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
  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 static inline void
 149 xchk_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. */
 164 STATIC int
 165 xchk_teardown(
 166         struct xfs_scrub        *sc,
 167         int                     error)
 168 {
 169         struct xfs_inode        *ip_in = XFS_I(file_inode(sc->file));
 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                         xfs_iunlock(sc->ip, sc->ilock_flags);
 182                 if (sc->ip != ip_in &&
 183                     !xfs_internal_inum(sc->mp, sc->ip->i_ino))
 184                         xchk_irele(sc, sc->ip);
 185                 sc->ip = NULL;
 186         }
 187         if (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR)
 188                 mnt_drop_write_file(sc->file);
 189         if (sc->buf) {
 190                 if (sc->buf_cleanup)
 191                         sc->buf_cleanup(sc->buf);
 192                 kvfree(sc->buf);
 193                 sc->buf_cleanup = NULL;
 194                 sc->buf = NULL;
 195         }
 196
 197         xchk_fsgates_disable(sc);
 198         return error;
 199 }
 200
 201 /* Scrubbing dispatch. */
 202
 203 static const struct xchk_meta_ops meta_scrub_ops[] = {
 204         [XFS_SCRUB_TYPE_PROBE] = {      /* ioctl presence test */
 205                 .type   = ST_NONE,
 206                 .setup  = xchk_setup_fs,
 207                 .scrub  = xchk_probe,
 208                 .repair = xrep_probe,
 209         },
 210         [XFS_SCRUB_TYPE_SB] = {         /* superblock */
 211                 .type   = ST_PERAG,
 212                 .setup  = xchk_setup_agheader,
 213                 .scrub  = xchk_superblock,
 214                 .repair = xrep_superblock,
 215         },
 216         [XFS_SCRUB_TYPE_AGF] = {        /* agf */
 217                 .type   = ST_PERAG,
 218                 .setup  = xchk_setup_agheader,
 219                 .scrub  = xchk_agf,
 220                 .repair = xrep_agf,
 221         },
 222         [XFS_SCRUB_TYPE_AGFL]= {        /* agfl */
 223                 .type   = ST_PERAG,
 224                 .setup  = xchk_setup_agheader,
 225                 .scrub  = xchk_agfl,
 226                 .repair = xrep_agfl,
 227         },
 228         [XFS_SCRUB_TYPE_AGI] = {        /* agi */
 229                 .type   = ST_PERAG,
 230                 .setup  = xchk_setup_agheader,
 231                 .scrub  = xchk_agi,
 232                 .repair = xrep_agi,
 233         },
 234         [XFS_SCRUB_TYPE_BNOBT] = {      /* bnobt */
 235                 .type   = ST_PERAG,
 236                 .setup  = xchk_setup_ag_allocbt,
 237                 .scrub  = xchk_bnobt,
 238                 .repair = xrep_notsupported,
 239         },
 240         [XFS_SCRUB_TYPE_CNTBT] = {      /* cntbt */
 241                 .type   = ST_PERAG,
 242                 .setup  = xchk_setup_ag_allocbt,
 243                 .scrub  = xchk_cntbt,
 244                 .repair = xrep_notsupported,
 245         },
 246         [XFS_SCRUB_TYPE_INOBT] = {      /* inobt */
 247                 .type   = ST_PERAG,
 248                 .setup  = xchk_setup_ag_iallocbt,
 249                 .scrub  = xchk_inobt,
 250                 .repair = xrep_notsupported,
 251         },
 252         [XFS_SCRUB_TYPE_FINOBT] = {     /* finobt */
 253                 .type   = ST_PERAG,
 254                 .setup  = xchk_setup_ag_iallocbt,
 255                 .scrub  = xchk_finobt,
 256                 .has    = xfs_has_finobt,
 257                 .repair = xrep_notsupported,
 258         },
 259         [XFS_SCRUB_TYPE_RMAPBT] = {     /* rmapbt */
 260                 .type   = ST_PERAG,
 261                 .setup  = xchk_setup_ag_rmapbt,
 262                 .scrub  = xchk_rmapbt,
 263                 .has    = xfs_has_rmapbt,
 264                 .repair = xrep_notsupported,
 265         },
 266         [XFS_SCRUB_TYPE_REFCNTBT] = {   /* refcountbt */
 267                 .type   = ST_PERAG,
 268                 .setup  = xchk_setup_ag_refcountbt,
 269                 .scrub  = xchk_refcountbt,
 270                 .has    = xfs_has_reflink,
 271                 .repair = xrep_notsupported,
 272         },
 273         [XFS_SCRUB_TYPE_INODE] = {      /* inode record */
 274                 .type   = ST_INODE,
 275                 .setup  = xchk_setup_inode,
 276                 .scrub  = xchk_inode,
 277                 .repair = xrep_notsupported,
 278         },
 279         [XFS_SCRUB_TYPE_BMBTD] = {      /* inode data fork */
 280                 .type   = ST_INODE,
 281                 .setup  = xchk_setup_inode_bmap,
 282                 .scrub  = xchk_bmap_data,
 283                 .repair = xrep_notsupported,
 284         },
 285         [XFS_SCRUB_TYPE_BMBTA] = {      /* inode attr fork */
 286                 .type   = ST_INODE,
 287                 .setup  = xchk_setup_inode_bmap,
 288                 .scrub  = xchk_bmap_attr,
 289                 .repair = xrep_notsupported,
 290         },
 291         [XFS_SCRUB_TYPE_BMBTC] = {      /* inode CoW fork */
 292                 .type   = ST_INODE,
 293                 .setup  = xchk_setup_inode_bmap,
 294                 .scrub  = xchk_bmap_cow,
 295                 .repair = xrep_notsupported,
 296         },
 297         [XFS_SCRUB_TYPE_DIR] = {        /* directory */
 298                 .type   = ST_INODE,
 299                 .setup  = xchk_setup_directory,
 300                 .scrub  = xchk_directory,
 301                 .repair = xrep_notsupported,
 302         },
 303         [XFS_SCRUB_TYPE_XATTR] = {      /* extended attributes */
 304                 .type   = ST_INODE,
 305                 .setup  = xchk_setup_xattr,
 306                 .scrub  = xchk_xattr,
 307                 .repair = xrep_notsupported,
 308         },
 309         [XFS_SCRUB_TYPE_SYMLINK] = {    /* symbolic link */
 310                 .type   = ST_INODE,
 311                 .setup  = xchk_setup_symlink,
 312                 .scrub  = xchk_symlink,
 313                 .repair = xrep_notsupported,
 314         },
 315         [XFS_SCRUB_TYPE_PARENT] = {     /* parent pointers */
 316                 .type   = ST_INODE,
 317                 .setup  = xchk_setup_parent,
 318                 .scrub  = xchk_parent,
 319                 .repair = xrep_notsupported,
 320         },
 321         [XFS_SCRUB_TYPE_RTBITMAP] = {   /* realtime bitmap */
 322                 .type   = ST_FS,
 323                 .setup  = xchk_setup_rt,
 324                 .scrub  = xchk_rtbitmap,
 325                 .has    = xfs_has_realtime,
 326                 .repair = xrep_notsupported,
 327         },
 328         [XFS_SCRUB_TYPE_RTSUM] = {      /* realtime summary */
 329                 .type   = ST_FS,
 330                 .setup  = xchk_setup_rt,
 331                 .scrub  = xchk_rtsummary,
 332                 .has    = xfs_has_realtime,
 333                 .repair = xrep_notsupported,
 334         },
 335         [XFS_SCRUB_TYPE_UQUOTA] = {     /* user quota */
 336                 .type   = ST_FS,
 337                 .setup  = xchk_setup_quota,
 338                 .scrub  = xchk_quota,
 339                 .repair = xrep_notsupported,
 340         },
 341         [XFS_SCRUB_TYPE_GQUOTA] = {     /* group quota */
 342                 .type   = ST_FS,
 343                 .setup  = xchk_setup_quota,
 344                 .scrub  = xchk_quota,
 345                 .repair = xrep_notsupported,
 346         },
 347         [XFS_SCRUB_TYPE_PQUOTA] = {     /* project quota */
 348                 .type   = ST_FS,
 349                 .setup  = xchk_setup_quota,
 350                 .scrub  = xchk_quota,
 351                 .repair = xrep_notsupported,
 352         },
 353         [XFS_SCRUB_TYPE_FSCOUNTERS] = { /* fs summary counters */
 354                 .type   = ST_FS,
 355                 .setup  = xchk_setup_fscounters,
 356                 .scrub  = xchk_fscounters,
 357                 .repair = xrep_notsupported,
 358         },
 359 };
 360
 361 static int
 362 xchk_validate_inputs(
 363         struct xfs_mount                *mp,
 364         struct xfs_scrub_metadata       *sm)
 365 {
 366         int                             error;
 367         const struct xchk_meta_ops      *ops;
 368
 369         error = -EINVAL;
 370         /* Check our inputs. */
 371         sm->sm_flags &= ~XFS_SCRUB_FLAGS_OUT;
 372         if (sm->sm_flags & ~XFS_SCRUB_FLAGS_IN)
 373                 goto out;
 374         /* sm_reserved[] must be zero */
 375         if (memchr_inv(sm->sm_reserved, 0, sizeof(sm->sm_reserved)))
 376                 goto out;
 377
 378         error = -ENOENT;
 379         /* Do we know about this type of metadata? */
 380         if (sm->sm_type >= XFS_SCRUB_TYPE_NR)
 381                 goto out;
 382         ops = &meta_scrub_ops[sm->sm_type];
 383         if (ops->setup == NULL || ops->scrub == NULL)
 384                 goto out;
 385         /* Does this fs even support this type of metadata? */
 386         if (ops->has && !ops->has(mp))
 387                 goto out;
 388
 389         error = -EINVAL;
 390         /* restricting fields must be appropriate for type */
 391         switch (ops->type) {
 392         case ST_NONE:
 393         case ST_FS:
 394                 if (sm->sm_ino || sm->sm_gen || sm->sm_agno)
 395                         goto out;
 396                 break;
 397         case ST_PERAG:
 398                 if (sm->sm_ino || sm->sm_gen ||
 399                     sm->sm_agno >= mp->m_sb.sb_agcount)
 400                         goto out;
 401                 break;
 402         case ST_INODE:
 403                 if (sm->sm_agno || (sm->sm_gen && !sm->sm_ino))
 404                         goto out;
 405                 break;
 406         default:
 407                 goto out;
 408         }
 409
 410         /*
 411          * We only want to repair read-write v5+ filesystems.  Defer the check
 412          * for ops->repair until after our scrub confirms that we need to
 413          * perform repairs so that we avoid failing due to not supporting
 414          * repairing an object that doesn't need repairs.
 415          */
 416         if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) {
 417                 error = -EOPNOTSUPP;
 418                 if (!xfs_has_crc(mp))
 419                         goto out;
 420
 421                 error = -EROFS;
 422                 if (xfs_is_readonly(mp))
 423                         goto out;
 424         }
 425
 426         error = 0;
 427 out:
 428         return error;
 429 }
 430
 431 #ifdef CONFIG_XFS_ONLINE_REPAIR
 432 static inline void xchk_postmortem(struct xfs_scrub *sc)
 433 {
 434         /*
 435          * Userspace asked us to repair something, we repaired it, rescanned
 436          * it, and the rescan says it's still broken.  Scream about this in
 437          * the system logs.
 438          */
 439         if ((sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) &&
 440             (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
 441                                  XFS_SCRUB_OFLAG_XCORRUPT)))
 442                 xrep_failure(sc->mp);
 443 }
 444 #else
 445 static inline void xchk_postmortem(struct xfs_scrub *sc)
 446 {
 447         /*
 448          * Userspace asked us to scrub something, it's broken, and we have no
 449          * way of fixing it.  Scream in the logs.
 450          */
 451         if (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
 452                                 XFS_SCRUB_OFLAG_XCORRUPT))
 453                 xfs_alert_ratelimited(sc->mp,
 454                                 "Corruption detected during scrub.");
 455 }
 456 #endif /* CONFIG_XFS_ONLINE_REPAIR */
 457
 458 /* Dispatch metadata scrubbing. */
 459 int
 460 xfs_scrub_metadata(
 461         struct file                     *file,
 462         struct xfs_scrub_metadata       *sm)
 463 {
 464         struct xfs_scrub                *sc;
 465         struct xfs_mount                *mp = XFS_I(file_inode(file))->i_mount;
 466         int                             error = 0;
 467
 468         BUILD_BUG_ON(sizeof(meta_scrub_ops) !=
 469                 (sizeof(struct xchk_meta_ops) * XFS_SCRUB_TYPE_NR));
 470
 471         trace_xchk_start(XFS_I(file_inode(file)), sm, error);
 472
 473         /* Forbidden if we are shut down or mounted norecovery. */
 474         error = -ESHUTDOWN;
 475         if (xfs_is_shutdown(mp))
 476                 goto out;
 477         error = -ENOTRECOVERABLE;
 478         if (xfs_has_norecovery(mp))
 479                 goto out;
 480
 481         error = xchk_validate_inputs(mp, sm);
 482         if (error)
 483                 goto out;
 484
 485         xfs_warn_mount(mp, XFS_OPSTATE_WARNED_SCRUB,
 486  "EXPERIMENTAL online scrub feature in use. Use at your own risk!");
 487
 488         sc = kzalloc(sizeof(struct xfs_scrub), XCHK_GFP_FLAGS);
 489         if (!sc) {
 490                 error = -ENOMEM;
 491                 goto out;
 492         }
 493
 494         sc->mp = mp;
 495         sc->file = file;
 496         sc->sm = sm;
 497         sc->ops = &meta_scrub_ops[sm->sm_type];
 498         sc->sick_mask = xchk_health_mask_for_scrub_type(sm->sm_type);
 499 retry_op:
 500         /*
 501          * When repairs are allowed, prevent freezing or readonly remount while
 502          * scrub is running with a real transaction.
 503          */
 504         if (sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) {
 505                 error = mnt_want_write_file(sc->file);
 506                 if (error)
 507                         goto out_sc;
 508         }
 509
 510         /* Set up for the operation. */
 511         error = sc->ops->setup(sc);
 512         if (error == -EDEADLOCK && !(sc->flags & XCHK_TRY_HARDER))
 513                 goto try_harder;
 514         if (error == -ECHRNG && !(sc->flags & XCHK_NEED_DRAIN))
 515                 goto need_drain;
 516         if (error)
 517                 goto out_teardown;
 518
 519         /* Scrub for errors. */
 520         error = sc->ops->scrub(sc);
 521         if (error == -EDEADLOCK && !(sc->flags & XCHK_TRY_HARDER))
 522                 goto try_harder;
 523         if (error == -ECHRNG && !(sc->flags & XCHK_NEED_DRAIN))
 524                 goto need_drain;
 525         if (error || (sm->sm_flags & XFS_SCRUB_OFLAG_INCOMPLETE))
 526                 goto out_teardown;
 527
 528         xchk_update_health(sc);
 529
 530         if ((sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR) &&
 531             !(sc->flags & XREP_ALREADY_FIXED)) {
 532                 bool needs_fix;
 533
 534                 /* Let debug users force us into the repair routines. */
 535                 if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_FORCE_SCRUB_REPAIR))
 536                         sc->sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
 537
 538                 needs_fix = (sc->sm->sm_flags & (XFS_SCRUB_OFLAG_CORRUPT |
 539                                                  XFS_SCRUB_OFLAG_XCORRUPT |
 540                                                  XFS_SCRUB_OFLAG_PREEN));
 541                 /*
 542                  * If userspace asked for a repair but it wasn't necessary,
 543                  * report that back to userspace.
 544                  */
 545                 if (!needs_fix) {
 546                         sc->sm->sm_flags |= XFS_SCRUB_OFLAG_NO_REPAIR_NEEDED;
 547                         goto out_nofix;
 548                 }
 549
 550                 /*
 551                  * If it's broken, userspace wants us to fix it, and we haven't
 552                  * already tried to fix it, then attempt a repair.
 553                  */
 554                 error = xrep_attempt(sc);
 555                 if (error == -EAGAIN) {
 556                         /*
 557                          * Either the repair function succeeded or it couldn't
 558                          * get all the resources it needs; either way, we go
 559                          * back to the beginning and call the scrub function.
 560                          */
 561                         error = xchk_teardown(sc, 0);
 562                         if (error) {
 563                                 xrep_failure(mp);
 564                                 goto out_sc;
 565                         }
 566                         goto retry_op;
 567                 }
 568         }
 569
 570 out_nofix:
 571         xchk_postmortem(sc);
 572 out_teardown:
 573         error = xchk_teardown(sc, error);
 574 out_sc:
 575         kfree(sc);
 576 out:
 577         trace_xchk_done(XFS_I(file_inode(file)), sm, error);
 578         if (error == -EFSCORRUPTED || error == -EFSBADCRC) {
 579                 sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
 580                 error = 0;
 581         }
 582         return error;
 583 need_drain:
 584         error = xchk_teardown(sc, 0);
 585         if (error)
 586                 goto out_sc;
 587         sc->flags |= XCHK_NEED_DRAIN;
 588         goto retry_op;
 589 try_harder:
 590         /*
 591          * Scrubbers return -EDEADLOCK to mean 'try harder'.  Tear down
 592          * everything we hold, then set up again with preparation for
 593          * worst-case scenarios.
 594          */
 595         error = xchk_teardown(sc, 0);
 596         if (error)
 597                 goto out_sc;
 598         sc->flags |= XCHK_TRY_HARDER;
 599         goto retry_op;
 600 }