// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (C) 2018 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_btree.h"
#include "xfs_log_format.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_alloc.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc.h"
#include "xfs_ialloc_btree.h"
#include "xfs_rmap.h"
#include "xfs_rmap_btree.h"
#include "xfs_refcount_btree.h"
#include "xfs_ag.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/trace.h"
#include "scrub/repair.h"
#include "scrub/bitmap.h"

/* Superblock */

/* Repair the superblock. */
int
xrep_superblock(
        struct xfs_scrub        *sc)
{
        struct xfs_mount        *mp = sc->mp;
        struct xfs_buf          *bp;
        xfs_agnumber_t          agno;
        int                     error;

        /* Don't try to repair AG 0's sb; let xfs_repair deal with it. */
        agno = sc->sm->sm_agno;
        if (agno == 0)
                return -EOPNOTSUPP;

        error = xfs_sb_get_secondary(mp, sc->tp, agno, &bp);
        if (error)
                return error;

        /* Copy AG 0's superblock to this one. */
        xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
        xfs_sb_to_disk(bp->b_addr, &mp->m_sb);

        /* Write this to disk. */
        xfs_trans_buf_set_type(sc->tp, bp, XFS_BLFT_SB_BUF);
        xfs_trans_log_buf(sc->tp, bp, 0, BBTOB(bp->b_length) - 1);
        return error;
}

/* AGF */

struct xrep_agf_allocbt {
        struct xfs_scrub        *sc;
        xfs_agblock_t           freeblks;
        xfs_agblock_t           longest;
};

/* Record free space shape information. */
STATIC int
xrep_agf_walk_allocbt(
        struct xfs_btree_cur            *cur,
        const struct xfs_alloc_rec_incore *rec,
        void                            *priv)
{
        struct xrep_agf_allocbt         *raa = priv;
        int                             error = 0;

        if (xchk_should_terminate(raa->sc, &error))
                return error;

        raa->freeblks += rec->ar_blockcount;
        if (rec->ar_blockcount > raa->longest)
                raa->longest = rec->ar_blockcount;
        return error;
}

/* Does this AGFL block look sane? */
STATIC int
xrep_agf_check_agfl_block(
        struct xfs_mount        *mp,
        xfs_agblock_t           agbno,
        void                    *priv)
{
        struct xfs_scrub        *sc = priv;

        if (!xfs_verify_agbno(mp, sc->sa.pag->pag_agno, agbno))
                return -EFSCORRUPTED;
        return 0;
}

/*
 * Offset within the xrep_find_ag_btree array for each btree type.  Avoid the
 * XFS_BTNUM_ names here to avoid creating a sparse array.
 */
enum {
        XREP_AGF_BNOBT = 0,
        XREP_AGF_CNTBT,
        XREP_AGF_RMAPBT,
        XREP_AGF_REFCOUNTBT,
        XREP_AGF_END,
        XREP_AGF_MAX
};

/* Check a btree root candidate. */
static inline bool
xrep_check_btree_root(
        struct xfs_scrub                *sc,
        struct xrep_find_ag_btree       *fab)
{
        struct xfs_mount                *mp = sc->mp;
        xfs_agnumber_t                  agno = sc->sm->sm_agno;

        return xfs_verify_agbno(mp, agno, fab->root) &&
               fab->height <= XFS_BTREE_MAXLEVELS;
}

/*
 * Given the btree roots described by *fab, find the roots, check them for
 * sanity, and pass the root data back out via *fab.
 *
 * This is /also/ a chicken and egg problem because we have to use the rmapbt
 * (rooted in the AGF) to find the btrees rooted in the AGF.  We also have no
 * idea if the btrees make any sense.  If we hit obvious corruptions in those
 * btrees we'll bail out.
 */
STATIC int
xrep_agf_find_btrees(
        struct xfs_scrub                *sc,
        struct xfs_buf                  *agf_bp,
        struct xrep_find_ag_btree       *fab,
        struct xfs_buf                  *agfl_bp)
{
        struct xfs_agf                  *old_agf = agf_bp->b_addr;
        int                             error;

        /* Go find the root data. */
        error = xrep_find_ag_btree_roots(sc, agf_bp, fab, agfl_bp);
        if (error)
                return error;

        /* We must find the bnobt, cntbt, and rmapbt roots. */
        if (!xrep_check_btree_root(sc, &fab[XREP_AGF_BNOBT]) ||
            !xrep_check_btree_root(sc, &fab[XREP_AGF_CNTBT]) ||
            !xrep_check_btree_root(sc, &fab[XREP_AGF_RMAPBT]))
                return -EFSCORRUPTED;

        /*
         * We relied on the rmapbt to reconstruct the AGF.  If we get a
         * different root then something's seriously wrong.
         */
        if (fab[XREP_AGF_RMAPBT].root !=
            be32_to_cpu(old_agf->agf_roots[XFS_BTNUM_RMAPi]))
                return -EFSCORRUPTED;

        /* We must find the refcountbt root if that feature is enabled. */
        if (xfs_has_reflink(sc->mp) &&
            !xrep_check_btree_root(sc, &fab[XREP_AGF_REFCOUNTBT]))
                return -EFSCORRUPTED;

        return 0;
}

/*
 * Reinitialize the AGF header, making an in-core copy of the old contents so
 * that we know which in-core state needs to be reinitialized.
 */
STATIC void
xrep_agf_init_header(
        struct xfs_scrub        *sc,
        struct xfs_buf          *agf_bp,
        struct xfs_agf          *old_agf)
{
        struct xfs_mount        *mp = sc->mp;
        struct xfs_agf          *agf = agf_bp->b_addr;

        memcpy(old_agf, agf, sizeof(*old_agf));
        memset(agf, 0, BBTOB(agf_bp->b_length));
        agf->agf_magicnum = cpu_to_be32(XFS_AGF_MAGIC);
        agf->agf_versionnum = cpu_to_be32(XFS_AGF_VERSION);
        agf->agf_seqno = cpu_to_be32(sc->sa.pag->pag_agno);
        agf->agf_length = cpu_to_be32(xfs_ag_block_count(mp,
                                                        sc->sa.pag->pag_agno));
        agf->agf_flfirst = old_agf->agf_flfirst;
        agf->agf_fllast = old_agf->agf_fllast;
        agf->agf_flcount = old_agf->agf_flcount;
        if (xfs_has_crc(mp))
                uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid);

        /* Mark the incore AGF data stale until we're done fixing things. */
        ASSERT(sc->sa.pag->pagf_init);
        sc->sa.pag->pagf_init = 0;
}

/* Set btree root information in an AGF. */
STATIC void
xrep_agf_set_roots(
        struct xfs_scrub                *sc,
        struct xfs_agf                  *agf,
        struct xrep_find_ag_btree       *fab)
{
        agf->agf_roots[XFS_BTNUM_BNOi] =
                        cpu_to_be32(fab[XREP_AGF_BNOBT].root);
        agf->agf_levels[XFS_BTNUM_BNOi] =
                        cpu_to_be32(fab[XREP_AGF_BNOBT].height);

        agf->agf_roots[XFS_BTNUM_CNTi] =
                        cpu_to_be32(fab[XREP_AGF_CNTBT].root);
        agf->agf_levels[XFS_BTNUM_CNTi] =
                        cpu_to_be32(fab[XREP_AGF_CNTBT].height);

        agf->agf_roots[XFS_BTNUM_RMAPi] =
                        cpu_to_be32(fab[XREP_AGF_RMAPBT].root);
        agf->agf_levels[XFS_BTNUM_RMAPi] =
                        cpu_to_be32(fab[XREP_AGF_RMAPBT].height);

        if (xfs_has_reflink(sc->mp)) {
                agf->agf_refcount_root =
                                cpu_to_be32(fab[XREP_AGF_REFCOUNTBT].root);
                agf->agf_refcount_level =
                                cpu_to_be32(fab[XREP_AGF_REFCOUNTBT].height);
        }
}

/* Update all AGF fields which derive from btree contents. */
STATIC int
xrep_agf_calc_from_btrees(
        struct xfs_scrub        *sc,
        struct xfs_buf          *agf_bp)
{
        struct xrep_agf_allocbt raa = { .sc = sc };
        struct xfs_btree_cur    *cur = NULL;
        struct xfs_agf          *agf = agf_bp->b_addr;
        struct xfs_mount        *mp = sc->mp;
        xfs_agblock_t           btreeblks;
        xfs_agblock_t           blocks;
        int                     error;

        /* Update the AGF counters from the bnobt. */
        cur = xfs_allocbt_init_cursor(mp, sc->tp, agf_bp,
                        sc->sa.pag, XFS_BTNUM_BNO);
        error = xfs_alloc_query_all(cur, xrep_agf_walk_allocbt, &raa);
        if (error)
                goto err;
        error = xfs_btree_count_blocks(cur, &blocks);
        if (error)
                goto err;
        xfs_btree_del_cursor(cur, error);
        btreeblks = blocks - 1;
        agf->agf_freeblks = cpu_to_be32(raa.freeblks);
        agf->agf_longest = cpu_to_be32(raa.longest);

        /* Update the AGF counters from the cntbt. */
        cur = xfs_allocbt_init_cursor(mp, sc->tp, agf_bp,
                        sc->sa.pag, XFS_BTNUM_CNT);
        error = xfs_btree_count_blocks(cur, &blocks);
        if (error)
                goto err;
        xfs_btree_del_cursor(cur, error);
        btreeblks += blocks - 1;

        /* Update the AGF counters from the rmapbt. */
        cur = xfs_rmapbt_init_cursor(mp, sc->tp, agf_bp, sc->sa.pag);
        error = xfs_btree_count_blocks(cur, &blocks);
        if (error)
                goto err;
        xfs_btree_del_cursor(cur, error);
        agf->agf_rmap_blocks = cpu_to_be32(blocks);
        btreeblks += blocks - 1;

        agf->agf_btreeblks = cpu_to_be32(btreeblks);

        /* Update the AGF counters from the refcountbt. */
        if (xfs_has_reflink(mp)) {
                cur = xfs_refcountbt_init_cursor(mp, sc->tp, agf_bp,
                                sc->sa.pag);
                error = xfs_btree_count_blocks(cur, &blocks);
                if (error)
                        goto err;
                xfs_btree_del_cursor(cur, error);
                agf->agf_refcount_blocks = cpu_to_be32(blocks);
        }

        return 0;
err:
        xfs_btree_del_cursor(cur, error);
        return error;
}

/* Commit the new AGF and reinitialize the incore state. */
STATIC int
xrep_agf_commit_new(
        struct xfs_scrub        *sc,
        struct xfs_buf          *agf_bp)
{
        struct xfs_perag        *pag;
        struct xfs_agf          *agf = agf_bp->b_addr;

        /* Trigger fdblocks recalculation */
        xfs_force_summary_recalc(sc->mp);

        /* Write this to disk. */
        xfs_trans_buf_set_type(sc->tp, agf_bp, XFS_BLFT_AGF_BUF);
        xfs_trans_log_buf(sc->tp, agf_bp, 0, BBTOB(agf_bp->b_length) - 1);

        /* Now reinitialize the in-core counters we changed. */
        pag = sc->sa.pag;
        pag->pagf_btreeblks = be32_to_cpu(agf->agf_btreeblks);
        pag->pagf_freeblks = be32_to_cpu(agf->agf_freeblks);
        pag->pagf_longest = be32_to_cpu(agf->agf_longest);
        pag->pagf_levels[XFS_BTNUM_BNOi] =
                        be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNOi]);
        pag->pagf_levels[XFS_BTNUM_CNTi] =
                        be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNTi]);
        pag->pagf_levels[XFS_BTNUM_RMAPi] =
                        be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAPi]);
        pag->pagf_refcount_level = be32_to_cpu(agf->agf_refcount_level);
        pag->pagf_init = 1;

        return 0;
}

/* Repair the AGF. v5 filesystems only. */
int
xrep_agf(
        struct xfs_scrub                *sc)
{
        struct xrep_find_ag_btree       fab[XREP_AGF_MAX] = {
                [XREP_AGF_BNOBT] = {
                        .rmap_owner = XFS_RMAP_OWN_AG,
                        .buf_ops = &xfs_bnobt_buf_ops,
                },
                [XREP_AGF_CNTBT] = {
                        .rmap_owner = XFS_RMAP_OWN_AG,
                        .buf_ops = &xfs_cntbt_buf_ops,
                },
                [XREP_AGF_RMAPBT] = {
                        .rmap_owner = XFS_RMAP_OWN_AG,
                        .buf_ops = &xfs_rmapbt_buf_ops,
                },
                [XREP_AGF_REFCOUNTBT] = {
                        .rmap_owner = XFS_RMAP_OWN_REFC,
                        .buf_ops = &xfs_refcountbt_buf_ops,
                },
                [XREP_AGF_END] = {
                        .buf_ops = NULL,
                },
        };
        struct xfs_agf                  old_agf;
        struct xfs_mount                *mp = sc->mp;
        struct xfs_buf                  *agf_bp;
        struct xfs_buf                  *agfl_bp;
        struct xfs_agf                  *agf;
        int                             error;

        /* We require the rmapbt to rebuild anything. */
        if (!xfs_has_rmapbt(mp))
                return -EOPNOTSUPP;

        /*
         * Make sure we have the AGF buffer, as scrub might have decided it
         * was corrupt after xfs_alloc_read_agf failed with -EFSCORRUPTED.
         */
        error = xfs_trans_read_buf(mp, sc->tp, mp->m_ddev_targp,
                        XFS_AG_DADDR(mp, sc->sa.pag->pag_agno,
                                                XFS_AGF_DADDR(mp)),
                        XFS_FSS_TO_BB(mp, 1), 0, &agf_bp, NULL);
        if (error)
                return error;
        agf_bp->b_ops = &xfs_agf_buf_ops;
        agf = agf_bp->b_addr;

        /*
         * Load the AGFL so that we can screen out OWN_AG blocks that are on
         * the AGFL now; these blocks might have once been part of the
         * bno/cnt/rmap btrees but are not now.  This is a chicken and egg
         * problem: the AGF is corrupt, so we have to trust the AGFL contents
         * because we can't do any serious cross-referencing with any of the
         * btrees rooted in the AGF.  If the AGFL contents are obviously bad
         * then we'll bail out.
         */
        error = xfs_alloc_read_agfl(mp, sc->tp, sc->sa.pag->pag_agno, &agfl_bp);
        if (error)
                return error;

        /*
         * Spot-check the AGFL blocks; if they're obviously corrupt then
         * there's nothing we can do but bail out.
         */
        error = xfs_agfl_walk(sc->mp, agf_bp->b_addr, agfl_bp,
                        xrep_agf_check_agfl_block, sc);
        if (error)
                return error;

        /*
         * Find the AGF btree roots.  This is also a chicken-and-egg situation;
         * see the function for more details.
         */
        error = xrep_agf_find_btrees(sc, agf_bp, fab, agfl_bp);
        if (error)
                return error;

        /* Start rewriting the header and implant the btrees we found. */
        xrep_agf_init_header(sc, agf_bp, &old_agf);
        xrep_agf_set_roots(sc, agf, fab);
        error = xrep_agf_calc_from_btrees(sc, agf_bp);
        if (error)
                goto out_revert;

        /* Commit the changes and reinitialize incore state. */
        return xrep_agf_commit_new(sc, agf_bp);

out_revert:
        /* Mark the incore AGF state stale and revert the AGF. */
        sc->sa.pag->pagf_init = 0;
        memcpy(agf, &old_agf, sizeof(old_agf));
        return error;
}

/* AGFL */

struct xrep_agfl {
        /* Bitmap of other OWN_AG metadata blocks. */
        struct xbitmap          agmetablocks;

        /* Bitmap of free space. */
        struct xbitmap          *freesp;

        struct xfs_scrub        *sc;
};

/* Record all OWN_AG (free space btree) information from the rmap data. */
STATIC int
xrep_agfl_walk_rmap(
        struct xfs_btree_cur    *cur,
        const struct xfs_rmap_irec *rec,
        void                    *priv)
{
        struct xrep_agfl        *ra = priv;
        xfs_fsblock_t           fsb;
        int                     error = 0;

        if (xchk_should_terminate(ra->sc, &error))
                return error;

        /* Record all the OWN_AG blocks. */
        if (rec->rm_owner == XFS_RMAP_OWN_AG) {
                fsb = XFS_AGB_TO_FSB(cur->bc_mp, cur->bc_ag.pag->pag_agno,
                                rec->rm_startblock);
                error = xbitmap_set(ra->freesp, fsb, rec->rm_blockcount);
                if (error)
                        return error;
        }

        return xbitmap_set_btcur_path(&ra->agmetablocks, cur);
}

/*
 * Map out all the non-AGFL OWN_AG space in this AG so that we can deduce
 * which blocks belong to the AGFL.
 *
 * Compute the set of old AGFL blocks by subtracting from the list of OWN_AG
 * blocks the list of blocks owned by all other OWN_AG metadata (bnobt, cntbt,
 * rmapbt).  These are the old AGFL blocks, so return that list and the number
 * of blocks we're actually going to put back on the AGFL.
 */
STATIC int
xrep_agfl_collect_blocks(
        struct xfs_scrub        *sc,
        struct xfs_buf          *agf_bp,
        struct xbitmap          *agfl_extents,
        xfs_agblock_t           *flcount)
{
        struct xrep_agfl        ra;
        struct xfs_mount        *mp = sc->mp;
        struct xfs_btree_cur    *cur;
        int                     error;

        ra.sc = sc;
        ra.freesp = agfl_extents;
        xbitmap_init(&ra.agmetablocks);

        /* Find all space used by the free space btrees & rmapbt. */
        cur = xfs_rmapbt_init_cursor(mp, sc->tp, agf_bp, sc->sa.pag);
        error = xfs_rmap_query_all(cur, xrep_agfl_walk_rmap, &ra);
        if (error)
                goto err;
        xfs_btree_del_cursor(cur, error);

        /* Find all blocks currently being used by the bnobt. */
        cur = xfs_allocbt_init_cursor(mp, sc->tp, agf_bp,
                        sc->sa.pag, XFS_BTNUM_BNO);
        error = xbitmap_set_btblocks(&ra.agmetablocks, cur);
        if (error)
                goto err;
        xfs_btree_del_cursor(cur, error);

        /* Find all blocks currently being used by the cntbt. */
        cur = xfs_allocbt_init_cursor(mp, sc->tp, agf_bp,
                        sc->sa.pag, XFS_BTNUM_CNT);
        error = xbitmap_set_btblocks(&ra.agmetablocks, cur);
        if (error)
                goto err;

        xfs_btree_del_cursor(cur, error);

        /*
         * Drop the freesp meta blocks that are in use by btrees.
         * The remaining blocks /should/ be AGFL blocks.
         */
        error = xbitmap_disunion(agfl_extents, &ra.agmetablocks);
        xbitmap_destroy(&ra.agmetablocks);
        if (error)
                return error;

        /*
         * Calculate the new AGFL size.  If we found more blocks than fit in
         * the AGFL we'll free them later.
         */
        *flcount = min_t(uint64_t, xbitmap_hweight(agfl_extents),
                         xfs_agfl_size(mp));
        return 0;

err:
        xbitmap_destroy(&ra.agmetablocks);
        xfs_btree_del_cursor(cur, error);
        return error;
}

/* Update the AGF and reset the in-core state. */
STATIC void
xrep_agfl_update_agf(
        struct xfs_scrub        *sc,
        struct xfs_buf          *agf_bp,
        xfs_agblock_t           flcount)
{
        struct xfs_agf          *agf = agf_bp->b_addr;

        ASSERT(flcount <= xfs_agfl_size(sc->mp));

        /* Trigger fdblocks recalculation */
        xfs_force_summary_recalc(sc->mp);

        /* Update the AGF counters. */
        if (sc->sa.pag->pagf_init)
                sc->sa.pag->pagf_flcount = flcount;
        agf->agf_flfirst = cpu_to_be32(0);
        agf->agf_flcount = cpu_to_be32(flcount);
        agf->agf_fllast = cpu_to_be32(flcount - 1);

        xfs_alloc_log_agf(sc->tp, agf_bp,
                        XFS_AGF_FLFIRST | XFS_AGF_FLLAST | XFS_AGF_FLCOUNT);
}

/* Write out a totally new AGFL. */
STATIC void
xrep_agfl_init_header(
        struct xfs_scrub        *sc,
        struct xfs_buf          *agfl_bp,
        struct xbitmap          *agfl_extents,
        xfs_agblock_t           flcount)
{
        struct xfs_mount        *mp = sc->mp;
        __be32                  *agfl_bno;
        struct xbitmap_range    *br;
        struct xbitmap_range    *n;
        struct xfs_agfl         *agfl;
        xfs_agblock_t           agbno;
        unsigned int            fl_off;

        ASSERT(flcount <= xfs_agfl_size(mp));

        /*
         * Start rewriting the header by setting the bno[] array to
         * NULLAGBLOCK, then setting AGFL header fields.
         */
        agfl = XFS_BUF_TO_AGFL(agfl_bp);
        memset(agfl, 0xFF, BBTOB(agfl_bp->b_length));
        agfl->agfl_magicnum = cpu_to_be32(XFS_AGFL_MAGIC);
        agfl->agfl_seqno = cpu_to_be32(sc->sa.pag->pag_agno);
        uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_meta_uuid);

        /*
         * Fill the AGFL with the remaining blocks.  If agfl_extents has more
         * blocks than fit in the AGFL, they will be freed in a subsequent
         * step.
         */
        fl_off = 0;
        agfl_bno = xfs_buf_to_agfl_bno(agfl_bp);
        for_each_xbitmap_extent(br, n, agfl_extents) {
                agbno = XFS_FSB_TO_AGBNO(mp, br->start);

                trace_xrep_agfl_insert(mp, sc->sa.pag->pag_agno, agbno,
                                br->len);

                while (br->len > 0 && fl_off < flcount) {
                        agfl_bno[fl_off] = cpu_to_be32(agbno);
                        fl_off++;
                        agbno++;

                        /*
                         * We've now used br->start by putting it in the AGFL,
                         * so bump br so that we don't reap the block later.
                         */
                        br->start++;
                        br->len--;
                }

                if (br->len)
                        break;
                list_del(&br->list);
                kmem_free(br);
        }

        /* Write new AGFL to disk. */
        xfs_trans_buf_set_type(sc->tp, agfl_bp, XFS_BLFT_AGFL_BUF);
        xfs_trans_log_buf(sc->tp, agfl_bp, 0, BBTOB(agfl_bp->b_length) - 1);
}

/* Repair the AGFL. */
int
xrep_agfl(
        struct xfs_scrub        *sc)
{
        struct xbitmap          agfl_extents;
        struct xfs_mount        *mp = sc->mp;
        struct xfs_buf          *agf_bp;
        struct xfs_buf          *agfl_bp;
        xfs_agblock_t           flcount;
        int                     error;

        /* We require the rmapbt to rebuild anything. */
        if (!xfs_has_rmapbt(mp))
                return -EOPNOTSUPP;

        xbitmap_init(&agfl_extents);

        /*
         * Read the AGF so that we can query the rmapbt.  We hope that there's
         * nothing wrong with the AGF, but all the AG header repair functions
         * have this chicken-and-egg problem.
         */
        error = xfs_alloc_read_agf(mp, sc->tp, sc->sa.pag->pag_agno, 0,
                        &agf_bp);
        if (error)
                return error;

        /*
         * Make sure we have the AGFL buffer, as scrub might have decided it
         * was corrupt after xfs_alloc_read_agfl failed with -EFSCORRUPTED.
         */
        error = xfs_trans_read_buf(mp, sc->tp, mp->m_ddev_targp,
                        XFS_AG_DADDR(mp, sc->sa.pag->pag_agno,
                                                XFS_AGFL_DADDR(mp)),
                        XFS_FSS_TO_BB(mp, 1), 0, &agfl_bp, NULL);
        if (error)
                return error;
        agfl_bp->b_ops = &xfs_agfl_buf_ops;

        /* Gather all the extents we're going to put on the new AGFL. */
        error = xrep_agfl_collect_blocks(sc, agf_bp, &agfl_extents, &flcount);
        if (error)
                goto err;

        /*
         * Update AGF and AGFL.  We reset the global free block counter when
         * we adjust the AGF flcount (which can fail) so avoid updating any
         * buffers until we know that part works.
         */
        xrep_agfl_update_agf(sc, agf_bp, flcount);
        xrep_agfl_init_header(sc, agfl_bp, &agfl_extents, flcount);

        /*
         * Ok, the AGFL should be ready to go now.  Roll the transaction to
         * make the new AGFL permanent before we start using it to return
         * freespace overflow to the freespace btrees.
         */
        sc->sa.agf_bp = agf_bp;
        sc->sa.agfl_bp = agfl_bp;
        error = xrep_roll_ag_trans(sc);
        if (error)
                goto err;

        /* Dump any AGFL overflow. */
        error = xrep_reap_extents(sc, &agfl_extents, &XFS_RMAP_OINFO_AG,
                        XFS_AG_RESV_AGFL);
err:
        xbitmap_destroy(&agfl_extents);
        return error;
}

/* AGI */

/*
 * Offset within the xrep_find_ag_btree array for each btree type.  Avoid the
 * XFS_BTNUM_ names here to avoid creating a sparse array.
 */
enum {
        XREP_AGI_INOBT = 0,
        XREP_AGI_FINOBT,
        XREP_AGI_END,
        XREP_AGI_MAX
};

/*
 * Given the inode btree roots described by *fab, find the roots, check them
 * for sanity, and pass the root data back out via *fab.
 */
STATIC int
xrep_agi_find_btrees(
        struct xfs_scrub                *sc,
        struct xrep_find_ag_btree       *fab)
{
        struct xfs_buf                  *agf_bp;
        struct xfs_mount                *mp = sc->mp;
        int                             error;

        /* Read the AGF. */
        error = xfs_alloc_read_agf(mp, sc->tp, sc->sa.pag->pag_agno, 0,
                        &agf_bp);
        if (error)
                return error;

        /* Find the btree roots. */
        error = xrep_find_ag_btree_roots(sc, agf_bp, fab, NULL);
        if (error)
                return error;

        /* We must find the inobt root. */
        if (!xrep_check_btree_root(sc, &fab[XREP_AGI_INOBT]))
                return -EFSCORRUPTED;

        /* We must find the finobt root if that feature is enabled. */
        if (xfs_has_finobt(mp) &&
            !xrep_check_btree_root(sc, &fab[XREP_AGI_FINOBT]))
                return -EFSCORRUPTED;

        return 0;
}

/*
 * Reinitialize the AGI header, making an in-core copy of the old contents so
 * that we know which in-core state needs to be reinitialized.
 */
STATIC void
xrep_agi_init_header(
        struct xfs_scrub        *sc,
        struct xfs_buf          *agi_bp,
        struct xfs_agi          *old_agi)
{
        struct xfs_agi          *agi = agi_bp->b_addr;
        struct xfs_mount        *mp = sc->mp;

        memcpy(old_agi, agi, sizeof(*old_agi));
        memset(agi, 0, BBTOB(agi_bp->b_length));
        agi->agi_magicnum = cpu_to_be32(XFS_AGI_MAGIC);
        agi->agi_versionnum = cpu_to_be32(XFS_AGI_VERSION);
        agi->agi_seqno = cpu_to_be32(sc->sa.pag->pag_agno);
        agi->agi_length = cpu_to_be32(xfs_ag_block_count(mp,
                                                        sc->sa.pag->pag_agno));
        agi->agi_newino = cpu_to_be32(NULLAGINO);
        agi->agi_dirino = cpu_to_be32(NULLAGINO);
        if (xfs_has_crc(mp))
                uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid);

        /* We don't know how to fix the unlinked list yet. */
        memcpy(&agi->agi_unlinked, &old_agi->agi_unlinked,
                        sizeof(agi->agi_unlinked));

        /* Mark the incore AGF data stale until we're done fixing things. */
        ASSERT(sc->sa.pag->pagi_init);
        sc->sa.pag->pagi_init = 0;
}

/* Set btree root information in an AGI. */
STATIC void
xrep_agi_set_roots(
        struct xfs_scrub                *sc,
        struct xfs_agi                  *agi,
        struct xrep_find_ag_btree       *fab)
{
        agi->agi_root = cpu_to_be32(fab[XREP_AGI_INOBT].root);
        agi->agi_level = cpu_to_be32(fab[XREP_AGI_INOBT].height);

        if (xfs_has_finobt(sc->mp)) {
                agi->agi_free_root = cpu_to_be32(fab[XREP_AGI_FINOBT].root);
                agi->agi_free_level = cpu_to_be32(fab[XREP_AGI_FINOBT].height);
        }
}

/* Update the AGI counters. */
STATIC int
xrep_agi_calc_from_btrees(
        struct xfs_scrub        *sc,
        struct xfs_buf          *agi_bp)
{
        struct xfs_btree_cur    *cur;
        struct xfs_agi          *agi = agi_bp->b_addr;
        struct xfs_mount        *mp = sc->mp;
        xfs_agino_t             count;
        xfs_agino_t             freecount;
        int                     error;

        cur = xfs_inobt_init_cursor(mp, sc->tp, agi_bp,
                        sc->sa.pag, XFS_BTNUM_INO);
        error = xfs_ialloc_count_inodes(cur, &count, &freecount);
        if (error)
                goto err;
        if (xfs_has_inobtcounts(mp)) {
                xfs_agblock_t   blocks;

                error = xfs_btree_count_blocks(cur, &blocks);
                if (error)
                        goto err;
                agi->agi_iblocks = cpu_to_be32(blocks);
        }
        xfs_btree_del_cursor(cur, error);

        agi->agi_count = cpu_to_be32(count);
        agi->agi_freecount = cpu_to_be32(freecount);

        if (xfs_has_finobt(mp) && xfs_has_inobtcounts(mp)) {
                xfs_agblock_t   blocks;

                cur = xfs_inobt_init_cursor(mp, sc->tp, agi_bp,
                                sc->sa.pag, XFS_BTNUM_FINO);
                error = xfs_btree_count_blocks(cur, &blocks);
                if (error)
                        goto err;
                xfs_btree_del_cursor(cur, error);
                agi->agi_fblocks = cpu_to_be32(blocks);
        }

        return 0;
err:
        xfs_btree_del_cursor(cur, error);
        return error;
}

/* Trigger reinitialization of the in-core data. */
STATIC int
xrep_agi_commit_new(
        struct xfs_scrub        *sc,
        struct xfs_buf          *agi_bp)
{
        struct xfs_perag        *pag;
        struct xfs_agi          *agi = agi_bp->b_addr;

        /* Trigger inode count recalculation */
        xfs_force_summary_recalc(sc->mp);

        /* Write this to disk. */
        xfs_trans_buf_set_type(sc->tp, agi_bp, XFS_BLFT_AGI_BUF);
        xfs_trans_log_buf(sc->tp, agi_bp, 0, BBTOB(agi_bp->b_length) - 1);

        /* Now reinitialize the in-core counters if necessary. */
        pag = sc->sa.pag;
        pag->pagi_count = be32_to_cpu(agi->agi_count);
        pag->pagi_freecount = be32_to_cpu(agi->agi_freecount);
        pag->pagi_init = 1;

        return 0;
}

/* Repair the AGI. */
int
xrep_agi(
        struct xfs_scrub                *sc)
{
        struct xrep_find_ag_btree       fab[XREP_AGI_MAX] = {
                [XREP_AGI_INOBT] = {
                        .rmap_owner = XFS_RMAP_OWN_INOBT,
                        .buf_ops = &xfs_inobt_buf_ops,
                },
                [XREP_AGI_FINOBT] = {
                        .rmap_owner = XFS_RMAP_OWN_INOBT,
                        .buf_ops = &xfs_finobt_buf_ops,
                },
                [XREP_AGI_END] = {
                        .buf_ops = NULL
                },
        };
        struct xfs_agi                  old_agi;
        struct xfs_mount                *mp = sc->mp;
        struct xfs_buf                  *agi_bp;
        struct xfs_agi                  *agi;
        int                             error;

        /* We require the rmapbt to rebuild anything. */
        if (!xfs_has_rmapbt(mp))
                return -EOPNOTSUPP;

        /*
         * Make sure we have the AGI buffer, as scrub might have decided it
         * was corrupt after xfs_ialloc_read_agi failed with -EFSCORRUPTED.
         */
        error = xfs_trans_read_buf(mp, sc->tp, mp->m_ddev_targp,
                        XFS_AG_DADDR(mp, sc->sa.pag->pag_agno,
                                                XFS_AGI_DADDR(mp)),
                        XFS_FSS_TO_BB(mp, 1), 0, &agi_bp, NULL);
        if (error)
                return error;
        agi_bp->b_ops = &xfs_agi_buf_ops;
        agi = agi_bp->b_addr;

        /* Find the AGI btree roots. */
        error = xrep_agi_find_btrees(sc, fab);
        if (error)
                return error;

        /* Start rewriting the header and implant the btrees we found. */
        xrep_agi_init_header(sc, agi_bp, &old_agi);
        xrep_agi_set_roots(sc, agi, fab);
        error = xrep_agi_calc_from_btrees(sc, agi_bp);
        if (error)
                goto out_revert;

        /* Reinitialize in-core state. */
        return xrep_agi_commit_new(sc, agi_bp);

out_revert:
        /* Mark the incore AGI state stale and revert the AGI. */
        sc->sa.pag->pagi_init = 0;
        memcpy(agi, &old_agi, sizeof(old_agi));
        return error;
}