/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * Copyright (c) 2018 Red Hat, Inc.
 * All rights reserved.
 */

#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_sb.h"
#include "xfs_mount.h"
#include "xfs_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_rmap_btree.h"
#include "xfs_alloc.h"
#include "xfs_ialloc.h"
#include "xfs_rmap.h"
#include "xfs_ag.h"
#include "xfs_ag_resv.h"
#include "xfs_health.h"
#include "xfs_error.h"
#include "xfs_bmap.h"
#include "xfs_defer.h"
#include "xfs_log_format.h"
#include "xfs_trans.h"

static int
xfs_get_aghdr_buf(
        struct xfs_mount        *mp,
        xfs_daddr_t             blkno,
        size_t                  numblks,
        struct xfs_buf          **bpp,
        const struct xfs_buf_ops *ops)
{
        struct xfs_buf          *bp;
        int                     error;

        error = xfs_buf_get_uncached(mp->m_ddev_targp, numblks, 0, &bp);
        if (error)
                return error;

        xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
        bp->b_bn = blkno;
        bp->b_maps[0].bm_bn = blkno;
        bp->b_ops = ops;

        *bpp = bp;
        return 0;
}

static inline bool is_log_ag(struct xfs_mount *mp, struct aghdr_init_data *id)
{
        return mp->m_sb.sb_logstart > 0 &&
               id->agno == XFS_FSB_TO_AGNO(mp, mp->m_sb.sb_logstart);
}

/*
 * Generic btree root block init function
 */
static void
xfs_btroot_init(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp,
        struct aghdr_init_data  *id)
{
        xfs_btree_init_block(mp, bp, id->type, 0, 0, id->agno);
}

/* Finish initializing a free space btree. */
static void
xfs_freesp_init_recs(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp,
        struct aghdr_init_data  *id)
{
        struct xfs_alloc_rec    *arec;
        struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);

        arec = XFS_ALLOC_REC_ADDR(mp, XFS_BUF_TO_BLOCK(bp), 1);
        arec->ar_startblock = cpu_to_be32(mp->m_ag_prealloc_blocks);

        if (is_log_ag(mp, id)) {
                struct xfs_alloc_rec    *nrec;
                xfs_agblock_t           start = XFS_FSB_TO_AGBNO(mp,
                                                        mp->m_sb.sb_logstart);

                ASSERT(start >= mp->m_ag_prealloc_blocks);
                if (start != mp->m_ag_prealloc_blocks) {
                        /*
                         * Modify first record to pad stripe align of log
                         */
                        arec->ar_blockcount = cpu_to_be32(start -
                                                mp->m_ag_prealloc_blocks);
                        nrec = arec + 1;

                        /*
                         * Insert second record at start of internal log
                         * which then gets trimmed.
                         */
                        nrec->ar_startblock = cpu_to_be32(
                                        be32_to_cpu(arec->ar_startblock) +
                                        be32_to_cpu(arec->ar_blockcount));
                        arec = nrec;
                        be16_add_cpu(&block->bb_numrecs, 1);
                }
                /*
                 * Change record start to after the internal log
                 */
                be32_add_cpu(&arec->ar_startblock, mp->m_sb.sb_logblocks);
        }

        /*
         * Calculate the record block count and check for the case where
         * the log might have consumed all available space in the AG. If
         * so, reset the record count to 0 to avoid exposure of an invalid
         * record start block.
         */
        arec->ar_blockcount = cpu_to_be32(id->agsize -
                                          be32_to_cpu(arec->ar_startblock));
        if (!arec->ar_blockcount)
                block->bb_numrecs = 0;
}

/*
 * Alloc btree root block init functions
 */
static void
xfs_bnoroot_init(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp,
        struct aghdr_init_data  *id)
{
        xfs_btree_init_block(mp, bp, XFS_BTNUM_BNO, 0, 1, id->agno);
        xfs_freesp_init_recs(mp, bp, id);
}

static void
xfs_cntroot_init(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp,
        struct aghdr_init_data  *id)
{
        xfs_btree_init_block(mp, bp, XFS_BTNUM_CNT, 0, 1, id->agno);
        xfs_freesp_init_recs(mp, bp, id);
}

/*
 * Reverse map root block init
 */
static void
xfs_rmaproot_init(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp,
        struct aghdr_init_data  *id)
{
        struct xfs_btree_block  *block = XFS_BUF_TO_BLOCK(bp);
        struct xfs_rmap_rec     *rrec;

        xfs_btree_init_block(mp, bp, XFS_BTNUM_RMAP, 0, 4, id->agno);

        /*
         * mark the AG header regions as static metadata The BNO
         * btree block is the first block after the headers, so
         * it's location defines the size of region the static
         * metadata consumes.
         *
         * Note: unlike mkfs, we never have to account for log
         * space when growing the data regions
         */
        rrec = XFS_RMAP_REC_ADDR(block, 1);
        rrec->rm_startblock = 0;
        rrec->rm_blockcount = cpu_to_be32(XFS_BNO_BLOCK(mp));
        rrec->rm_owner = cpu_to_be64(XFS_RMAP_OWN_FS);
        rrec->rm_offset = 0;

        /* account freespace btree root blocks */
        rrec = XFS_RMAP_REC_ADDR(block, 2);
        rrec->rm_startblock = cpu_to_be32(XFS_BNO_BLOCK(mp));
        rrec->rm_blockcount = cpu_to_be32(2);
        rrec->rm_owner = cpu_to_be64(XFS_RMAP_OWN_AG);
        rrec->rm_offset = 0;

        /* account inode btree root blocks */
        rrec = XFS_RMAP_REC_ADDR(block, 3);
        rrec->rm_startblock = cpu_to_be32(XFS_IBT_BLOCK(mp));
        rrec->rm_blockcount = cpu_to_be32(XFS_RMAP_BLOCK(mp) -
                                          XFS_IBT_BLOCK(mp));
        rrec->rm_owner = cpu_to_be64(XFS_RMAP_OWN_INOBT);
        rrec->rm_offset = 0;

        /* account for rmap btree root */
        rrec = XFS_RMAP_REC_ADDR(block, 4);
        rrec->rm_startblock = cpu_to_be32(XFS_RMAP_BLOCK(mp));
        rrec->rm_blockcount = cpu_to_be32(1);
        rrec->rm_owner = cpu_to_be64(XFS_RMAP_OWN_AG);
        rrec->rm_offset = 0;

        /* account for refc btree root */
        if (xfs_sb_version_hasreflink(&mp->m_sb)) {
                rrec = XFS_RMAP_REC_ADDR(block, 5);
                rrec->rm_startblock = cpu_to_be32(xfs_refc_block(mp));
                rrec->rm_blockcount = cpu_to_be32(1);
                rrec->rm_owner = cpu_to_be64(XFS_RMAP_OWN_REFC);
                rrec->rm_offset = 0;
                be16_add_cpu(&block->bb_numrecs, 1);
        }

        /* account for the log space */
        if (is_log_ag(mp, id)) {
                rrec = XFS_RMAP_REC_ADDR(block,
                                be16_to_cpu(block->bb_numrecs) + 1);
                rrec->rm_startblock = cpu_to_be32(
                                XFS_FSB_TO_AGBNO(mp, mp->m_sb.sb_logstart));
                rrec->rm_blockcount = cpu_to_be32(mp->m_sb.sb_logblocks);
                rrec->rm_owner = cpu_to_be64(XFS_RMAP_OWN_LOG);
                rrec->rm_offset = 0;
                be16_add_cpu(&block->bb_numrecs, 1);
        }
}

/*
 * Initialise new secondary superblocks with the pre-grow geometry, but mark
 * them as "in progress" so we know they haven't yet been activated. This will
 * get cleared when the update with the new geometry information is done after
 * changes to the primary are committed. This isn't strictly necessary, but we
 * get it for free with the delayed buffer write lists and it means we can tell
 * if a grow operation didn't complete properly after the fact.
 */
static void
xfs_sbblock_init(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp,
        struct aghdr_init_data  *id)
{
        struct xfs_dsb          *dsb = bp->b_addr;

        xfs_sb_to_disk(dsb, &mp->m_sb);
        dsb->sb_inprogress = 1;
}

static void
xfs_agfblock_init(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp,
        struct aghdr_init_data  *id)
{
        struct xfs_agf          *agf = bp->b_addr;
        xfs_extlen_t            tmpsize;

        agf->agf_magicnum = cpu_to_be32(XFS_AGF_MAGIC);
        agf->agf_versionnum = cpu_to_be32(XFS_AGF_VERSION);
        agf->agf_seqno = cpu_to_be32(id->agno);
        agf->agf_length = cpu_to_be32(id->agsize);
        agf->agf_roots[XFS_BTNUM_BNOi] = cpu_to_be32(XFS_BNO_BLOCK(mp));
        agf->agf_roots[XFS_BTNUM_CNTi] = cpu_to_be32(XFS_CNT_BLOCK(mp));
        agf->agf_levels[XFS_BTNUM_BNOi] = cpu_to_be32(1);
        agf->agf_levels[XFS_BTNUM_CNTi] = cpu_to_be32(1);
        if (xfs_sb_version_hasrmapbt(&mp->m_sb)) {
                agf->agf_roots[XFS_BTNUM_RMAPi] =
                                        cpu_to_be32(XFS_RMAP_BLOCK(mp));
                agf->agf_levels[XFS_BTNUM_RMAPi] = cpu_to_be32(1);
                agf->agf_rmap_blocks = cpu_to_be32(1);
        }

        agf->agf_flfirst = cpu_to_be32(1);
        agf->agf_fllast = 0;
        agf->agf_flcount = 0;
        tmpsize = id->agsize - mp->m_ag_prealloc_blocks;
        agf->agf_freeblks = cpu_to_be32(tmpsize);
        agf->agf_longest = cpu_to_be32(tmpsize);
        if (xfs_sb_version_hascrc(&mp->m_sb))
                uuid_copy(&agf->agf_uuid, &mp->m_sb.sb_meta_uuid);
        if (xfs_sb_version_hasreflink(&mp->m_sb)) {
                agf->agf_refcount_root = cpu_to_be32(
                                xfs_refc_block(mp));
                agf->agf_refcount_level = cpu_to_be32(1);
                agf->agf_refcount_blocks = cpu_to_be32(1);
        }

        if (is_log_ag(mp, id)) {
                int64_t logblocks = mp->m_sb.sb_logblocks;

                be32_add_cpu(&agf->agf_freeblks, -logblocks);
                agf->agf_longest = cpu_to_be32(id->agsize -
                        XFS_FSB_TO_AGBNO(mp, mp->m_sb.sb_logstart) - logblocks);
        }
}

static void
xfs_agflblock_init(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp,
        struct aghdr_init_data  *id)
{
        struct xfs_agfl         *agfl = XFS_BUF_TO_AGFL(bp);
        __be32                  *agfl_bno;
        int                     bucket;

        if (xfs_sb_version_hascrc(&mp->m_sb)) {
                agfl->agfl_magicnum = cpu_to_be32(XFS_AGFL_MAGIC);
                agfl->agfl_seqno = cpu_to_be32(id->agno);
                uuid_copy(&agfl->agfl_uuid, &mp->m_sb.sb_meta_uuid);
        }

        agfl_bno = xfs_buf_to_agfl_bno(bp);
        for (bucket = 0; bucket < xfs_agfl_size(mp); bucket++)
                agfl_bno[bucket] = cpu_to_be32(NULLAGBLOCK);
}

static void
xfs_agiblock_init(
        struct xfs_mount        *mp,
        struct xfs_buf          *bp,
        struct aghdr_init_data  *id)
{
        struct xfs_agi          *agi = bp->b_addr;
        int                     bucket;

        agi->agi_magicnum = cpu_to_be32(XFS_AGI_MAGIC);
        agi->agi_versionnum = cpu_to_be32(XFS_AGI_VERSION);
        agi->agi_seqno = cpu_to_be32(id->agno);
        agi->agi_length = cpu_to_be32(id->agsize);
        agi->agi_count = 0;
        agi->agi_root = cpu_to_be32(XFS_IBT_BLOCK(mp));
        agi->agi_level = cpu_to_be32(1);
        agi->agi_freecount = 0;
        agi->agi_newino = cpu_to_be32(NULLAGINO);
        agi->agi_dirino = cpu_to_be32(NULLAGINO);
        if (xfs_sb_version_hascrc(&mp->m_sb))
                uuid_copy(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid);
        if (xfs_sb_version_hasfinobt(&mp->m_sb)) {
                agi->agi_free_root = cpu_to_be32(XFS_FIBT_BLOCK(mp));
                agi->agi_free_level = cpu_to_be32(1);
        }
        for (bucket = 0; bucket < XFS_AGI_UNLINKED_BUCKETS; bucket++)
                agi->agi_unlinked[bucket] = cpu_to_be32(NULLAGINO);
        if (xfs_sb_version_hasinobtcounts(&mp->m_sb)) {
                agi->agi_iblocks = cpu_to_be32(1);
                if (xfs_sb_version_hasfinobt(&mp->m_sb))
                        agi->agi_fblocks = cpu_to_be32(1);
        }
}

typedef void (*aghdr_init_work_f)(struct xfs_mount *mp, struct xfs_buf *bp,
                                  struct aghdr_init_data *id);
static int
xfs_ag_init_hdr(
        struct xfs_mount        *mp,
        struct aghdr_init_data  *id,
        aghdr_init_work_f       work,
        const struct xfs_buf_ops *ops)
{
        struct xfs_buf          *bp;
        int                     error;

        error = xfs_get_aghdr_buf(mp, id->daddr, id->numblks, &bp, ops);
        if (error)
                return error;

        (*work)(mp, bp, id);

        xfs_buf_delwri_queue(bp, &id->buffer_list);
        xfs_buf_relse(bp);
        return 0;
}

struct xfs_aghdr_grow_data {
        xfs_daddr_t             daddr;
        size_t                  numblks;
        const struct xfs_buf_ops *ops;
        aghdr_init_work_f       work;
        xfs_btnum_t             type;
        bool                    need_init;
};

/*
 * Prepare new AG headers to be written to disk. We use uncached buffers here,
 * as it is assumed these new AG headers are currently beyond the currently
 * valid filesystem address space. Using cached buffers would trip over EOFS
 * corruption detection alogrithms in the buffer cache lookup routines.
 *
 * This is a non-transactional function, but the prepared buffers are added to a
 * delayed write buffer list supplied by the caller so they can submit them to
 * disk and wait on them as required.
 */
int
xfs_ag_init_headers(
        struct xfs_mount        *mp,
        struct aghdr_init_data  *id)

{
        struct xfs_aghdr_grow_data aghdr_data[] = {
        { /* SB */
                .daddr = XFS_AG_DADDR(mp, id->agno, XFS_SB_DADDR),
                .numblks = XFS_FSS_TO_BB(mp, 1),
                .ops = &xfs_sb_buf_ops,
                .work = &xfs_sbblock_init,
                .need_init = true
        },
        { /* AGF */
                .daddr = XFS_AG_DADDR(mp, id->agno, XFS_AGF_DADDR(mp)),
                .numblks = XFS_FSS_TO_BB(mp, 1),
                .ops = &xfs_agf_buf_ops,
                .work = &xfs_agfblock_init,
                .need_init = true
        },
        { /* AGFL */
                .daddr = XFS_AG_DADDR(mp, id->agno, XFS_AGFL_DADDR(mp)),
                .numblks = XFS_FSS_TO_BB(mp, 1),
                .ops = &xfs_agfl_buf_ops,
                .work = &xfs_agflblock_init,
                .need_init = true
        },
        { /* AGI */
                .daddr = XFS_AG_DADDR(mp, id->agno, XFS_AGI_DADDR(mp)),
                .numblks = XFS_FSS_TO_BB(mp, 1),
                .ops = &xfs_agi_buf_ops,
                .work = &xfs_agiblock_init,
                .need_init = true
        },
        { /* BNO root block */
                .daddr = XFS_AGB_TO_DADDR(mp, id->agno, XFS_BNO_BLOCK(mp)),
                .numblks = BTOBB(mp->m_sb.sb_blocksize),
                .ops = &xfs_bnobt_buf_ops,
                .work = &xfs_bnoroot_init,
                .need_init = true
        },
        { /* CNT root block */
                .daddr = XFS_AGB_TO_DADDR(mp, id->agno, XFS_CNT_BLOCK(mp)),
                .numblks = BTOBB(mp->m_sb.sb_blocksize),
                .ops = &xfs_cntbt_buf_ops,
                .work = &xfs_cntroot_init,
                .need_init = true
        },
        { /* INO root block */
                .daddr = XFS_AGB_TO_DADDR(mp, id->agno, XFS_IBT_BLOCK(mp)),
                .numblks = BTOBB(mp->m_sb.sb_blocksize),
                .ops = &xfs_inobt_buf_ops,
                .work = &xfs_btroot_init,
                .type = XFS_BTNUM_INO,
                .need_init = true
        },
        { /* FINO root block */
                .daddr = XFS_AGB_TO_DADDR(mp, id->agno, XFS_FIBT_BLOCK(mp)),
                .numblks = BTOBB(mp->m_sb.sb_blocksize),
                .ops = &xfs_finobt_buf_ops,
                .work = &xfs_btroot_init,
                .type = XFS_BTNUM_FINO,
                .need_init =  xfs_sb_version_hasfinobt(&mp->m_sb)
        },
        { /* RMAP root block */
                .daddr = XFS_AGB_TO_DADDR(mp, id->agno, XFS_RMAP_BLOCK(mp)),
                .numblks = BTOBB(mp->m_sb.sb_blocksize),
                .ops = &xfs_rmapbt_buf_ops,
                .work = &xfs_rmaproot_init,
                .need_init = xfs_sb_version_hasrmapbt(&mp->m_sb)
        },
        { /* REFC root block */
                .daddr = XFS_AGB_TO_DADDR(mp, id->agno, xfs_refc_block(mp)),
                .numblks = BTOBB(mp->m_sb.sb_blocksize),
                .ops = &xfs_refcountbt_buf_ops,
                .work = &xfs_btroot_init,
                .type = XFS_BTNUM_REFC,
                .need_init = xfs_sb_version_hasreflink(&mp->m_sb)
        },
        { /* NULL terminating block */
                .daddr = XFS_BUF_DADDR_NULL,
        }
        };
        struct  xfs_aghdr_grow_data *dp;
        int                     error = 0;

        /* Account for AG free space in new AG */
        id->nfree += id->agsize - mp->m_ag_prealloc_blocks;
        for (dp = &aghdr_data[0]; dp->daddr != XFS_BUF_DADDR_NULL; dp++) {
                if (!dp->need_init)
                        continue;

                id->daddr = dp->daddr;
                id->numblks = dp->numblks;
                id->type = dp->type;
                error = xfs_ag_init_hdr(mp, id, dp->work, dp->ops);
                if (error)
                        break;
        }
        return error;
}

int
xfs_ag_shrink_space(
        struct xfs_mount        *mp,
        struct xfs_trans        **tpp,
        xfs_agnumber_t          agno,
        xfs_extlen_t            delta)
{
        struct xfs_alloc_arg    args = {
                .tp     = *tpp,
                .mp     = mp,
                .type   = XFS_ALLOCTYPE_THIS_BNO,
                .minlen = delta,
                .maxlen = delta,
                .oinfo  = XFS_RMAP_OINFO_SKIP_UPDATE,
                .resv   = XFS_AG_RESV_NONE,
                .prod   = 1
        };
        struct xfs_buf          *agibp, *agfbp;
        struct xfs_agi          *agi;
        struct xfs_agf          *agf;
        int                     error, err2;

        ASSERT(agno == mp->m_sb.sb_agcount - 1);
        error = xfs_ialloc_read_agi(mp, *tpp, agno, &agibp);
        if (error)
                return error;

        agi = agibp->b_addr;

        error = xfs_alloc_read_agf(mp, *tpp, agno, 0, &agfbp);
        if (error)
                return error;

        agf = agfbp->b_addr;
        /* some extra paranoid checks before we shrink the ag */
        if (XFS_IS_CORRUPT(mp, agf->agf_length != agi->agi_length))
                return -EFSCORRUPTED;
        if (delta >= agi->agi_length)
                return -EINVAL;

        args.fsbno = XFS_AGB_TO_FSB(mp, agno,
                                    be32_to_cpu(agi->agi_length) - delta);

        /*
         * Disable perag reservations so it doesn't cause the allocation request
         * to fail. We'll reestablish reservation before we return.
         */
        error = xfs_ag_resv_free(agibp->b_pag);
        if (error)
                return error;

        /* internal log shouldn't also show up in the free space btrees */
        error = xfs_alloc_vextent(&args);
        if (!error && args.agbno == NULLAGBLOCK)
                error = -ENOSPC;

        if (error) {
                /*
                 * if extent allocation fails, need to roll the transaction to
                 * ensure that the AGFL fixup has been committed anyway.
                 */
                xfs_trans_bhold(*tpp, agfbp);
                err2 = xfs_trans_roll(tpp);
                if (err2)
                        return err2;
                xfs_trans_bjoin(*tpp, agfbp);
                goto resv_init_out;
        }

        /*
         * if successfully deleted from freespace btrees, need to confirm
         * per-AG reservation works as expected.
         */
        be32_add_cpu(&agi->agi_length, -delta);
        be32_add_cpu(&agf->agf_length, -delta);

        err2 = xfs_ag_resv_init(agibp->b_pag, *tpp);
        if (err2) {
                be32_add_cpu(&agi->agi_length, delta);
                be32_add_cpu(&agf->agf_length, delta);
                if (err2 != -ENOSPC)
                        goto resv_err;

                __xfs_bmap_add_free(*tpp, args.fsbno, delta, NULL, true);

                /*
                 * Roll the transaction before trying to re-init the per-ag
                 * reservation. The new transaction is clean so it will cancel
                 * without any side effects.
                 */
                error = xfs_defer_finish(tpp);
                if (error)
                        return error;

                error = -ENOSPC;
                goto resv_init_out;
        }
        xfs_ialloc_log_agi(*tpp, agibp, XFS_AGI_LENGTH);
        xfs_alloc_log_agf(*tpp, agfbp, XFS_AGF_LENGTH);
        return 0;
resv_init_out:
        err2 = xfs_ag_resv_init(agibp->b_pag, *tpp);
        if (!err2)
                return error;
resv_err:
        xfs_warn(mp, "Error %d reserving per-AG metadata reserve pool.", err2);
        xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_INCORE);
        return err2;
}

/*
 * Extent the AG indicated by the @id by the length passed in
 */
int
xfs_ag_extend_space(
        struct xfs_mount        *mp,
        struct xfs_trans        *tp,
        struct aghdr_init_data  *id,
        xfs_extlen_t            len)
{
        struct xfs_buf          *bp;
        struct xfs_agi          *agi;
        struct xfs_agf          *agf;
        int                     error;

        /*
         * Change the agi length.
         */
        error = xfs_ialloc_read_agi(mp, tp, id->agno, &bp);
        if (error)
                return error;

        agi = bp->b_addr;
        be32_add_cpu(&agi->agi_length, len);
        ASSERT(id->agno == mp->m_sb.sb_agcount - 1 ||
               be32_to_cpu(agi->agi_length) == mp->m_sb.sb_agblocks);
        xfs_ialloc_log_agi(tp, bp, XFS_AGI_LENGTH);

        /*
         * Change agf length.
         */
        error = xfs_alloc_read_agf(mp, tp, id->agno, 0, &bp);
        if (error)
                return error;

        agf = bp->b_addr;
        be32_add_cpu(&agf->agf_length, len);
        ASSERT(agf->agf_length == agi->agi_length);
        xfs_alloc_log_agf(tp, bp, XFS_AGF_LENGTH);

        /*
         * Free the new space.
         *
         * XFS_RMAP_OINFO_SKIP_UPDATE is used here to tell the rmap btree that
         * this doesn't actually exist in the rmap btree.
         */
        error = xfs_rmap_free(tp, bp, id->agno,
                                be32_to_cpu(agf->agf_length) - len,
                                len, &XFS_RMAP_OINFO_SKIP_UPDATE);
        if (error)
                return error;

        return  xfs_free_extent(tp, XFS_AGB_TO_FSB(mp, id->agno,
                                        be32_to_cpu(agf->agf_length) - len),
                                len, &XFS_RMAP_OINFO_SKIP_UPDATE,
                                XFS_AG_RESV_NONE);
}

/* Retrieve AG geometry. */
int
xfs_ag_get_geometry(
        struct xfs_mount        *mp,
        xfs_agnumber_t          agno,
        struct xfs_ag_geometry  *ageo)
{
        struct xfs_buf          *agi_bp;
        struct xfs_buf          *agf_bp;
        struct xfs_agi          *agi;
        struct xfs_agf          *agf;
        struct xfs_perag        *pag;
        unsigned int            freeblks;
        int                     error;

        if (agno >= mp->m_sb.sb_agcount)
                return -EINVAL;

        /* Lock the AG headers. */
        error = xfs_ialloc_read_agi(mp, NULL, agno, &agi_bp);
        if (error)
                return error;
        error = xfs_alloc_read_agf(mp, NULL, agno, 0, &agf_bp);
        if (error)
                goto out_agi;

        pag = agi_bp->b_pag;

        /* Fill out form. */
        memset(ageo, 0, sizeof(*ageo));
        ageo->ag_number = agno;

        agi = agi_bp->b_addr;
        ageo->ag_icount = be32_to_cpu(agi->agi_count);
        ageo->ag_ifree = be32_to_cpu(agi->agi_freecount);

        agf = agf_bp->b_addr;
        ageo->ag_length = be32_to_cpu(agf->agf_length);
        freeblks = pag->pagf_freeblks +
                   pag->pagf_flcount +
                   pag->pagf_btreeblks -
                   xfs_ag_resv_needed(pag, XFS_AG_RESV_NONE);
        ageo->ag_freeblks = freeblks;
        xfs_ag_geom_health(pag, ageo);

        /* Release resources. */
        xfs_buf_relse(agf_bp);
out_agi:
        xfs_buf_relse(agi_bp);
        return error;
}