&
416 !(sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR))
417 return -EINVAL;
418
419 /*
420 * We only want to repair read-write v5+ filesystems. Defer the check
421 * for ops->repair until after our scrub confirms that we need to
422 * perform repairs so that we avoid failing due to not supporting
423 * repairing an object that doesn't need repairs.
424 */
425 if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) {
426 error = -EOPNOTSUPP;
427 if (!xfs_has_crc(mp))
428 goto out;
429
430 error = -EROFS;
431 if (xfs_is_readonly(mp))
432 goto out;
433 }
434
435 error = 0;
436out:
437 return error;
438}
439
440#ifdef CONFIG_XFS_ONLINE_REPAIR
441static inline void xchk_postmortem(struct xfs_scrub *sc)
442{
443 /*
444 * Userspace asked us to repair something, we repaired it, rescanned
445 * it, and the rescan says it's still broken. Scream about this in
446 * the system logs.
447 */
448 if ((sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) &&
449 (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
450 XFS_SCRUB_OFLAG_XCORRUPT)))
451 xrep_failure(sc->mp);
452}
453#else
454static inline void xchk_postmortem(struct xfs_scrub *sc)
455{
456 /*
457 * Userspace asked us to scrub something, it's broken, and we have no
458 * way of fixing it. Scream in the logs.
459 */
460 if (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
461 XFS_SCRUB_OFLAG_XCORRUPT))
462 xfs_alert_ratelimited(sc->mp,
463 "Corruption detected during scrub.");
464}
465#endif /* CONFIG_XFS_ONLINE_REPAIR */
466
467/* Dispatch metadata scrubbing. */
468int
469xfs_scrub_metadata(
470 struct file *file,
471 struct xfs_scrub_metadata *sm)
472{
473 struct xchk_stats_run run = { };
474 struct xfs_scrub *sc;
475 struct xfs_mount *mp = XFS_I(file_inode(file))->i_mount;
476 u64 check_start;
477 int error = 0;
478
479 BUILD_BUG_ON(sizeof(meta_scrub_ops) !=
480 (sizeof(struct xchk_meta_ops) * XFS_SCRUB_TYPE_NR));
481
482 trace_xchk_start(XFS_I(file_inode(file)), sm, error);
483
484 /* Forbidden if we are shut down or mounted norecovery. */
485 error = -ESHUTDOWN;
486 if (xfs_is_shutdown(mp))
487 goto out;
488 error = -ENOTRECOVERABLE;
489 if (xfs_has_norecovery(mp))
490 goto out;
491
492 error = xchk_validate_inputs(mp, sm);
493 if (error)
494 goto out;
495
496 xfs_warn_mount(mp, XFS_OPSTATE_WARNED_SCRUB,
497 "EXPERIMENTAL online scrub feature in use. Use at your own risk!");
498
499 sc = kzalloc(sizeof(struct xfs_scrub), XCHK_GFP_FLAGS);
500 if (!sc) {
501 error = -ENOMEM;
502 goto out;
503 }
504
505 sc->mp = mp;
506 sc->file = file;
507 sc->sm = sm;
508 sc->ops = &meta_scrub_ops[sm->sm_type];
509 sc->sick_mask = xchk_health_mask_for_scrub_type(sm->sm_type);
510retry_op:
511 /*
512 * When repairs are allowed, prevent freezing or readonly remount while
513 * scrub is running with a real transaction.
514 */
515 if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) {
516 error = mnt_want_write_file(sc->file);
517 if (error)
518 goto out_sc;
519
520 sc->flags |= XCHK_HAVE_FREEZE_PROT;
521 }
522
523 /* Set up for the operation. */
524 error = sc->ops->setup(sc);
525 if (error == -EDEADLOCK && !(sc->flags & XCHK_TRY_HARDER))
526 goto try_harder;
527 if (error == -ECHRNG && !(sc->flags & XCHK_NEED_DRAIN))
528 goto need_drain;
529 if (error)
530 goto out_teardown;
531
532 /* Scrub for errors. */
533 check_start = xchk_stats_now();
534 if ((sc->flags & XREP_ALREADY_FIXED) && sc->ops->repair_eval != NULL)
535 error = sc->ops->repair_eval(sc);
536 else
537 error = sc->ops->scrub(sc);
538 run.scrub_ns += xchk_stats_elapsed_ns(check_start);
539 if (error == -EDEADLOCK && !(sc->flags & XCHK_TRY_HARDER))
540 goto try_harder;
541 if (error == -ECHRNG && !(sc->flags & XCHK_NEED_DRAIN))
542 goto need_drain;
543 if (error || (sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE))
544 goto out_teardown;
545
546 xchk_update_health(sc);
547
548 if (xchk_could_repair(sc)) {
549 /*
550 * If userspace asked for a repair but it wasn't necessary,
551 * report that back to userspace.
552 */
553 if (!xrep_will_attempt(sc)) {
554 sc->sm->sm_flags |= XFS_SCRUB_OFLAG_NO_REPAIR_NEEDED;
555 goto out_nofix;
556 }
557
558 /*
559 * If it's broken, userspace wants us to fix it, and we haven't
560 * already tried to fix it, then attempt a repair.
561 */
562 error = xrep_attempt(sc, &run);
563 if (error == -EAGAIN) {
564 /*
565 * Either the repair function succeeded or it couldn't
566 * get all the resources it needs; either way, we go
567 * back to the beginning and call the scrub function.
568 */
569 error = xchk_teardown(sc, 0);
570 if (error) {
571 xrep_failure(mp);
572 goto out_sc;
573 }
574 goto retry_op;
575 }
576 }
577
578out_nofix:
579 xchk_postmortem(sc);
580out_teardown:
581 error = xchk_teardown(sc, error);
582out_sc:
583 if (error != -ENOENT)
584 xchk_stats_merge(mp, sm, &run);
585 kfree(sc);
586out:
587 trace_xchk_done(XFS_I(file_inode(file)), sm, error);
588 if (error == -EFSCORRUPTED || error == -EFSBADCRC) {
589 sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
590 error = 0;
591 }
592 return error;
593need_drain:
594 error = xchk_teardown(sc, 0);
595 if (error)
596 goto out_sc;
597 sc->flags |= XCHK_NEED_DRAIN;
598 run.retries++;
599 goto retry_op;
600try_harder:
601 /*
602 * Scrubbers return -EDEADLOCK to mean 'try harder'. Tear down
603 * everything we hold, then set up again with preparation for
604 * worst-case scenarios.
605 */
606 error = xchk_teardown(sc, 0);
607 if (error)
608 goto out_sc;
609 sc->flags |= XCHK_TRY_HARDER;
610 run.retries++;
611 goto retry_op;
612}