fs/xfs/scrub/scrub.c

   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_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 #include "scrub/stats.h"
  26 #include "scrub/xfile.h"
  27
  28 /*
  29  * Online Scrub and Repair
  30  *
  31  * Traditionally, XFS (the kernel driver) did not know how to check or
  32  * repair on-disk data structures.  That task was left to the xfs_check
  33  * and xfs_repair tools, both of which require taking the filesystem
  34  * offline for a thorough but time consuming examination.  Online
  35  * scrub & repair, on the other hand, enables us to check the metadata
  36  * for obvious errors while carefully stepping around the filesystem's
  37  * ongoing operations, locking rules, etc.
  38  *
  39  * Given that most XFS metadata consist of records stored in a btree,
  40  * most of the checking functions iterate the btree blocks themselves
  41  * looking for irregularities.  When a record block is encountered, each
  42  * record can be checked for obviously bad values.  Record values can
  43  * also be cross-referenced against other btrees to look for potential
  44  * misunderstandings between pieces of metadata.
  45  *
  46  * It is expected that the checkers responsible for per-AG metadata
  47  * structures will lock the AG headers (AGI, AGF, AGFL), iterate the
  48  * metadata structure, and perform any relevant cross-referencing before
  49  * unlocking the AG and returning the results to userspace.  These
  50  * scrubbers must not keep an AG locked for too long to avoid tying up
  51  * the block and inode allocators.
  52  *
  53  * Block maps and b-trees rooted in an inode present a special challenge
  54  * because they can involve extents from any AG.  The general scrubber
  55  * structure of lock -> check -> xref -> unlock still holds, but AG
  56  * locking order rules /must/ be obeyed to avoid deadlocks.  The
  57  * ordering rule, of course, is that we must lock in increasing AG
  58  * order.  Helper functions are provided to track which AG headers we've
  59  * already locked.  If we detect an imminent locking order violation, we
  60  * can signal a potential deadlock, in which case the scrubber can jump
  61  * out to the top level, lock all the AGs in order, and retry the scrub.
  62  *
  63  * For file data (directories, extended attributes, symlinks) scrub, we
  64  * can simply lock the inode and walk the data.  For btree data
  65  * (directories and attributes) we follow the same btree-scrubbing
  66  * strategy outlined previously to check the records.
  67  *
  68  * We use a bit of trickery with transactions to avoid buffer deadlocks
  69  * if there is a cycle in the metadata.  The basic problem is that
  70  * travelling down a btree involves locking the current buffer at each
  71  * tree level.  If a pointer should somehow point back to a buffer that
  72  * we've already examined, we will deadlock due to the second buffer
  73  * locking attempt.  Note however that grabbing a buffer in transaction
  74  * context links the locked buffer to the transaction.  If we try to
  75  * re-grab the buffer in the context of the same transaction, we avoid
  76  * the second lock attempt and continue.  Between the verifier and the
  77  * scrubber, something will notice that something is amiss and report
  78  * the corruption.  Therefore, each scrubber will allocate an empty
  79  * transaction, attach buffers to it, and cancel the transaction at the
  80  * end of the scrub run.  Cancelling a non-dirty transaction simply
  81  * unlocks the buffers.
  82  *
  83  * There are four pieces of data that scrub can communicate to
  84  * userspace.  The first is the error code (errno), which can be used to
  85  * communicate operational errors in performing the scrub.  There are
  86  * also three flags that can be set in the scrub context.  If the data
  87  * structure itself is corrupt, the CORRUPT flag will be set.  If
  88  * the metadata is correct but otherwise suboptimal, the PREEN flag
  89  * will be set.
  90  *
  91  * We perform secondary validation of filesystem metadata by
  92  * cross-referencing every record with all other available metadata.
  93  * For example, for block mapping extents, we verify that there are no
  94  * records in the free space and inode btrees corresponding to that
  95  * space extent and that there is a corresponding entry in the reverse
  96  * mapping btree.  Inconsistent metadata is noted by setting the
  97  * XCORRUPT flag; btree query function errors are noted by setting the
  98  * XFAIL flag and deleting the cursor to prevent further attempts to
  99  * cross-reference with a defective btree.
 100  *
 101  * If a piece of metadata proves corrupt or suboptimal, the userspace
 102  * program can ask the kernel to apply some tender loving care (TLC) to
 103  * the metadata object by setting the REPAIR flag and re-calling the
 104  * scrub ioctl.  "Corruption" is defined by metadata violating the
 105  * on-disk specification; operations cannot continue if the violation is
 106  * left untreated.  It is possible for XFS to continue if an object is
 107  * "suboptimal", however performance may be degraded.  Repairs are
 108  * usually performed by rebuilding the metadata entirely out of
 109  * redundant metadata.  Optimizing, on the other hand, can sometimes be
 110  * done without rebuilding entire structures.
 111  *
 112  * Generally speaking, the repair code has the following code structure:
 113  * Lock -> scrub -> repair -> commit -> re-lock -> re-scrub -> unlock.
 114  * The first check helps us figure out if we need to rebuild or simply
 115  * optimize the structure so that the rebuild knows what to do.  The
 116  * second check evaluates the completeness of the repair; that is what
 117  * is reported to userspace.
 118  *
 119  * A quick note on symbol prefixes:
 120  * - "xfs_" are general XFS symbols.
 121  * - "xchk_" are symbols related to metadata checking.
 122  * - "xrep_" are symbols related to metadata repair.
 123  * - "xfs_scrub_" are symbols that tie online fsck to the rest of XFS.
 124  */
 125
 126 /*
 127  * Scrub probe -- userspace uses this to probe if we're willing to scrub
 128  * or repair a given mountpoint.  This will be used by xfs_scrub to
 129  * probe the kernel's abilities to scrub (and repair) the metadata.  We
 130  * do this by validating the ioctl inputs from userspace, preparing the
 131  * filesystem for a scrub (or a repair) operation, and immediately
 132  * returning to userspace.  Userspace can use the returned errno and
 133  * structure state to decide (in broad terms) if scrub/repair are
 134  * supported by the running kernel.
 135  */
 136 static int
 137 xchk_probe(
 138         struct xfs_scrub        *sc)
 139 {
 140         int                     error = 0;
 141
 142         if (xchk_should_terminate(sc, &error))
 143                 return error;
 144
 145         return 0;
 146 }
 147
 148 /* Scrub setup and teardown */
 149
 150 static inline void
 151 xchk_fsgates_disable(
 152         struct xfs_scrub        *sc)
 153 {
 154         if (!(sc->flags & XCHK_FSGATES_ALL))
 155                 return;
 156
 157         trace_xchk_fsgates_disable(sc, sc->flags & XCHK_FSGATES_ALL);
 158
 159         if (sc->flags & XCHK_FSGATES_DRAIN)
 160                 xfs_drain_wait_disable();
 161
 162         sc->flags &= ~XCHK_FSGATES_ALL;
 163 }
 164
 165 /* Free all the resources and finish the transactions. */
 166 STATIC int
 167 xchk_teardown(
 168         struct xfs_scrub        *sc,
 169         int                     error)
 170 {
 171         xchk_ag_free(sc, &sc->sa);
 172         if (sc->tp) {
 173                 if (error == 0 && (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR))
 174                         error = xfs_trans_commit(sc->tp);
 175                 else
 176                         xfs_trans_cancel(sc->tp);
 177                 sc->tp = NULL;
 178         }
 179         if (sc->ip) {
 180                 if (sc->ilock_flags)
 181                         xchk_iunlock(sc, sc->ilock_flags);
 182                 xchk_irele(sc, sc->ip);
 183                 sc->ip = NULL;
 184         }
 185         if (sc->flags & XCHK_HAVE_FREEZE_PROT) {
 186                 sc->flags &= ~XCHK_HAVE_FREEZE_PROT;
 187                 mnt_drop_write_file(sc->file);
 188         }
 189         if (sc->xfile) {
 190                 xfile_destroy(sc->xfile);
 191                 sc->xfile = NULL;
 192         }
 193         if (sc->buf) {
 194                 if (sc->buf_cleanup)
 195                         sc->buf_cleanup(sc->buf);
 196                 kvfree(sc->buf);
 197                 sc->buf_cleanup = NULL;
 198                 sc->buf = NULL;
 199         }
 200
 201         xchk_fsgates_disable(sc);
 202         return error;
 203 }
 204
 205 /* Scrubbing dispatch. */
 206
 207 static const struct xchk_meta_ops meta_scrub_ops[] = {
 208         [XFS_SCRUB_TYPE_PROBE] = {      /* ioctl presence test */
 209                 .type   = ST_NONE,
 210                 .setup  = xchk_setup_fs,
 211                 .scrub  = xchk_probe,
 212                 .repair = xrep_probe,
 213         },
 214         [XFS_SCRUB_TYPE_SB] = {         /* superblock */
 215                 .type   = ST_PERAG,
 216                 .setup  = xchk_setup_agheader,
 217                 .scrub  = xchk_superblock,
 218                 .repair = xrep_superblock,
 219         },
 220         [XFS_SCRUB_TYPE_AGF] = {        /* agf */
 221                 .type   = ST_PERAG,
 222                 .setup  = xchk_setup_agheader,
 223                 .scrub  = xchk_agf,
 224                 .repair = xrep_agf,
 225         },
 226         [XFS_SCRUB_TYPE_AGFL]= {        /* agfl */
 227                 .type   = ST_PERAG,
 228                 .setup  = xchk_setup_agheader,
 229                 .scrub  = xchk_agfl,
 230                 .repair = xrep_agfl,
 231         },
 232         [XFS_SCRUB_TYPE_AGI] = {        /* agi */
 233                 .type   = ST_PERAG,
 234                 .setup  = xchk_setup_agheader,
 235                 .scrub  = xchk_agi,
 236                 .repair = xrep_agi,
 237         },
 238         [XFS_SCRUB_TYPE_BNOBT] = {      /* bnobt */
 239                 .type   = ST_PERAG,
 240                 .setup  = xchk_setup_ag_allocbt,
 241                 .scrub  = xchk_bnobt,
 242                 .repair = xrep_notsupported,
 243         },
 244         [XFS_SCRUB_TYPE_CNTBT] = {      /* cntbt */
 245                 .type   = ST_PERAG,
 246                 .setup  = xchk_setup_ag_allocbt,
 247                 .scrub  = xchk_cntbt,
 248                 .repair = xrep_notsupported,
 249         },
 250         [XFS_SCRUB_TYPE_INOBT] = {      /* inobt */
 251                 .type   = ST_PERAG,
 252                 .setup  = xchk_setup_ag_iallocbt,
 253                 .scrub  = xchk_inobt,
 254                 .repair = xrep_notsupported,
 255         },
 256         [XFS_SCRUB_TYPE_FINOBT] = {     /* finobt */
 257                 .type   = ST_PERAG,
 258                 .setup  = xchk_setup_ag_iallocbt,
 259                 .scrub  = xchk_finobt,
 260                 .has    = xfs_has_finobt,
 261                 .repair = xrep_notsupported,
 262         },
 263         [XFS_SCRUB_TYPE_RMAPBT] = {     /* rmapbt */
 264                 .type   = ST_PERAG,
 265                 .setup  = xchk_setup_ag_rmapbt,
 266                 .scrub  = xchk_rmapbt,
 267                 .has    = xfs_has_rmapbt,
 268                 .repair = xrep_notsupported,
 269         },
 270         [XFS_SCRUB_TYPE_REFCNTBT] = {   /* refcountbt */
 271                 .type   = ST_PERAG,
 272                 .setup  = xchk_setup_ag_refcountbt,
 273                 .scrub  = xchk_refcountbt,
 274                 .has    = xfs_has_reflink,
 275                 .repair = xrep_notsupported,
 276         },
 277         [XFS_SCRUB_TYPE_INODE] = {      /* inode record */
 278                 .type   = ST_INODE,
 279                 .setup  = xchk_setup_inode,
 280                 .scrub  = xchk_inode,
 281                 .repair = xrep_notsupported,
 282         },
 283         [XFS_SCRUB_TYPE_BMBTD] = {      /* inode data fork */
 284                 .type   = ST_INODE,
 285                 .setup  = xchk_setup_inode_bmap,
 286                 .scrub  = xchk_bmap_data,
 287                 .repair = xrep_notsupported,
 288         },
 289         [XFS_SCRUB_TYPE_BMBTA] = {      /* inode attr fork */
 290                 .type   = ST_INODE,
 291                 .setup  = xchk_setup_inode_bmap,
 292                 .scrub  = xchk_bmap_attr,
 293                 .repair = xrep_notsupported,
 294         },
 295         [XFS_SCRUB_TYPE_BMBTC] = {      /* inode CoW fork */
 296                 .type   = ST_INODE,
 297                 .setup  = xchk_setup_inode_bmap,
 298                 .scrub  = xchk_bmap_cow,
 299                 .repair = xrep_notsupported,
 300         },
 301         [XFS_SCRUB_TYPE_DIR] = {        /* directory */
 302                 .type   = ST_INODE,
 303                 .setup  = xchk_setup_directory,
 304                 .scrub  = xchk_directory,
 305                 .repair = xrep_notsupported,
 306         },
 307         [XFS_SCRUB_TYPE_XATTR] = {      /* extended attributes */
 308                 .type   = ST_INODE,
 309                 .setup  = xchk_setup_xattr,
 310                 .scrub  = xchk_xattr,
 311                 .repair = xrep_notsupported,
 312         },
 313         [XFS_SCRUB_TYPE_SYMLINK] = {    /* symbolic link */
 314                 .type   = ST_INODE,
 315                 .setup  = xchk_setup_symlink,
 316                 .scrub  = xchk_symlink,
 317                 .repair = xrep_notsupported,
 318         },
 319         [XFS_SCRUB_TYPE_PARENT] = {     /* parent pointers */
 320                 .type   = ST_INODE,
 321                 .setup  = xchk_setup_parent,
 322                 .scrub  = xchk_parent,
 323                 .repair = xrep_notsupported,
 324         },
 325         [XFS_SCRUB_TYPE_RTBITMAP] = {   /* realtime bitmap */
 326                 .type   = ST_FS,
 327                 .setup  = xchk_setup_rtbitmap,
 328                 .scrub  = xchk_rtbitmap,
 329                 .has    = xfs_has_realtime,
 330                 .repair = xrep_notsupported,
 331         },
 332         [XFS_SCRUB_TYPE_RTSUM] = {      /* realtime summary */
 333                 .type   = ST_FS,
 334                 .setup  = xchk_setup_rtsummary,
 335                 .scrub  = xchk_rtsummary,
 336                 .has    = xfs_has_realtime,
 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_notsupported,
 344         },
 345         [XFS_SCRUB_TYPE_GQUOTA] = {     /* group quota */
 346                 .type   = ST_FS,
 347                 .setup  = xchk_setup_quota,
 348                 .scrub  = xchk_quota,
 349                 .repair = xrep_notsupported,
 350         },
 351         [XFS_SCRUB_TYPE_PQUOTA] = {     /* project quota */
 352                 .type   = ST_FS,
 353                 .setup  = xchk_setup_quota,
 354                 .scrub  = xchk_quota,
 355                 .repair = xrep_notsupported,
 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
 365 static int
 366 xchk_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;
 436 out:
 437         return error;
 438 }
 439
 440 #ifdef CONFIG_XFS_ONLINE_REPAIR
 441 static 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
 454 static 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. */
 468 int
 469 xfs_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);
 510 retry_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         error = sc->ops->scrub(sc);
 535         run.scrub_ns += xchk_stats_elapsed_ns(check_start);
 536         if (error == -EDEADLOCK && !(sc->flags & XCHK_TRY_HARDER))
 537                 goto try_harder;
 538         if (error == -ECHRNG && !(sc->flags & XCHK_NEED_DRAIN))
 539                 goto need_drain;
 540         if (error || (sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE))
 541                 goto out_teardown;
 542
 543         xchk_update_health(sc);
 544
 545         if ((sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) &&
 546             !(sc->flags & XREP_ALREADY_FIXED)) {
 547                 bool needs_fix = xchk_needs_repair(sc->sm);
 548
 549                 /* Userspace asked us to rebuild the structure regardless. */
 550                 if (sc->sm->sm_flags & XFS_SCRUB_IFLAG_FORCE_REBUILD)
 551                         needs_fix = true;
 552
 553                 /* Let debug users force us into the repair routines. */
 554                 if (XFS_TEST_ERROR(needs_fix, mp, XFS_ERRTAG_FORCE_SCRUB_REPAIR))
 555                         needs_fix = true;
 556
 557                 /*
 558                  * If userspace asked for a repair but it wasn't necessary,
 559                  * report that back to userspace.
 560                  */
 561                 if (!needs_fix) {
 562                         sc->sm->sm_flags |= XFS_SCRUB_OFLAG_NO_REPAIR_NEEDED;
 563                         goto out_nofix;
 564                 }
 565
 566                 /*
 567                  * If it's broken, userspace wants us to fix it, and we haven't
 568                  * already tried to fix it, then attempt a repair.
 569                  */
 570                 error = xrep_attempt(sc, &run);
 571                 if (error == -EAGAIN) {
 572                         /*
 573                          * Either the repair function succeeded or it couldn't
 574                          * get all the resources it needs; either way, we go
 575                          * back to the beginning and call the scrub function.
 576                          */
 577                         error = xchk_teardown(sc, 0);
 578                         if (error) {
 579                                 xrep_failure(mp);
 580                                 goto out_sc;
 581                         }
 582                         goto retry_op;
 583                 }
 584         }
 585
 586 out_nofix:
 587         xchk_postmortem(sc);
 588 out_teardown:
 589         error = xchk_teardown(sc, error);
 590 out_sc:
 591         kfree(sc);
 592 out:
 593         trace_xchk_done(XFS_I(file_inode(file)), sm, error);
 594         if (error == -EFSCORRUPTED || error == -EFSBADCRC) {
 595                 sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
 596                 error = 0;
 597         }
 598         if (error != -ENOENT)
 599                 xchk_stats_merge(mp, sm, &run);
 600         return error;
 601 need_drain:
 602         error = xchk_teardown(sc, 0);
 603         if (error)
 604                 goto out_sc;
 605         sc->flags |= XCHK_NEED_DRAIN;
 606         run.retries++;
 607         goto retry_op;
 608 try_harder:
 609         /*
 610          * Scrubbers return -EDEADLOCK to mean 'try harder'.  Tear down
 611          * everything we hold, then set up again with preparation for
 612          * worst-case scenarios.
 613          */
 614         error = xchk_teardown(sc, 0);
 615         if (error)
 616                 goto out_sc;
 617         sc->flags |= XCHK_TRY_HARDER;
 618         run.retries++;
 619         goto retry_op;
 620 }