linux/fs/xfs/scrub/agheader.c

/*
 * Copyright (C) 2017 Oracle.  All Rights Reserved.
 *
 * Author: Darrick J. Wong <darrick.wong@oracle.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
 */
#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_alloc.h"
#include "xfs_ialloc.h"
#include "scrub/xfs_scrub.h"
#include "scrub/scrub.h"
#include "scrub/common.h"
#include "scrub/trace.h"

/*
 * Set up scrub to check all the static metadata in each AG.
 * This means the SB, AGF, AGI, and AGFL headers.
 */
int
xfs_scrub_setup_ag_header(
	struct xfs_scrub_context	*sc,
	struct xfs_inode		*ip)
{
	struct xfs_mount		*mp = sc->mp;

	if (sc->sm->sm_agno >= mp->m_sb.sb_agcount ||
	    sc->sm->sm_ino || sc->sm->sm_gen)
		return -EINVAL;
	return xfs_scrub_setup_fs(sc, ip);
}

/* Walk all the blocks in the AGFL. */
int
xfs_scrub_walk_agfl(
	struct xfs_scrub_context	*sc,
	int				(*fn)(struct xfs_scrub_context *,
					      xfs_agblock_t bno, void *),
	void				*priv)
{
	struct xfs_agf			*agf;
	__be32				*agfl_bno;
	struct xfs_mount		*mp = sc->mp;
	unsigned int			flfirst;
	unsigned int			fllast;
	int				i;
	int				error;

	agf = XFS_BUF_TO_AGF(sc->sa.agf_bp);
	agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, sc->sa.agfl_bp);
	flfirst = be32_to_cpu(agf->agf_flfirst);
	fllast = be32_to_cpu(agf->agf_fllast);

	/* Nothing to walk in an empty AGFL. */
	if (agf->agf_flcount == cpu_to_be32(0))
		return 0;

	/* first to last is a consecutive list. */
	if (fllast >= flfirst) {
		for (i = flfirst; i <= fllast; i++) {
			error = fn(sc, be32_to_cpu(agfl_bno[i]), priv);
			if (error)
				return error;
			if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
				return error;
		}

		return 0;
	}

	/* first to the end */
	for (i = flfirst; i < XFS_AGFL_SIZE(mp); i++) {
		error = fn(sc, be32_to_cpu(agfl_bno[i]), priv);
		if (error)
			return error;
		if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
			return error;
	}

	/* the start to last. */
	for (i = 0; i <= fllast; i++) {
		error = fn(sc, be32_to_cpu(agfl_bno[i]), priv);
		if (error)
			return error;
		if (sc->sm->sm_flags & XFS_SCRUB_OFLAG_CORRUPT)
			return error;
	}

	return 0;
}

/* Superblock */

/*
 * Scrub the filesystem superblock.
 *
 * Note: We do /not/ attempt to check AG 0's superblock.  Mount is
 * responsible for validating all the geometry information in sb 0, so
 * if the filesystem is capable of initiating online scrub, then clearly
 * sb 0 is ok and we can use its information to check everything else.
 */
int
xfs_scrub_superblock(
	struct xfs_scrub_context	*sc)
{
	struct xfs_mount		*mp = sc->mp;
	struct xfs_buf			*bp;
	struct xfs_dsb			*sb;
	xfs_agnumber_t			agno;
	uint32_t			v2_ok;
	__be32				features_mask;
	int				error;
	__be16				vernum_mask;

	agno = sc->sm->sm_agno;
	if (agno == 0)
		return 0;

	error = xfs_trans_read_buf(mp, sc->tp, mp->m_ddev_targp,
		  XFS_AGB_TO_DADDR(mp, agno, XFS_SB_BLOCK(mp)),
		  XFS_FSS_TO_BB(mp, 1), 0, &bp, &xfs_sb_buf_ops);
	if (!xfs_scrub_process_error(sc, agno, XFS_SB_BLOCK(mp), &error))
		return error;

	sb = XFS_BUF_TO_SBP(bp);

	/*
	 * Verify the geometries match.  Fields that are permanently
	 * set by mkfs are checked; fields that can be updated later
	 * (and are not propagated to backup superblocks) are preen
	 * checked.
	 */
	if (sb->sb_blocksize != cpu_to_be32(mp->m_sb.sb_blocksize))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_dblocks != cpu_to_be64(mp->m_sb.sb_dblocks))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_rblocks != cpu_to_be64(mp->m_sb.sb_rblocks))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_rextents != cpu_to_be64(mp->m_sb.sb_rextents))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (!uuid_equal(&sb->sb_uuid, &mp->m_sb.sb_uuid))
		xfs_scrub_block_set_preen(sc, bp);

	if (sb->sb_logstart != cpu_to_be64(mp->m_sb.sb_logstart))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_rootino != cpu_to_be64(mp->m_sb.sb_rootino))
		xfs_scrub_block_set_preen(sc, bp);

	if (sb->sb_rbmino != cpu_to_be64(mp->m_sb.sb_rbmino))
		xfs_scrub_block_set_preen(sc, bp);

	if (sb->sb_rsumino != cpu_to_be64(mp->m_sb.sb_rsumino))
		xfs_scrub_block_set_preen(sc, bp);

	if (sb->sb_rextsize != cpu_to_be32(mp->m_sb.sb_rextsize))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_agblocks != cpu_to_be32(mp->m_sb.sb_agblocks))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_agcount != cpu_to_be32(mp->m_sb.sb_agcount))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_rbmblocks != cpu_to_be32(mp->m_sb.sb_rbmblocks))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_logblocks != cpu_to_be32(mp->m_sb.sb_logblocks))
		xfs_scrub_block_set_corrupt(sc, bp);

	/* Check sb_versionnum bits that are set at mkfs time. */
	vernum_mask = cpu_to_be16(~XFS_SB_VERSION_OKBITS |
				  XFS_SB_VERSION_NUMBITS |
				  XFS_SB_VERSION_ALIGNBIT |
				  XFS_SB_VERSION_DALIGNBIT |
				  XFS_SB_VERSION_SHAREDBIT |
				  XFS_SB_VERSION_LOGV2BIT |
				  XFS_SB_VERSION_SECTORBIT |
				  XFS_SB_VERSION_EXTFLGBIT |
				  XFS_SB_VERSION_DIRV2BIT);
	if ((sb->sb_versionnum & vernum_mask) !=
	    (cpu_to_be16(mp->m_sb.sb_versionnum) & vernum_mask))
		xfs_scrub_block_set_corrupt(sc, bp);

	/* Check sb_versionnum bits that can be set after mkfs time. */
	vernum_mask = cpu_to_be16(XFS_SB_VERSION_ATTRBIT |
				  XFS_SB_VERSION_NLINKBIT |
				  XFS_SB_VERSION_QUOTABIT);
	if ((sb->sb_versionnum & vernum_mask) !=
	    (cpu_to_be16(mp->m_sb.sb_versionnum) & vernum_mask))
		xfs_scrub_block_set_preen(sc, bp);

	if (sb->sb_sectsize != cpu_to_be16(mp->m_sb.sb_sectsize))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_inodesize != cpu_to_be16(mp->m_sb.sb_inodesize))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_inopblock != cpu_to_be16(mp->m_sb.sb_inopblock))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (memcmp(sb->sb_fname, mp->m_sb.sb_fname, sizeof(sb->sb_fname)))
		xfs_scrub_block_set_preen(sc, bp);

	if (sb->sb_blocklog != mp->m_sb.sb_blocklog)
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_sectlog != mp->m_sb.sb_sectlog)
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_inodelog != mp->m_sb.sb_inodelog)
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_inopblog != mp->m_sb.sb_inopblog)
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_agblklog != mp->m_sb.sb_agblklog)
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_rextslog != mp->m_sb.sb_rextslog)
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_imax_pct != mp->m_sb.sb_imax_pct)
		xfs_scrub_block_set_preen(sc, bp);

	/*
	 * Skip the summary counters since we track them in memory anyway.
	 * sb_icount, sb_ifree, sb_fdblocks, sb_frexents
	 */

	if (sb->sb_uquotino != cpu_to_be64(mp->m_sb.sb_uquotino))
		xfs_scrub_block_set_preen(sc, bp);

	if (sb->sb_gquotino != cpu_to_be64(mp->m_sb.sb_gquotino))
		xfs_scrub_block_set_preen(sc, bp);

	/*
	 * Skip the quota flags since repair will force quotacheck.
	 * sb_qflags
	 */

	if (sb->sb_flags != mp->m_sb.sb_flags)
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_shared_vn != mp->m_sb.sb_shared_vn)
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_inoalignmt != cpu_to_be32(mp->m_sb.sb_inoalignmt))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_unit != cpu_to_be32(mp->m_sb.sb_unit))
		xfs_scrub_block_set_preen(sc, bp);

	if (sb->sb_width != cpu_to_be32(mp->m_sb.sb_width))
		xfs_scrub_block_set_preen(sc, bp);

	if (sb->sb_dirblklog != mp->m_sb.sb_dirblklog)
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_logsectlog != mp->m_sb.sb_logsectlog)
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_logsectsize != cpu_to_be16(mp->m_sb.sb_logsectsize))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (sb->sb_logsunit != cpu_to_be32(mp->m_sb.sb_logsunit))
		xfs_scrub_block_set_corrupt(sc, bp);

	/* Do we see any invalid bits in sb_features2? */
	if (!xfs_sb_version_hasmorebits(&mp->m_sb)) {
		if (sb->sb_features2 != 0)
			xfs_scrub_block_set_corrupt(sc, bp);
	} else {
		v2_ok = XFS_SB_VERSION2_OKBITS;
		if (XFS_SB_VERSION_NUM(&mp->m_sb) >= XFS_SB_VERSION_5)
			v2_ok |= XFS_SB_VERSION2_CRCBIT;

		if (!!(sb->sb_features2 & cpu_to_be32(~v2_ok)))
			xfs_scrub_block_set_corrupt(sc, bp);

		if (sb->sb_features2 != sb->sb_bad_features2)
			xfs_scrub_block_set_preen(sc, bp);
	}

	/* Check sb_features2 flags that are set at mkfs time. */
	features_mask = cpu_to_be32(XFS_SB_VERSION2_LAZYSBCOUNTBIT |
				    XFS_SB_VERSION2_PROJID32BIT |
				    XFS_SB_VERSION2_CRCBIT |
				    XFS_SB_VERSION2_FTYPE);
	if ((sb->sb_features2 & features_mask) !=
	    (cpu_to_be32(mp->m_sb.sb_features2) & features_mask))
		xfs_scrub_block_set_corrupt(sc, bp);

	/* Check sb_features2 flags that can be set after mkfs time. */
	features_mask = cpu_to_be32(XFS_SB_VERSION2_ATTR2BIT);
	if ((sb->sb_features2 & features_mask) !=
	    (cpu_to_be32(mp->m_sb.sb_features2) & features_mask))
		xfs_scrub_block_set_corrupt(sc, bp);

	if (!xfs_sb_version_hascrc(&mp->m_sb)) {
		/* all v5 fields must be zero */
		if (memchr_inv(&sb->sb_features_compat, 0,
				sizeof(struct xfs_dsb) -
				offsetof(struct xfs_dsb, sb_features_compat)))
			xfs_scrub_block_set_corrupt(sc, bp);
	} else {
		/* Check compat flags; all are set at mkfs time. */
		features_mask = cpu_to_be32(XFS_SB_FEAT_COMPAT_UNKNOWN);
		if ((sb->sb_features_compat & features_mask) !=
		    (cpu_to_be32(mp->m_sb.sb_features_compat) & features_mask))
			xfs_scrub_block_set_corrupt(sc, bp);

		/* Check ro compat flags; all are set at mkfs time. */
		features_mask = cpu_to_be32(XFS_SB_FEAT_RO_COMPAT_UNKNOWN |
					    XFS_SB_FEAT_RO_COMPAT_FINOBT |
					    XFS_SB_FEAT_RO_COMPAT_RMAPBT |
					    XFS_SB_FEAT_RO_COMPAT_REFLINK);
		if ((sb->sb_features_ro_compat & features_mask) !=
		    (cpu_to_be32(mp->m_sb.sb_features_ro_compat) &
		     features_mask))
			xfs_scrub_block_set_corrupt(sc, bp);

		/* Check incompat flags; all are set at mkfs time. */
		features_mask = cpu_to_be32(XFS_SB_FEAT_INCOMPAT_UNKNOWN |
					    XFS_SB_FEAT_INCOMPAT_FTYPE |
					    XFS_SB_FEAT_INCOMPAT_SPINODES |
					    XFS_SB_FEAT_INCOMPAT_META_UUID);
		if ((sb->sb_features_incompat & features_mask) !=
		    (cpu_to_be32(mp->m_sb.sb_features_incompat) &
		     features_mask))
			xfs_scrub_block_set_corrupt(sc, bp);

		/* Check log incompat flags; all are set at mkfs time. */
		features_mask = cpu_to_be32(XFS_SB_FEAT_INCOMPAT_LOG_UNKNOWN);
		if ((sb->sb_features_log_incompat & features_mask) !=
		    (cpu_to_be32(mp->m_sb.sb_features_log_incompat) &
		     features_mask))
			xfs_scrub_block_set_corrupt(sc, bp);

		/* Don't care about sb_crc */

		if (sb->sb_spino_align != cpu_to_be32(mp->m_sb.sb_spino_align))
			xfs_scrub_block_set_corrupt(sc, bp);

		if (sb->sb_pquotino != cpu_to_be64(mp->m_sb.sb_pquotino))
			xfs_scrub_block_set_preen(sc, bp);

		/* Don't care about sb_lsn */
	}

	if (xfs_sb_version_hasmetauuid(&mp->m_sb)) {
		/* The metadata UUID must be the same for all supers */
		if (!uuid_equal(&sb->sb_meta_uuid, &mp->m_sb.sb_meta_uuid))
			xfs_scrub_block_set_corrupt(sc, bp);
	}

	/* Everything else must be zero. */
	if (memchr_inv(sb + 1, 0,
			BBTOB(bp->b_length) - sizeof(struct xfs_dsb)))
		xfs_scrub_block_set_corrupt(sc, bp);

	return error;
}

/* AGF */

/* Scrub the AGF. */
int
xfs_scrub_agf(
	struct xfs_scrub_context	*sc)
{
	struct xfs_mount		*mp = sc->mp;
	struct xfs_agf			*agf;
	xfs_agnumber_t			agno;
	xfs_agblock_t			agbno;
	xfs_agblock_t			eoag;
	xfs_agblock_t			agfl_first;
	xfs_agblock_t			agfl_last;
	xfs_agblock_t			agfl_count;
	xfs_agblock_t			fl_count;
	int				level;
	int				error = 0;

	agno = sc->sa.agno = sc->sm->sm_agno;
	error = xfs_scrub_ag_read_headers(sc, agno, &sc->sa.agi_bp,
			&sc->sa.agf_bp, &sc->sa.agfl_bp);
	if (!xfs_scrub_process_error(sc, agno, XFS_AGF_BLOCK(sc->mp), &error))
		goto out;

	agf = XFS_BUF_TO_AGF(sc->sa.agf_bp);

	/* Check the AG length */
	eoag = be32_to_cpu(agf->agf_length);
	if (eoag != xfs_ag_block_count(mp, agno))
		xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);

	/* Check the AGF btree roots and levels */
	agbno = be32_to_cpu(agf->agf_roots[XFS_BTNUM_BNO]);
	if (!xfs_verify_agbno(mp, agno, agbno))
		xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);

	agbno = be32_to_cpu(agf->agf_roots[XFS_BTNUM_CNT]);
	if (!xfs_verify_agbno(mp, agno, agbno))
		xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);

	level = be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]);
	if (level <= 0 || level > XFS_BTREE_MAXLEVELS)
		xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);

	level = be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]);
	if (level <= 0 || level > XFS_BTREE_MAXLEVELS)
		xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);

	if (xfs_sb_version_hasrmapbt(&mp->m_sb)) {
		agbno = be32_to_cpu(agf->agf_roots[XFS_BTNUM_RMAP]);
		if (!xfs_verify_agbno(mp, agno, agbno))
			xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);

		level = be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]);
		if (level <= 0 || level > XFS_BTREE_MAXLEVELS)
			xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);
	}

	if (xfs_sb_version_hasreflink(&mp->m_sb)) {
		agbno = be32_to_cpu(agf->agf_refcount_root);
		if (!xfs_verify_agbno(mp, agno, agbno))
			xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);

		level = be32_to_cpu(agf->agf_refcount_level);
		if (level <= 0 || level > XFS_BTREE_MAXLEVELS)
			xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);
	}

	/* Check the AGFL counters */
	agfl_first = be32_to_cpu(agf->agf_flfirst);
	agfl_last = be32_to_cpu(agf->agf_fllast);
	agfl_count = be32_to_cpu(agf->agf_flcount);
	if (agfl_last > agfl_first)
		fl_count = agfl_last - agfl_first + 1;
	else
		fl_count = XFS_AGFL_SIZE(mp) - agfl_first + agfl_last + 1;
	if (agfl_count != 0 && fl_count != agfl_count)
		xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);

out:
	return error;
}

/* AGFL */

struct xfs_scrub_agfl_info {
	unsigned int			sz_entries;
	unsigned int			nr_entries;
	xfs_agblock_t			*entries;
};

/* Scrub an AGFL block. */
STATIC int
xfs_scrub_agfl_block(
	struct xfs_scrub_context	*sc,
	xfs_agblock_t			agbno,
	void				*priv)
{
	struct xfs_mount		*mp = sc->mp;
	struct xfs_scrub_agfl_info	*sai = priv;
	xfs_agnumber_t			agno = sc->sa.agno;

	if (xfs_verify_agbno(mp, agno, agbno) &&
	    sai->nr_entries < sai->sz_entries)
		sai->entries[sai->nr_entries++] = agbno;
	else
		xfs_scrub_block_set_corrupt(sc, sc->sa.agfl_bp);

	return 0;
}

static int
xfs_scrub_agblock_cmp(
	const void		*pa,
	const void		*pb)
{
	const xfs_agblock_t	*a = pa;
	const xfs_agblock_t	*b = pb;

	return (int)*a - (int)*b;
}

/* Scrub the AGFL. */
int
xfs_scrub_agfl(
	struct xfs_scrub_context	*sc)
{
	struct xfs_scrub_agfl_info	sai = { 0 };
	struct xfs_agf			*agf;
	xfs_agnumber_t			agno;
	unsigned int			agflcount;
	unsigned int			i;
	int				error;

	agno = sc->sa.agno = sc->sm->sm_agno;
	error = xfs_scrub_ag_read_headers(sc, agno, &sc->sa.agi_bp,
			&sc->sa.agf_bp, &sc->sa.agfl_bp);
	if (!xfs_scrub_process_error(sc, agno, XFS_AGFL_BLOCK(sc->mp), &error))
		goto out;
	if (!sc->sa.agf_bp)
		return -EFSCORRUPTED;

	/* Allocate buffer to ensure uniqueness of AGFL entries. */
	agf = XFS_BUF_TO_AGF(sc->sa.agf_bp);
	agflcount = be32_to_cpu(agf->agf_flcount);
	if (agflcount > XFS_AGFL_SIZE(sc->mp)) {
		xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);
		goto out;
	}
	sai.sz_entries = agflcount;
	sai.entries = kmem_zalloc(sizeof(xfs_agblock_t) * agflcount, KM_NOFS);
	if (!sai.entries) {
		error = -ENOMEM;
		goto out;
	}

	/* Check the blocks in the AGFL. */
	error = xfs_scrub_walk_agfl(sc, xfs_scrub_agfl_block, &sai);
	if (error)
		goto out_free;

	if (agflcount != sai.nr_entries) {
		xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);
		goto out_free;
	}

	/* Sort entries, check for duplicates. */
	sort(sai.entries, sai.nr_entries, sizeof(sai.entries[0]),
			xfs_scrub_agblock_cmp, NULL);
	for (i = 1; i < sai.nr_entries; i++) {
		if (sai.entries[i] == sai.entries[i - 1]) {
			xfs_scrub_block_set_corrupt(sc, sc->sa.agf_bp);
			break;
		}
	}

out_free:
	kmem_free(sai.entries);
out:
	return error;
}

/* AGI */

/* Scrub the AGI. */
int
xfs_scrub_agi(
	struct xfs_scrub_context	*sc)
{
	struct xfs_mount		*mp = sc->mp;
	struct xfs_agi			*agi;
	xfs_agnumber_t			agno;
	xfs_agblock_t			agbno;
	xfs_agblock_t			eoag;
	xfs_agino_t			agino;
	xfs_agino_t			first_agino;
	xfs_agino_t			last_agino;
	xfs_agino_t			icount;
	int				i;
	int				level;
	int				error = 0;

	agno = sc->sa.agno = sc->sm->sm_agno;
	error = xfs_scrub_ag_read_headers(sc, agno, &sc->sa.agi_bp,
			&sc->sa.agf_bp, &sc->sa.agfl_bp);
	if (!xfs_scrub_process_error(sc, agno, XFS_AGI_BLOCK(sc->mp), &error))
		goto out;

	agi = XFS_BUF_TO_AGI(sc->sa.agi_bp);

	/* Check the AG length */
	eoag = be32_to_cpu(agi->agi_length);
	if (eoag != xfs_ag_block_count(mp, agno))
		xfs_scrub_block_set_corrupt(sc, sc->sa.agi_bp);

	/* Check btree roots and levels */
	agbno = be32_to_cpu(agi->agi_root);
	if (!xfs_verify_agbno(mp, agno, agbno))
		xfs_scrub_block_set_corrupt(sc, sc->sa.agi_bp);

	level = be32_to_cpu(agi->agi_level);
	if (level <= 0 || level > XFS_BTREE_MAXLEVELS)
		xfs_scrub_block_set_corrupt(sc, sc->sa.agi_bp);

	if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
		agbno = be32_to_cpu(agi->agi_free_root);
		if (!xfs_verify_agbno(mp, agno, agbno))
			xfs_scrub_block_set_corrupt(sc, sc->sa.agi_bp);

		level = be32_to_cpu(agi->agi_free_level);
		if (level <= 0 || level > XFS_BTREE_MAXLEVELS)
			xfs_scrub_block_set_corrupt(sc, sc->sa.agi_bp);
	}

	/* Check inode counters */
	xfs_ialloc_agino_range(mp, agno, &first_agino, &last_agino);
	icount = be32_to_cpu(agi->agi_count);
	if (icount > last_agino - first_agino + 1 ||
	    icount < be32_to_cpu(agi->agi_freecount))
		xfs_scrub_block_set_corrupt(sc, sc->sa.agi_bp);

	/* Check inode pointers */
	agino = be32_to_cpu(agi->agi_newino);
	if (agino != NULLAGINO && !xfs_verify_agino(mp, agno, agino))
		xfs_scrub_block_set_corrupt(sc, sc->sa.agi_bp);

	agino = be32_to_cpu(agi->agi_dirino);
	if (agino != NULLAGINO && !xfs_verify_agino(mp, agno, agino))
		xfs_scrub_block_set_corrupt(sc, sc->sa.agi_bp);

	/* Check unlinked inode buckets */
	for (i = 0; i < XFS_AGI_UNLINKED_BUCKETS; i++) {
		agino = be32_to_cpu(agi->agi_unlinked[i]);
		if (agino == NULLAGINO)
			continue;
		if (!xfs_verify_agino(mp, agno, agino))
			xfs_scrub_block_set_corrupt(sc, sc->sa.agi_bp);
	}

	if (agi->agi_pad32 != cpu_to_be32(0))
		xfs_scrub_block_set_corrupt(sc, sc->sa.agi_bp);

out:
	return error;
}