1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (C) 2017 Oracle. All Rights Reserved.
4 * Author: Darrick J. Wong <darrick.wong@oracle.com>
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_defer.h"
13 #include "xfs_btree.h"
14 #include "xfs_bit.h"
15 #include "xfs_log_format.h"
16 #include "xfs_trans.h"
17 #include "xfs_sb.h"
18 #include "xfs_inode.h"
19 #include "xfs_icache.h"
20 #include "xfs_itable.h"
21 #include "xfs_alloc.h"
22 #include "xfs_alloc_btree.h"
23 #include "xfs_bmap.h"
24 #include "xfs_bmap_btree.h"
25 #include "xfs_ialloc.h"
26 #include "xfs_ialloc_btree.h"
27 #include "xfs_refcount.h"
28 #include "xfs_refcount_btree.h"
29 #include "xfs_rmap.h"
30 #include "xfs_rmap_btree.h"
31 #include "xfs_quota.h"
32 #include "xfs_qm.h"
33 #include "xfs_errortag.h"
34 #include "xfs_error.h"
35 #include "xfs_log.h"
36 #include "xfs_trans_priv.h"
37 #include "scrub/xfs_scrub.h"
38 #include "scrub/scrub.h"
39 #include "scrub/common.h"
40 #include "scrub/trace.h"
41 #include "scrub/btree.h"
42 #include "scrub/repair.h"
43
44 /*
45 * Online Scrub and Repair
46 *
47 * Traditionally, XFS (the kernel driver) did not know how to check or
48 * repair on-disk data structures. That task was left to the xfs_check
49 * and xfs_repair tools, both of which require taking the filesystem
50 * offline for a thorough but time consuming examination. Online
51 * scrub & repair, on the other hand, enables us to check the metadata
52 * for obvious errors while carefully stepping around the filesystem's
53 * ongoing operations, locking rules, etc.
54 *
55 * Given that most XFS metadata consist of records stored in a btree,
56 * most of the checking functions iterate the btree blocks themselves
57 * looking for irregularities. When a record block is encountered, each
58 * record can be checked for obviously bad values. Record values can
59 * also be cross-referenced against other btrees to look for potential
60 * misunderstandings between pieces of metadata.
61 *
62 * It is expected that the checkers responsible for per-AG metadata
63 * structures will lock the AG headers (AGI, AGF, AGFL), iterate the
64 * metadata structure, and perform any relevant cross-referencing before
65 * unlocking the AG and returning the results to userspace. These
66 * scrubbers must not keep an AG locked for too long to avoid tying up
67 * the block and inode allocators.
68 *
69 * Block maps and b-trees rooted in an inode present a special challenge
70 * because they can involve extents from any AG. The general scrubber
71 * structure of lock -> check -> xref -> unlock still holds, but AG
72 * locking order rules /must/ be obeyed to avoid deadlocks. The
73 * ordering rule, of course, is that we must lock in increasing AG
74 * order. Helper functions are provided to track which AG headers we've
75 * already locked. If we detect an imminent locking order violation, we
76 * can signal a potential deadlock, in which case the scrubber can jump
77 * out to the top level, lock all the AGs in order, and retry the scrub.
78 *
79 * For file data (directories, extended attributes, symlinks) scrub, we
80 * can simply lock the inode and walk the data. For btree data
81 * (directories and attributes) we follow the same btree-scrubbing
82 * strategy outlined previously to check the records.
83 *
84 * We use a bit of trickery with transactions to avoid buffer deadlocks
85 * if there is a cycle in the metadata. The basic problem is that
86 * travelling down a btree involves locking the current buffer at each
87 * tree level. If a pointer should somehow point back to a buffer that
88 * we've already examined, we will deadlock due to the second buffer
89 * locking attempt. Note however that grabbing a buffer in transaction
90 * context links the locked buffer to the transaction. If we try to
91 * re-grab the buffer in the context of the same transaction, we avoid
92 * the second lock attempt and continue. Between the verifier and the
93 * scrubber, something will notice that something is amiss and report
94 * the corruption. Therefore, each scrubber will allocate an empty
95 * transaction, attach buffers to it, and cancel the transaction at the
96 * end of the scrub run. Cancelling a non-dirty transaction simply
97 * unlocks the buffers.
98 *
99 * There are four pieces of data that scrub can communicate to
100 * userspace. The first is the error code (errno), which can be used to
101 * communicate operational errors in performing the scrub. There are
102 * also three flags that can be set in the scrub context. If the data
103 * structure itself is corrupt, the CORRUPT flag will be set. If
104 * the metadata is correct but otherwise suboptimal, the PREEN flag
105 * will be set.
106 *
107 * We perform secondary validation of filesystem metadata by
108 * cross-referencing every record with all other available metadata.
109 * For example, for block mapping extents, we verify that there are no
110 * records in the free space and inode btrees corresponding to that
111 * space extent and that there is a corresponding entry in the reverse
112 * mapping btree. Inconsistent metadata is noted by setting the
113 * XCORRUPT flag; btree query function errors are noted by setting the
114 * XFAIL flag and deleting the cursor to prevent further attempts to
115 * cross-reference with a defective btree.
116 *
117 * If a piece of metadata proves corrupt or suboptimal, the userspace
118 * program can ask the kernel to apply some tender loving care (TLC) to
119 * the metadata object by setting the REPAIR flag and re-calling the
120 * scrub ioctl. "Corruption" is defined by metadata violating the
121 * on-disk specification; operations cannot continue if the violation is
122 * left untreated. It is possible for XFS to continue if an object is
123 * "suboptimal", however performance may be degraded. Repairs are
124 * usually performed by rebuilding the metadata entirely out of
125 * redundant metadata. Optimizing, on the other hand, can sometimes be
126 * done without rebuilding entire structures.
127 *
128 * Generally speaking, the repair code has the following code structure:
129 * Lock -> scrub -> repair -> commit -> re-lock -> re-scrub -> unlock.
130 * The first check helps us figure out if we need to rebuild or simply
131 * optimize the structure so that the rebuild knows what to do. The
132 * second check evaluates the completeness of the repair; that is what
133 * is reported to userspace.
134 *
135 * A quick note on symbol prefixes:
136 * - "xfs_" are general XFS symbols.
137 * - "xchk_" are symbols related to metadata checking.
138 * - "xrep_" are symbols related to metadata repair.
139 * - "xfs_scrub_" are symbols that tie online fsck to the rest of XFS.
140 */
141
142 /*
143 * Scrub probe -- userspace uses this to probe if we're willing to scrub
144 * or repair a given mountpoint. This will be used by xfs_scrub to
145 * probe the kernel's abilities to scrub (and repair) the metadata. We
146 * do this by validating the ioctl inputs from userspace, preparing the
147 * filesystem for a scrub (or a repair) operation, and immediately
148 * returning to userspace. Userspace can use the returned errno and
149 * structure state to decide (in broad terms) if scrub/repair are
150 * supported by the running kernel.
151 */
152 static int
xchk_probe(struct xfs_scrub * sc)153 xchk_probe(
154 struct xfs_scrub *sc)
155 {
156 int error = 0;
157
158 if (xchk_should_terminate(sc, &error))
159 return error;
160
161 return 0;
162 }
163
164 /* Scrub setup and teardown */
165
166 /* Free all the resources and finish the transactions. */
167 STATIC int
xchk_teardown(struct xfs_scrub * sc,struct xfs_inode * ip_in,int error)168 xchk_teardown(
169 struct xfs_scrub *sc,
170 struct xfs_inode *ip_in,
171 int error)
172 {
173 xchk_ag_free(sc, &sc->sa);
174 if (sc->tp) {
175 if (error == 0 && (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR))
176 error = xfs_trans_commit(sc->tp);
177 else
178 xfs_trans_cancel(sc->tp);
179 sc->tp = NULL;
180 }
181 if (sc->ip) {
182 if (sc->ilock_flags)
183 xfs_iunlock(sc->ip, sc->ilock_flags);
184 if (sc->ip != ip_in &&
185 !xfs_internal_inum(sc->mp, sc->ip->i_ino))
186 xfs_irele(sc->ip);
187 sc->ip = NULL;
188 }
189 if (sc->has_quotaofflock)
190 mutex_unlock(&sc->mp->m_quotainfo->qi_quotaofflock);
191 if (sc->buf) {
192 kmem_free(sc->buf);
193 sc->buf = NULL;
194 }
195 return error;
196 }
197
198 /* Scrubbing dispatch. */
199
200 static const struct xchk_meta_ops meta_scrub_ops[] = {
201 [XFS_SCRUB_TYPE_PROBE] = { /* ioctl presence test */
202 .type = ST_NONE,
203 .setup = xchk_setup_fs,
204 .scrub = xchk_probe,
205 .repair = xrep_probe,
206 },
207 [XFS_SCRUB_TYPE_SB] = { /* superblock */
208 .type = ST_PERAG,
209 .setup = xchk_setup_fs,
210 .scrub = xchk_superblock,
211 .repair = xrep_superblock,
212 },
213 [XFS_SCRUB_TYPE_AGF] = { /* agf */
214 .type = ST_PERAG,
215 .setup = xchk_setup_fs,
216 .scrub = xchk_agf,
217 .repair = xrep_agf,
218 },
219 [XFS_SCRUB_TYPE_AGFL]= { /* agfl */
220 .type = ST_PERAG,
221 .setup = xchk_setup_fs,
222 .scrub = xchk_agfl,
223 .repair = xrep_agfl,
224 },
225 [XFS_SCRUB_TYPE_AGI] = { /* agi */
226 .type = ST_PERAG,
227 .setup = xchk_setup_fs,
228 .scrub = xchk_agi,
229 .repair = xrep_agi,
230 },
231 [XFS_SCRUB_TYPE_BNOBT] = { /* bnobt */
232 .type = ST_PERAG,
233 .setup = xchk_setup_ag_allocbt,
234 .scrub = xchk_bnobt,
235 .repair = xrep_notsupported,
236 },
237 [XFS_SCRUB_TYPE_CNTBT] = { /* cntbt */
238 .type = ST_PERAG,
239 .setup = xchk_setup_ag_allocbt,
240 .scrub = xchk_cntbt,
241 .repair = xrep_notsupported,
242 },
243 [XFS_SCRUB_TYPE_INOBT] = { /* inobt */
244 .type = ST_PERAG,
245 .setup = xchk_setup_ag_iallocbt,
246 .scrub = xchk_inobt,
247 .repair = xrep_notsupported,
248 },
249 [XFS_SCRUB_TYPE_FINOBT] = { /* finobt */
250 .type = ST_PERAG,
251 .setup = xchk_setup_ag_iallocbt,
252 .scrub = xchk_finobt,
253 .has = xfs_sb_version_hasfinobt,
254 .repair = xrep_notsupported,
255 },
256 [XFS_SCRUB_TYPE_RMAPBT] = { /* rmapbt */
257 .type = ST_PERAG,
258 .setup = xchk_setup_ag_rmapbt,
259 .scrub = xchk_rmapbt,
260 .has = xfs_sb_version_hasrmapbt,
261 .repair = xrep_notsupported,
262 },
263 [XFS_SCRUB_TYPE_REFCNTBT] = { /* refcountbt */
264 .type = ST_PERAG,
265 .setup = xchk_setup_ag_refcountbt,
266 .scrub = xchk_refcountbt,
267 .has = xfs_sb_version_hasreflink,
268 .repair = xrep_notsupported,
269 },
270 [XFS_SCRUB_TYPE_INODE] = { /* inode record */
271 .type = ST_INODE,
272 .setup = xchk_setup_inode,
273 .scrub = xchk_inode,
274 .repair = xrep_notsupported,
275 },
276 [XFS_SCRUB_TYPE_BMBTD] = { /* inode data fork */
277 .type = ST_INODE,
278 .setup = xchk_setup_inode_bmap,
279 .scrub = xchk_bmap_data,
280 .repair = xrep_notsupported,
281 },
282 [XFS_SCRUB_TYPE_BMBTA] = { /* inode attr fork */
283 .type = ST_INODE,
284 .setup = xchk_setup_inode_bmap,
285 .scrub = xchk_bmap_attr,
286 .repair = xrep_notsupported,
287 },
288 [XFS_SCRUB_TYPE_BMBTC] = { /* inode CoW fork */
289 .type = ST_INODE,
290 .setup = xchk_setup_inode_bmap,
291 .scrub = xchk_bmap_cow,
292 .repair = xrep_notsupported,
293 },
294 [XFS_SCRUB_TYPE_DIR] = { /* directory */
295 .type = ST_INODE,
296 .setup = xchk_setup_directory,
297 .scrub = xchk_directory,
298 .repair = xrep_notsupported,
299 },
300 [XFS_SCRUB_TYPE_XATTR] = { /* extended attributes */
301 .type = ST_INODE,
302 .setup = xchk_setup_xattr,
303 .scrub = xchk_xattr,
304 .repair = xrep_notsupported,
305 },
306 [XFS_SCRUB_TYPE_SYMLINK] = { /* symbolic link */
307 .type = ST_INODE,
308 .setup = xchk_setup_symlink,
309 .scrub = xchk_symlink,
310 .repair = xrep_notsupported,
311 },
312 [XFS_SCRUB_TYPE_PARENT] = { /* parent pointers */
313 .type = ST_INODE,
314 .setup = xchk_setup_parent,
315 .scrub = xchk_parent,
316 .repair = xrep_notsupported,
317 },
318 [XFS_SCRUB_TYPE_RTBITMAP] = { /* realtime bitmap */
319 .type = ST_FS,
320 .setup = xchk_setup_rt,
321 .scrub = xchk_rtbitmap,
322 .has = xfs_sb_version_hasrealtime,
323 .repair = xrep_notsupported,
324 },
325 [XFS_SCRUB_TYPE_RTSUM] = { /* realtime summary */
326 .type = ST_FS,
327 .setup = xchk_setup_rt,
328 .scrub = xchk_rtsummary,
329 .has = xfs_sb_version_hasrealtime,
330 .repair = xrep_notsupported,
331 },
332 [XFS_SCRUB_TYPE_UQUOTA] = { /* user quota */
333 .type = ST_FS,
334 .setup = xchk_setup_quota,
335 .scrub = xchk_quota,
336 .repair = xrep_notsupported,
337 },
338 [XFS_SCRUB_TYPE_GQUOTA] = { /* group quota */
339 .type = ST_FS,
340 .setup = xchk_setup_quota,
341 .scrub = xchk_quota,
342 .repair = xrep_notsupported,
343 },
344 [XFS_SCRUB_TYPE_PQUOTA] = { /* project quota */
345 .type = ST_FS,
346 .setup = xchk_setup_quota,
347 .scrub = xchk_quota,
348 .repair = xrep_notsupported,
349 },
350 };
351
352 /* This isn't a stable feature, warn once per day. */
353 static inline void
xchk_experimental_warning(struct xfs_mount * mp)354 xchk_experimental_warning(
355 struct xfs_mount *mp)
356 {
357 static struct ratelimit_state scrub_warning = RATELIMIT_STATE_INIT(
358 "xchk_warning", 86400 * HZ, 1);
359 ratelimit_set_flags(&scrub_warning, RATELIMIT_MSG_ON_RELEASE);
360
361 if (__ratelimit(&scrub_warning))
362 xfs_alert(mp,
363 "EXPERIMENTAL online scrub feature in use. Use at your own risk!");
364 }
365
366 static int
xchk_validate_inputs(struct xfs_mount * mp,struct xfs_scrub_metadata * sm)367 xchk_validate_inputs(
368 struct xfs_mount *mp,
369 struct xfs_scrub_metadata *sm)
370 {
371 int error;
372 const struct xchk_meta_ops *ops;
373
374 error = -EINVAL;
375 /* Check our inputs. */
376 sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
377 if (sm->sm_flags & ~XFS_SCRUB_FLAGS_IN)
378 goto out;
379 /* sm_reserved[] must be zero */
380 if (memchr_inv(sm->sm_reserved, 0, sizeof(sm->sm_reserved)))
381 goto out;
382
383 error = -ENOENT;
384 /* Do we know about this type of metadata? */
385 if (sm->sm_type >= XFS_SCRUB_TYPE_NR)
386 goto out;
387 ops = &meta_scrub_ops[sm->sm_type];
388 if (ops->setup == NULL || ops->scrub == NULL)
389 goto out;
390 /* Does this fs even support this type of metadata? */
391 if (ops->has && !ops->has(&mp->m_sb))
392 goto out;
393
394 error = -EINVAL;
395 /* restricting fields must be appropriate for type */
396 switch (ops->type) {
397 case ST_NONE:
398 case ST_FS:
399 if (sm->sm_ino || sm->sm_gen || sm->sm_agno)
400 goto out;
401 break;
402 case ST_PERAG:
403 if (sm->sm_ino || sm->sm_gen ||
404 sm->sm_agno >= mp->m_sb.sb_agcount)
405 goto out;
406 break;
407 case ST_INODE:
408 if (sm->sm_agno || (sm->sm_gen && !sm->sm_ino))
409 goto out;
410 break;
411 default:
412 goto out;
413 }
414
415 error = -EOPNOTSUPP;
416 /*
417 * We won't scrub any filesystem that doesn't have the ability
418 * to record unwritten extents. The option was made default in
419 * 2003, removed from mkfs in 2007, and cannot be disabled in
420 * v5, so if we find a filesystem without this flag it's either
421 * really old or totally unsupported. Avoid it either way.
422 * We also don't support v1-v3 filesystems, which aren't
423 * mountable.
424 */
425 if (!xfs_sb_version_hasextflgbit(&mp->m_sb))
426 goto out;
427
428 /*
429 * We only want to repair read-write v5+ filesystems. Defer the check
430 * for ops->repair until after our scrub confirms that we need to
431 * perform repairs so that we avoid failing due to not supporting
432 * repairing an object that doesn't need repairs.
433 */
434 if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) {
435 error = -EOPNOTSUPP;
436 if (!xfs_sb_version_hascrc(&mp->m_sb))
437 goto out;
438
439 error = -EROFS;
440 if (mp->m_flags & XFS_MOUNT_RDONLY)
441 goto out;
442 }
443
444 error = 0;
445 out:
446 return error;
447 }
448
449 #ifdef CONFIG_XFS_ONLINE_REPAIR
xchk_postmortem(struct xfs_scrub * sc)450 static inline void xchk_postmortem(struct xfs_scrub *sc)
451 {
452 /*
453 * Userspace asked us to repair something, we repaired it, rescanned
454 * it, and the rescan says it's still broken. Scream about this in
455 * the system logs.
456 */
457 if ((sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) &&
458 (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
459 XFS_SCRUB_OFLAG_XCORRUPT)))
460 xrep_failure(sc->mp);
461 }
462 #else
xchk_postmortem(struct xfs_scrub * sc)463 static inline void xchk_postmortem(struct xfs_scrub *sc)
464 {
465 /*
466 * Userspace asked us to scrub something, it's broken, and we have no
467 * way of fixing it. Scream in the logs.
468 */
469 if (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
470 XFS_SCRUB_OFLAG_XCORRUPT))
471 xfs_alert_ratelimited(sc->mp,
472 "Corruption detected during scrub.");
473 }
474 #endif /* CONFIG_XFS_ONLINE_REPAIR */
475
476 /* Dispatch metadata scrubbing. */
477 int
xfs_scrub_metadata(struct xfs_inode * ip,struct xfs_scrub_metadata * sm)478 xfs_scrub_metadata(
479 struct xfs_inode *ip,
480 struct xfs_scrub_metadata *sm)
481 {
482 struct xfs_scrub sc;
483 struct xfs_mount *mp = ip->i_mount;
484 bool try_harder = false;
485 bool already_fixed = false;
486 int error = 0;
487
488 BUILD_BUG_ON(sizeof(meta_scrub_ops) !=
489 (sizeof(struct xchk_meta_ops) * XFS_SCRUB_TYPE_NR));
490
491 trace_xchk_start(ip, sm, error);
492
493 /* Forbidden if we are shut down or mounted norecovery. */
494 error = -ESHUTDOWN;
495 if (XFS_FORCED_SHUTDOWN(mp))
496 goto out;
497 error = -ENOTRECOVERABLE;
498 if (mp->m_flags & XFS_MOUNT_NORECOVERY)
499 goto out;
500
501 error = xchk_validate_inputs(mp, sm);
502 if (error)
503 goto out;
504
505 xchk_experimental_warning(mp);
506
507 retry_op:
508 /* Set up for the operation. */
509 memset(&sc, 0, sizeof(sc));
510 sc.mp = ip->i_mount;
511 sc.sm = sm;
512 sc.ops = &meta_scrub_ops[sm->sm_type];
513 sc.try_harder = try_harder;
514 sc.sa.agno = NULLAGNUMBER;
515 error = sc.ops->setup(&sc, ip);
516 if (error)
517 goto out_teardown;
518
519 /* Scrub for errors. */
520 error = sc.ops->scrub(&sc);
521 if (!try_harder && error == -EDEADLOCK) {
522 /*
523 * Scrubbers return -EDEADLOCK to mean 'try harder'.
524 * Tear down everything we hold, then set up again with
525 * preparation for worst-case scenarios.
526 */
527 error = xchk_teardown(&sc, ip, 0);
528 if (error)
529 goto out;
530 try_harder = true;
531 goto retry_op;
532 } else if (error)
533 goto out_teardown;
534
535 if ((sc.sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) && !already_fixed) {
536 bool needs_fix;
537
538 /* Let debug users force us into the repair routines. */
539 if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_FORCE_SCRUB_REPAIR))
540 sc.sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
541
542 needs_fix = (sc.sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
543 XFS_SCRUB_OFLAG_XCORRUPT |
544 XFS_SCRUB_OFLAG_PREEN));
545 /*
546 * If userspace asked for a repair but it wasn't necessary,
547 * report that back to userspace.
548 */
549 if (!needs_fix) {
550 sc.sm->sm_flags |= XFS_SCRUB_OFLAG_NO_REPAIR_NEEDED;
551 goto out_nofix;
552 }
553
554 /*
555 * If it's broken, userspace wants us to fix it, and we haven't
556 * already tried to fix it, then attempt a repair.
557 */
558 error = xrep_attempt(ip, &sc, &already_fixed);
559 if (error == -EAGAIN) {
560 if (sc.try_harder)
561 try_harder = true;
562 error = xchk_teardown(&sc, ip, 0);
563 if (error) {
564 xrep_failure(mp);
565 goto out;
566 }
567 goto retry_op;
568 }
569 }
570
571 out_nofix:
572 xchk_postmortem(&sc);
573 out_teardown:
574 error = xchk_teardown(&sc, ip, error);
575 out:
576 trace_xchk_done(ip, sm, error);
577 if (error == -EFSCORRUPTED || error == -EFSBADCRC) {
578 sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
579 error = 0;
580 }
581 return error;
582 }
583