xfs: restore old agirotor behavior

[tomoyo/tomoyo-test1.git] / fs / xfs / libxfs / xfs_ialloc.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_ialloc_btree.h"
#include "xfs_alloc.h"
#include "xfs_errortag.h"
#include "xfs_error.h"
#include "xfs_bmap.h"
#include "xfs_trans.h"
#include "xfs_buf_item.h"
#include "xfs_icreate_item.h"
#include "xfs_icache.h"
#include "xfs_trace.h"
#include "xfs_log.h"
#include "xfs_rmap.h"
#include "xfs_ag.h"

/*
 * Lookup a record by ino in the btree given by cur.
 */
int                                     /* error */
xfs_inobt_lookup(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        xfs_agino_t             ino,    /* starting inode of chunk */
        xfs_lookup_t            dir,    /* <=, >=, == */
        int                     *stat)  /* success/failure */
{
        cur->bc_rec.i.ir_startino = ino;
        cur->bc_rec.i.ir_holemask = 0;
        cur->bc_rec.i.ir_count = 0;
        cur->bc_rec.i.ir_freecount = 0;
        cur->bc_rec.i.ir_free = 0;
        return xfs_btree_lookup(cur, dir, stat);
}

/*
 * Update the record referred to by cur to the value given.
 * This either works (return 0) or gets an EFSCORRUPTED error.
 */
STATIC int                              /* error */
xfs_inobt_update(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        xfs_inobt_rec_incore_t  *irec)  /* btree record */
{
        union xfs_btree_rec     rec;

        rec.inobt.ir_startino = cpu_to_be32(irec->ir_startino);
        if (xfs_has_sparseinodes(cur->bc_mp)) {
                rec.inobt.ir_u.sp.ir_holemask = cpu_to_be16(irec->ir_holemask);
                rec.inobt.ir_u.sp.ir_count = irec->ir_count;
                rec.inobt.ir_u.sp.ir_freecount = irec->ir_freecount;
        } else {
                /* ir_holemask/ir_count not supported on-disk */
                rec.inobt.ir_u.f.ir_freecount = cpu_to_be32(irec->ir_freecount);
        }
        rec.inobt.ir_free = cpu_to_be64(irec->ir_free);
        return xfs_btree_update(cur, &rec);
}

/* Convert on-disk btree record to incore inobt record. */
void
xfs_inobt_btrec_to_irec(
        struct xfs_mount                *mp,
        const union xfs_btree_rec       *rec,
        struct xfs_inobt_rec_incore     *irec)
{
        irec->ir_startino = be32_to_cpu(rec->inobt.ir_startino);
        if (xfs_has_sparseinodes(mp)) {
                irec->ir_holemask = be16_to_cpu(rec->inobt.ir_u.sp.ir_holemask);
                irec->ir_count = rec->inobt.ir_u.sp.ir_count;
                irec->ir_freecount = rec->inobt.ir_u.sp.ir_freecount;
        } else {
                /*
                 * ir_holemask/ir_count not supported on-disk. Fill in hardcoded
                 * values for full inode chunks.
                 */
                irec->ir_holemask = XFS_INOBT_HOLEMASK_FULL;
                irec->ir_count = XFS_INODES_PER_CHUNK;
                irec->ir_freecount =
                                be32_to_cpu(rec->inobt.ir_u.f.ir_freecount);
        }
        irec->ir_free = be64_to_cpu(rec->inobt.ir_free);
}

/*
 * Get the data from the pointed-to record.
 */
int
xfs_inobt_get_rec(
        struct xfs_btree_cur            *cur,
        struct xfs_inobt_rec_incore     *irec,
        int                             *stat)
{
        struct xfs_mount                *mp = cur->bc_mp;
        union xfs_btree_rec             *rec;
        int                             error;
        uint64_t                        realfree;

        error = xfs_btree_get_rec(cur, &rec, stat);
        if (error || *stat == 0)
                return error;

        xfs_inobt_btrec_to_irec(mp, rec, irec);

        if (!xfs_verify_agino(cur->bc_ag.pag, irec->ir_startino))
                goto out_bad_rec;
        if (irec->ir_count < XFS_INODES_PER_HOLEMASK_BIT ||
            irec->ir_count > XFS_INODES_PER_CHUNK)
                goto out_bad_rec;
        if (irec->ir_freecount > XFS_INODES_PER_CHUNK)
                goto out_bad_rec;

        /* if there are no holes, return the first available offset */
        if (!xfs_inobt_issparse(irec->ir_holemask))
                realfree = irec->ir_free;
        else
                realfree = irec->ir_free & xfs_inobt_irec_to_allocmask(irec);
        if (hweight64(realfree) != irec->ir_freecount)
                goto out_bad_rec;

        return 0;

out_bad_rec:
        xfs_warn(mp,
                "%s Inode BTree record corruption in AG %d detected!",
                cur->bc_btnum == XFS_BTNUM_INO ? "Used" : "Free",
                cur->bc_ag.pag->pag_agno);
        xfs_warn(mp,
"start inode 0x%x, count 0x%x, free 0x%x freemask 0x%llx, holemask 0x%x",
                irec->ir_startino, irec->ir_count, irec->ir_freecount,
                irec->ir_free, irec->ir_holemask);
        return -EFSCORRUPTED;
}

/*
 * Insert a single inobt record. Cursor must already point to desired location.
 */
int
xfs_inobt_insert_rec(
        struct xfs_btree_cur    *cur,
        uint16_t                holemask,
        uint8_t                 count,
        int32_t                 freecount,
        xfs_inofree_t           free,
        int                     *stat)
{
        cur->bc_rec.i.ir_holemask = holemask;
        cur->bc_rec.i.ir_count = count;
        cur->bc_rec.i.ir_freecount = freecount;
        cur->bc_rec.i.ir_free = free;
        return xfs_btree_insert(cur, stat);
}

/*
 * Insert records describing a newly allocated inode chunk into the inobt.
 */
STATIC int
xfs_inobt_insert(
        struct xfs_perag        *pag,
        struct xfs_trans        *tp,
        struct xfs_buf          *agbp,
        xfs_agino_t             newino,
        xfs_agino_t             newlen,
        xfs_btnum_t             btnum)
{
        struct xfs_btree_cur    *cur;
        xfs_agino_t             thisino;
        int                     i;
        int                     error;

        cur = xfs_inobt_init_cursor(pag, tp, agbp, btnum);

        for (thisino = newino;
             thisino < newino + newlen;
             thisino += XFS_INODES_PER_CHUNK) {
                error = xfs_inobt_lookup(cur, thisino, XFS_LOOKUP_EQ, &i);
                if (error) {
                        xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
                        return error;
                }
                ASSERT(i == 0);

                error = xfs_inobt_insert_rec(cur, XFS_INOBT_HOLEMASK_FULL,
                                             XFS_INODES_PER_CHUNK,
                                             XFS_INODES_PER_CHUNK,
                                             XFS_INOBT_ALL_FREE, &i);
                if (error) {
                        xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
                        return error;
                }
                ASSERT(i == 1);
        }

        xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);

        return 0;
}

/*
 * Verify that the number of free inodes in the AGI is correct.
 */
#ifdef DEBUG
static int
xfs_check_agi_freecount(
        struct xfs_btree_cur    *cur)
{
        if (cur->bc_nlevels == 1) {
                xfs_inobt_rec_incore_t rec;
                int             freecount = 0;
                int             error;
                int             i;

                error = xfs_inobt_lookup(cur, 0, XFS_LOOKUP_GE, &i);
                if (error)
                        return error;

                do {
                        error = xfs_inobt_get_rec(cur, &rec, &i);
                        if (error)
                                return error;

                        if (i) {
                                freecount += rec.ir_freecount;
                                error = xfs_btree_increment(cur, 0, &i);
                                if (error)
                                        return error;
                        }
                } while (i == 1);

                if (!xfs_is_shutdown(cur->bc_mp))
                        ASSERT(freecount == cur->bc_ag.pag->pagi_freecount);
        }
        return 0;
}
#else
#define xfs_check_agi_freecount(cur)    0
#endif

/*
 * Initialise a new set of inodes. When called without a transaction context
 * (e.g. from recovery) we initiate a delayed write of the inode buffers rather
 * than logging them (which in a transaction context puts them into the AIL
 * for writeback rather than the xfsbufd queue).
 */
int
xfs_ialloc_inode_init(
        struct xfs_mount        *mp,
        struct xfs_trans        *tp,
        struct list_head        *buffer_list,
        int                     icount,
        xfs_agnumber_t          agno,
        xfs_agblock_t           agbno,
        xfs_agblock_t           length,
        unsigned int            gen)
{
        struct xfs_buf          *fbuf;
        struct xfs_dinode       *free;
        int                     nbufs;
        int                     version;
        int                     i, j;
        xfs_daddr_t             d;
        xfs_ino_t               ino = 0;
        int                     error;

        /*
         * Loop over the new block(s), filling in the inodes.  For small block
         * sizes, manipulate the inodes in buffers  which are multiples of the
         * blocks size.
         */
        nbufs = length / M_IGEO(mp)->blocks_per_cluster;

        /*
         * Figure out what version number to use in the inodes we create.  If
         * the superblock version has caught up to the one that supports the new
         * inode format, then use the new inode version.  Otherwise use the old
         * version so that old kernels will continue to be able to use the file
         * system.
         *
         * For v3 inodes, we also need to write the inode number into the inode,
         * so calculate the first inode number of the chunk here as
         * XFS_AGB_TO_AGINO() only works within a filesystem block, not
         * across multiple filesystem blocks (such as a cluster) and so cannot
         * be used in the cluster buffer loop below.
         *
         * Further, because we are writing the inode directly into the buffer
         * and calculating a CRC on the entire inode, we have ot log the entire
         * inode so that the entire range the CRC covers is present in the log.
         * That means for v3 inode we log the entire buffer rather than just the
         * inode cores.
         */
        if (xfs_has_v3inodes(mp)) {
                version = 3;
                ino = XFS_AGINO_TO_INO(mp, agno, XFS_AGB_TO_AGINO(mp, agbno));

                /*
                 * log the initialisation that is about to take place as an
                 * logical operation. This means the transaction does not
                 * need to log the physical changes to the inode buffers as log
                 * recovery will know what initialisation is actually needed.
                 * Hence we only need to log the buffers as "ordered" buffers so
                 * they track in the AIL as if they were physically logged.
                 */
                if (tp)
                        xfs_icreate_log(tp, agno, agbno, icount,
                                        mp->m_sb.sb_inodesize, length, gen);
        } else
                version = 2;

        for (j = 0; j < nbufs; j++) {
                /*
                 * Get the block.
                 */
                d = XFS_AGB_TO_DADDR(mp, agno, agbno +
                                (j * M_IGEO(mp)->blocks_per_cluster));
                error = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
                                mp->m_bsize * M_IGEO(mp)->blocks_per_cluster,
                                XBF_UNMAPPED, &fbuf);
                if (error)
                        return error;

                /* Initialize the inode buffers and log them appropriately. */
                fbuf->b_ops = &xfs_inode_buf_ops;
                xfs_buf_zero(fbuf, 0, BBTOB(fbuf->b_length));
                for (i = 0; i < M_IGEO(mp)->inodes_per_cluster; i++) {
                        int     ioffset = i << mp->m_sb.sb_inodelog;

                        free = xfs_make_iptr(mp, fbuf, i);
                        free->di_magic = cpu_to_be16(XFS_DINODE_MAGIC);
                        free->di_version = version;
                        free->di_gen = cpu_to_be32(gen);
                        free->di_next_unlinked = cpu_to_be32(NULLAGINO);

                        if (version == 3) {
                                free->di_ino = cpu_to_be64(ino);
                                ino++;
                                uuid_copy(&free->di_uuid,
                                          &mp->m_sb.sb_meta_uuid);
                                xfs_dinode_calc_crc(mp, free);
                        } else if (tp) {
                                /* just log the inode core */
                                xfs_trans_log_buf(tp, fbuf, ioffset,
                                          ioffset + XFS_DINODE_SIZE(mp) - 1);
                        }
                }

                if (tp) {
                        /*
                         * Mark the buffer as an inode allocation buffer so it
                         * sticks in AIL at the point of this allocation
                         * transaction. This ensures the they are on disk before
                         * the tail of the log can be moved past this
                         * transaction (i.e. by preventing relogging from moving
                         * it forward in the log).
                         */
                        xfs_trans_inode_alloc_buf(tp, fbuf);
                        if (version == 3) {
                                /*
                                 * Mark the buffer as ordered so that they are
                                 * not physically logged in the transaction but
                                 * still tracked in the AIL as part of the
                                 * transaction and pin the log appropriately.
                                 */
                                xfs_trans_ordered_buf(tp, fbuf);
                        }
                } else {
                        fbuf->b_flags |= XBF_DONE;
                        xfs_buf_delwri_queue(fbuf, buffer_list);
                        xfs_buf_relse(fbuf);
                }
        }
        return 0;
}

/*
 * Align startino and allocmask for a recently allocated sparse chunk such that
 * they are fit for insertion (or merge) into the on-disk inode btrees.
 *
 * Background:
 *
 * When enabled, sparse inode support increases the inode alignment from cluster
 * size to inode chunk size. This means that the minimum range between two
 * non-adjacent inode records in the inobt is large enough for a full inode
 * record. This allows for cluster sized, cluster aligned block allocation
 * without need to worry about whether the resulting inode record overlaps with
 * another record in the tree. Without this basic rule, we would have to deal
 * with the consequences of overlap by potentially undoing recent allocations in
 * the inode allocation codepath.
 *
 * Because of this alignment rule (which is enforced on mount), there are two
 * inobt possibilities for newly allocated sparse chunks. One is that the
 * aligned inode record for the chunk covers a range of inodes not already
 * covered in the inobt (i.e., it is safe to insert a new sparse record). The
 * other is that a record already exists at the aligned startino that considers
 * the newly allocated range as sparse. In the latter case, record content is
 * merged in hope that sparse inode chunks fill to full chunks over time.
 */
STATIC void
xfs_align_sparse_ino(
        struct xfs_mount                *mp,
        xfs_agino_t                     *startino,
        uint16_t                        *allocmask)
{
        xfs_agblock_t                   agbno;
        xfs_agblock_t                   mod;
        int                             offset;

        agbno = XFS_AGINO_TO_AGBNO(mp, *startino);
        mod = agbno % mp->m_sb.sb_inoalignmt;
        if (!mod)
                return;

        /* calculate the inode offset and align startino */
        offset = XFS_AGB_TO_AGINO(mp, mod);
        *startino -= offset;

        /*
         * Since startino has been aligned down, left shift allocmask such that
         * it continues to represent the same physical inodes relative to the
         * new startino.
         */
        *allocmask <<= offset / XFS_INODES_PER_HOLEMASK_BIT;
}

/*
 * Determine whether the source inode record can merge into the target. Both
 * records must be sparse, the inode ranges must match and there must be no
 * allocation overlap between the records.
 */
STATIC bool
__xfs_inobt_can_merge(
        struct xfs_inobt_rec_incore     *trec,  /* tgt record */
        struct xfs_inobt_rec_incore     *srec)  /* src record */
{
        uint64_t                        talloc;
        uint64_t                        salloc;

        /* records must cover the same inode range */
        if (trec->ir_startino != srec->ir_startino)
                return false;

        /* both records must be sparse */
        if (!xfs_inobt_issparse(trec->ir_holemask) ||
            !xfs_inobt_issparse(srec->ir_holemask))
                return false;

        /* both records must track some inodes */
        if (!trec->ir_count || !srec->ir_count)
                return false;

        /* can't exceed capacity of a full record */
        if (trec->ir_count + srec->ir_count > XFS_INODES_PER_CHUNK)
                return false;

        /* verify there is no allocation overlap */
        talloc = xfs_inobt_irec_to_allocmask(trec);
        salloc = xfs_inobt_irec_to_allocmask(srec);
        if (talloc & salloc)
                return false;

        return true;
}

/*
 * Merge the source inode record into the target. The caller must call
 * __xfs_inobt_can_merge() to ensure the merge is valid.
 */
STATIC void
__xfs_inobt_rec_merge(
        struct xfs_inobt_rec_incore     *trec,  /* target */
        struct xfs_inobt_rec_incore     *srec)  /* src */
{
        ASSERT(trec->ir_startino == srec->ir_startino);

        /* combine the counts */
        trec->ir_count += srec->ir_count;
        trec->ir_freecount += srec->ir_freecount;

        /*
         * Merge the holemask and free mask. For both fields, 0 bits refer to
         * allocated inodes. We combine the allocated ranges with bitwise AND.
         */
        trec->ir_holemask &= srec->ir_holemask;
        trec->ir_free &= srec->ir_free;
}

/*
 * Insert a new sparse inode chunk into the associated inode btree. The inode
 * record for the sparse chunk is pre-aligned to a startino that should match
 * any pre-existing sparse inode record in the tree. This allows sparse chunks
 * to fill over time.
 *
 * This function supports two modes of handling preexisting records depending on
 * the merge flag. If merge is true, the provided record is merged with the
 * existing record and updated in place. The merged record is returned in nrec.
 * If merge is false, an existing record is replaced with the provided record.
 * If no preexisting record exists, the provided record is always inserted.
 *
 * It is considered corruption if a merge is requested and not possible. Given
 * the sparse inode alignment constraints, this should never happen.
 */
STATIC int
xfs_inobt_insert_sprec(
        struct xfs_perag                *pag,
        struct xfs_trans                *tp,
        struct xfs_buf                  *agbp,
        int                             btnum,
        struct xfs_inobt_rec_incore     *nrec,  /* in/out: new/merged rec. */
        bool                            merge)  /* merge or replace */
{
        struct xfs_mount                *mp = pag->pag_mount;
        struct xfs_btree_cur            *cur;
        int                             error;
        int                             i;
        struct xfs_inobt_rec_incore     rec;

        cur = xfs_inobt_init_cursor(pag, tp, agbp, btnum);

        /* the new record is pre-aligned so we know where to look */
        error = xfs_inobt_lookup(cur, nrec->ir_startino, XFS_LOOKUP_EQ, &i);
        if (error)
                goto error;
        /* if nothing there, insert a new record and return */
        if (i == 0) {
                error = xfs_inobt_insert_rec(cur, nrec->ir_holemask,
                                             nrec->ir_count, nrec->ir_freecount,
                                             nrec->ir_free, &i);
                if (error)
                        goto error;
                if (XFS_IS_CORRUPT(mp, i != 1)) {
                        error = -EFSCORRUPTED;
                        goto error;
                }

                goto out;
        }

        /*
         * A record exists at this startino. Merge or replace the record
         * depending on what we've been asked to do.
         */
        if (merge) {
                error = xfs_inobt_get_rec(cur, &rec, &i);
                if (error)
                        goto error;
                if (XFS_IS_CORRUPT(mp, i != 1)) {
                        error = -EFSCORRUPTED;
                        goto error;
                }
                if (XFS_IS_CORRUPT(mp, rec.ir_startino != nrec->ir_startino)) {
                        error = -EFSCORRUPTED;
                        goto error;
                }

                /*
                 * This should never fail. If we have coexisting records that
                 * cannot merge, something is seriously wrong.
                 */
                if (XFS_IS_CORRUPT(mp, !__xfs_inobt_can_merge(nrec, &rec))) {
                        error = -EFSCORRUPTED;
                        goto error;
                }

                trace_xfs_irec_merge_pre(mp, pag->pag_agno, rec.ir_startino,
                                         rec.ir_holemask, nrec->ir_startino,
                                         nrec->ir_holemask);

                /* merge to nrec to output the updated record */
                __xfs_inobt_rec_merge(nrec, &rec);

                trace_xfs_irec_merge_post(mp, pag->pag_agno, nrec->ir_startino,
                                          nrec->ir_holemask);

                error = xfs_inobt_rec_check_count(mp, nrec);
                if (error)
                        goto error;
        }

        error = xfs_inobt_update(cur, nrec);
        if (error)
                goto error;

out:
        xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
        return 0;
error:
        xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Allocate new inodes in the allocation group specified by agbp.  Returns 0 if
 * inodes were allocated in this AG; -EAGAIN if there was no space in this AG so
 * the caller knows it can try another AG, a hard -ENOSPC when over the maximum
 * inode count threshold, or the usual negative error code for other errors.
 */
STATIC int
xfs_ialloc_ag_alloc(
        struct xfs_perag        *pag,
        struct xfs_trans        *tp,
        struct xfs_buf          *agbp)
{
        struct xfs_agi          *agi;
        struct xfs_alloc_arg    args;
        int                     error;
        xfs_agino_t             newino;         /* new first inode's number */
        xfs_agino_t             newlen;         /* new number of inodes */
        int                     isaligned = 0;  /* inode allocation at stripe */
                                                /* unit boundary */
        /* init. to full chunk */
        struct xfs_inobt_rec_incore rec;
        struct xfs_ino_geometry *igeo = M_IGEO(tp->t_mountp);
        uint16_t                allocmask = (uint16_t) -1;
        int                     do_sparse = 0;

        memset(&args, 0, sizeof(args));
        args.tp = tp;
        args.mp = tp->t_mountp;
        args.fsbno = NULLFSBLOCK;
        args.oinfo = XFS_RMAP_OINFO_INODES;
        args.pag = pag;

#ifdef DEBUG
        /* randomly do sparse inode allocations */
        if (xfs_has_sparseinodes(tp->t_mountp) &&
            igeo->ialloc_min_blks < igeo->ialloc_blks)
                do_sparse = get_random_u32_below(2);
#endif

        /*
         * Locking will ensure that we don't have two callers in here
         * at one time.
         */
        newlen = igeo->ialloc_inos;
        if (igeo->maxicount &&
            percpu_counter_read_positive(&args.mp->m_icount) + newlen >
                                                        igeo->maxicount)
                return -ENOSPC;
        args.minlen = args.maxlen = igeo->ialloc_blks;
        /*
         * First try to allocate inodes contiguous with the last-allocated
         * chunk of inodes.  If the filesystem is striped, this will fill
         * an entire stripe unit with inodes.
         */
        agi = agbp->b_addr;
        newino = be32_to_cpu(agi->agi_newino);
        args.agbno = XFS_AGINO_TO_AGBNO(args.mp, newino) +
                     igeo->ialloc_blks;
        if (do_sparse)
                goto sparse_alloc;
        if (likely(newino != NULLAGINO &&
                  (args.agbno < be32_to_cpu(agi->agi_length)))) {
                args.prod = 1;

                /*
                 * We need to take into account alignment here to ensure that
                 * we don't modify the free list if we fail to have an exact
                 * block. If we don't have an exact match, and every oher
                 * attempt allocation attempt fails, we'll end up cancelling
                 * a dirty transaction and shutting down.
                 *
                 * For an exact allocation, alignment must be 1,
                 * however we need to take cluster alignment into account when
                 * fixing up the freelist. Use the minalignslop field to
                 * indicate that extra blocks might be required for alignment,
                 * but not to use them in the actual exact allocation.
                 */
                args.alignment = 1;
                args.minalignslop = igeo->cluster_align - 1;

                /* Allow space for the inode btree to split. */
                args.minleft = igeo->inobt_maxlevels;
                error = xfs_alloc_vextent_exact_bno(&args,
                                XFS_AGB_TO_FSB(args.mp, pag->pag_agno,
                                                args.agbno));
                if (error)
                        return error;

                /*
                 * This request might have dirtied the transaction if the AG can
                 * satisfy the request, but the exact block was not available.
                 * If the allocation did fail, subsequent requests will relax
                 * the exact agbno requirement and increase the alignment
                 * instead. It is critical that the total size of the request
                 * (len + alignment + slop) does not increase from this point
                 * on, so reset minalignslop to ensure it is not included in
                 * subsequent requests.
                 */
                args.minalignslop = 0;
        }

        if (unlikely(args.fsbno == NULLFSBLOCK)) {
                /*
                 * Set the alignment for the allocation.
                 * If stripe alignment is turned on then align at stripe unit
                 * boundary.
                 * If the cluster size is smaller than a filesystem block
                 * then we're doing I/O for inodes in filesystem block size
                 * pieces, so don't need alignment anyway.
                 */
                isaligned = 0;
                if (igeo->ialloc_align) {
                        ASSERT(!xfs_has_noalign(args.mp));
                        args.alignment = args.mp->m_dalign;
                        isaligned = 1;
                } else
                        args.alignment = igeo->cluster_align;
                /*
                 * Allocate a fixed-size extent of inodes.
                 */
                args.prod = 1;
                /*
                 * Allow space for the inode btree to split.
                 */
                args.minleft = igeo->inobt_maxlevels;
                error = xfs_alloc_vextent_near_bno(&args,
                                XFS_AGB_TO_FSB(args.mp, pag->pag_agno,
                                                be32_to_cpu(agi->agi_root)));
                if (error)
                        return error;
        }

        /*
         * If stripe alignment is turned on, then try again with cluster
         * alignment.
         */
        if (isaligned && args.fsbno == NULLFSBLOCK) {
                args.alignment = igeo->cluster_align;
                error = xfs_alloc_vextent_near_bno(&args,
                                XFS_AGB_TO_FSB(args.mp, pag->pag_agno,
                                                be32_to_cpu(agi->agi_root)));
                if (error)
                        return error;
        }

        /*
         * Finally, try a sparse allocation if the filesystem supports it and
         * the sparse allocation length is smaller than a full chunk.
         */
        if (xfs_has_sparseinodes(args.mp) &&
            igeo->ialloc_min_blks < igeo->ialloc_blks &&
            args.fsbno == NULLFSBLOCK) {
sparse_alloc:
                args.alignment = args.mp->m_sb.sb_spino_align;
                args.prod = 1;

                args.minlen = igeo->ialloc_min_blks;
                args.maxlen = args.minlen;

                /*
                 * The inode record will be aligned to full chunk size. We must
                 * prevent sparse allocation from AG boundaries that result in
                 * invalid inode records, such as records that start at agbno 0
                 * or extend beyond the AG.
                 *
                 * Set min agbno to the first aligned, non-zero agbno and max to
                 * the last aligned agbno that is at least one full chunk from
                 * the end of the AG.
                 */
                args.min_agbno = args.mp->m_sb.sb_inoalignmt;
                args.max_agbno = round_down(args.mp->m_sb.sb_agblocks,
                                            args.mp->m_sb.sb_inoalignmt) -
                                 igeo->ialloc_blks;

                error = xfs_alloc_vextent_near_bno(&args,
                                XFS_AGB_TO_FSB(args.mp, pag->pag_agno,
                                                be32_to_cpu(agi->agi_root)));
                if (error)
                        return error;

                newlen = XFS_AGB_TO_AGINO(args.mp, args.len);
                ASSERT(newlen <= XFS_INODES_PER_CHUNK);
                allocmask = (1 << (newlen / XFS_INODES_PER_HOLEMASK_BIT)) - 1;
        }

        if (args.fsbno == NULLFSBLOCK)
                return -EAGAIN;

        ASSERT(args.len == args.minlen);

        /*
         * Stamp and write the inode buffers.
         *
         * Seed the new inode cluster with a random generation number. This
         * prevents short-term reuse of generation numbers if a chunk is
         * freed and then immediately reallocated. We use random numbers
         * rather than a linear progression to prevent the next generation
         * number from being easily guessable.
         */
        error = xfs_ialloc_inode_init(args.mp, tp, NULL, newlen, pag->pag_agno,
                        args.agbno, args.len, get_random_u32());

        if (error)
                return error;
        /*
         * Convert the results.
         */
        newino = XFS_AGB_TO_AGINO(args.mp, args.agbno);

        if (xfs_inobt_issparse(~allocmask)) {
                /*
                 * We've allocated a sparse chunk. Align the startino and mask.
                 */
                xfs_align_sparse_ino(args.mp, &newino, &allocmask);

                rec.ir_startino = newino;
                rec.ir_holemask = ~allocmask;
                rec.ir_count = newlen;
                rec.ir_freecount = newlen;
                rec.ir_free = XFS_INOBT_ALL_FREE;

                /*
                 * Insert the sparse record into the inobt and allow for a merge
                 * if necessary. If a merge does occur, rec is updated to the
                 * merged record.
                 */
                error = xfs_inobt_insert_sprec(pag, tp, agbp,
                                XFS_BTNUM_INO, &rec, true);
                if (error == -EFSCORRUPTED) {
                        xfs_alert(args.mp,
        "invalid sparse inode record: ino 0x%llx holemask 0x%x count %u",
                                  XFS_AGINO_TO_INO(args.mp, pag->pag_agno,
                                                   rec.ir_startino),
                                  rec.ir_holemask, rec.ir_count);
                        xfs_force_shutdown(args.mp, SHUTDOWN_CORRUPT_INCORE);
                }
                if (error)
                        return error;

                /*
                 * We can't merge the part we've just allocated as for the inobt
                 * due to finobt semantics. The original record may or may not
                 * exist independent of whether physical inodes exist in this
                 * sparse chunk.
                 *
                 * We must update the finobt record based on the inobt record.
                 * rec contains the fully merged and up to date inobt record
                 * from the previous call. Set merge false to replace any
                 * existing record with this one.
                 */
                if (xfs_has_finobt(args.mp)) {
                        error = xfs_inobt_insert_sprec(pag, tp, agbp,
                                       XFS_BTNUM_FINO, &rec, false);
                        if (error)
                                return error;
                }
        } else {
                /* full chunk - insert new records to both btrees */
                error = xfs_inobt_insert(pag, tp, agbp, newino, newlen,
                                         XFS_BTNUM_INO);
                if (error)
                        return error;

                if (xfs_has_finobt(args.mp)) {
                        error = xfs_inobt_insert(pag, tp, agbp, newino,
                                                 newlen, XFS_BTNUM_FINO);
                        if (error)
                                return error;
                }
        }

        /*
         * Update AGI counts and newino.
         */
        be32_add_cpu(&agi->agi_count, newlen);
        be32_add_cpu(&agi->agi_freecount, newlen);
        pag->pagi_freecount += newlen;
        pag->pagi_count += newlen;
        agi->agi_newino = cpu_to_be32(newino);

        /*
         * Log allocation group header fields
         */
        xfs_ialloc_log_agi(tp, agbp,
                XFS_AGI_COUNT | XFS_AGI_FREECOUNT | XFS_AGI_NEWINO);
        /*
         * Modify/log superblock values for inode count and inode free count.
         */
        xfs_trans_mod_sb(tp, XFS_TRANS_SB_ICOUNT, (long)newlen);
        xfs_trans_mod_sb(tp, XFS_TRANS_SB_IFREE, (long)newlen);
        return 0;
}

/*
 * Try to retrieve the next record to the left/right from the current one.
 */
STATIC int
xfs_ialloc_next_rec(
        struct xfs_btree_cur    *cur,
        xfs_inobt_rec_incore_t  *rec,
        int                     *done,
        int                     left)
{
        int                     error;
        int                     i;

        if (left)
                error = xfs_btree_decrement(cur, 0, &i);
        else
                error = xfs_btree_increment(cur, 0, &i);

        if (error)
                return error;
        *done = !i;
        if (i) {
                error = xfs_inobt_get_rec(cur, rec, &i);
                if (error)
                        return error;
                if (XFS_IS_CORRUPT(cur->bc_mp, i != 1))
                        return -EFSCORRUPTED;
        }

        return 0;
}

STATIC int
xfs_ialloc_get_rec(
        struct xfs_btree_cur    *cur,
        xfs_agino_t             agino,
        xfs_inobt_rec_incore_t  *rec,
        int                     *done)
{
        int                     error;
        int                     i;

        error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_EQ, &i);
        if (error)
                return error;
        *done = !i;
        if (i) {
                error = xfs_inobt_get_rec(cur, rec, &i);
                if (error)
                        return error;
                if (XFS_IS_CORRUPT(cur->bc_mp, i != 1))
                        return -EFSCORRUPTED;
        }

        return 0;
}

/*
 * Return the offset of the first free inode in the record. If the inode chunk
 * is sparsely allocated, we convert the record holemask to inode granularity
 * and mask off the unallocated regions from the inode free mask.
 */
STATIC int
xfs_inobt_first_free_inode(
        struct xfs_inobt_rec_incore     *rec)
{
        xfs_inofree_t                   realfree;

        /* if there are no holes, return the first available offset */
        if (!xfs_inobt_issparse(rec->ir_holemask))
                return xfs_lowbit64(rec->ir_free);

        realfree = xfs_inobt_irec_to_allocmask(rec);
        realfree &= rec->ir_free;

        return xfs_lowbit64(realfree);
}

/*
 * Allocate an inode using the inobt-only algorithm.
 */
STATIC int
xfs_dialloc_ag_inobt(
        struct xfs_perag        *pag,
        struct xfs_trans        *tp,
        struct xfs_buf          *agbp,
        xfs_ino_t               parent,
        xfs_ino_t               *inop)
{
        struct xfs_mount        *mp = tp->t_mountp;
        struct xfs_agi          *agi = agbp->b_addr;
        xfs_agnumber_t          pagno = XFS_INO_TO_AGNO(mp, parent);
        xfs_agino_t             pagino = XFS_INO_TO_AGINO(mp, parent);
        struct xfs_btree_cur    *cur, *tcur;
        struct xfs_inobt_rec_incore rec, trec;
        xfs_ino_t               ino;
        int                     error;
        int                     offset;
        int                     i, j;
        int                     searchdistance = 10;

        ASSERT(xfs_perag_initialised_agi(pag));
        ASSERT(xfs_perag_allows_inodes(pag));
        ASSERT(pag->pagi_freecount > 0);

 restart_pagno:
        cur = xfs_inobt_init_cursor(pag, tp, agbp, XFS_BTNUM_INO);
        /*
         * If pagino is 0 (this is the root inode allocation) use newino.
         * This must work because we've just allocated some.
         */
        if (!pagino)
                pagino = be32_to_cpu(agi->agi_newino);

        error = xfs_check_agi_freecount(cur);
        if (error)
                goto error0;

        /*
         * If in the same AG as the parent, try to get near the parent.
         */
        if (pagno == pag->pag_agno) {
                int             doneleft;       /* done, to the left */
                int             doneright;      /* done, to the right */

                error = xfs_inobt_lookup(cur, pagino, XFS_LOOKUP_LE, &i);
                if (error)
                        goto error0;
                if (XFS_IS_CORRUPT(mp, i != 1)) {
                        error = -EFSCORRUPTED;
                        goto error0;
                }

                error = xfs_inobt_get_rec(cur, &rec, &j);
                if (error)
                        goto error0;
                if (XFS_IS_CORRUPT(mp, j != 1)) {
                        error = -EFSCORRUPTED;
                        goto error0;
                }

                if (rec.ir_freecount > 0) {
                        /*
                         * Found a free inode in the same chunk
                         * as the parent, done.
                         */
                        goto alloc_inode;
                }


                /*
                 * In the same AG as parent, but parent's chunk is full.
                 */

                /* duplicate the cursor, search left & right simultaneously */
                error = xfs_btree_dup_cursor(cur, &tcur);
                if (error)
                        goto error0;

                /*
                 * Skip to last blocks looked up if same parent inode.
                 */
                if (pagino != NULLAGINO &&
                    pag->pagl_pagino == pagino &&
                    pag->pagl_leftrec != NULLAGINO &&
                    pag->pagl_rightrec != NULLAGINO) {
                        error = xfs_ialloc_get_rec(tcur, pag->pagl_leftrec,
                                                   &trec, &doneleft);
                        if (error)
                                goto error1;

                        error = xfs_ialloc_get_rec(cur, pag->pagl_rightrec,
                                                   &rec, &doneright);
                        if (error)
                                goto error1;
                } else {
                        /* search left with tcur, back up 1 record */
                        error = xfs_ialloc_next_rec(tcur, &trec, &doneleft, 1);
                        if (error)
                                goto error1;

                        /* search right with cur, go forward 1 record. */
                        error = xfs_ialloc_next_rec(cur, &rec, &doneright, 0);
                        if (error)
                                goto error1;
                }

                /*
                 * Loop until we find an inode chunk with a free inode.
                 */
                while (--searchdistance > 0 && (!doneleft || !doneright)) {
                        int     useleft;  /* using left inode chunk this time */

                        /* figure out the closer block if both are valid. */
                        if (!doneleft && !doneright) {
                                useleft = pagino -
                                 (trec.ir_startino + XFS_INODES_PER_CHUNK - 1) <
                                  rec.ir_startino - pagino;
                        } else {
                                useleft = !doneleft;
                        }

                        /* free inodes to the left? */
                        if (useleft && trec.ir_freecount) {
                                xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
                                cur = tcur;

                                pag->pagl_leftrec = trec.ir_startino;
                                pag->pagl_rightrec = rec.ir_startino;
                                pag->pagl_pagino = pagino;
                                rec = trec;
                                goto alloc_inode;
                        }

                        /* free inodes to the right? */
                        if (!useleft && rec.ir_freecount) {
                                xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);

                                pag->pagl_leftrec = trec.ir_startino;
                                pag->pagl_rightrec = rec.ir_startino;
                                pag->pagl_pagino = pagino;
                                goto alloc_inode;
                        }

                        /* get next record to check */
                        if (useleft) {
                                error = xfs_ialloc_next_rec(tcur, &trec,
                                                                 &doneleft, 1);
                        } else {
                                error = xfs_ialloc_next_rec(cur, &rec,
                                                                 &doneright, 0);
                        }
                        if (error)
                                goto error1;
                }

                if (searchdistance <= 0) {
                        /*
                         * Not in range - save last search
                         * location and allocate a new inode
                         */
                        xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
                        pag->pagl_leftrec = trec.ir_startino;
                        pag->pagl_rightrec = rec.ir_startino;
                        pag->pagl_pagino = pagino;

                } else {
                        /*
                         * We've reached the end of the btree. because
                         * we are only searching a small chunk of the
                         * btree each search, there is obviously free
                         * inodes closer to the parent inode than we
                         * are now. restart the search again.
                         */
                        pag->pagl_pagino = NULLAGINO;
                        pag->pagl_leftrec = NULLAGINO;
                        pag->pagl_rightrec = NULLAGINO;
                        xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
                        xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
                        goto restart_pagno;
                }
        }

        /*
         * In a different AG from the parent.
         * See if the most recently allocated block has any free.
         */
        if (agi->agi_newino != cpu_to_be32(NULLAGINO)) {
                error = xfs_inobt_lookup(cur, be32_to_cpu(agi->agi_newino),
                                         XFS_LOOKUP_EQ, &i);
                if (error)
                        goto error0;

                if (i == 1) {
                        error = xfs_inobt_get_rec(cur, &rec, &j);
                        if (error)
                                goto error0;

                        if (j == 1 && rec.ir_freecount > 0) {
                                /*
                                 * The last chunk allocated in the group
                                 * still has a free inode.
                                 */
                                goto alloc_inode;
                        }
                }
        }

        /*
         * None left in the last group, search the whole AG
         */
        error = xfs_inobt_lookup(cur, 0, XFS_LOOKUP_GE, &i);
        if (error)
                goto error0;
        if (XFS_IS_CORRUPT(mp, i != 1)) {
                error = -EFSCORRUPTED;
                goto error0;
        }

        for (;;) {
                error = xfs_inobt_get_rec(cur, &rec, &i);
                if (error)
                        goto error0;
                if (XFS_IS_CORRUPT(mp, i != 1)) {
                        error = -EFSCORRUPTED;
                        goto error0;
                }
                if (rec.ir_freecount > 0)
                        break;
                error = xfs_btree_increment(cur, 0, &i);
                if (error)
                        goto error0;
                if (XFS_IS_CORRUPT(mp, i != 1)) {
                        error = -EFSCORRUPTED;
                        goto error0;
                }
        }

alloc_inode:
        offset = xfs_inobt_first_free_inode(&rec);
        ASSERT(offset >= 0);
        ASSERT(offset < XFS_INODES_PER_CHUNK);
        ASSERT((XFS_AGINO_TO_OFFSET(mp, rec.ir_startino) %
                                   XFS_INODES_PER_CHUNK) == 0);
        ino = XFS_AGINO_TO_INO(mp, pag->pag_agno, rec.ir_startino + offset);
        rec.ir_free &= ~XFS_INOBT_MASK(offset);
        rec.ir_freecount--;
        error = xfs_inobt_update(cur, &rec);
        if (error)
                goto error0;
        be32_add_cpu(&agi->agi_freecount, -1);
        xfs_ialloc_log_agi(tp, agbp, XFS_AGI_FREECOUNT);
        pag->pagi_freecount--;

        error = xfs_check_agi_freecount(cur);
        if (error)
                goto error0;

        xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
        xfs_trans_mod_sb(tp, XFS_TRANS_SB_IFREE, -1);
        *inop = ino;
        return 0;
error1:
        xfs_btree_del_cursor(tcur, XFS_BTREE_ERROR);
error0:
        xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Use the free inode btree to allocate an inode based on distance from the
 * parent. Note that the provided cursor may be deleted and replaced.
 */
STATIC int
xfs_dialloc_ag_finobt_near(
        xfs_agino_t                     pagino,
        struct xfs_btree_cur            **ocur,
        struct xfs_inobt_rec_incore     *rec)
{
        struct xfs_btree_cur            *lcur = *ocur;  /* left search cursor */
        struct xfs_btree_cur            *rcur;  /* right search cursor */
        struct xfs_inobt_rec_incore     rrec;
        int                             error;
        int                             i, j;

        error = xfs_inobt_lookup(lcur, pagino, XFS_LOOKUP_LE, &i);
        if (error)
                return error;

        if (i == 1) {
                error = xfs_inobt_get_rec(lcur, rec, &i);
                if (error)
                        return error;
                if (XFS_IS_CORRUPT(lcur->bc_mp, i != 1))
                        return -EFSCORRUPTED;

                /*
                 * See if we've landed in the parent inode record. The finobt
                 * only tracks chunks with at least one free inode, so record
                 * existence is enough.
                 */
                if (pagino >= rec->ir_startino &&
                    pagino < (rec->ir_startino + XFS_INODES_PER_CHUNK))
                        return 0;
        }

        error = xfs_btree_dup_cursor(lcur, &rcur);
        if (error)
                return error;

        error = xfs_inobt_lookup(rcur, pagino, XFS_LOOKUP_GE, &j);
        if (error)
                goto error_rcur;
        if (j == 1) {
                error = xfs_inobt_get_rec(rcur, &rrec, &j);
                if (error)
                        goto error_rcur;
                if (XFS_IS_CORRUPT(lcur->bc_mp, j != 1)) {
                        error = -EFSCORRUPTED;
                        goto error_rcur;
                }
        }

        if (XFS_IS_CORRUPT(lcur->bc_mp, i != 1 && j != 1)) {
                error = -EFSCORRUPTED;
                goto error_rcur;
        }
        if (i == 1 && j == 1) {
                /*
                 * Both the left and right records are valid. Choose the closer
                 * inode chunk to the target.
                 */
                if ((pagino - rec->ir_startino + XFS_INODES_PER_CHUNK - 1) >
                    (rrec.ir_startino - pagino)) {
                        *rec = rrec;
                        xfs_btree_del_cursor(lcur, XFS_BTREE_NOERROR);
                        *ocur = rcur;
                } else {
                        xfs_btree_del_cursor(rcur, XFS_BTREE_NOERROR);
                }
        } else if (j == 1) {
                /* only the right record is valid */
                *rec = rrec;
                xfs_btree_del_cursor(lcur, XFS_BTREE_NOERROR);
                *ocur = rcur;
        } else if (i == 1) {
                /* only the left record is valid */
                xfs_btree_del_cursor(rcur, XFS_BTREE_NOERROR);
        }

        return 0;

error_rcur:
        xfs_btree_del_cursor(rcur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Use the free inode btree to find a free inode based on a newino hint. If
 * the hint is NULL, find the first free inode in the AG.
 */
STATIC int
xfs_dialloc_ag_finobt_newino(
        struct xfs_agi                  *agi,
        struct xfs_btree_cur            *cur,
        struct xfs_inobt_rec_incore     *rec)
{
        int error;
        int i;

        if (agi->agi_newino != cpu_to_be32(NULLAGINO)) {
                error = xfs_inobt_lookup(cur, be32_to_cpu(agi->agi_newino),
                                         XFS_LOOKUP_EQ, &i);
                if (error)
                        return error;
                if (i == 1) {
                        error = xfs_inobt_get_rec(cur, rec, &i);
                        if (error)
                                return error;
                        if (XFS_IS_CORRUPT(cur->bc_mp, i != 1))
                                return -EFSCORRUPTED;
                        return 0;
                }
        }

        /*
         * Find the first inode available in the AG.
         */
        error = xfs_inobt_lookup(cur, 0, XFS_LOOKUP_GE, &i);
        if (error)
                return error;
        if (XFS_IS_CORRUPT(cur->bc_mp, i != 1))
                return -EFSCORRUPTED;

        error = xfs_inobt_get_rec(cur, rec, &i);
        if (error)
                return error;
        if (XFS_IS_CORRUPT(cur->bc_mp, i != 1))
                return -EFSCORRUPTED;

        return 0;
}

/*
 * Update the inobt based on a modification made to the finobt. Also ensure that
 * the records from both trees are equivalent post-modification.
 */
STATIC int
xfs_dialloc_ag_update_inobt(
        struct xfs_btree_cur            *cur,   /* inobt cursor */
        struct xfs_inobt_rec_incore     *frec,  /* finobt record */
        int                             offset) /* inode offset */
{
        struct xfs_inobt_rec_incore     rec;
        int                             error;
        int                             i;

        error = xfs_inobt_lookup(cur, frec->ir_startino, XFS_LOOKUP_EQ, &i);
        if (error)
                return error;
        if (XFS_IS_CORRUPT(cur->bc_mp, i != 1))
                return -EFSCORRUPTED;

        error = xfs_inobt_get_rec(cur, &rec, &i);
        if (error)
                return error;
        if (XFS_IS_CORRUPT(cur->bc_mp, i != 1))
                return -EFSCORRUPTED;
        ASSERT((XFS_AGINO_TO_OFFSET(cur->bc_mp, rec.ir_startino) %
                                   XFS_INODES_PER_CHUNK) == 0);

        rec.ir_free &= ~XFS_INOBT_MASK(offset);
        rec.ir_freecount--;

        if (XFS_IS_CORRUPT(cur->bc_mp,
                           rec.ir_free != frec->ir_free ||
                           rec.ir_freecount != frec->ir_freecount))
                return -EFSCORRUPTED;

        return xfs_inobt_update(cur, &rec);
}

/*
 * Allocate an inode using the free inode btree, if available. Otherwise, fall
 * back to the inobt search algorithm.
 *
 * The caller selected an AG for us, and made sure that free inodes are
 * available.
 */
static int
xfs_dialloc_ag(
        struct xfs_perag        *pag,
        struct xfs_trans        *tp,
        struct xfs_buf          *agbp,
        xfs_ino_t               parent,
        xfs_ino_t               *inop)
{
        struct xfs_mount                *mp = tp->t_mountp;
        struct xfs_agi                  *agi = agbp->b_addr;
        xfs_agnumber_t                  pagno = XFS_INO_TO_AGNO(mp, parent);
        xfs_agino_t                     pagino = XFS_INO_TO_AGINO(mp, parent);
        struct xfs_btree_cur            *cur;   /* finobt cursor */
        struct xfs_btree_cur            *icur;  /* inobt cursor */
        struct xfs_inobt_rec_incore     rec;
        xfs_ino_t                       ino;
        int                             error;
        int                             offset;
        int                             i;

        if (!xfs_has_finobt(mp))
                return xfs_dialloc_ag_inobt(pag, tp, agbp, parent, inop);

        /*
         * If pagino is 0 (this is the root inode allocation) use newino.
         * This must work because we've just allocated some.
         */
        if (!pagino)
                pagino = be32_to_cpu(agi->agi_newino);

        cur = xfs_inobt_init_cursor(pag, tp, agbp, XFS_BTNUM_FINO);

        error = xfs_check_agi_freecount(cur);
        if (error)
                goto error_cur;

        /*
         * The search algorithm depends on whether we're in the same AG as the
         * parent. If so, find the closest available inode to the parent. If
         * not, consider the agi hint or find the first free inode in the AG.
         */
        if (pag->pag_agno == pagno)
                error = xfs_dialloc_ag_finobt_near(pagino, &cur, &rec);
        else
                error = xfs_dialloc_ag_finobt_newino(agi, cur, &rec);
        if (error)
                goto error_cur;

        offset = xfs_inobt_first_free_inode(&rec);
        ASSERT(offset >= 0);
        ASSERT(offset < XFS_INODES_PER_CHUNK);
        ASSERT((XFS_AGINO_TO_OFFSET(mp, rec.ir_startino) %
                                   XFS_INODES_PER_CHUNK) == 0);
        ino = XFS_AGINO_TO_INO(mp, pag->pag_agno, rec.ir_startino + offset);

        /*
         * Modify or remove the finobt record.
         */
        rec.ir_free &= ~XFS_INOBT_MASK(offset);
        rec.ir_freecount--;
        if (rec.ir_freecount)
                error = xfs_inobt_update(cur, &rec);
        else
                error = xfs_btree_delete(cur, &i);
        if (error)
                goto error_cur;

        /*
         * The finobt has now been updated appropriately. We haven't updated the
         * agi and superblock yet, so we can create an inobt cursor and validate
         * the original freecount. If all is well, make the equivalent update to
         * the inobt using the finobt record and offset information.
         */
        icur = xfs_inobt_init_cursor(pag, tp, agbp, XFS_BTNUM_INO);

        error = xfs_check_agi_freecount(icur);
        if (error)
                goto error_icur;

        error = xfs_dialloc_ag_update_inobt(icur, &rec, offset);
        if (error)
                goto error_icur;

        /*
         * Both trees have now been updated. We must update the perag and
         * superblock before we can check the freecount for each btree.
         */
        be32_add_cpu(&agi->agi_freecount, -1);
        xfs_ialloc_log_agi(tp, agbp, XFS_AGI_FREECOUNT);
        pag->pagi_freecount--;

        xfs_trans_mod_sb(tp, XFS_TRANS_SB_IFREE, -1);

        error = xfs_check_agi_freecount(icur);
        if (error)
                goto error_icur;
        error = xfs_check_agi_freecount(cur);
        if (error)
                goto error_icur;

        xfs_btree_del_cursor(icur, XFS_BTREE_NOERROR);
        xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
        *inop = ino;
        return 0;

error_icur:
        xfs_btree_del_cursor(icur, XFS_BTREE_ERROR);
error_cur:
        xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
        return error;
}

static int
xfs_dialloc_roll(
        struct xfs_trans        **tpp,
        struct xfs_buf          *agibp)
{
        struct xfs_trans        *tp = *tpp;
        struct xfs_dquot_acct   *dqinfo;
        int                     error;

        /*
         * Hold to on to the agibp across the commit so no other allocation can
         * come in and take the free inodes we just allocated for our caller.
         */
        xfs_trans_bhold(tp, agibp);

        /*
         * We want the quota changes to be associated with the next transaction,
         * NOT this one. So, detach the dqinfo from this and attach it to the
         * next transaction.
         */
        dqinfo = tp->t_dqinfo;
        tp->t_dqinfo = NULL;

        error = xfs_trans_roll(&tp);

        /* Re-attach the quota info that we detached from prev trx. */
        tp->t_dqinfo = dqinfo;

        /*
         * Join the buffer even on commit error so that the buffer is released
         * when the caller cancels the transaction and doesn't have to handle
         * this error case specially.
         */
        xfs_trans_bjoin(tp, agibp);
        *tpp = tp;
        return error;
}

static bool
xfs_dialloc_good_ag(
        struct xfs_perag        *pag,
        struct xfs_trans        *tp,
        umode_t                 mode,
        int                     flags,
        bool                    ok_alloc)
{
        struct xfs_mount        *mp = tp->t_mountp;
        xfs_extlen_t            ineed;
        xfs_extlen_t            longest = 0;
        int                     needspace;
        int                     error;

        if (!pag)
                return false;
        if (!xfs_perag_allows_inodes(pag))
                return false;

        if (!xfs_perag_initialised_agi(pag)) {
                error = xfs_ialloc_read_agi(pag, tp, NULL);
                if (error)
                        return false;
        }

        if (pag->pagi_freecount)
                return true;
        if (!ok_alloc)
                return false;

        if (!xfs_perag_initialised_agf(pag)) {
                error = xfs_alloc_read_agf(pag, tp, flags, NULL);
                if (error)
                        return false;
        }

        /*
         * Check that there is enough free space for the file plus a chunk of
         * inodes if we need to allocate some. If this is the first pass across
         * the AGs, take into account the potential space needed for alignment
         * of inode chunks when checking the longest contiguous free space in
         * the AG - this prevents us from getting ENOSPC because we have free
         * space larger than ialloc_blks but alignment constraints prevent us
         * from using it.
         *
         * If we can't find an AG with space for full alignment slack to be
         * taken into account, we must be near ENOSPC in all AGs.  Hence we
         * don't include alignment for the second pass and so if we fail
         * allocation due to alignment issues then it is most likely a real
         * ENOSPC condition.
         *
         * XXX(dgc): this calculation is now bogus thanks to the per-ag
         * reservations that xfs_alloc_fix_freelist() now does via
         * xfs_alloc_space_available(). When the AG fills up, pagf_freeblks will
         * be more than large enough for the check below to succeed, but
         * xfs_alloc_space_available() will fail because of the non-zero
         * metadata reservation and hence we won't actually be able to allocate
         * more inodes in this AG. We do soooo much unnecessary work near ENOSPC
         * because of this.
         */
        ineed = M_IGEO(mp)->ialloc_min_blks;
        if (flags && ineed > 1)
                ineed += M_IGEO(mp)->cluster_align;
        longest = pag->pagf_longest;
        if (!longest)
                longest = pag->pagf_flcount > 0;
        needspace = S_ISDIR(mode) || S_ISREG(mode) || S_ISLNK(mode);

        if (pag->pagf_freeblks < needspace + ineed || longest < ineed)
                return false;
        return true;
}

static int
xfs_dialloc_try_ag(
        struct xfs_perag        *pag,
        struct xfs_trans        **tpp,
        xfs_ino_t               parent,
        xfs_ino_t               *new_ino,
        bool                    ok_alloc)
{
        struct xfs_buf          *agbp;
        xfs_ino_t               ino;
        int                     error;

        /*
         * Then read in the AGI buffer and recheck with the AGI buffer
         * lock held.
         */
        error = xfs_ialloc_read_agi(pag, *tpp, &agbp);
        if (error)
                return error;

        if (!pag->pagi_freecount) {
                if (!ok_alloc) {
                        error = -EAGAIN;
                        goto out_release;
                }

                error = xfs_ialloc_ag_alloc(pag, *tpp, agbp);
                if (error < 0)
                        goto out_release;

                /*
                 * We successfully allocated space for an inode cluster in this
                 * AG.  Roll the transaction so that we can allocate one of the
                 * new inodes.
                 */
                ASSERT(pag->pagi_freecount > 0);
                error = xfs_dialloc_roll(tpp, agbp);
                if (error)
                        goto out_release;
        }

        /* Allocate an inode in the found AG */
        error = xfs_dialloc_ag(pag, *tpp, agbp, parent, &ino);
        if (!error)
                *new_ino = ino;
        return error;

out_release:
        xfs_trans_brelse(*tpp, agbp);
        return error;
}

/*
 * Allocate an on-disk inode.
 *
 * Mode is used to tell whether the new inode is a directory and hence where to
 * locate it. The on-disk inode that is allocated will be returned in @new_ino
 * on success, otherwise an error will be set to indicate the failure (e.g.
 * -ENOSPC).
 */
int
xfs_dialloc(
        struct xfs_trans        **tpp,
        xfs_ino_t               parent,
        umode_t                 mode,
        xfs_ino_t               *new_ino)
{
        struct xfs_mount        *mp = (*tpp)->t_mountp;
        xfs_agnumber_t          agno;
        int                     error = 0;
        xfs_agnumber_t          start_agno;
        struct xfs_perag        *pag;
        struct xfs_ino_geometry *igeo = M_IGEO(mp);
        bool                    ok_alloc = true;
        bool                    low_space = false;
        int                     flags;
        xfs_ino_t               ino = NULLFSINO;

        /*
         * Directories, symlinks, and regular files frequently allocate at least
         * one block, so factor that potential expansion when we examine whether
         * an AG has enough space for file creation.
         */
        if (S_ISDIR(mode))
                start_agno = (atomic_inc_return(&mp->m_agirotor) - 1) %
                                mp->m_maxagi;
        else {
                start_agno = XFS_INO_TO_AGNO(mp, parent);
                if (start_agno >= mp->m_maxagi)
                        start_agno = 0;
        }

        /*
         * If we have already hit the ceiling of inode blocks then clear
         * ok_alloc so we scan all available agi structures for a free
         * inode.
         *
         * Read rough value of mp->m_icount by percpu_counter_read_positive,
         * which will sacrifice the preciseness but improve the performance.
         */
        if (igeo->maxicount &&
            percpu_counter_read_positive(&mp->m_icount) + igeo->ialloc_inos
                                                        > igeo->maxicount) {
                ok_alloc = false;
        }

        /*
         * If we are near to ENOSPC, we want to prefer allocation from AGs that
         * have free inodes in them rather than use up free space allocating new
         * inode chunks. Hence we turn off allocation for the first non-blocking
         * pass through the AGs if we are near ENOSPC to consume free inodes
         * that we can immediately allocate, but then we allow allocation on the
         * second pass if we fail to find an AG with free inodes in it.
         */
        if (percpu_counter_read_positive(&mp->m_fdblocks) <
                        mp->m_low_space[XFS_LOWSP_1_PCNT]) {
                ok_alloc = false;
                low_space = true;
        }

        /*
         * Loop until we find an allocation group that either has free inodes
         * or in which we can allocate some inodes.  Iterate through the
         * allocation groups upward, wrapping at the end.
         */
        flags = XFS_ALLOC_FLAG_TRYLOCK;
retry:
        for_each_perag_wrap_at(mp, start_agno, mp->m_maxagi, agno, pag) {
                if (xfs_dialloc_good_ag(pag, *tpp, mode, flags, ok_alloc)) {
                        error = xfs_dialloc_try_ag(pag, tpp, parent,
                                        &ino, ok_alloc);
                        if (error != -EAGAIN)
                                break;
                        error = 0;
                }

                if (xfs_is_shutdown(mp)) {
                        error = -EFSCORRUPTED;
                        break;
                }
        }
        if (pag)
                xfs_perag_rele(pag);
        if (error)
                return error;
        if (ino == NULLFSINO) {
                if (flags) {
                        flags = 0;
                        if (low_space)
                                ok_alloc = true;
                        goto retry;
                }
                return -ENOSPC;
        }
        *new_ino = ino;
        return 0;
}

/*
 * Free the blocks of an inode chunk. We must consider that the inode chunk
 * might be sparse and only free the regions that are allocated as part of the
 * chunk.
 */
STATIC void
xfs_difree_inode_chunk(
        struct xfs_trans                *tp,
        xfs_agnumber_t                  agno,
        struct xfs_inobt_rec_incore     *rec)
{
        struct xfs_mount                *mp = tp->t_mountp;
        xfs_agblock_t                   sagbno = XFS_AGINO_TO_AGBNO(mp,
                                                        rec->ir_startino);
        int                             startidx, endidx;
        int                             nextbit;
        xfs_agblock_t                   agbno;
        int                             contigblk;
        DECLARE_BITMAP(holemask, XFS_INOBT_HOLEMASK_BITS);

        if (!xfs_inobt_issparse(rec->ir_holemask)) {
                /* not sparse, calculate extent info directly */
                xfs_free_extent_later(tp, XFS_AGB_TO_FSB(mp, agno, sagbno),
                                  M_IGEO(mp)->ialloc_blks,
                                  &XFS_RMAP_OINFO_INODES);
                return;
        }

        /* holemask is only 16-bits (fits in an unsigned long) */
        ASSERT(sizeof(rec->ir_holemask) <= sizeof(holemask[0]));
        holemask[0] = rec->ir_holemask;

        /*
         * Find contiguous ranges of zeroes (i.e., allocated regions) in the
         * holemask and convert the start/end index of each range to an extent.
         * We start with the start and end index both pointing at the first 0 in
         * the mask.
         */
        startidx = endidx = find_first_zero_bit(holemask,
                                                XFS_INOBT_HOLEMASK_BITS);
        nextbit = startidx + 1;
        while (startidx < XFS_INOBT_HOLEMASK_BITS) {
                nextbit = find_next_zero_bit(holemask, XFS_INOBT_HOLEMASK_BITS,
                                             nextbit);
                /*
                 * If the next zero bit is contiguous, update the end index of
                 * the current range and continue.
                 */
                if (nextbit != XFS_INOBT_HOLEMASK_BITS &&
                    nextbit == endidx + 1) {
                        endidx = nextbit;
                        goto next;
                }

                /*
                 * nextbit is not contiguous with the current end index. Convert
                 * the current start/end to an extent and add it to the free
                 * list.
                 */
                agbno = sagbno + (startidx * XFS_INODES_PER_HOLEMASK_BIT) /
                                  mp->m_sb.sb_inopblock;
                contigblk = ((endidx - startidx + 1) *
                             XFS_INODES_PER_HOLEMASK_BIT) /
                            mp->m_sb.sb_inopblock;

                ASSERT(agbno % mp->m_sb.sb_spino_align == 0);
                ASSERT(contigblk % mp->m_sb.sb_spino_align == 0);
                xfs_free_extent_later(tp, XFS_AGB_TO_FSB(mp, agno, agbno),
                                  contigblk, &XFS_RMAP_OINFO_INODES);

                /* reset range to current bit and carry on... */
                startidx = endidx = nextbit;

next:
                nextbit++;
        }
}

STATIC int
xfs_difree_inobt(
        struct xfs_perag                *pag,
        struct xfs_trans                *tp,
        struct xfs_buf                  *agbp,
        xfs_agino_t                     agino,
        struct xfs_icluster             *xic,
        struct xfs_inobt_rec_incore     *orec)
{
        struct xfs_mount                *mp = pag->pag_mount;
        struct xfs_agi                  *agi = agbp->b_addr;
        struct xfs_btree_cur            *cur;
        struct xfs_inobt_rec_incore     rec;
        int                             ilen;
        int                             error;
        int                             i;
        int                             off;

        ASSERT(agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC));
        ASSERT(XFS_AGINO_TO_AGBNO(mp, agino) < be32_to_cpu(agi->agi_length));

        /*
         * Initialize the cursor.
         */
        cur = xfs_inobt_init_cursor(pag, tp, agbp, XFS_BTNUM_INO);

        error = xfs_check_agi_freecount(cur);
        if (error)
                goto error0;

        /*
         * Look for the entry describing this inode.
         */
        if ((error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_LE, &i))) {
                xfs_warn(mp, "%s: xfs_inobt_lookup() returned error %d.",
                        __func__, error);
                goto error0;
        }
        if (XFS_IS_CORRUPT(mp, i != 1)) {
                error = -EFSCORRUPTED;
                goto error0;
        }
        error = xfs_inobt_get_rec(cur, &rec, &i);
        if (error) {
                xfs_warn(mp, "%s: xfs_inobt_get_rec() returned error %d.",
                        __func__, error);
                goto error0;
        }
        if (XFS_IS_CORRUPT(mp, i != 1)) {
                error = -EFSCORRUPTED;
                goto error0;
        }
        /*
         * Get the offset in the inode chunk.
         */
        off = agino - rec.ir_startino;
        ASSERT(off >= 0 && off < XFS_INODES_PER_CHUNK);
        ASSERT(!(rec.ir_free & XFS_INOBT_MASK(off)));
        /*
         * Mark the inode free & increment the count.
         */
        rec.ir_free |= XFS_INOBT_MASK(off);
        rec.ir_freecount++;

        /*
         * When an inode chunk is free, it becomes eligible for removal. Don't
         * remove the chunk if the block size is large enough for multiple inode
         * chunks (that might not be free).
         */
        if (!xfs_has_ikeep(mp) && rec.ir_free == XFS_INOBT_ALL_FREE &&
            mp->m_sb.sb_inopblock <= XFS_INODES_PER_CHUNK) {
                struct xfs_perag        *pag = agbp->b_pag;

                xic->deleted = true;
                xic->first_ino = XFS_AGINO_TO_INO(mp, pag->pag_agno,
                                rec.ir_startino);
                xic->alloc = xfs_inobt_irec_to_allocmask(&rec);

                /*
                 * Remove the inode cluster from the AGI B+Tree, adjust the
                 * AGI and Superblock inode counts, and mark the disk space
                 * to be freed when the transaction is committed.
                 */
                ilen = rec.ir_freecount;
                be32_add_cpu(&agi->agi_count, -ilen);
                be32_add_cpu(&agi->agi_freecount, -(ilen - 1));
                xfs_ialloc_log_agi(tp, agbp, XFS_AGI_COUNT | XFS_AGI_FREECOUNT);
                pag->pagi_freecount -= ilen - 1;
                pag->pagi_count -= ilen;
                xfs_trans_mod_sb(tp, XFS_TRANS_SB_ICOUNT, -ilen);
                xfs_trans_mod_sb(tp, XFS_TRANS_SB_IFREE, -(ilen - 1));

                if ((error = xfs_btree_delete(cur, &i))) {
                        xfs_warn(mp, "%s: xfs_btree_delete returned error %d.",
                                __func__, error);
                        goto error0;
                }

                xfs_difree_inode_chunk(tp, pag->pag_agno, &rec);
        } else {
                xic->deleted = false;

                error = xfs_inobt_update(cur, &rec);
                if (error) {
                        xfs_warn(mp, "%s: xfs_inobt_update returned error %d.",
                                __func__, error);
                        goto error0;
                }

                /*
                 * Change the inode free counts and log the ag/sb changes.
                 */
                be32_add_cpu(&agi->agi_freecount, 1);
                xfs_ialloc_log_agi(tp, agbp, XFS_AGI_FREECOUNT);
                pag->pagi_freecount++;
                xfs_trans_mod_sb(tp, XFS_TRANS_SB_IFREE, 1);
        }

        error = xfs_check_agi_freecount(cur);
        if (error)
                goto error0;

        *orec = rec;
        xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
        return 0;

error0:
        xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Free an inode in the free inode btree.
 */
STATIC int
xfs_difree_finobt(
        struct xfs_perag                *pag,
        struct xfs_trans                *tp,
        struct xfs_buf                  *agbp,
        xfs_agino_t                     agino,
        struct xfs_inobt_rec_incore     *ibtrec) /* inobt record */
{
        struct xfs_mount                *mp = pag->pag_mount;
        struct xfs_btree_cur            *cur;
        struct xfs_inobt_rec_incore     rec;
        int                             offset = agino - ibtrec->ir_startino;
        int                             error;
        int                             i;

        cur = xfs_inobt_init_cursor(pag, tp, agbp, XFS_BTNUM_FINO);

        error = xfs_inobt_lookup(cur, ibtrec->ir_startino, XFS_LOOKUP_EQ, &i);
        if (error)
                goto error;
        if (i == 0) {
                /*
                 * If the record does not exist in the finobt, we must have just
                 * freed an inode in a previously fully allocated chunk. If not,
                 * something is out of sync.
                 */
                if (XFS_IS_CORRUPT(mp, ibtrec->ir_freecount != 1)) {
                        error = -EFSCORRUPTED;
                        goto error;
                }

                error = xfs_inobt_insert_rec(cur, ibtrec->ir_holemask,
                                             ibtrec->ir_count,
                                             ibtrec->ir_freecount,
                                             ibtrec->ir_free, &i);
                if (error)
                        goto error;
                ASSERT(i == 1);

                goto out;
        }

        /*
         * Read and update the existing record. We could just copy the ibtrec
         * across here, but that would defeat the purpose of having redundant
         * metadata. By making the modifications independently, we can catch
         * corruptions that we wouldn't see if we just copied from one record
         * to another.
         */
        error = xfs_inobt_get_rec(cur, &rec, &i);
        if (error)
                goto error;
        if (XFS_IS_CORRUPT(mp, i != 1)) {
                error = -EFSCORRUPTED;
                goto error;
        }

        rec.ir_free |= XFS_INOBT_MASK(offset);
        rec.ir_freecount++;

        if (XFS_IS_CORRUPT(mp,
                           rec.ir_free != ibtrec->ir_free ||
                           rec.ir_freecount != ibtrec->ir_freecount)) {
                error = -EFSCORRUPTED;
                goto error;
        }

        /*
         * The content of inobt records should always match between the inobt
         * and finobt. The lifecycle of records in the finobt is different from
         * the inobt in that the finobt only tracks records with at least one
         * free inode. Hence, if all of the inodes are free and we aren't
         * keeping inode chunks permanently on disk, remove the record.
         * Otherwise, update the record with the new information.
         *
         * Note that we currently can't free chunks when the block size is large
         * enough for multiple chunks. Leave the finobt record to remain in sync
         * with the inobt.
         */
        if (!xfs_has_ikeep(mp) && rec.ir_free == XFS_INOBT_ALL_FREE &&
            mp->m_sb.sb_inopblock <= XFS_INODES_PER_CHUNK) {
                error = xfs_btree_delete(cur, &i);
                if (error)
                        goto error;
                ASSERT(i == 1);
        } else {
                error = xfs_inobt_update(cur, &rec);
                if (error)
                        goto error;
        }

out:
        error = xfs_check_agi_freecount(cur);
        if (error)
                goto error;

        xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
        return 0;

error:
        xfs_btree_del_cursor(cur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Free disk inode.  Carefully avoids touching the incore inode, all
 * manipulations incore are the caller's responsibility.
 * The on-disk inode is not changed by this operation, only the
 * btree (free inode mask) is changed.
 */
int
xfs_difree(
        struct xfs_trans        *tp,
        struct xfs_perag        *pag,
        xfs_ino_t               inode,
        struct xfs_icluster     *xic)
{
        /* REFERENCED */
        xfs_agblock_t           agbno;  /* block number containing inode */
        struct xfs_buf          *agbp;  /* buffer for allocation group header */
        xfs_agino_t             agino;  /* allocation group inode number */
        int                     error;  /* error return value */
        struct xfs_mount        *mp = tp->t_mountp;
        struct xfs_inobt_rec_incore rec;/* btree record */

        /*
         * Break up inode number into its components.
         */
        if (pag->pag_agno != XFS_INO_TO_AGNO(mp, inode)) {
                xfs_warn(mp, "%s: agno != pag->pag_agno (%d != %d).",
                        __func__, XFS_INO_TO_AGNO(mp, inode), pag->pag_agno);
                ASSERT(0);
                return -EINVAL;
        }
        agino = XFS_INO_TO_AGINO(mp, inode);
        if (inode != XFS_AGINO_TO_INO(mp, pag->pag_agno, agino))  {
                xfs_warn(mp, "%s: inode != XFS_AGINO_TO_INO() (%llu != %llu).",
                        __func__, (unsigned long long)inode,
                        (unsigned long long)XFS_AGINO_TO_INO(mp, pag->pag_agno, agino));
                ASSERT(0);
                return -EINVAL;
        }
        agbno = XFS_AGINO_TO_AGBNO(mp, agino);
        if (agbno >= mp->m_sb.sb_agblocks)  {
                xfs_warn(mp, "%s: agbno >= mp->m_sb.sb_agblocks (%d >= %d).",
                        __func__, agbno, mp->m_sb.sb_agblocks);
                ASSERT(0);
                return -EINVAL;
        }
        /*
         * Get the allocation group header.
         */
        error = xfs_ialloc_read_agi(pag, tp, &agbp);
        if (error) {
                xfs_warn(mp, "%s: xfs_ialloc_read_agi() returned error %d.",
                        __func__, error);
                return error;
        }

        /*
         * Fix up the inode allocation btree.
         */
        error = xfs_difree_inobt(pag, tp, agbp, agino, xic, &rec);
        if (error)
                goto error0;

        /*
         * Fix up the free inode btree.
         */
        if (xfs_has_finobt(mp)) {
                error = xfs_difree_finobt(pag, tp, agbp, agino, &rec);
                if (error)
                        goto error0;
        }

        return 0;

error0:
        return error;
}

STATIC int
xfs_imap_lookup(
        struct xfs_perag        *pag,
        struct xfs_trans        *tp,
        xfs_agino_t             agino,
        xfs_agblock_t           agbno,
        xfs_agblock_t           *chunk_agbno,
        xfs_agblock_t           *offset_agbno,
        int                     flags)
{
        struct xfs_mount        *mp = pag->pag_mount;
        struct xfs_inobt_rec_incore rec;
        struct xfs_btree_cur    *cur;
        struct xfs_buf          *agbp;
        int                     error;
        int                     i;

        error = xfs_ialloc_read_agi(pag, tp, &agbp);
        if (error) {
                xfs_alert(mp,
                        "%s: xfs_ialloc_read_agi() returned error %d, agno %d",
                        __func__, error, pag->pag_agno);
                return error;
        }

        /*
         * Lookup the inode record for the given agino. If the record cannot be
         * found, then it's an invalid inode number and we should abort. Once
         * we have a record, we need to ensure it contains the inode number
         * we are looking up.
         */
        cur = xfs_inobt_init_cursor(pag, tp, agbp, XFS_BTNUM_INO);
        error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_LE, &i);
        if (!error) {
                if (i)
                        error = xfs_inobt_get_rec(cur, &rec, &i);
                if (!error && i == 0)
                        error = -EINVAL;
        }

        xfs_trans_brelse(tp, agbp);
        xfs_btree_del_cursor(cur, error);
        if (error)
                return error;

        /* check that the returned record contains the required inode */
        if (rec.ir_startino > agino ||
            rec.ir_startino + M_IGEO(mp)->ialloc_inos <= agino)
                return -EINVAL;

        /* for untrusted inodes check it is allocated first */
        if ((flags & XFS_IGET_UNTRUSTED) &&
            (rec.ir_free & XFS_INOBT_MASK(agino - rec.ir_startino)))
                return -EINVAL;

        *chunk_agbno = XFS_AGINO_TO_AGBNO(mp, rec.ir_startino);
        *offset_agbno = agbno - *chunk_agbno;
        return 0;
}

/*
 * Return the location of the inode in imap, for mapping it into a buffer.
 */
int
xfs_imap(
        struct xfs_perag        *pag,
        struct xfs_trans        *tp,
        xfs_ino_t               ino,    /* inode to locate */
        struct xfs_imap         *imap,  /* location map structure */
        uint                    flags)  /* flags for inode btree lookup */
{
        struct xfs_mount        *mp = pag->pag_mount;
        xfs_agblock_t           agbno;  /* block number of inode in the alloc group */
        xfs_agino_t             agino;  /* inode number within alloc group */
        xfs_agblock_t           chunk_agbno;    /* first block in inode chunk */
        xfs_agblock_t           cluster_agbno;  /* first block in inode cluster */
        int                     error;  /* error code */
        int                     offset; /* index of inode in its buffer */
        xfs_agblock_t           offset_agbno;   /* blks from chunk start to inode */

        ASSERT(ino != NULLFSINO);

        /*
         * Split up the inode number into its parts.
         */
        agino = XFS_INO_TO_AGINO(mp, ino);
        agbno = XFS_AGINO_TO_AGBNO(mp, agino);
        if (agbno >= mp->m_sb.sb_agblocks ||
            ino != XFS_AGINO_TO_INO(mp, pag->pag_agno, agino)) {
                error = -EINVAL;
#ifdef DEBUG
                /*
                 * Don't output diagnostic information for untrusted inodes
                 * as they can be invalid without implying corruption.
                 */
                if (flags & XFS_IGET_UNTRUSTED)
                        return error;
                if (agbno >= mp->m_sb.sb_agblocks) {
                        xfs_alert(mp,
                "%s: agbno (0x%llx) >= mp->m_sb.sb_agblocks (0x%lx)",
                                __func__, (unsigned long long)agbno,
                                (unsigned long)mp->m_sb.sb_agblocks);
                }
                if (ino != XFS_AGINO_TO_INO(mp, pag->pag_agno, agino)) {
                        xfs_alert(mp,
                "%s: ino (0x%llx) != XFS_AGINO_TO_INO() (0x%llx)",
                                __func__, ino,
                                XFS_AGINO_TO_INO(mp, pag->pag_agno, agino));
                }
                xfs_stack_trace();
#endif /* DEBUG */
                return error;
        }

        /*
         * For bulkstat and handle lookups, we have an untrusted inode number
         * that we have to verify is valid. We cannot do this just by reading
         * the inode buffer as it may have been unlinked and removed leaving
         * inodes in stale state on disk. Hence we have to do a btree lookup
         * in all cases where an untrusted inode number is passed.
         */
        if (flags & XFS_IGET_UNTRUSTED) {
                error = xfs_imap_lookup(pag, tp, agino, agbno,
                                        &chunk_agbno, &offset_agbno, flags);
                if (error)
                        return error;
                goto out_map;
        }

        /*
         * If the inode cluster size is the same as the blocksize or
         * smaller we get to the buffer by simple arithmetics.
         */
        if (M_IGEO(mp)->blocks_per_cluster == 1) {
                offset = XFS_INO_TO_OFFSET(mp, ino);
                ASSERT(offset < mp->m_sb.sb_inopblock);

                imap->im_blkno = XFS_AGB_TO_DADDR(mp, pag->pag_agno, agbno);
                imap->im_len = XFS_FSB_TO_BB(mp, 1);
                imap->im_boffset = (unsigned short)(offset <<
                                                        mp->m_sb.sb_inodelog);
                return 0;
        }

        /*
         * If the inode chunks are aligned then use simple maths to
         * find the location. Otherwise we have to do a btree
         * lookup to find the location.
         */
        if (M_IGEO(mp)->inoalign_mask) {
                offset_agbno = agbno & M_IGEO(mp)->inoalign_mask;
                chunk_agbno = agbno - offset_agbno;
        } else {
                error = xfs_imap_lookup(pag, tp, agino, agbno,
                                        &chunk_agbno, &offset_agbno, flags);
                if (error)
                        return error;
        }

out_map:
        ASSERT(agbno >= chunk_agbno);
        cluster_agbno = chunk_agbno +
                ((offset_agbno / M_IGEO(mp)->blocks_per_cluster) *
                 M_IGEO(mp)->blocks_per_cluster);
        offset = ((agbno - cluster_agbno) * mp->m_sb.sb_inopblock) +
                XFS_INO_TO_OFFSET(mp, ino);

        imap->im_blkno = XFS_AGB_TO_DADDR(mp, pag->pag_agno, cluster_agbno);
        imap->im_len = XFS_FSB_TO_BB(mp, M_IGEO(mp)->blocks_per_cluster);
        imap->im_boffset = (unsigned short)(offset << mp->m_sb.sb_inodelog);

        /*
         * If the inode number maps to a block outside the bounds
         * of the file system then return NULL rather than calling
         * read_buf and panicing when we get an error from the
         * driver.
         */
        if ((imap->im_blkno + imap->im_len) >
            XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks)) {
                xfs_alert(mp,
        "%s: (im_blkno (0x%llx) + im_len (0x%llx)) > sb_dblocks (0x%llx)",
                        __func__, (unsigned long long) imap->im_blkno,
                        (unsigned long long) imap->im_len,
                        XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks));
                return -EINVAL;
        }
        return 0;
}

/*
 * Log specified fields for the ag hdr (inode section). The growth of the agi
 * structure over time requires that we interpret the buffer as two logical
 * regions delineated by the end of the unlinked list. This is due to the size
 * of the hash table and its location in the middle of the agi.
 *
 * For example, a request to log a field before agi_unlinked and a field after
 * agi_unlinked could cause us to log the entire hash table and use an excessive
 * amount of log space. To avoid this behavior, log the region up through
 * agi_unlinked in one call and the region after agi_unlinked through the end of
 * the structure in another.
 */
void
xfs_ialloc_log_agi(
        struct xfs_trans        *tp,
        struct xfs_buf          *bp,
        uint32_t                fields)
{
        int                     first;          /* first byte number */
        int                     last;           /* last byte number */
        static const short      offsets[] = {   /* field starting offsets */
                                        /* keep in sync with bit definitions */
                offsetof(xfs_agi_t, agi_magicnum),
                offsetof(xfs_agi_t, agi_versionnum),
                offsetof(xfs_agi_t, agi_seqno),
                offsetof(xfs_agi_t, agi_length),
                offsetof(xfs_agi_t, agi_count),
                offsetof(xfs_agi_t, agi_root),
                offsetof(xfs_agi_t, agi_level),
                offsetof(xfs_agi_t, agi_freecount),
                offsetof(xfs_agi_t, agi_newino),
                offsetof(xfs_agi_t, agi_dirino),
                offsetof(xfs_agi_t, agi_unlinked),
                offsetof(xfs_agi_t, agi_free_root),
                offsetof(xfs_agi_t, agi_free_level),
                offsetof(xfs_agi_t, agi_iblocks),
                sizeof(xfs_agi_t)
        };
#ifdef DEBUG
        struct xfs_agi          *agi = bp->b_addr;

        ASSERT(agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC));
#endif

        /*
         * Compute byte offsets for the first and last fields in the first
         * region and log the agi buffer. This only logs up through
         * agi_unlinked.
         */
        if (fields & XFS_AGI_ALL_BITS_R1) {
                xfs_btree_offsets(fields, offsets, XFS_AGI_NUM_BITS_R1,
                                  &first, &last);
                xfs_trans_log_buf(tp, bp, first, last);
        }

        /*
         * Mask off the bits in the first region and calculate the first and
         * last field offsets for any bits in the second region.
         */
        fields &= ~XFS_AGI_ALL_BITS_R1;
        if (fields) {
                xfs_btree_offsets(fields, offsets, XFS_AGI_NUM_BITS_R2,
                                  &first, &last);
                xfs_trans_log_buf(tp, bp, first, last);
        }
}

static xfs_failaddr_t
xfs_agi_verify(
        struct xfs_buf  *bp)
{
        struct xfs_mount *mp = bp->b_mount;
        struct xfs_agi  *agi = bp->b_addr;
        int             i;

        if (xfs_has_crc(mp)) {
                if (!uuid_equal(&agi->agi_uuid, &mp->m_sb.sb_meta_uuid))
                        return __this_address;
                if (!xfs_log_check_lsn(mp, be64_to_cpu(agi->agi_lsn)))
                        return __this_address;
        }

        /*
         * Validate the magic number of the agi block.
         */
        if (!xfs_verify_magic(bp, agi->agi_magicnum))
                return __this_address;
        if (!XFS_AGI_GOOD_VERSION(be32_to_cpu(agi->agi_versionnum)))
                return __this_address;

        if (be32_to_cpu(agi->agi_level) < 1 ||
            be32_to_cpu(agi->agi_level) > M_IGEO(mp)->inobt_maxlevels)
                return __this_address;

        if (xfs_has_finobt(mp) &&
            (be32_to_cpu(agi->agi_free_level) < 1 ||
             be32_to_cpu(agi->agi_free_level) > M_IGEO(mp)->inobt_maxlevels))
                return __this_address;

        /*
         * during growfs operations, the perag is not fully initialised,
         * so we can't use it for any useful checking. growfs ensures we can't
         * use it by using uncached buffers that don't have the perag attached
         * so we can detect and avoid this problem.
         */
        if (bp->b_pag && be32_to_cpu(agi->agi_seqno) != bp->b_pag->pag_agno)
                return __this_address;

        for (i = 0; i < XFS_AGI_UNLINKED_BUCKETS; i++) {
                if (agi->agi_unlinked[i] == cpu_to_be32(NULLAGINO))
                        continue;
                if (!xfs_verify_ino(mp, be32_to_cpu(agi->agi_unlinked[i])))
                        return __this_address;
        }

        return NULL;
}

static void
xfs_agi_read_verify(
        struct xfs_buf  *bp)
{
        struct xfs_mount *mp = bp->b_mount;
        xfs_failaddr_t  fa;

        if (xfs_has_crc(mp) &&
            !xfs_buf_verify_cksum(bp, XFS_AGI_CRC_OFF))
                xfs_verifier_error(bp, -EFSBADCRC, __this_address);
        else {
                fa = xfs_agi_verify(bp);
                if (XFS_TEST_ERROR(fa, mp, XFS_ERRTAG_IALLOC_READ_AGI))
                        xfs_verifier_error(bp, -EFSCORRUPTED, fa);
        }
}

static void
xfs_agi_write_verify(
        struct xfs_buf  *bp)
{
        struct xfs_mount        *mp = bp->b_mount;
        struct xfs_buf_log_item *bip = bp->b_log_item;
        struct xfs_agi          *agi = bp->b_addr;
        xfs_failaddr_t          fa;

        fa = xfs_agi_verify(bp);
        if (fa) {
                xfs_verifier_error(bp, -EFSCORRUPTED, fa);
                return;
        }

        if (!xfs_has_crc(mp))
                return;

        if (bip)
                agi->agi_lsn = cpu_to_be64(bip->bli_item.li_lsn);
        xfs_buf_update_cksum(bp, XFS_AGI_CRC_OFF);
}

const struct xfs_buf_ops xfs_agi_buf_ops = {
        .name = "xfs_agi",
        .magic = { cpu_to_be32(XFS_AGI_MAGIC), cpu_to_be32(XFS_AGI_MAGIC) },
        .verify_read = xfs_agi_read_verify,
        .verify_write = xfs_agi_write_verify,
        .verify_struct = xfs_agi_verify,
};

/*
 * Read in the allocation group header (inode allocation section)
 */
int
xfs_read_agi(
        struct xfs_perag        *pag,
        struct xfs_trans        *tp,
        struct xfs_buf          **agibpp)
{
        struct xfs_mount        *mp = pag->pag_mount;
        int                     error;

        trace_xfs_read_agi(pag->pag_mount, pag->pag_agno);

        error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
                        XFS_AG_DADDR(mp, pag->pag_agno, XFS_AGI_DADDR(mp)),
                        XFS_FSS_TO_BB(mp, 1), 0, agibpp, &xfs_agi_buf_ops);
        if (error)
                return error;
        if (tp)
                xfs_trans_buf_set_type(tp, *agibpp, XFS_BLFT_AGI_BUF);

        xfs_buf_set_ref(*agibpp, XFS_AGI_REF);
        return 0;
}

/*
 * Read in the agi and initialise the per-ag data. If the caller supplies a
 * @agibpp, return the locked AGI buffer to them, otherwise release it.
 */
int
xfs_ialloc_read_agi(
        struct xfs_perag        *pag,
        struct xfs_trans        *tp,
        struct xfs_buf          **agibpp)
{
        struct xfs_buf          *agibp;
        struct xfs_agi          *agi;
        int                     error;

        trace_xfs_ialloc_read_agi(pag->pag_mount, pag->pag_agno);

        error = xfs_read_agi(pag, tp, &agibp);
        if (error)
                return error;

        agi = agibp->b_addr;
        if (!xfs_perag_initialised_agi(pag)) {
                pag->pagi_freecount = be32_to_cpu(agi->agi_freecount);
                pag->pagi_count = be32_to_cpu(agi->agi_count);
                set_bit(XFS_AGSTATE_AGI_INIT, &pag->pag_opstate);
        }

        /*
         * It's possible for these to be out of sync if
         * we are in the middle of a forced shutdown.
         */
        ASSERT(pag->pagi_freecount == be32_to_cpu(agi->agi_freecount) ||
                xfs_is_shutdown(pag->pag_mount));
        if (agibpp)
                *agibpp = agibp;
        else
                xfs_trans_brelse(tp, agibp);
        return 0;
}

/* Is there an inode record covering a given range of inode numbers? */
int
xfs_ialloc_has_inode_record(
        struct xfs_btree_cur    *cur,
        xfs_agino_t             low,
        xfs_agino_t             high,
        bool                    *exists)
{
        struct xfs_inobt_rec_incore     irec;
        xfs_agino_t             agino;
        uint16_t                holemask;
        int                     has_record;
        int                     i;
        int                     error;

        *exists = false;
        error = xfs_inobt_lookup(cur, low, XFS_LOOKUP_LE, &has_record);
        while (error == 0 && has_record) {
                error = xfs_inobt_get_rec(cur, &irec, &has_record);
                if (error || irec.ir_startino > high)
                        break;

                agino = irec.ir_startino;
                holemask = irec.ir_holemask;
                for (i = 0; i < XFS_INOBT_HOLEMASK_BITS; holemask >>= 1,
                                i++, agino += XFS_INODES_PER_HOLEMASK_BIT) {
                        if (holemask & 1)
                                continue;
                        if (agino + XFS_INODES_PER_HOLEMASK_BIT > low &&
                                        agino <= high) {
                                *exists = true;
                                return 0;
                        }
                }

                error = xfs_btree_increment(cur, 0, &has_record);
        }
        return error;
}

/* Is there an inode record covering a given extent? */
int
xfs_ialloc_has_inodes_at_extent(
        struct xfs_btree_cur    *cur,
        xfs_agblock_t           bno,
        xfs_extlen_t            len,
        bool                    *exists)
{
        xfs_agino_t             low;
        xfs_agino_t             high;

        low = XFS_AGB_TO_AGINO(cur->bc_mp, bno);
        high = XFS_AGB_TO_AGINO(cur->bc_mp, bno + len) - 1;

        return xfs_ialloc_has_inode_record(cur, low, high, exists);
}

struct xfs_ialloc_count_inodes {
        xfs_agino_t                     count;
        xfs_agino_t                     freecount;
};

/* Record inode counts across all inobt records. */
STATIC int
xfs_ialloc_count_inodes_rec(
        struct xfs_btree_cur            *cur,
        const union xfs_btree_rec       *rec,
        void                            *priv)
{
        struct xfs_inobt_rec_incore     irec;
        struct xfs_ialloc_count_inodes  *ci = priv;

        xfs_inobt_btrec_to_irec(cur->bc_mp, rec, &irec);
        ci->count += irec.ir_count;
        ci->freecount += irec.ir_freecount;

        return 0;
}

/* Count allocated and free inodes under an inobt. */
int
xfs_ialloc_count_inodes(
        struct xfs_btree_cur            *cur,
        xfs_agino_t                     *count,
        xfs_agino_t                     *freecount)
{
        struct xfs_ialloc_count_inodes  ci = {0};
        int                             error;

        ASSERT(cur->bc_btnum == XFS_BTNUM_INO);
        error = xfs_btree_query_all(cur, xfs_ialloc_count_inodes_rec, &ci);
        if (error)
                return error;

        *count = ci.count;
        *freecount = ci.freecount;
        return 0;
}

/*
 * Initialize inode-related geometry information.
 *
 * Compute the inode btree min and max levels and set maxicount.
 *
 * Set the inode cluster size.  This may still be overridden by the file
 * system block size if it is larger than the chosen cluster size.
 *
 * For v5 filesystems, scale the cluster size with the inode size to keep a
 * constant ratio of inode per cluster buffer, but only if mkfs has set the
 * inode alignment value appropriately for larger cluster sizes.
 *
 * Then compute the inode cluster alignment information.
 */
void
xfs_ialloc_setup_geometry(
        struct xfs_mount        *mp)
{
        struct xfs_sb           *sbp = &mp->m_sb;
        struct xfs_ino_geometry *igeo = M_IGEO(mp);
        uint64_t                icount;
        uint                    inodes;

        igeo->new_diflags2 = 0;
        if (xfs_has_bigtime(mp))
                igeo->new_diflags2 |= XFS_DIFLAG2_BIGTIME;
        if (xfs_has_large_extent_counts(mp))
                igeo->new_diflags2 |= XFS_DIFLAG2_NREXT64;

        /* Compute inode btree geometry. */
        igeo->agino_log = sbp->sb_inopblog + sbp->sb_agblklog;
        igeo->inobt_mxr[0] = xfs_inobt_maxrecs(mp, sbp->sb_blocksize, 1);
        igeo->inobt_mxr[1] = xfs_inobt_maxrecs(mp, sbp->sb_blocksize, 0);
        igeo->inobt_mnr[0] = igeo->inobt_mxr[0] / 2;
        igeo->inobt_mnr[1] = igeo->inobt_mxr[1] / 2;

        igeo->ialloc_inos = max_t(uint16_t, XFS_INODES_PER_CHUNK,
                        sbp->sb_inopblock);
        igeo->ialloc_blks = igeo->ialloc_inos >> sbp->sb_inopblog;

        if (sbp->sb_spino_align)
                igeo->ialloc_min_blks = sbp->sb_spino_align;
        else
                igeo->ialloc_min_blks = igeo->ialloc_blks;

        /* Compute and fill in value of m_ino_geo.inobt_maxlevels. */
        inodes = (1LL << XFS_INO_AGINO_BITS(mp)) >> XFS_INODES_PER_CHUNK_LOG;
        igeo->inobt_maxlevels = xfs_btree_compute_maxlevels(igeo->inobt_mnr,
                        inodes);
        ASSERT(igeo->inobt_maxlevels <= xfs_iallocbt_maxlevels_ondisk());

        /*
         * Set the maximum inode count for this filesystem, being careful not
         * to use obviously garbage sb_inopblog/sb_inopblock values.  Regular
         * users should never get here due to failing sb verification, but
         * certain users (xfs_db) need to be usable even with corrupt metadata.
         */
        if (sbp->sb_imax_pct && igeo->ialloc_blks) {
                /*
                 * Make sure the maximum inode count is a multiple
                 * of the units we allocate inodes in.
                 */
                icount = sbp->sb_dblocks * sbp->sb_imax_pct;
                do_div(icount, 100);
                do_div(icount, igeo->ialloc_blks);
                igeo->maxicount = XFS_FSB_TO_INO(mp,
                                icount * igeo->ialloc_blks);
        } else {
                igeo->maxicount = 0;
        }

        /*
         * Compute the desired size of an inode cluster buffer size, which
         * starts at 8K and (on v5 filesystems) scales up with larger inode
         * sizes.
         *
         * Preserve the desired inode cluster size because the sparse inodes
         * feature uses that desired size (not the actual size) to compute the
         * sparse inode alignment.  The mount code validates this value, so we
         * cannot change the behavior.
         */
        igeo->inode_cluster_size_raw = XFS_INODE_BIG_CLUSTER_SIZE;
        if (xfs_has_v3inodes(mp)) {
                int     new_size = igeo->inode_cluster_size_raw;

                new_size *= mp->m_sb.sb_inodesize / XFS_DINODE_MIN_SIZE;
                if (mp->m_sb.sb_inoalignmt >= XFS_B_TO_FSBT(mp, new_size))
                        igeo->inode_cluster_size_raw = new_size;
        }

        /* Calculate inode cluster ratios. */
        if (igeo->inode_cluster_size_raw > mp->m_sb.sb_blocksize)
                igeo->blocks_per_cluster = XFS_B_TO_FSBT(mp,
                                igeo->inode_cluster_size_raw);
        else
                igeo->blocks_per_cluster = 1;
        igeo->inode_cluster_size = XFS_FSB_TO_B(mp, igeo->blocks_per_cluster);
        igeo->inodes_per_cluster = XFS_FSB_TO_INO(mp, igeo->blocks_per_cluster);

        /* Calculate inode cluster alignment. */
        if (xfs_has_align(mp) &&
            mp->m_sb.sb_inoalignmt >= igeo->blocks_per_cluster)
                igeo->cluster_align = mp->m_sb.sb_inoalignmt;
        else
                igeo->cluster_align = 1;
        igeo->inoalign_mask = igeo->cluster_align - 1;
        igeo->cluster_align_inodes = XFS_FSB_TO_INO(mp, igeo->cluster_align);

        /*
         * If we are using stripe alignment, check whether
         * the stripe unit is a multiple of the inode alignment
         */
        if (mp->m_dalign && igeo->inoalign_mask &&
            !(mp->m_dalign & igeo->inoalign_mask))
                igeo->ialloc_align = mp->m_dalign;
        else
                igeo->ialloc_align = 0;
}

/* Compute the location of the root directory inode that is laid out by mkfs. */
xfs_ino_t
xfs_ialloc_calc_rootino(
        struct xfs_mount        *mp,
        int                     sunit)
{
        struct xfs_ino_geometry *igeo = M_IGEO(mp);
        xfs_agblock_t           first_bno;

        /*
         * Pre-calculate the geometry of AG 0.  We know what it looks like
         * because libxfs knows how to create allocation groups now.
         *
         * first_bno is the first block in which mkfs could possibly have
         * allocated the root directory inode, once we factor in the metadata
         * that mkfs formats before it.  Namely, the four AG headers...
         */
        first_bno = howmany(4 * mp->m_sb.sb_sectsize, mp->m_sb.sb_blocksize);

        /* ...the two free space btree roots... */
        first_bno += 2;

        /* ...the inode btree root... */
        first_bno += 1;

        /* ...the initial AGFL... */
        first_bno += xfs_alloc_min_freelist(mp, NULL);

        /* ...the free inode btree root... */
        if (xfs_has_finobt(mp))
                first_bno++;

        /* ...the reverse mapping btree root... */
        if (xfs_has_rmapbt(mp))
                first_bno++;

        /* ...the reference count btree... */
        if (xfs_has_reflink(mp))
                first_bno++;

        /*
         * ...and the log, if it is allocated in the first allocation group.
         *
         * This can happen with filesystems that only have a single
         * allocation group, or very odd geometries created by old mkfs
         * versions on very small filesystems.
         */
        if (xfs_ag_contains_log(mp, 0))
                 first_bno += mp->m_sb.sb_logblocks;

        /*
         * Now round first_bno up to whatever allocation alignment is given
         * by the filesystem or was passed in.
         */
        if (xfs_has_dalign(mp) && igeo->ialloc_align > 0)
                first_bno = roundup(first_bno, sunit);
        else if (xfs_has_align(mp) &&
                        mp->m_sb.sb_inoalignmt > 1)
                first_bno = roundup(first_bno, mp->m_sb.sb_inoalignmt);

        return XFS_AGINO_TO_INO(mp, 0, XFS_AGB_TO_AGINO(mp, first_bno));
}

/*
 * Ensure there are not sparse inode clusters that cross the new EOAG.
 *
 * This is a no-op for non-spinode filesystems since clusters are always fully
 * allocated and checking the bnobt suffices.  However, a spinode filesystem
 * could have a record where the upper inodes are free blocks.  If those blocks
 * were removed from the filesystem, the inode record would extend beyond EOAG,
 * which will be flagged as corruption.
 */
int
xfs_ialloc_check_shrink(
        struct xfs_perag        *pag,
        struct xfs_trans        *tp,
        struct xfs_buf          *agibp,
        xfs_agblock_t           new_length)
{
        struct xfs_inobt_rec_incore rec;
        struct xfs_btree_cur    *cur;
        xfs_agino_t             agino;
        int                     has;
        int                     error;

        if (!xfs_has_sparseinodes(pag->pag_mount))
                return 0;

        cur = xfs_inobt_init_cursor(pag, tp, agibp, XFS_BTNUM_INO);

        /* Look up the inobt record that would correspond to the new EOFS. */
        agino = XFS_AGB_TO_AGINO(pag->pag_mount, new_length);
        error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_LE, &has);
        if (error || !has)
                goto out;

        error = xfs_inobt_get_rec(cur, &rec, &has);
        if (error)
                goto out;

        if (!has) {
                error = -EFSCORRUPTED;
                goto out;
        }

        /* If the record covers inodes that would be beyond EOFS, bail out. */
        if (rec.ir_startino + XFS_INODES_PER_CHUNK > agino) {
                error = -ENOSPC;
                goto out;
        }
out:
        xfs_btree_del_cursor(cur, error);
        return error;
}