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1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Copyright (C) 2017 Oracle.  All Rights Reserved.
4  * Author: Darrick J. Wong <[email protected]>
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_errortag.h"
18 #include "xfs_error.h"
19 #include "xfs_scrub.h"
20 #include "scrub/scrub.h"
21 #include "scrub/common.h"
22 #include "scrub/trace.h"
23 #include "scrub/repair.h"
24 #include "scrub/health.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  */
134 static int
135 xchk_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
148 /* Free all the resources and finish the transactions. */
149 STATIC int
150 xchk_teardown(
151         struct xfs_scrub        *sc,
152         int                     error)
153 {
154         struct xfs_inode        *ip_in = XFS_I(file_inode(sc->file));
155
156         xchk_ag_free(sc, &sc->sa);
157         if (sc->tp) {
158                 if (error == 0 && (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR))
159                         error = xfs_trans_commit(sc->tp);
160                 else
161                         xfs_trans_cancel(sc->tp);
162                 sc->tp = NULL;
163         }
164         if (sc->ip) {
165                 if (sc->ilock_flags)
166                         xfs_iunlock(sc->ip, sc->ilock_flags);
167                 if (sc->ip != ip_in &&
168                     !xfs_internal_inum(sc->mp, sc->ip->i_ino))
169                         xfs_irele(sc->ip);
170                 sc->ip = NULL;
171         }
172         if (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR)
173                 mnt_drop_write_file(sc->file);
174         if (sc->flags & XCHK_REAPING_DISABLED)
175                 xchk_start_reaping(sc);
176         if (sc->buf) {
177                 kmem_free(sc->buf);
178                 sc->buf = NULL;
179         }
180         return error;
181 }
182
183 /* Scrubbing dispatch. */
184
185 static const struct xchk_meta_ops meta_scrub_ops[] = {
186         [XFS_SCRUB_TYPE_PROBE] = {      /* ioctl presence test */
187                 .type   = ST_NONE,
188                 .setup  = xchk_setup_fs,
189                 .scrub  = xchk_probe,
190                 .repair = xrep_probe,
191         },
192         [XFS_SCRUB_TYPE_SB] = {         /* superblock */
193                 .type   = ST_PERAG,
194                 .setup  = xchk_setup_fs,
195                 .scrub  = xchk_superblock,
196                 .repair = xrep_superblock,
197         },
198         [XFS_SCRUB_TYPE_AGF] = {        /* agf */
199                 .type   = ST_PERAG,
200                 .setup  = xchk_setup_fs,
201                 .scrub  = xchk_agf,
202                 .repair = xrep_agf,
203         },
204         [XFS_SCRUB_TYPE_AGFL]= {        /* agfl */
205                 .type   = ST_PERAG,
206                 .setup  = xchk_setup_fs,
207                 .scrub  = xchk_agfl,
208                 .repair = xrep_agfl,
209         },
210         [XFS_SCRUB_TYPE_AGI] = {        /* agi */
211                 .type   = ST_PERAG,
212                 .setup  = xchk_setup_fs,
213                 .scrub  = xchk_agi,
214                 .repair = xrep_agi,
215         },
216         [XFS_SCRUB_TYPE_BNOBT] = {      /* bnobt */
217                 .type   = ST_PERAG,
218                 .setup  = xchk_setup_ag_allocbt,
219                 .scrub  = xchk_bnobt,
220                 .repair = xrep_notsupported,
221         },
222         [XFS_SCRUB_TYPE_CNTBT] = {      /* cntbt */
223                 .type   = ST_PERAG,
224                 .setup  = xchk_setup_ag_allocbt,
225                 .scrub  = xchk_cntbt,
226                 .repair = xrep_notsupported,
227         },
228         [XFS_SCRUB_TYPE_INOBT] = {      /* inobt */
229                 .type   = ST_PERAG,
230                 .setup  = xchk_setup_ag_iallocbt,
231                 .scrub  = xchk_inobt,
232                 .repair = xrep_notsupported,
233         },
234         [XFS_SCRUB_TYPE_FINOBT] = {     /* finobt */
235                 .type   = ST_PERAG,
236                 .setup  = xchk_setup_ag_iallocbt,
237                 .scrub  = xchk_finobt,
238                 .has    = xfs_has_finobt,
239                 .repair = xrep_notsupported,
240         },
241         [XFS_SCRUB_TYPE_RMAPBT] = {     /* rmapbt */
242                 .type   = ST_PERAG,
243                 .setup  = xchk_setup_ag_rmapbt,
244                 .scrub  = xchk_rmapbt,
245                 .has    = xfs_has_rmapbt,
246                 .repair = xrep_notsupported,
247         },
248         [XFS_SCRUB_TYPE_REFCNTBT] = {   /* refcountbt */
249                 .type   = ST_PERAG,
250                 .setup  = xchk_setup_ag_refcountbt,
251                 .scrub  = xchk_refcountbt,
252                 .has    = xfs_has_reflink,
253                 .repair = xrep_notsupported,
254         },
255         [XFS_SCRUB_TYPE_INODE] = {      /* inode record */
256                 .type   = ST_INODE,
257                 .setup  = xchk_setup_inode,
258                 .scrub  = xchk_inode,
259                 .repair = xrep_notsupported,
260         },
261         [XFS_SCRUB_TYPE_BMBTD] = {      /* inode data fork */
262                 .type   = ST_INODE,
263                 .setup  = xchk_setup_inode_bmap,
264                 .scrub  = xchk_bmap_data,
265                 .repair = xrep_notsupported,
266         },
267         [XFS_SCRUB_TYPE_BMBTA] = {      /* inode attr fork */
268                 .type   = ST_INODE,
269                 .setup  = xchk_setup_inode_bmap,
270                 .scrub  = xchk_bmap_attr,
271                 .repair = xrep_notsupported,
272         },
273         [XFS_SCRUB_TYPE_BMBTC] = {      /* inode CoW fork */
274                 .type   = ST_INODE,
275                 .setup  = xchk_setup_inode_bmap,
276                 .scrub  = xchk_bmap_cow,
277                 .repair = xrep_notsupported,
278         },
279         [XFS_SCRUB_TYPE_DIR] = {        /* directory */
280                 .type   = ST_INODE,
281                 .setup  = xchk_setup_directory,
282                 .scrub  = xchk_directory,
283                 .repair = xrep_notsupported,
284         },
285         [XFS_SCRUB_TYPE_XATTR] = {      /* extended attributes */
286                 .type   = ST_INODE,
287                 .setup  = xchk_setup_xattr,
288                 .scrub  = xchk_xattr,
289                 .repair = xrep_notsupported,
290         },
291         [XFS_SCRUB_TYPE_SYMLINK] = {    /* symbolic link */
292                 .type   = ST_INODE,
293                 .setup  = xchk_setup_symlink,
294                 .scrub  = xchk_symlink,
295                 .repair = xrep_notsupported,
296         },
297         [XFS_SCRUB_TYPE_PARENT] = {     /* parent pointers */
298                 .type   = ST_INODE,
299                 .setup  = xchk_setup_parent,
300                 .scrub  = xchk_parent,
301                 .repair = xrep_notsupported,
302         },
303         [XFS_SCRUB_TYPE_RTBITMAP] = {   /* realtime bitmap */
304                 .type   = ST_FS,
305                 .setup  = xchk_setup_rt,
306                 .scrub  = xchk_rtbitmap,
307                 .has    = xfs_has_realtime,
308                 .repair = xrep_notsupported,
309         },
310         [XFS_SCRUB_TYPE_RTSUM] = {      /* realtime summary */
311                 .type   = ST_FS,
312                 .setup  = xchk_setup_rt,
313                 .scrub  = xchk_rtsummary,
314                 .has    = xfs_has_realtime,
315                 .repair = xrep_notsupported,
316         },
317         [XFS_SCRUB_TYPE_UQUOTA] = {     /* user quota */
318                 .type   = ST_FS,
319                 .setup  = xchk_setup_quota,
320                 .scrub  = xchk_quota,
321                 .repair = xrep_notsupported,
322         },
323         [XFS_SCRUB_TYPE_GQUOTA] = {     /* group quota */
324                 .type   = ST_FS,
325                 .setup  = xchk_setup_quota,
326                 .scrub  = xchk_quota,
327                 .repair = xrep_notsupported,
328         },
329         [XFS_SCRUB_TYPE_PQUOTA] = {     /* project quota */
330                 .type   = ST_FS,
331                 .setup  = xchk_setup_quota,
332                 .scrub  = xchk_quota,
333                 .repair = xrep_notsupported,
334         },
335         [XFS_SCRUB_TYPE_FSCOUNTERS] = { /* fs summary counters */
336                 .type   = ST_FS,
337                 .setup  = xchk_setup_fscounters,
338                 .scrub  = xchk_fscounters,
339                 .repair = xrep_notsupported,
340         },
341 };
342
343 /* This isn't a stable feature, warn once per day. */
344 static inline void
345 xchk_experimental_warning(
346         struct xfs_mount        *mp)
347 {
348         static struct ratelimit_state scrub_warning = RATELIMIT_STATE_INIT(
349                         "xchk_warning", 86400 * HZ, 1);
350         ratelimit_set_flags(&scrub_warning, RATELIMIT_MSG_ON_RELEASE);
351
352         if (__ratelimit(&scrub_warning))
353                 xfs_alert(mp,
354 "EXPERIMENTAL online scrub feature in use. Use at your own risk!");
355 }
356
357 static int
358 xchk_validate_inputs(
359         struct xfs_mount                *mp,
360         struct xfs_scrub_metadata       *sm)
361 {
362         int                             error;
363         const struct xchk_meta_ops      *ops;
364
365         error = -EINVAL;
366         /* Check our inputs. */
367         sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
368         if (sm->sm_flags & ~XFS_SCRUB_FLAGS_IN)
369                 goto out;
370         /* sm_reserved[] must be zero */
371         if (memchr_inv(sm->sm_reserved, 0, sizeof(sm->sm_reserved)))
372                 goto out;
373
374         error = -ENOENT;
375         /* Do we know about this type of metadata? */
376         if (sm->sm_type >= XFS_SCRUB_TYPE_NR)
377                 goto out;
378         ops = &meta_scrub_ops[sm->sm_type];
379         if (ops->setup == NULL || ops->scrub == NULL)
380                 goto out;
381         /* Does this fs even support this type of metadata? */
382         if (ops->has && !ops->has(mp))
383                 goto out;
384
385         error = -EINVAL;
386         /* restricting fields must be appropriate for type */
387         switch (ops->type) {
388         case ST_NONE:
389         case ST_FS:
390                 if (sm->sm_ino || sm->sm_gen || sm->sm_agno)
391                         goto out;
392                 break;
393         case ST_PERAG:
394                 if (sm->sm_ino || sm->sm_gen ||
395                     sm->sm_agno >= mp->m_sb.sb_agcount)
396                         goto out;
397                 break;
398         case ST_INODE:
399                 if (sm->sm_agno || (sm->sm_gen && !sm->sm_ino))
400                         goto out;
401                 break;
402         default:
403                 goto out;
404         }
405
406         /*
407          * We only want to repair read-write v5+ filesystems.  Defer the check
408          * for ops->repair until after our scrub confirms that we need to
409          * perform repairs so that we avoid failing due to not supporting
410          * repairing an object that doesn't need repairs.
411          */
412         if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) {
413                 error = -EOPNOTSUPP;
414                 if (!xfs_has_crc(mp))
415                         goto out;
416
417                 error = -EROFS;
418                 if (xfs_is_readonly(mp))
419                         goto out;
420         }
421
422         error = 0;
423 out:
424         return error;
425 }
426
427 #ifdef CONFIG_XFS_ONLINE_REPAIR
428 static inline void xchk_postmortem(struct xfs_scrub *sc)
429 {
430         /*
431          * Userspace asked us to repair something, we repaired it, rescanned
432          * it, and the rescan says it's still broken.  Scream about this in
433          * the system logs.
434          */
435         if ((sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) &&
436             (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
437                                  XFS_SCRUB_OFLAG_XCORRUPT)))
438                 xrep_failure(sc->mp);
439 }
440 #else
441 static inline void xchk_postmortem(struct xfs_scrub *sc)
442 {
443         /*
444          * Userspace asked us to scrub something, it's broken, and we have no
445          * way of fixing it.  Scream in the logs.
446          */
447         if (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
448                                 XFS_SCRUB_OFLAG_XCORRUPT))
449                 xfs_alert_ratelimited(sc->mp,
450                                 "Corruption detected during scrub.");
451 }
452 #endif /* CONFIG_XFS_ONLINE_REPAIR */
453
454 /* Dispatch metadata scrubbing. */
455 int
456 xfs_scrub_metadata(
457         struct file                     *file,
458         struct xfs_scrub_metadata       *sm)
459 {
460         struct xfs_scrub                *sc;
461         struct xfs_mount                *mp = XFS_I(file_inode(file))->i_mount;
462         int                             error = 0;
463
464         BUILD_BUG_ON(sizeof(meta_scrub_ops) !=
465                 (sizeof(struct xchk_meta_ops) * XFS_SCRUB_TYPE_NR));
466
467         trace_xchk_start(XFS_I(file_inode(file)), sm, error);
468
469         /* Forbidden if we are shut down or mounted norecovery. */
470         error = -ESHUTDOWN;
471         if (xfs_is_shutdown(mp))
472                 goto out;
473         error = -ENOTRECOVERABLE;
474         if (xfs_has_norecovery(mp))
475                 goto out;
476
477         error = xchk_validate_inputs(mp, sm);
478         if (error)
479                 goto out;
480
481         xchk_experimental_warning(mp);
482
483         sc = kmem_zalloc(sizeof(struct xfs_scrub), KM_NOFS | KM_MAYFAIL);
484         if (!sc) {
485                 error = -ENOMEM;
486                 goto out;
487         }
488
489         sc->mp = mp;
490         sc->file = file;
491         sc->sm = sm;
492         sc->ops = &meta_scrub_ops[sm->sm_type];
493         sc->sick_mask = xchk_health_mask_for_scrub_type(sm->sm_type);
494 retry_op:
495         /*
496          * When repairs are allowed, prevent freezing or readonly remount while
497          * scrub is running with a real transaction.
498          */
499         if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) {
500                 error = mnt_want_write_file(sc->file);
501                 if (error)
502                         goto out_sc;
503         }
504
505         /* Set up for the operation. */
506         error = sc->ops->setup(sc);
507         if (error)
508                 goto out_teardown;
509
510         /* Scrub for errors. */
511         error = sc->ops->scrub(sc);
512         if (!(sc->flags & XCHK_TRY_HARDER) && error == -EDEADLOCK) {
513                 /*
514                  * Scrubbers return -EDEADLOCK to mean 'try harder'.
515                  * Tear down everything we hold, then set up again with
516                  * preparation for worst-case scenarios.
517                  */
518                 error = xchk_teardown(sc, 0);
519                 if (error)
520                         goto out_sc;
521                 sc->flags |= XCHK_TRY_HARDER;
522                 goto retry_op;
523         } else if (error || (sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE))
524                 goto out_teardown;
525
526         xchk_update_health(sc);
527
528         if ((sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) &&
529             !(sc->flags & XREP_ALREADY_FIXED)) {
530                 bool needs_fix;
531
532                 /* Let debug users force us into the repair routines. */
533                 if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_FORCE_SCRUB_REPAIR))
534                         sc->sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
535
536                 needs_fix = (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
537                                                  XFS_SCRUB_OFLAG_XCORRUPT |
538                                                  XFS_SCRUB_OFLAG_PREEN));
539                 /*
540                  * If userspace asked for a repair but it wasn't necessary,
541                  * report that back to userspace.
542                  */
543                 if (!needs_fix) {
544                         sc->sm->sm_flags |= XFS_SCRUB_OFLAG_NO_REPAIR_NEEDED;
545                         goto out_nofix;
546                 }
547
548                 /*
549                  * If it's broken, userspace wants us to fix it, and we haven't
550                  * already tried to fix it, then attempt a repair.
551                  */
552                 error = xrep_attempt(sc);
553                 if (error == -EAGAIN) {
554                         /*
555                          * Either the repair function succeeded or it couldn't
556                          * get all the resources it needs; either way, we go
557                          * back to the beginning and call the scrub function.
558                          */
559                         error = xchk_teardown(sc, 0);
560                         if (error) {
561                                 xrep_failure(mp);
562                                 goto out_sc;
563                         }
564                         goto retry_op;
565                 }
566         }
567
568 out_nofix:
569         xchk_postmortem(sc);
570 out_teardown:
571         error = xchk_teardown(sc, error);
572 out_sc:
573         kmem_free(sc);
574 out:
575         trace_xchk_done(XFS_I(file_inode(file)), sm, error);
576         if (error == -EFSCORRUPTED || error == -EFSBADCRC) {
577                 sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
578                 error = 0;
579         }
580         return error;
581 }
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