// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2017 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <darrick.wong@oracle.com>
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_defer.h"
#include "xfs_btree.h"
#include "xfs_bit.h"
#include "xfs_log_format.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_inode.h"
#include "xfs_icache.h"
#include "xfs_itable.h"
#include "xfs_alloc.h"
#include "xfs_alloc_btree.h"
#include "xfs_bmap.h"
#include "xfs_bmap_btree.h"
#include "xfs_ialloc.h"
#include "xfs_ialloc_btree.h"
#include "xfs_refcount.h"
#include "xfs_refcount_btree.h"
#include "xfs_rmap.h"
#include "xfs_rmap_btree.h"
#include "xfs_log.h"
#include "xfs_trans_priv.h"
#include "xfs_attr.h"
#include "xfs_reflink.h"
#include "scrub/xfs_scrub.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/trace.h"
#include "scrub/btree.h"
#include "scrub/repair.h"
#include "scrub/health.h"

/* Common code for the metadata scrubbers. */

/*
 * Handling operational errors.
 *
 * The *_process_error() family of functions are used to process error return
 * codes from functions called as part of a scrub operation.
 *
 * If there's no error, we return true to tell the caller that it's ok
 * to move on to the next check in its list.
 *
 * For non-verifier errors (e.g. ENOMEM) we return false to tell the
 * caller that something bad happened, and we preserve *error so that
 * the caller can return the *error up the stack to userspace.
 *
 * Verifier errors (EFSBADCRC/EFSCORRUPTED) are recorded by setting
 * OFLAG_CORRUPT in sm_flags and the *error is cleared.  In other words,
 * we track verifier errors (and failed scrub checks) via OFLAG_CORRUPT,
 * not via return codes.  We return false to tell the caller that
 * something bad happened.  Since the error has been cleared, the caller
 * will (presumably) return that zero and scrubbing will move on to
 * whatever's next.
 *
 * ftrace can be used to record the precise metadata location and the
 * approximate code location of the failed operation.
 */

/* Check for operational errors. */
static bool
__xchk_process_error(
        struct xfs_scrub        *sc,
        xfs_agnumber_t          agno,
        xfs_agblock_t           bno,
        int                     *error,
        __u32                   errflag,
        void                    *ret_ip)
{
        switch (*error) {
        case 0:
                return true;
        case -EDEADLOCK:
                /* Used to restart an op with deadlock avoidance. */
                trace_xchk_deadlock_retry(sc->ip, sc->sm, *error);
                break;
        case -EFSBADCRC:
        case -EFSCORRUPTED:
                /* Note the badness but don't abort. */
                sc->sm->sm_flags |= errflag;
                *error = 0;
                /* fall through */
        default:
                trace_xchk_op_error(sc, agno, bno, *error,
                                ret_ip);
                break;
        }
        return false;
}

bool
xchk_process_error(
        struct xfs_scrub        *sc,
        xfs_agnumber_t          agno,
        xfs_agblock_t           bno,
        int                     *error)
{
        return __xchk_process_error(sc, agno, bno, error,
                        XFS_SCRUB_OFLAG_CORRUPT, __return_address);
}

bool
xchk_xref_process_error(
        struct xfs_scrub        *sc,
        xfs_agnumber_t          agno,
        xfs_agblock_t           bno,
        int                     *error)
{
        return __xchk_process_error(sc, agno, bno, error,
                        XFS_SCRUB_OFLAG_XFAIL, __return_address);
}

/* Check for operational errors for a file offset. */
static bool
__xchk_fblock_process_error(
        struct xfs_scrub        *sc,
        int                     whichfork,
        xfs_fileoff_t           offset,
        int                     *error,
        __u32                   errflag,
        void                    *ret_ip)
{
        switch (*error) {
        case 0:
                return true;
        case -EDEADLOCK:
                /* Used to restart an op with deadlock avoidance. */
                trace_xchk_deadlock_retry(sc->ip, sc->sm, *error);
                break;
        case -EFSBADCRC:
        case -EFSCORRUPTED:
                /* Note the badness but don't abort. */
                sc->sm->sm_flags |= errflag;
                *error = 0;
                /* fall through */
        default:
                trace_xchk_file_op_error(sc, whichfork, offset, *error,
                                ret_ip);
                break;
        }
        return false;
}

bool
xchk_fblock_process_error(
        struct xfs_scrub        *sc,
        int                     whichfork,
        xfs_fileoff_t           offset,
        int                     *error)
{
        return __xchk_fblock_process_error(sc, whichfork, offset, error,
                        XFS_SCRUB_OFLAG_CORRUPT, __return_address);
}

bool
xchk_fblock_xref_process_error(
        struct xfs_scrub        *sc,
        int                     whichfork,
        xfs_fileoff_t           offset,
        int                     *error)
{
        return __xchk_fblock_process_error(sc, whichfork, offset, error,
                        XFS_SCRUB_OFLAG_XFAIL, __return_address);
}

/*
 * Handling scrub corruption/optimization/warning checks.
 *
 * The *_set_{corrupt,preen,warning}() family of functions are used to
 * record the presence of metadata that is incorrect (corrupt), could be
 * optimized somehow (preen), or should be flagged for administrative
 * review but is not incorrect (warn).
 *
 * ftrace can be used to record the precise metadata location and
 * approximate code location of the failed check.
 */

/* Record a block which could be optimized. */
void
xchk_block_set_preen(
        struct xfs_scrub        *sc,
        struct xfs_buf          *bp)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_PREEN;
        trace_xchk_block_preen(sc, bp->b_bn, __return_address);
}

/*
 * Record an inode which could be optimized.  The trace data will
 * include the block given by bp if bp is given; otherwise it will use
 * the block location of the inode record itself.
 */
void
xchk_ino_set_preen(
        struct xfs_scrub        *sc,
        xfs_ino_t               ino)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_PREEN;
        trace_xchk_ino_preen(sc, ino, __return_address);
}

/* Record something being wrong with the filesystem primary superblock. */
void
xchk_set_corrupt(
        struct xfs_scrub        *sc)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
        trace_xchk_fs_error(sc, 0, __return_address);
}

/* Record a corrupt block. */
void
xchk_block_set_corrupt(
        struct xfs_scrub        *sc,
        struct xfs_buf          *bp)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
        trace_xchk_block_error(sc, bp->b_bn, __return_address);
}

/* Record a corruption while cross-referencing. */
void
xchk_block_xref_set_corrupt(
        struct xfs_scrub        *sc,
        struct xfs_buf          *bp)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_XCORRUPT;
        trace_xchk_block_error(sc, bp->b_bn, __return_address);
}

/*
 * Record a corrupt inode.  The trace data will include the block given
 * by bp if bp is given; otherwise it will use the block location of the
 * inode record itself.
 */
void
xchk_ino_set_corrupt(
        struct xfs_scrub        *sc,
        xfs_ino_t               ino)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
        trace_xchk_ino_error(sc, ino, __return_address);
}

/* Record a corruption while cross-referencing with an inode. */
void
xchk_ino_xref_set_corrupt(
        struct xfs_scrub        *sc,
        xfs_ino_t               ino)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_XCORRUPT;
        trace_xchk_ino_error(sc, ino, __return_address);
}

/* Record corruption in a block indexed by a file fork. */
void
xchk_fblock_set_corrupt(
        struct xfs_scrub        *sc,
        int                     whichfork,
        xfs_fileoff_t           offset)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
        trace_xchk_fblock_error(sc, whichfork, offset, __return_address);
}

/* Record a corruption while cross-referencing a fork block. */
void
xchk_fblock_xref_set_corrupt(
        struct xfs_scrub        *sc,
        int                     whichfork,
        xfs_fileoff_t           offset)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_XCORRUPT;
        trace_xchk_fblock_error(sc, whichfork, offset, __return_address);
}

/*
 * Warn about inodes that need administrative review but is not
 * incorrect.
 */
void
xchk_ino_set_warning(
        struct xfs_scrub        *sc,
        xfs_ino_t               ino)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_WARNING;
        trace_xchk_ino_warning(sc, ino, __return_address);
}

/* Warn about a block indexed by a file fork that needs review. */
void
xchk_fblock_set_warning(
        struct xfs_scrub        *sc,
        int                     whichfork,
        xfs_fileoff_t           offset)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_WARNING;
        trace_xchk_fblock_warning(sc, whichfork, offset, __return_address);
}

/* Signal an incomplete scrub. */
void
xchk_set_incomplete(
        struct xfs_scrub        *sc)
{
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_INCOMPLETE;
        trace_xchk_incomplete(sc, __return_address);
}

/*
 * rmap scrubbing -- compute the number of blocks with a given owner,
 * at least according to the reverse mapping data.
 */

struct xchk_rmap_ownedby_info {
        const struct xfs_owner_info     *oinfo;
        xfs_filblks_t                   *blocks;
};

STATIC int
xchk_count_rmap_ownedby_irec(
        struct xfs_btree_cur            *cur,
        struct xfs_rmap_irec            *rec,
        void                            *priv)
{
        struct xchk_rmap_ownedby_info   *sroi = priv;
        bool                            irec_attr;
        bool                            oinfo_attr;

        irec_attr = rec->rm_flags & XFS_RMAP_ATTR_FORK;
        oinfo_attr = sroi->oinfo->oi_flags & XFS_OWNER_INFO_ATTR_FORK;

        if (rec->rm_owner != sroi->oinfo->oi_owner)
                return 0;

        if (XFS_RMAP_NON_INODE_OWNER(rec->rm_owner) || irec_attr == oinfo_attr)
                (*sroi->blocks) += rec->rm_blockcount;

        return 0;
}

/*
 * Calculate the number of blocks the rmap thinks are owned by something.
 * The caller should pass us an rmapbt cursor.
 */
int
xchk_count_rmap_ownedby_ag(
        struct xfs_scrub                *sc,
        struct xfs_btree_cur            *cur,
        const struct xfs_owner_info     *oinfo,
        xfs_filblks_t                   *blocks)
{
        struct xchk_rmap_ownedby_info   sroi = {
                .oinfo                  = oinfo,
                .blocks                 = blocks,
        };

        *blocks = 0;
        return xfs_rmap_query_all(cur, xchk_count_rmap_ownedby_irec,
                        &sroi);
}

/*
 * AG scrubbing
 *
 * These helpers facilitate locking an allocation group's header
 * buffers, setting up cursors for all btrees that are present, and
 * cleaning everything up once we're through.
 */

/* Decide if we want to return an AG header read failure. */
static inline bool
want_ag_read_header_failure(
        struct xfs_scrub        *sc,
        unsigned int            type)
{
        /* Return all AG header read failures when scanning btrees. */
        if (sc->sm->sm_type != XFS_SCRUB_TYPE_AGF &&
            sc->sm->sm_type != XFS_SCRUB_TYPE_AGFL &&
            sc->sm->sm_type != XFS_SCRUB_TYPE_AGI)
                return true;
        /*
         * If we're scanning a given type of AG header, we only want to
         * see read failures from that specific header.  We'd like the
         * other headers to cross-check them, but this isn't required.
         */
        if (sc->sm->sm_type == type)
                return true;
        return false;
}

/*
 * Grab all the headers for an AG.
 *
 * The headers should be released by xchk_ag_free, but as a fail
 * safe we attach all the buffers we grab to the scrub transaction so
 * they'll all be freed when we cancel it.
 */
int
xchk_ag_read_headers(
        struct xfs_scrub        *sc,
        xfs_agnumber_t          agno,
        struct xfs_buf          **agi,
        struct xfs_buf          **agf,
        struct xfs_buf          **agfl)
{
        struct xfs_mount        *mp = sc->mp;
        int                     error;

        error = xfs_ialloc_read_agi(mp, sc->tp, agno, agi);
        if (error && want_ag_read_header_failure(sc, XFS_SCRUB_TYPE_AGI))
                goto out;

        error = xfs_alloc_read_agf(mp, sc->tp, agno, 0, agf);
        if (error && want_ag_read_header_failure(sc, XFS_SCRUB_TYPE_AGF))
                goto out;

        error = xfs_alloc_read_agfl(mp, sc->tp, agno, agfl);
        if (error && want_ag_read_header_failure(sc, XFS_SCRUB_TYPE_AGFL))
                goto out;
        error = 0;
out:
        return error;
}

/* Release all the AG btree cursors. */
void
xchk_ag_btcur_free(
        struct xchk_ag          *sa)
{
        if (sa->refc_cur)
                xfs_btree_del_cursor(sa->refc_cur, XFS_BTREE_ERROR);
        if (sa->rmap_cur)
                xfs_btree_del_cursor(sa->rmap_cur, XFS_BTREE_ERROR);
        if (sa->fino_cur)
                xfs_btree_del_cursor(sa->fino_cur, XFS_BTREE_ERROR);
        if (sa->ino_cur)
                xfs_btree_del_cursor(sa->ino_cur, XFS_BTREE_ERROR);
        if (sa->cnt_cur)
                xfs_btree_del_cursor(sa->cnt_cur, XFS_BTREE_ERROR);
        if (sa->bno_cur)
                xfs_btree_del_cursor(sa->bno_cur, XFS_BTREE_ERROR);

        sa->refc_cur = NULL;
        sa->rmap_cur = NULL;
        sa->fino_cur = NULL;
        sa->ino_cur = NULL;
        sa->bno_cur = NULL;
        sa->cnt_cur = NULL;
}

/* Initialize all the btree cursors for an AG. */
int
xchk_ag_btcur_init(
        struct xfs_scrub        *sc,
        struct xchk_ag          *sa)
{
        struct xfs_mount        *mp = sc->mp;
        xfs_agnumber_t          agno = sa->agno;

        xchk_perag_get(sc->mp, sa);
        if (sa->agf_bp &&
            xchk_ag_btree_healthy_enough(sc, sa->pag, XFS_BTNUM_BNO)) {
                /* Set up a bnobt cursor for cross-referencing. */
                sa->bno_cur = xfs_allocbt_init_cursor(mp, sc->tp, sa->agf_bp,
                                agno, XFS_BTNUM_BNO);
                if (!sa->bno_cur)
                        goto err;
        }

        if (sa->agf_bp &&
            xchk_ag_btree_healthy_enough(sc, sa->pag, XFS_BTNUM_CNT)) {
                /* Set up a cntbt cursor for cross-referencing. */
                sa->cnt_cur = xfs_allocbt_init_cursor(mp, sc->tp, sa->agf_bp,
                                agno, XFS_BTNUM_CNT);
                if (!sa->cnt_cur)
                        goto err;
        }

        /* Set up a inobt cursor for cross-referencing. */
        if (sa->agi_bp &&
            xchk_ag_btree_healthy_enough(sc, sa->pag, XFS_BTNUM_INO)) {
                sa->ino_cur = xfs_inobt_init_cursor(mp, sc->tp, sa->agi_bp,
                                        agno, XFS_BTNUM_INO);
                if (!sa->ino_cur)
                        goto err;
        }

        /* Set up a finobt cursor for cross-referencing. */
        if (sa->agi_bp && xfs_sb_version_hasfinobt(&mp->m_sb) &&
            xchk_ag_btree_healthy_enough(sc, sa->pag, XFS_BTNUM_FINO)) {
                sa->fino_cur = xfs_inobt_init_cursor(mp, sc->tp, sa->agi_bp,
                                agno, XFS_BTNUM_FINO);
                if (!sa->fino_cur)
                        goto err;
        }

        /* Set up a rmapbt cursor for cross-referencing. */
        if (sa->agf_bp && xfs_sb_version_hasrmapbt(&mp->m_sb) &&
            xchk_ag_btree_healthy_enough(sc, sa->pag, XFS_BTNUM_RMAP)) {
                sa->rmap_cur = xfs_rmapbt_init_cursor(mp, sc->tp, sa->agf_bp,
                                agno);
                if (!sa->rmap_cur)
                        goto err;
        }

        /* Set up a refcountbt cursor for cross-referencing. */
        if (sa->agf_bp && xfs_sb_version_hasreflink(&mp->m_sb) &&
            xchk_ag_btree_healthy_enough(sc, sa->pag, XFS_BTNUM_REFC)) {
                sa->refc_cur = xfs_refcountbt_init_cursor(mp, sc->tp,
                                sa->agf_bp, agno);
                if (!sa->refc_cur)
                        goto err;
        }

        return 0;
err:
        return -ENOMEM;
}

/* Release the AG header context and btree cursors. */
void
xchk_ag_free(
        struct xfs_scrub        *sc,
        struct xchk_ag          *sa)
{
        xchk_ag_btcur_free(sa);
        if (sa->agfl_bp) {
                xfs_trans_brelse(sc->tp, sa->agfl_bp);
                sa->agfl_bp = NULL;
        }
        if (sa->agf_bp) {
                xfs_trans_brelse(sc->tp, sa->agf_bp);
                sa->agf_bp = NULL;
        }
        if (sa->agi_bp) {
                xfs_trans_brelse(sc->tp, sa->agi_bp);
                sa->agi_bp = NULL;
        }
        if (sa->pag) {
                xfs_perag_put(sa->pag);
                sa->pag = NULL;
        }
        sa->agno = NULLAGNUMBER;
}

/*
 * For scrub, grab the AGI and the AGF headers, in that order.  Locking
 * order requires us to get the AGI before the AGF.  We use the
 * transaction to avoid deadlocking on crosslinked metadata buffers;
 * either the caller passes one in (bmap scrub) or we have to create a
 * transaction ourselves.
 */
int
xchk_ag_init(
        struct xfs_scrub        *sc,
        xfs_agnumber_t          agno,
        struct xchk_ag          *sa)
{
        int                     error;

        sa->agno = agno;
        error = xchk_ag_read_headers(sc, agno, &sa->agi_bp,
                        &sa->agf_bp, &sa->agfl_bp);
        if (error)
                return error;

        return xchk_ag_btcur_init(sc, sa);
}

/*
 * Grab the per-ag structure if we haven't already gotten it.  Teardown of the
 * xchk_ag will release it for us.
 */
void
xchk_perag_get(
        struct xfs_mount        *mp,
        struct xchk_ag          *sa)
{
        if (!sa->pag)
                sa->pag = xfs_perag_get(mp, sa->agno);
}

/* Per-scrubber setup functions */

/*
 * Grab an empty transaction so that we can re-grab locked buffers if
 * one of our btrees turns out to be cyclic.
 *
 * If we're going to repair something, we need to ask for the largest possible
 * log reservation so that we can handle the worst case scenario for metadata
 * updates while rebuilding a metadata item.  We also need to reserve as many
 * blocks in the head transaction as we think we're going to need to rebuild
 * the metadata object.
 */
int
xchk_trans_alloc(
        struct xfs_scrub        *sc,
        uint                    resblks)
{
        if (sc->sm->sm_flags & XFS_SCRUB_IFLAG_REPAIR)
                return xfs_trans_alloc(sc->mp, &M_RES(sc->mp)->tr_itruncate,
                                resblks, 0, 0, &sc->tp);

        return xfs_trans_alloc_empty(sc->mp, &sc->tp);
}

/* Set us up with a transaction and an empty context. */
int
xchk_setup_fs(
        struct xfs_scrub        *sc,
        struct xfs_inode        *ip)
{
        uint                    resblks;

        resblks = xrep_calc_ag_resblks(sc);
        return xchk_trans_alloc(sc, resblks);
}

/* Set us up with AG headers and btree cursors. */
int
xchk_setup_ag_btree(
        struct xfs_scrub        *sc,
        struct xfs_inode        *ip,
        bool                    force_log)
{
        struct xfs_mount        *mp = sc->mp;
        int                     error;

        /*
         * If the caller asks us to checkpont the log, do so.  This
         * expensive operation should be performed infrequently and only
         * as a last resort.  Any caller that sets force_log should
         * document why they need to do so.
         */
        if (force_log) {
                error = xchk_checkpoint_log(mp);
                if (error)
                        return error;
        }

        error = xchk_setup_fs(sc, ip);
        if (error)
                return error;

        return xchk_ag_init(sc, sc->sm->sm_agno, &sc->sa);
}

/* Push everything out of the log onto disk. */
int
xchk_checkpoint_log(
        struct xfs_mount        *mp)
{
        int                     error;

        error = xfs_log_force(mp, XFS_LOG_SYNC);
        if (error)
                return error;
        xfs_ail_push_all_sync(mp->m_ail);
        return 0;
}

/*
 * Given an inode and the scrub control structure, grab either the
 * inode referenced in the control structure or the inode passed in.
 * The inode is not locked.
 */
int
xchk_get_inode(
        struct xfs_scrub        *sc,
        struct xfs_inode        *ip_in)
{
        struct xfs_imap         imap;
        struct xfs_mount        *mp = sc->mp;
        struct xfs_inode        *ip = NULL;
        int                     error;

        /* We want to scan the inode we already had opened. */
        if (sc->sm->sm_ino == 0 || sc->sm->sm_ino == ip_in->i_ino) {
                sc->ip = ip_in;
                return 0;
        }

        /* Look up the inode, see if the generation number matches. */
        if (xfs_internal_inum(mp, sc->sm->sm_ino))
                return -ENOENT;
        error = xfs_iget(mp, NULL, sc->sm->sm_ino,
                        XFS_IGET_UNTRUSTED | XFS_IGET_DONTCACHE, 0, &ip);
        switch (error) {
        case -ENOENT:
                /* Inode doesn't exist, just bail out. */
                return error;
        case 0:
                /* Got an inode, continue. */
                break;
        case -EINVAL:
                /*
                 * -EINVAL with IGET_UNTRUSTED could mean one of several
                 * things: userspace gave us an inode number that doesn't
                 * correspond to fs space, or doesn't have an inobt entry;
                 * or it could simply mean that the inode buffer failed the
                 * read verifiers.
                 *
                 * Try just the inode mapping lookup -- if it succeeds, then
                 * the inode buffer verifier failed and something needs fixing.
                 * Otherwise, we really couldn't find it so tell userspace
                 * that it no longer exists.
                 */
                error = xfs_imap(sc->mp, sc->tp, sc->sm->sm_ino, &imap,
                                XFS_IGET_UNTRUSTED | XFS_IGET_DONTCACHE);
                if (error)
                        return -ENOENT;
                error = -EFSCORRUPTED;
                /* fall through */
        default:
                trace_xchk_op_error(sc,
                                XFS_INO_TO_AGNO(mp, sc->sm->sm_ino),
                                XFS_INO_TO_AGBNO(mp, sc->sm->sm_ino),
                                error, __return_address);
                return error;
        }
        if (VFS_I(ip)->i_generation != sc->sm->sm_gen) {
                xfs_irele(ip);
                return -ENOENT;
        }

        sc->ip = ip;
        return 0;
}

/* Set us up to scrub a file's contents. */
int
xchk_setup_inode_contents(
        struct xfs_scrub        *sc,
        struct xfs_inode        *ip,
        unsigned int            resblks)
{
        int                     error;

        error = xchk_get_inode(sc, ip);
        if (error)
                return error;

        /* Got the inode, lock it and we're ready to go. */
        sc->ilock_flags = XFS_IOLOCK_EXCL | XFS_MMAPLOCK_EXCL;
        xfs_ilock(sc->ip, sc->ilock_flags);
        error = xchk_trans_alloc(sc, resblks);
        if (error)
                goto out;
        sc->ilock_flags |= XFS_ILOCK_EXCL;
        xfs_ilock(sc->ip, XFS_ILOCK_EXCL);

out:
        /* scrub teardown will unlock and release the inode for us */
        return error;
}

/*
 * Predicate that decides if we need to evaluate the cross-reference check.
 * If there was an error accessing the cross-reference btree, just delete
 * the cursor and skip the check.
 */
bool
xchk_should_check_xref(
        struct xfs_scrub        *sc,
        int                     *error,
        struct xfs_btree_cur    **curpp)
{
        /* No point in xref if we already know we're corrupt. */
        if (xchk_skip_xref(sc->sm))
                return false;

        if (*error == 0)
                return true;

        if (curpp) {
                /* If we've already given up on xref, just bail out. */
                if (!*curpp)
                        return false;

                /* xref error, delete cursor and bail out. */
                xfs_btree_del_cursor(*curpp, XFS_BTREE_ERROR);
                *curpp = NULL;
        }

        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_XFAIL;
        trace_xchk_xref_error(sc, *error, __return_address);

        /*
         * Errors encountered during cross-referencing with another
         * data structure should not cause this scrubber to abort.
         */
        *error = 0;
        return false;
}

/* Run the structure verifiers on in-memory buffers to detect bad memory. */
void
xchk_buffer_recheck(
        struct xfs_scrub        *sc,
        struct xfs_buf          *bp)
{
        xfs_failaddr_t          fa;

        if (bp->b_ops == NULL) {
                xchk_block_set_corrupt(sc, bp);
                return;
        }
        if (bp->b_ops->verify_struct == NULL) {
                xchk_set_incomplete(sc);
                return;
        }
        fa = bp->b_ops->verify_struct(bp);
        if (!fa)
                return;
        sc->sm->sm_flags |= XFS_SCRUB_OFLAG_CORRUPT;
        trace_xchk_block_error(sc, bp->b_bn, fa);
}

/*
 * Scrub the attr/data forks of a metadata inode.  The metadata inode must be
 * pointed to by sc->ip and the ILOCK must be held.
 */
int
xchk_metadata_inode_forks(
        struct xfs_scrub        *sc)
{
        __u32                   smtype;
        bool                    shared;
        int                     error;

        if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
                return 0;

        /* Metadata inodes don't live on the rt device. */
        if (sc->ip->i_d.di_flags & XFS_DIFLAG_REALTIME) {
                xchk_ino_set_corrupt(sc, sc->ip->i_ino);
                return 0;
        }

        /* They should never participate in reflink. */
        if (xfs_is_reflink_inode(sc->ip)) {
                xchk_ino_set_corrupt(sc, sc->ip->i_ino);
                return 0;
        }

        /* They also should never have extended attributes. */
        if (xfs_inode_hasattr(sc->ip)) {
                xchk_ino_set_corrupt(sc, sc->ip->i_ino);
                return 0;
        }

        /* Invoke the data fork scrubber. */
        smtype = sc->sm->sm_type;
        sc->sm->sm_type = XFS_SCRUB_TYPE_BMBTD;
        error = xchk_bmap_data(sc);
        sc->sm->sm_type = smtype;
        if (error || (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT))
                return error;

        /* Look for incorrect shared blocks. */
        if (xfs_sb_version_hasreflink(&sc->mp->m_sb)) {
                error = xfs_reflink_inode_has_shared_extents(sc->tp, sc->ip,
                                &shared);
                if (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0,
                                &error))
                        return error;
                if (shared)
                        xchk_ino_set_corrupt(sc, sc->ip->i_ino);
        }

        return error;
}

/*
 * Try to lock an inode in violation of the usual locking order rules.  For
 * example, trying to get the IOLOCK while in transaction context, or just
 * plain breaking AG-order or inode-order inode locking rules.  Either way,
 * the only way to avoid an ABBA deadlock is to use trylock and back off if
 * we can't.
 */
int
xchk_ilock_inverted(
        struct xfs_inode        *ip,
        uint                    lock_mode)
{
        int                     i;

        for (i = 0; i < 20; i++) {
                if (xfs_ilock_nowait(ip, lock_mode))
                        return 0;
                delay(1);
        }
        return -EDEADLOCK;
}

/* Pause background reaping of resources. */
void
xchk_stop_reaping(
        struct xfs_scrub        *sc)
{
        sc->flags |= XCHK_REAPING_DISABLED;
        xfs_stop_block_reaping(sc->mp);
}

/* Restart background reaping of resources. */
void
xchk_start_reaping(
        struct xfs_scrub        *sc)
{
        xfs_start_block_reaping(sc->mp);
        sc->flags &= ~XCHK_REAPING_DISABLED;
}