[XFS] implement generic xfs_btree_update

[linux-2.6] / fs / xfs / xfs_alloc.c

/*
 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir2.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_alloc.h"
#include "xfs_error.h"


#define XFS_ABSDIFF(a,b)        (((a) <= (b)) ? ((b) - (a)) : ((a) - (b)))

#define XFSA_FIXUP_BNO_OK       1
#define XFSA_FIXUP_CNT_OK       2

STATIC void
xfs_alloc_search_busy(xfs_trans_t *tp,
                    xfs_agnumber_t agno,
                    xfs_agblock_t bno,
                    xfs_extlen_t len);

#if defined(XFS_ALLOC_TRACE)
ktrace_t *xfs_alloc_trace_buf;

#define TRACE_ALLOC(s,a)        \
        xfs_alloc_trace_alloc(__func__, s, a, __LINE__)
#define TRACE_FREE(s,a,b,x,f)   \
        xfs_alloc_trace_free(__func__, s, mp, a, b, x, f, __LINE__)
#define TRACE_MODAGF(s,a,f)     \
        xfs_alloc_trace_modagf(__func__, s, mp, a, f, __LINE__)
#define TRACE_BUSY(__func__,s,ag,agb,l,sl,tp)   \
        xfs_alloc_trace_busy(__func__, s, mp, ag, agb, l, sl, tp, XFS_ALLOC_KTRACE_BUSY, __LINE__)
#define TRACE_UNBUSY(__func__,s,ag,sl,tp)       \
        xfs_alloc_trace_busy(__func__, s, mp, ag, -1, -1, sl, tp, XFS_ALLOC_KTRACE_UNBUSY, __LINE__)
#define TRACE_BUSYSEARCH(__func__,s,ag,agb,l,tp)        \
        xfs_alloc_trace_busy(__func__, s, mp, ag, agb, l, 0, tp, XFS_ALLOC_KTRACE_BUSYSEARCH, __LINE__)
#else
#define TRACE_ALLOC(s,a)
#define TRACE_FREE(s,a,b,x,f)
#define TRACE_MODAGF(s,a,f)
#define TRACE_BUSY(s,a,ag,agb,l,sl,tp)
#define TRACE_UNBUSY(fname,s,ag,sl,tp)
#define TRACE_BUSYSEARCH(fname,s,ag,agb,l,tp)
#endif  /* XFS_ALLOC_TRACE */

/*
 * Prototypes for per-ag allocation routines
 */

STATIC int xfs_alloc_ag_vextent_exact(xfs_alloc_arg_t *);
STATIC int xfs_alloc_ag_vextent_near(xfs_alloc_arg_t *);
STATIC int xfs_alloc_ag_vextent_size(xfs_alloc_arg_t *);
STATIC int xfs_alloc_ag_vextent_small(xfs_alloc_arg_t *,
        xfs_btree_cur_t *, xfs_agblock_t *, xfs_extlen_t *, int *);

/*
 * Internal functions.
 */

/*
 * Lookup the record equal to [bno, len] in the btree given by cur.
 */
STATIC int                              /* error */
xfs_alloc_lookup_eq(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        xfs_agblock_t           bno,    /* starting block of extent */
        xfs_extlen_t            len,    /* length of extent */
        int                     *stat)  /* success/failure */
{
        cur->bc_rec.a.ar_startblock = bno;
        cur->bc_rec.a.ar_blockcount = len;
        return xfs_btree_lookup(cur, XFS_LOOKUP_EQ, stat);
}

/*
 * Lookup the first record greater than or equal to [bno, len]
 * in the btree given by cur.
 */
STATIC int                              /* error */
xfs_alloc_lookup_ge(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        xfs_agblock_t           bno,    /* starting block of extent */
        xfs_extlen_t            len,    /* length of extent */
        int                     *stat)  /* success/failure */
{
        cur->bc_rec.a.ar_startblock = bno;
        cur->bc_rec.a.ar_blockcount = len;
        return xfs_btree_lookup(cur, XFS_LOOKUP_GE, stat);
}

/*
 * Lookup the first record less than or equal to [bno, len]
 * in the btree given by cur.
 */
STATIC int                              /* error */
xfs_alloc_lookup_le(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        xfs_agblock_t           bno,    /* starting block of extent */
        xfs_extlen_t            len,    /* length of extent */
        int                     *stat)  /* success/failure */
{
        cur->bc_rec.a.ar_startblock = bno;
        cur->bc_rec.a.ar_blockcount = len;
        return xfs_btree_lookup(cur, XFS_LOOKUP_LE, stat);
}

/*
 * Update the record referred to by cur to the value given
 * by [bno, len].
 * This either works (return 0) or gets an EFSCORRUPTED error.
 */
STATIC int                              /* error */
xfs_alloc_update(
        struct xfs_btree_cur    *cur,   /* btree cursor */
        xfs_agblock_t           bno,    /* starting block of extent */
        xfs_extlen_t            len)    /* length of extent */
{
        union xfs_btree_rec     rec;

        rec.alloc.ar_startblock = cpu_to_be32(bno);
        rec.alloc.ar_blockcount = cpu_to_be32(len);
        return xfs_btree_update(cur, &rec);
}

/*
 * Compute aligned version of the found extent.
 * Takes alignment and min length into account.
 */
STATIC void
xfs_alloc_compute_aligned(
        xfs_agblock_t   foundbno,       /* starting block in found extent */
        xfs_extlen_t    foundlen,       /* length in found extent */
        xfs_extlen_t    alignment,      /* alignment for allocation */
        xfs_extlen_t    minlen,         /* minimum length for allocation */
        xfs_agblock_t   *resbno,        /* result block number */
        xfs_extlen_t    *reslen)        /* result length */
{
        xfs_agblock_t   bno;
        xfs_extlen_t    diff;
        xfs_extlen_t    len;

        if (alignment > 1 && foundlen >= minlen) {
                bno = roundup(foundbno, alignment);
                diff = bno - foundbno;
                len = diff >= foundlen ? 0 : foundlen - diff;
        } else {
                bno = foundbno;
                len = foundlen;
        }
        *resbno = bno;
        *reslen = len;
}

/*
 * Compute best start block and diff for "near" allocations.
 * freelen >= wantlen already checked by caller.
 */
STATIC xfs_extlen_t                     /* difference value (absolute) */
xfs_alloc_compute_diff(
        xfs_agblock_t   wantbno,        /* target starting block */
        xfs_extlen_t    wantlen,        /* target length */
        xfs_extlen_t    alignment,      /* target alignment */
        xfs_agblock_t   freebno,        /* freespace's starting block */
        xfs_extlen_t    freelen,        /* freespace's length */
        xfs_agblock_t   *newbnop)       /* result: best start block from free */
{
        xfs_agblock_t   freeend;        /* end of freespace extent */
        xfs_agblock_t   newbno1;        /* return block number */
        xfs_agblock_t   newbno2;        /* other new block number */
        xfs_extlen_t    newlen1=0;      /* length with newbno1 */
        xfs_extlen_t    newlen2=0;      /* length with newbno2 */
        xfs_agblock_t   wantend;        /* end of target extent */

        ASSERT(freelen >= wantlen);
        freeend = freebno + freelen;
        wantend = wantbno + wantlen;
        if (freebno >= wantbno) {
                if ((newbno1 = roundup(freebno, alignment)) >= freeend)
                        newbno1 = NULLAGBLOCK;
        } else if (freeend >= wantend && alignment > 1) {
                newbno1 = roundup(wantbno, alignment);
                newbno2 = newbno1 - alignment;
                if (newbno1 >= freeend)
                        newbno1 = NULLAGBLOCK;
                else
                        newlen1 = XFS_EXTLEN_MIN(wantlen, freeend - newbno1);
                if (newbno2 < freebno)
                        newbno2 = NULLAGBLOCK;
                else
                        newlen2 = XFS_EXTLEN_MIN(wantlen, freeend - newbno2);
                if (newbno1 != NULLAGBLOCK && newbno2 != NULLAGBLOCK) {
                        if (newlen1 < newlen2 ||
                            (newlen1 == newlen2 &&
                             XFS_ABSDIFF(newbno1, wantbno) >
                             XFS_ABSDIFF(newbno2, wantbno)))
                                newbno1 = newbno2;
                } else if (newbno2 != NULLAGBLOCK)
                        newbno1 = newbno2;
        } else if (freeend >= wantend) {
                newbno1 = wantbno;
        } else if (alignment > 1) {
                newbno1 = roundup(freeend - wantlen, alignment);
                if (newbno1 > freeend - wantlen &&
                    newbno1 - alignment >= freebno)
                        newbno1 -= alignment;
                else if (newbno1 >= freeend)
                        newbno1 = NULLAGBLOCK;
        } else
                newbno1 = freeend - wantlen;
        *newbnop = newbno1;
        return newbno1 == NULLAGBLOCK ? 0 : XFS_ABSDIFF(newbno1, wantbno);
}

/*
 * Fix up the length, based on mod and prod.
 * len should be k * prod + mod for some k.
 * If len is too small it is returned unchanged.
 * If len hits maxlen it is left alone.
 */
STATIC void
xfs_alloc_fix_len(
        xfs_alloc_arg_t *args)          /* allocation argument structure */
{
        xfs_extlen_t    k;
        xfs_extlen_t    rlen;

        ASSERT(args->mod < args->prod);
        rlen = args->len;
        ASSERT(rlen >= args->minlen);
        ASSERT(rlen <= args->maxlen);
        if (args->prod <= 1 || rlen < args->mod || rlen == args->maxlen ||
            (args->mod == 0 && rlen < args->prod))
                return;
        k = rlen % args->prod;
        if (k == args->mod)
                return;
        if (k > args->mod) {
                if ((int)(rlen = rlen - k - args->mod) < (int)args->minlen)
                        return;
        } else {
                if ((int)(rlen = rlen - args->prod - (args->mod - k)) <
                    (int)args->minlen)
                        return;
        }
        ASSERT(rlen >= args->minlen);
        ASSERT(rlen <= args->maxlen);
        args->len = rlen;
}

/*
 * Fix up length if there is too little space left in the a.g.
 * Return 1 if ok, 0 if too little, should give up.
 */
STATIC int
xfs_alloc_fix_minleft(
        xfs_alloc_arg_t *args)          /* allocation argument structure */
{
        xfs_agf_t       *agf;           /* a.g. freelist header */
        int             diff;           /* free space difference */

        if (args->minleft == 0)
                return 1;
        agf = XFS_BUF_TO_AGF(args->agbp);
        diff = be32_to_cpu(agf->agf_freeblks)
                + be32_to_cpu(agf->agf_flcount)
                - args->len - args->minleft;
        if (diff >= 0)
                return 1;
        args->len += diff;              /* shrink the allocated space */
        if (args->len >= args->minlen)
                return 1;
        args->agbno = NULLAGBLOCK;
        return 0;
}

/*
 * Update the two btrees, logically removing from freespace the extent
 * starting at rbno, rlen blocks.  The extent is contained within the
 * actual (current) free extent fbno for flen blocks.
 * Flags are passed in indicating whether the cursors are set to the
 * relevant records.
 */
STATIC int                              /* error code */
xfs_alloc_fixup_trees(
        xfs_btree_cur_t *cnt_cur,       /* cursor for by-size btree */
        xfs_btree_cur_t *bno_cur,       /* cursor for by-block btree */
        xfs_agblock_t   fbno,           /* starting block of free extent */
        xfs_extlen_t    flen,           /* length of free extent */
        xfs_agblock_t   rbno,           /* starting block of returned extent */
        xfs_extlen_t    rlen,           /* length of returned extent */
        int             flags)          /* flags, XFSA_FIXUP_... */
{
        int             error;          /* error code */
        int             i;              /* operation results */
        xfs_agblock_t   nfbno1;         /* first new free startblock */
        xfs_agblock_t   nfbno2;         /* second new free startblock */
        xfs_extlen_t    nflen1=0;       /* first new free length */
        xfs_extlen_t    nflen2=0;       /* second new free length */

        /*
         * Look up the record in the by-size tree if necessary.
         */
        if (flags & XFSA_FIXUP_CNT_OK) {
#ifdef DEBUG
                if ((error = xfs_alloc_get_rec(cnt_cur, &nfbno1, &nflen1, &i)))
                        return error;
                XFS_WANT_CORRUPTED_RETURN(
                        i == 1 && nfbno1 == fbno && nflen1 == flen);
#endif
        } else {
                if ((error = xfs_alloc_lookup_eq(cnt_cur, fbno, flen, &i)))
                        return error;
                XFS_WANT_CORRUPTED_RETURN(i == 1);
        }
        /*
         * Look up the record in the by-block tree if necessary.
         */
        if (flags & XFSA_FIXUP_BNO_OK) {
#ifdef DEBUG
                if ((error = xfs_alloc_get_rec(bno_cur, &nfbno1, &nflen1, &i)))
                        return error;
                XFS_WANT_CORRUPTED_RETURN(
                        i == 1 && nfbno1 == fbno && nflen1 == flen);
#endif
        } else {
                if ((error = xfs_alloc_lookup_eq(bno_cur, fbno, flen, &i)))
                        return error;
                XFS_WANT_CORRUPTED_RETURN(i == 1);
        }
#ifdef DEBUG
        {
                xfs_alloc_block_t       *bnoblock;
                xfs_alloc_block_t       *cntblock;

                if (bno_cur->bc_nlevels == 1 &&
                    cnt_cur->bc_nlevels == 1) {
                        bnoblock = XFS_BUF_TO_ALLOC_BLOCK(bno_cur->bc_bufs[0]);
                        cntblock = XFS_BUF_TO_ALLOC_BLOCK(cnt_cur->bc_bufs[0]);
                        XFS_WANT_CORRUPTED_RETURN(
                                be16_to_cpu(bnoblock->bb_numrecs) ==
                                be16_to_cpu(cntblock->bb_numrecs));
                }
        }
#endif
        /*
         * Deal with all four cases: the allocated record is contained
         * within the freespace record, so we can have new freespace
         * at either (or both) end, or no freespace remaining.
         */
        if (rbno == fbno && rlen == flen)
                nfbno1 = nfbno2 = NULLAGBLOCK;
        else if (rbno == fbno) {
                nfbno1 = rbno + rlen;
                nflen1 = flen - rlen;
                nfbno2 = NULLAGBLOCK;
        } else if (rbno + rlen == fbno + flen) {
                nfbno1 = fbno;
                nflen1 = flen - rlen;
                nfbno2 = NULLAGBLOCK;
        } else {
                nfbno1 = fbno;
                nflen1 = rbno - fbno;
                nfbno2 = rbno + rlen;
                nflen2 = (fbno + flen) - nfbno2;
        }
        /*
         * Delete the entry from the by-size btree.
         */
        if ((error = xfs_alloc_delete(cnt_cur, &i)))
                return error;
        XFS_WANT_CORRUPTED_RETURN(i == 1);
        /*
         * Add new by-size btree entry(s).
         */
        if (nfbno1 != NULLAGBLOCK) {
                if ((error = xfs_alloc_lookup_eq(cnt_cur, nfbno1, nflen1, &i)))
                        return error;
                XFS_WANT_CORRUPTED_RETURN(i == 0);
                if ((error = xfs_alloc_insert(cnt_cur, &i)))
                        return error;
                XFS_WANT_CORRUPTED_RETURN(i == 1);
        }
        if (nfbno2 != NULLAGBLOCK) {
                if ((error = xfs_alloc_lookup_eq(cnt_cur, nfbno2, nflen2, &i)))
                        return error;
                XFS_WANT_CORRUPTED_RETURN(i == 0);
                if ((error = xfs_alloc_insert(cnt_cur, &i)))
                        return error;
                XFS_WANT_CORRUPTED_RETURN(i == 1);
        }
        /*
         * Fix up the by-block btree entry(s).
         */
        if (nfbno1 == NULLAGBLOCK) {
                /*
                 * No remaining freespace, just delete the by-block tree entry.
                 */
                if ((error = xfs_alloc_delete(bno_cur, &i)))
                        return error;
                XFS_WANT_CORRUPTED_RETURN(i == 1);
        } else {
                /*
                 * Update the by-block entry to start later|be shorter.
                 */
                if ((error = xfs_alloc_update(bno_cur, nfbno1, nflen1)))
                        return error;
        }
        if (nfbno2 != NULLAGBLOCK) {
                /*
                 * 2 resulting free entries, need to add one.
                 */
                if ((error = xfs_alloc_lookup_eq(bno_cur, nfbno2, nflen2, &i)))
                        return error;
                XFS_WANT_CORRUPTED_RETURN(i == 0);
                if ((error = xfs_alloc_insert(bno_cur, &i)))
                        return error;
                XFS_WANT_CORRUPTED_RETURN(i == 1);
        }
        return 0;
}

/*
 * Read in the allocation group free block array.
 */
STATIC int                              /* error */
xfs_alloc_read_agfl(
        xfs_mount_t     *mp,            /* mount point structure */
        xfs_trans_t     *tp,            /* transaction pointer */
        xfs_agnumber_t  agno,           /* allocation group number */
        xfs_buf_t       **bpp)          /* buffer for the ag free block array */
{
        xfs_buf_t       *bp;            /* return value */
        int             error;

        ASSERT(agno != NULLAGNUMBER);
        error = xfs_trans_read_buf(
                        mp, tp, mp->m_ddev_targp,
                        XFS_AG_DADDR(mp, agno, XFS_AGFL_DADDR(mp)),
                        XFS_FSS_TO_BB(mp, 1), 0, &bp);
        if (error)
                return error;
        ASSERT(bp);
        ASSERT(!XFS_BUF_GETERROR(bp));
        XFS_BUF_SET_VTYPE_REF(bp, B_FS_AGFL, XFS_AGFL_REF);
        *bpp = bp;
        return 0;
}

#if defined(XFS_ALLOC_TRACE)
/*
 * Add an allocation trace entry for an alloc call.
 */
STATIC void
xfs_alloc_trace_alloc(
        const char      *name,          /* function tag string */
        char            *str,           /* additional string */
        xfs_alloc_arg_t *args,          /* allocation argument structure */
        int             line)           /* source line number */
{
        ktrace_enter(xfs_alloc_trace_buf,
                (void *)(__psint_t)(XFS_ALLOC_KTRACE_ALLOC | (line << 16)),
                (void *)name,
                (void *)str,
                (void *)args->mp,
                (void *)(__psunsigned_t)args->agno,
                (void *)(__psunsigned_t)args->agbno,
                (void *)(__psunsigned_t)args->minlen,
                (void *)(__psunsigned_t)args->maxlen,
                (void *)(__psunsigned_t)args->mod,
                (void *)(__psunsigned_t)args->prod,
                (void *)(__psunsigned_t)args->minleft,
                (void *)(__psunsigned_t)args->total,
                (void *)(__psunsigned_t)args->alignment,
                (void *)(__psunsigned_t)args->len,
                (void *)((((__psint_t)args->type) << 16) |
                         (__psint_t)args->otype),
                (void *)(__psint_t)((args->wasdel << 3) |
                                    (args->wasfromfl << 2) |
                                    (args->isfl << 1) |
                                    (args->userdata << 0)));
}

/*
 * Add an allocation trace entry for a free call.
 */
STATIC void
xfs_alloc_trace_free(
        const char      *name,          /* function tag string */
        char            *str,           /* additional string */
        xfs_mount_t     *mp,            /* file system mount point */
        xfs_agnumber_t  agno,           /* allocation group number */
        xfs_agblock_t   agbno,          /* a.g. relative block number */
        xfs_extlen_t    len,            /* length of extent */
        int             isfl,           /* set if is freelist allocation/free */
        int             line)           /* source line number */
{
        ktrace_enter(xfs_alloc_trace_buf,
                (void *)(__psint_t)(XFS_ALLOC_KTRACE_FREE | (line << 16)),
                (void *)name,
                (void *)str,
                (void *)mp,
                (void *)(__psunsigned_t)agno,
                (void *)(__psunsigned_t)agbno,
                (void *)(__psunsigned_t)len,
                (void *)(__psint_t)isfl,
                NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}

/*
 * Add an allocation trace entry for modifying an agf.
 */
STATIC void
xfs_alloc_trace_modagf(
        const char      *name,          /* function tag string */
        char            *str,           /* additional string */
        xfs_mount_t     *mp,            /* file system mount point */
        xfs_agf_t       *agf,           /* new agf value */
        int             flags,          /* logging flags for agf */
        int             line)           /* source line number */
{
        ktrace_enter(xfs_alloc_trace_buf,
                (void *)(__psint_t)(XFS_ALLOC_KTRACE_MODAGF | (line << 16)),
                (void *)name,
                (void *)str,
                (void *)mp,
                (void *)(__psint_t)flags,
                (void *)(__psunsigned_t)be32_to_cpu(agf->agf_seqno),
                (void *)(__psunsigned_t)be32_to_cpu(agf->agf_length),
                (void *)(__psunsigned_t)be32_to_cpu(agf->agf_roots[XFS_BTNUM_BNO]),
                (void *)(__psunsigned_t)be32_to_cpu(agf->agf_roots[XFS_BTNUM_CNT]),
                (void *)(__psunsigned_t)be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]),
                (void *)(__psunsigned_t)be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]),
                (void *)(__psunsigned_t)be32_to_cpu(agf->agf_flfirst),
                (void *)(__psunsigned_t)be32_to_cpu(agf->agf_fllast),
                (void *)(__psunsigned_t)be32_to_cpu(agf->agf_flcount),
                (void *)(__psunsigned_t)be32_to_cpu(agf->agf_freeblks),
                (void *)(__psunsigned_t)be32_to_cpu(agf->agf_longest));
}

STATIC void
xfs_alloc_trace_busy(
        const char      *name,          /* function tag string */
        char            *str,           /* additional string */
        xfs_mount_t     *mp,            /* file system mount point */
        xfs_agnumber_t  agno,           /* allocation group number */
        xfs_agblock_t   agbno,          /* a.g. relative block number */
        xfs_extlen_t    len,            /* length of extent */
        int             slot,           /* perag Busy slot */
        xfs_trans_t     *tp,
        int             trtype,         /* type: add, delete, search */
        int             line)           /* source line number */
{
        ktrace_enter(xfs_alloc_trace_buf,
                (void *)(__psint_t)(trtype | (line << 16)),
                (void *)name,
                (void *)str,
                (void *)mp,
                (void *)(__psunsigned_t)agno,
                (void *)(__psunsigned_t)agbno,
                (void *)(__psunsigned_t)len,
                (void *)(__psint_t)slot,
                (void *)tp,
                NULL, NULL, NULL, NULL, NULL, NULL, NULL);
}
#endif  /* XFS_ALLOC_TRACE */

/*
 * Allocation group level functions.
 */

/*
 * Allocate a variable extent in the allocation group agno.
 * Type and bno are used to determine where in the allocation group the
 * extent will start.
 * Extent's length (returned in *len) will be between minlen and maxlen,
 * and of the form k * prod + mod unless there's nothing that large.
 * Return the starting a.g. block, or NULLAGBLOCK if we can't do it.
 */
STATIC int                      /* error */
xfs_alloc_ag_vextent(
        xfs_alloc_arg_t *args)  /* argument structure for allocation */
{
        int             error=0;

        ASSERT(args->minlen > 0);
        ASSERT(args->maxlen > 0);
        ASSERT(args->minlen <= args->maxlen);
        ASSERT(args->mod < args->prod);
        ASSERT(args->alignment > 0);
        /*
         * Branch to correct routine based on the type.
         */
        args->wasfromfl = 0;
        switch (args->type) {
        case XFS_ALLOCTYPE_THIS_AG:
                error = xfs_alloc_ag_vextent_size(args);
                break;
        case XFS_ALLOCTYPE_NEAR_BNO:
                error = xfs_alloc_ag_vextent_near(args);
                break;
        case XFS_ALLOCTYPE_THIS_BNO:
                error = xfs_alloc_ag_vextent_exact(args);
                break;
        default:
                ASSERT(0);
                /* NOTREACHED */
        }
        if (error)
                return error;
        /*
         * If the allocation worked, need to change the agf structure
         * (and log it), and the superblock.
         */
        if (args->agbno != NULLAGBLOCK) {
                xfs_agf_t       *agf;   /* allocation group freelist header */
#ifdef XFS_ALLOC_TRACE
                xfs_mount_t     *mp = args->mp;
#endif
                long            slen = (long)args->len;

                ASSERT(args->len >= args->minlen && args->len <= args->maxlen);
                ASSERT(!(args->wasfromfl) || !args->isfl);
                ASSERT(args->agbno % args->alignment == 0);
                if (!(args->wasfromfl)) {

                        agf = XFS_BUF_TO_AGF(args->agbp);
                        be32_add_cpu(&agf->agf_freeblks, -(args->len));
                        xfs_trans_agblocks_delta(args->tp,
                                                 -((long)(args->len)));
                        args->pag->pagf_freeblks -= args->len;
                        ASSERT(be32_to_cpu(agf->agf_freeblks) <=
                                be32_to_cpu(agf->agf_length));
                        TRACE_MODAGF(NULL, agf, XFS_AGF_FREEBLKS);
                        xfs_alloc_log_agf(args->tp, args->agbp,
                                                XFS_AGF_FREEBLKS);
                        /* search the busylist for these blocks */
                        xfs_alloc_search_busy(args->tp, args->agno,
                                        args->agbno, args->len);
                }
                if (!args->isfl)
                        xfs_trans_mod_sb(args->tp,
                                args->wasdel ? XFS_TRANS_SB_RES_FDBLOCKS :
                                        XFS_TRANS_SB_FDBLOCKS, -slen);
                XFS_STATS_INC(xs_allocx);
                XFS_STATS_ADD(xs_allocb, args->len);
        }
        return 0;
}

/*
 * Allocate a variable extent at exactly agno/bno.
 * Extent's length (returned in *len) will be between minlen and maxlen,
 * and of the form k * prod + mod unless there's nothing that large.
 * Return the starting a.g. block (bno), or NULLAGBLOCK if we can't do it.
 */
STATIC int                      /* error */
xfs_alloc_ag_vextent_exact(
        xfs_alloc_arg_t *args)  /* allocation argument structure */
{
        xfs_btree_cur_t *bno_cur;/* by block-number btree cursor */
        xfs_btree_cur_t *cnt_cur;/* by count btree cursor */
        xfs_agblock_t   end;    /* end of allocated extent */
        int             error;
        xfs_agblock_t   fbno;   /* start block of found extent */
        xfs_agblock_t   fend;   /* end block of found extent */
        xfs_extlen_t    flen;   /* length of found extent */
        int             i;      /* success/failure of operation */
        xfs_agblock_t   maxend; /* end of maximal extent */
        xfs_agblock_t   minend; /* end of minimal extent */
        xfs_extlen_t    rlen;   /* length of returned extent */

        ASSERT(args->alignment == 1);
        /*
         * Allocate/initialize a cursor for the by-number freespace btree.
         */
        bno_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
                args->agno, XFS_BTNUM_BNO);
        /*
         * Lookup bno and minlen in the btree (minlen is irrelevant, really).
         * Look for the closest free block <= bno, it must contain bno
         * if any free block does.
         */
        if ((error = xfs_alloc_lookup_le(bno_cur, args->agbno, args->minlen, &i)))
                goto error0;
        if (!i) {
                /*
                 * Didn't find it, return null.
                 */
                xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
                args->agbno = NULLAGBLOCK;
                return 0;
        }
        /*
         * Grab the freespace record.
         */
        if ((error = xfs_alloc_get_rec(bno_cur, &fbno, &flen, &i)))
                goto error0;
        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
        ASSERT(fbno <= args->agbno);
        minend = args->agbno + args->minlen;
        maxend = args->agbno + args->maxlen;
        fend = fbno + flen;
        /*
         * Give up if the freespace isn't long enough for the minimum request.
         */
        if (fend < minend) {
                xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
                args->agbno = NULLAGBLOCK;
                return 0;
        }
        /*
         * End of extent will be smaller of the freespace end and the
         * maximal requested end.
         */
        end = XFS_AGBLOCK_MIN(fend, maxend);
        /*
         * Fix the length according to mod and prod if given.
         */
        args->len = end - args->agbno;
        xfs_alloc_fix_len(args);
        if (!xfs_alloc_fix_minleft(args)) {
                xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
                return 0;
        }
        rlen = args->len;
        ASSERT(args->agbno + rlen <= fend);
        end = args->agbno + rlen;
        /*
         * We are allocating agbno for rlen [agbno .. end]
         * Allocate/initialize a cursor for the by-size btree.
         */
        cnt_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
                args->agno, XFS_BTNUM_CNT);
        ASSERT(args->agbno + args->len <=
                be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
        if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur, fbno, flen,
                        args->agbno, args->len, XFSA_FIXUP_BNO_OK))) {
                xfs_btree_del_cursor(cnt_cur, XFS_BTREE_ERROR);
                goto error0;
        }
        xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
        xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
        TRACE_ALLOC("normal", args);
        args->wasfromfl = 0;
        return 0;

error0:
        xfs_btree_del_cursor(bno_cur, XFS_BTREE_ERROR);
        TRACE_ALLOC("error", args);
        return error;
}

/*
 * Allocate a variable extent near bno in the allocation group agno.
 * Extent's length (returned in len) will be between minlen and maxlen,
 * and of the form k * prod + mod unless there's nothing that large.
 * Return the starting a.g. block, or NULLAGBLOCK if we can't do it.
 */
STATIC int                              /* error */
xfs_alloc_ag_vextent_near(
        xfs_alloc_arg_t *args)          /* allocation argument structure */
{
        xfs_btree_cur_t *bno_cur_gt;    /* cursor for bno btree, right side */
        xfs_btree_cur_t *bno_cur_lt;    /* cursor for bno btree, left side */
        xfs_btree_cur_t *cnt_cur;       /* cursor for count btree */
        xfs_agblock_t   gtbno;          /* start bno of right side entry */
        xfs_agblock_t   gtbnoa;         /* aligned ... */
        xfs_extlen_t    gtdiff;         /* difference to right side entry */
        xfs_extlen_t    gtlen;          /* length of right side entry */
        xfs_extlen_t    gtlena;         /* aligned ... */
        xfs_agblock_t   gtnew;          /* useful start bno of right side */
        int             error;          /* error code */
        int             i;              /* result code, temporary */
        int             j;              /* result code, temporary */
        xfs_agblock_t   ltbno;          /* start bno of left side entry */
        xfs_agblock_t   ltbnoa;         /* aligned ... */
        xfs_extlen_t    ltdiff;         /* difference to left side entry */
        /*REFERENCED*/
        xfs_agblock_t   ltend;          /* end bno of left side entry */
        xfs_extlen_t    ltlen;          /* length of left side entry */
        xfs_extlen_t    ltlena;         /* aligned ... */
        xfs_agblock_t   ltnew;          /* useful start bno of left side */
        xfs_extlen_t    rlen;           /* length of returned extent */
#if defined(DEBUG) && defined(__KERNEL__)
        /*
         * Randomly don't execute the first algorithm.
         */
        int             dofirst;        /* set to do first algorithm */

        dofirst = random32() & 1;
#endif
        /*
         * Get a cursor for the by-size btree.
         */
        cnt_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
                args->agno, XFS_BTNUM_CNT);
        ltlen = 0;
        bno_cur_lt = bno_cur_gt = NULL;
        /*
         * See if there are any free extents as big as maxlen.
         */
        if ((error = xfs_alloc_lookup_ge(cnt_cur, 0, args->maxlen, &i)))
                goto error0;
        /*
         * If none, then pick up the last entry in the tree unless the
         * tree is empty.
         */
        if (!i) {
                if ((error = xfs_alloc_ag_vextent_small(args, cnt_cur, &ltbno,
                                &ltlen, &i)))
                        goto error0;
                if (i == 0 || ltlen == 0) {
                        xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
                        return 0;
                }
                ASSERT(i == 1);
        }
        args->wasfromfl = 0;
        /*
         * First algorithm.
         * If the requested extent is large wrt the freespaces available
         * in this a.g., then the cursor will be pointing to a btree entry
         * near the right edge of the tree.  If it's in the last btree leaf
         * block, then we just examine all the entries in that block
         * that are big enough, and pick the best one.
         * This is written as a while loop so we can break out of it,
         * but we never loop back to the top.
         */
        while (xfs_btree_islastblock(cnt_cur, 0)) {
                xfs_extlen_t    bdiff;
                int             besti=0;
                xfs_extlen_t    blen=0;
                xfs_agblock_t   bnew=0;

#if defined(DEBUG) && defined(__KERNEL__)
                if (!dofirst)
                        break;
#endif
                /*
                 * Start from the entry that lookup found, sequence through
                 * all larger free blocks.  If we're actually pointing at a
                 * record smaller than maxlen, go to the start of this block,
                 * and skip all those smaller than minlen.
                 */
                if (ltlen || args->alignment > 1) {
                        cnt_cur->bc_ptrs[0] = 1;
                        do {
                                if ((error = xfs_alloc_get_rec(cnt_cur, &ltbno,
                                                &ltlen, &i)))
                                        goto error0;
                                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                                if (ltlen >= args->minlen)
                                        break;
                                if ((error = xfs_btree_increment(cnt_cur, 0, &i)))
                                        goto error0;
                        } while (i);
                        ASSERT(ltlen >= args->minlen);
                        if (!i)
                                break;
                }
                i = cnt_cur->bc_ptrs[0];
                for (j = 1, blen = 0, bdiff = 0;
                     !error && j && (blen < args->maxlen || bdiff > 0);
                     error = xfs_btree_increment(cnt_cur, 0, &j)) {
                        /*
                         * For each entry, decide if it's better than
                         * the previous best entry.
                         */
                        if ((error = xfs_alloc_get_rec(cnt_cur, &ltbno, &ltlen, &i)))
                                goto error0;
                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                        xfs_alloc_compute_aligned(ltbno, ltlen, args->alignment,
                                        args->minlen, &ltbnoa, &ltlena);
                        if (ltlena < args->minlen)
                                continue;
                        args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
                        xfs_alloc_fix_len(args);
                        ASSERT(args->len >= args->minlen);
                        if (args->len < blen)
                                continue;
                        ltdiff = xfs_alloc_compute_diff(args->agbno, args->len,
                                args->alignment, ltbno, ltlen, &ltnew);
                        if (ltnew != NULLAGBLOCK &&
                            (args->len > blen || ltdiff < bdiff)) {
                                bdiff = ltdiff;
                                bnew = ltnew;
                                blen = args->len;
                                besti = cnt_cur->bc_ptrs[0];
                        }
                }
                /*
                 * It didn't work.  We COULD be in a case where
                 * there's a good record somewhere, so try again.
                 */
                if (blen == 0)
                        break;
                /*
                 * Point at the best entry, and retrieve it again.
                 */
                cnt_cur->bc_ptrs[0] = besti;
                if ((error = xfs_alloc_get_rec(cnt_cur, &ltbno, &ltlen, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                ltend = ltbno + ltlen;
                ASSERT(ltend <= be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
                args->len = blen;
                if (!xfs_alloc_fix_minleft(args)) {
                        xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
                        TRACE_ALLOC("nominleft", args);
                        return 0;
                }
                blen = args->len;
                /*
                 * We are allocating starting at bnew for blen blocks.
                 */
                args->agbno = bnew;
                ASSERT(bnew >= ltbno);
                ASSERT(bnew + blen <= ltend);
                /*
                 * Set up a cursor for the by-bno tree.
                 */
                bno_cur_lt = xfs_allocbt_init_cursor(args->mp, args->tp,
                        args->agbp, args->agno, XFS_BTNUM_BNO);
                /*
                 * Fix up the btree entries.
                 */
                if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur_lt, ltbno,
                                ltlen, bnew, blen, XFSA_FIXUP_CNT_OK)))
                        goto error0;
                xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
                xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
                TRACE_ALLOC("first", args);
                return 0;
        }
        /*
         * Second algorithm.
         * Search in the by-bno tree to the left and to the right
         * simultaneously, until in each case we find a space big enough,
         * or run into the edge of the tree.  When we run into the edge,
         * we deallocate that cursor.
         * If both searches succeed, we compare the two spaces and pick
         * the better one.
         * With alignment, it's possible for both to fail; the upper
         * level algorithm that picks allocation groups for allocations
         * is not supposed to do this.
         */
        /*
         * Allocate and initialize the cursor for the leftward search.
         */
        bno_cur_lt = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
                args->agno, XFS_BTNUM_BNO);
        /*
         * Lookup <= bno to find the leftward search's starting point.
         */
        if ((error = xfs_alloc_lookup_le(bno_cur_lt, args->agbno, args->maxlen, &i)))
                goto error0;
        if (!i) {
                /*
                 * Didn't find anything; use this cursor for the rightward
                 * search.
                 */
                bno_cur_gt = bno_cur_lt;
                bno_cur_lt = NULL;
        }
        /*
         * Found something.  Duplicate the cursor for the rightward search.
         */
        else if ((error = xfs_btree_dup_cursor(bno_cur_lt, &bno_cur_gt)))
                goto error0;
        /*
         * Increment the cursor, so we will point at the entry just right
         * of the leftward entry if any, or to the leftmost entry.
         */
        if ((error = xfs_btree_increment(bno_cur_gt, 0, &i)))
                goto error0;
        if (!i) {
                /*
                 * It failed, there are no rightward entries.
                 */
                xfs_btree_del_cursor(bno_cur_gt, XFS_BTREE_NOERROR);
                bno_cur_gt = NULL;
        }
        /*
         * Loop going left with the leftward cursor, right with the
         * rightward cursor, until either both directions give up or
         * we find an entry at least as big as minlen.
         */
        do {
                if (bno_cur_lt) {
                        if ((error = xfs_alloc_get_rec(bno_cur_lt, &ltbno, &ltlen, &i)))
                                goto error0;
                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                        xfs_alloc_compute_aligned(ltbno, ltlen, args->alignment,
                                        args->minlen, &ltbnoa, &ltlena);
                        if (ltlena >= args->minlen)
                                break;
                        if ((error = xfs_btree_decrement(bno_cur_lt, 0, &i)))
                                goto error0;
                        if (!i) {
                                xfs_btree_del_cursor(bno_cur_lt,
                                                     XFS_BTREE_NOERROR);
                                bno_cur_lt = NULL;
                        }
                }
                if (bno_cur_gt) {
                        if ((error = xfs_alloc_get_rec(bno_cur_gt, &gtbno, &gtlen, &i)))
                                goto error0;
                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                        xfs_alloc_compute_aligned(gtbno, gtlen, args->alignment,
                                        args->minlen, &gtbnoa, &gtlena);
                        if (gtlena >= args->minlen)
                                break;
                        if ((error = xfs_btree_increment(bno_cur_gt, 0, &i)))
                                goto error0;
                        if (!i) {
                                xfs_btree_del_cursor(bno_cur_gt,
                                                     XFS_BTREE_NOERROR);
                                bno_cur_gt = NULL;
                        }
                }
        } while (bno_cur_lt || bno_cur_gt);
        /*
         * Got both cursors still active, need to find better entry.
         */
        if (bno_cur_lt && bno_cur_gt) {
                /*
                 * Left side is long enough, look for a right side entry.
                 */
                if (ltlena >= args->minlen) {
                        /*
                         * Fix up the length.
                         */
                        args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
                        xfs_alloc_fix_len(args);
                        rlen = args->len;
                        ltdiff = xfs_alloc_compute_diff(args->agbno, rlen,
                                args->alignment, ltbno, ltlen, &ltnew);
                        /*
                         * Not perfect.
                         */
                        if (ltdiff) {
                                /*
                                 * Look until we find a better one, run out of
                                 * space, or run off the end.
                                 */
                                while (bno_cur_lt && bno_cur_gt) {
                                        if ((error = xfs_alloc_get_rec(
                                                        bno_cur_gt, &gtbno,
                                                        &gtlen, &i)))
                                                goto error0;
                                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                                        xfs_alloc_compute_aligned(gtbno, gtlen,
                                                args->alignment, args->minlen,
                                                &gtbnoa, &gtlena);
                                        /*
                                         * The left one is clearly better.
                                         */
                                        if (gtbnoa >= args->agbno + ltdiff) {
                                                xfs_btree_del_cursor(
                                                        bno_cur_gt,
                                                        XFS_BTREE_NOERROR);
                                                bno_cur_gt = NULL;
                                                break;
                                        }
                                        /*
                                         * If we reach a big enough entry,
                                         * compare the two and pick the best.
                                         */
                                        if (gtlena >= args->minlen) {
                                                args->len =
                                                        XFS_EXTLEN_MIN(gtlena,
                                                                args->maxlen);
                                                xfs_alloc_fix_len(args);
                                                rlen = args->len;
                                                gtdiff = xfs_alloc_compute_diff(
                                                        args->agbno, rlen,
                                                        args->alignment,
                                                        gtbno, gtlen, &gtnew);
                                                /*
                                                 * Right side is better.
                                                 */
                                                if (gtdiff < ltdiff) {
                                                        xfs_btree_del_cursor(
                                                                bno_cur_lt,
                                                                XFS_BTREE_NOERROR);
                                                        bno_cur_lt = NULL;
                                                }
                                                /*
                                                 * Left side is better.
                                                 */
                                                else {
                                                        xfs_btree_del_cursor(
                                                                bno_cur_gt,
                                                                XFS_BTREE_NOERROR);
                                                        bno_cur_gt = NULL;
                                                }
                                                break;
                                        }
                                        /*
                                         * Fell off the right end.
                                         */
                                        if ((error = xfs_btree_increment(
                                                        bno_cur_gt, 0, &i)))
                                                goto error0;
                                        if (!i) {
                                                xfs_btree_del_cursor(
                                                        bno_cur_gt,
                                                        XFS_BTREE_NOERROR);
                                                bno_cur_gt = NULL;
                                                break;
                                        }
                                }
                        }
                        /*
                         * The left side is perfect, trash the right side.
                         */
                        else {
                                xfs_btree_del_cursor(bno_cur_gt,
                                                     XFS_BTREE_NOERROR);
                                bno_cur_gt = NULL;
                        }
                }
                /*
                 * It's the right side that was found first, look left.
                 */
                else {
                        /*
                         * Fix up the length.
                         */
                        args->len = XFS_EXTLEN_MIN(gtlena, args->maxlen);
                        xfs_alloc_fix_len(args);
                        rlen = args->len;
                        gtdiff = xfs_alloc_compute_diff(args->agbno, rlen,
                                args->alignment, gtbno, gtlen, &gtnew);
                        /*
                         * Right side entry isn't perfect.
                         */
                        if (gtdiff) {
                                /*
                                 * Look until we find a better one, run out of
                                 * space, or run off the end.
                                 */
                                while (bno_cur_lt && bno_cur_gt) {
                                        if ((error = xfs_alloc_get_rec(
                                                        bno_cur_lt, &ltbno,
                                                        &ltlen, &i)))
                                                goto error0;
                                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                                        xfs_alloc_compute_aligned(ltbno, ltlen,
                                                args->alignment, args->minlen,
                                                &ltbnoa, &ltlena);
                                        /*
                                         * The right one is clearly better.
                                         */
                                        if (ltbnoa <= args->agbno - gtdiff) {
                                                xfs_btree_del_cursor(
                                                        bno_cur_lt,
                                                        XFS_BTREE_NOERROR);
                                                bno_cur_lt = NULL;
                                                break;
                                        }
                                        /*
                                         * If we reach a big enough entry,
                                         * compare the two and pick the best.
                                         */
                                        if (ltlena >= args->minlen) {
                                                args->len = XFS_EXTLEN_MIN(
                                                        ltlena, args->maxlen);
                                                xfs_alloc_fix_len(args);
                                                rlen = args->len;
                                                ltdiff = xfs_alloc_compute_diff(
                                                        args->agbno, rlen,
                                                        args->alignment,
                                                        ltbno, ltlen, &ltnew);
                                                /*
                                                 * Left side is better.
                                                 */
                                                if (ltdiff < gtdiff) {
                                                        xfs_btree_del_cursor(
                                                                bno_cur_gt,
                                                                XFS_BTREE_NOERROR);
                                                        bno_cur_gt = NULL;
                                                }
                                                /*
                                                 * Right side is better.
                                                 */
                                                else {
                                                        xfs_btree_del_cursor(
                                                                bno_cur_lt,
                                                                XFS_BTREE_NOERROR);
                                                        bno_cur_lt = NULL;
                                                }
                                                break;
                                        }
                                        /*
                                         * Fell off the left end.
                                         */
                                        if ((error = xfs_btree_decrement(
                                                        bno_cur_lt, 0, &i)))
                                                goto error0;
                                        if (!i) {
                                                xfs_btree_del_cursor(bno_cur_lt,
                                                        XFS_BTREE_NOERROR);
                                                bno_cur_lt = NULL;
                                                break;
                                        }
                                }
                        }
                        /*
                         * The right side is perfect, trash the left side.
                         */
                        else {
                                xfs_btree_del_cursor(bno_cur_lt,
                                        XFS_BTREE_NOERROR);
                                bno_cur_lt = NULL;
                        }
                }
        }
        /*
         * If we couldn't get anything, give up.
         */
        if (bno_cur_lt == NULL && bno_cur_gt == NULL) {
                TRACE_ALLOC("neither", args);
                args->agbno = NULLAGBLOCK;
                return 0;
        }
        /*
         * At this point we have selected a freespace entry, either to the
         * left or to the right.  If it's on the right, copy all the
         * useful variables to the "left" set so we only have one
         * copy of this code.
         */
        if (bno_cur_gt) {
                bno_cur_lt = bno_cur_gt;
                bno_cur_gt = NULL;
                ltbno = gtbno;
                ltbnoa = gtbnoa;
                ltlen = gtlen;
                ltlena = gtlena;
                j = 1;
        } else
                j = 0;
        /*
         * Fix up the length and compute the useful address.
         */
        ltend = ltbno + ltlen;
        args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
        xfs_alloc_fix_len(args);
        if (!xfs_alloc_fix_minleft(args)) {
                TRACE_ALLOC("nominleft", args);
                xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
                xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
                return 0;
        }
        rlen = args->len;
        (void)xfs_alloc_compute_diff(args->agbno, rlen, args->alignment, ltbno,
                ltlen, &ltnew);
        ASSERT(ltnew >= ltbno);
        ASSERT(ltnew + rlen <= ltend);
        ASSERT(ltnew + rlen <= be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
        args->agbno = ltnew;
        if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur_lt, ltbno, ltlen,
                        ltnew, rlen, XFSA_FIXUP_BNO_OK)))
                goto error0;
        TRACE_ALLOC(j ? "gt" : "lt", args);
        xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
        xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
        return 0;

 error0:
        TRACE_ALLOC("error", args);
        if (cnt_cur != NULL)
                xfs_btree_del_cursor(cnt_cur, XFS_BTREE_ERROR);
        if (bno_cur_lt != NULL)
                xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_ERROR);
        if (bno_cur_gt != NULL)
                xfs_btree_del_cursor(bno_cur_gt, XFS_BTREE_ERROR);
        return error;
}

/*
 * Allocate a variable extent anywhere in the allocation group agno.
 * Extent's length (returned in len) will be between minlen and maxlen,
 * and of the form k * prod + mod unless there's nothing that large.
 * Return the starting a.g. block, or NULLAGBLOCK if we can't do it.
 */
STATIC int                              /* error */
xfs_alloc_ag_vextent_size(
        xfs_alloc_arg_t *args)          /* allocation argument structure */
{
        xfs_btree_cur_t *bno_cur;       /* cursor for bno btree */
        xfs_btree_cur_t *cnt_cur;       /* cursor for cnt btree */
        int             error;          /* error result */
        xfs_agblock_t   fbno;           /* start of found freespace */
        xfs_extlen_t    flen;           /* length of found freespace */
        int             i;              /* temp status variable */
        xfs_agblock_t   rbno;           /* returned block number */
        xfs_extlen_t    rlen;           /* length of returned extent */

        /*
         * Allocate and initialize a cursor for the by-size btree.
         */
        cnt_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
                args->agno, XFS_BTNUM_CNT);
        bno_cur = NULL;
        /*
         * Look for an entry >= maxlen+alignment-1 blocks.
         */
        if ((error = xfs_alloc_lookup_ge(cnt_cur, 0,
                        args->maxlen + args->alignment - 1, &i)))
                goto error0;
        /*
         * If none, then pick up the last entry in the tree unless the
         * tree is empty.
         */
        if (!i) {
                if ((error = xfs_alloc_ag_vextent_small(args, cnt_cur, &fbno,
                                &flen, &i)))
                        goto error0;
                if (i == 0 || flen == 0) {
                        xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
                        TRACE_ALLOC("noentry", args);
                        return 0;
                }
                ASSERT(i == 1);
        }
        /*
         * There's a freespace as big as maxlen+alignment-1, get it.
         */
        else {
                if ((error = xfs_alloc_get_rec(cnt_cur, &fbno, &flen, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
        }
        /*
         * In the first case above, we got the last entry in the
         * by-size btree.  Now we check to see if the space hits maxlen
         * once aligned; if not, we search left for something better.
         * This can't happen in the second case above.
         */
        xfs_alloc_compute_aligned(fbno, flen, args->alignment, args->minlen,
                &rbno, &rlen);
        rlen = XFS_EXTLEN_MIN(args->maxlen, rlen);
        XFS_WANT_CORRUPTED_GOTO(rlen == 0 ||
                        (rlen <= flen && rbno + rlen <= fbno + flen), error0);
        if (rlen < args->maxlen) {
                xfs_agblock_t   bestfbno;
                xfs_extlen_t    bestflen;
                xfs_agblock_t   bestrbno;
                xfs_extlen_t    bestrlen;

                bestrlen = rlen;
                bestrbno = rbno;
                bestflen = flen;
                bestfbno = fbno;
                for (;;) {
                        if ((error = xfs_btree_decrement(cnt_cur, 0, &i)))
                                goto error0;
                        if (i == 0)
                                break;
                        if ((error = xfs_alloc_get_rec(cnt_cur, &fbno, &flen,
                                        &i)))
                                goto error0;
                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                        if (flen < bestrlen)
                                break;
                        xfs_alloc_compute_aligned(fbno, flen, args->alignment,
                                args->minlen, &rbno, &rlen);
                        rlen = XFS_EXTLEN_MIN(args->maxlen, rlen);
                        XFS_WANT_CORRUPTED_GOTO(rlen == 0 ||
                                (rlen <= flen && rbno + rlen <= fbno + flen),
                                error0);
                        if (rlen > bestrlen) {
                                bestrlen = rlen;
                                bestrbno = rbno;
                                bestflen = flen;
                                bestfbno = fbno;
                                if (rlen == args->maxlen)
                                        break;
                        }
                }
                if ((error = xfs_alloc_lookup_eq(cnt_cur, bestfbno, bestflen,
                                &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                rlen = bestrlen;
                rbno = bestrbno;
                flen = bestflen;
                fbno = bestfbno;
        }
        args->wasfromfl = 0;
        /*
         * Fix up the length.
         */
        args->len = rlen;
        xfs_alloc_fix_len(args);
        if (rlen < args->minlen || !xfs_alloc_fix_minleft(args)) {
                xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
                TRACE_ALLOC("nominleft", args);
                args->agbno = NULLAGBLOCK;
                return 0;
        }
        rlen = args->len;
        XFS_WANT_CORRUPTED_GOTO(rlen <= flen, error0);
        /*
         * Allocate and initialize a cursor for the by-block tree.
         */
        bno_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
                args->agno, XFS_BTNUM_BNO);
        if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur, fbno, flen,
                        rbno, rlen, XFSA_FIXUP_CNT_OK)))
                goto error0;
        xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
        xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
        cnt_cur = bno_cur = NULL;
        args->len = rlen;
        args->agbno = rbno;
        XFS_WANT_CORRUPTED_GOTO(
                args->agbno + args->len <=
                        be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length),
                error0);
        TRACE_ALLOC("normal", args);
        return 0;

error0:
        TRACE_ALLOC("error", args);
        if (cnt_cur)
                xfs_btree_del_cursor(cnt_cur, XFS_BTREE_ERROR);
        if (bno_cur)
                xfs_btree_del_cursor(bno_cur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Deal with the case where only small freespaces remain.
 * Either return the contents of the last freespace record,
 * or allocate space from the freelist if there is nothing in the tree.
 */
STATIC int                      /* error */
xfs_alloc_ag_vextent_small(
        xfs_alloc_arg_t *args,  /* allocation argument structure */
        xfs_btree_cur_t *ccur,  /* by-size cursor */
        xfs_agblock_t   *fbnop, /* result block number */
        xfs_extlen_t    *flenp, /* result length */
        int             *stat)  /* status: 0-freelist, 1-normal/none */
{
        int             error;
        xfs_agblock_t   fbno;
        xfs_extlen_t    flen;
        int             i;

        if ((error = xfs_btree_decrement(ccur, 0, &i)))
                goto error0;
        if (i) {
                if ((error = xfs_alloc_get_rec(ccur, &fbno, &flen, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
        }
        /*
         * Nothing in the btree, try the freelist.  Make sure
         * to respect minleft even when pulling from the
         * freelist.
         */
        else if (args->minlen == 1 && args->alignment == 1 && !args->isfl &&
                 (be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_flcount)
                  > args->minleft)) {
                error = xfs_alloc_get_freelist(args->tp, args->agbp, &fbno, 0);
                if (error)
                        goto error0;
                if (fbno != NULLAGBLOCK) {
                        if (args->userdata) {
                                xfs_buf_t       *bp;

                                bp = xfs_btree_get_bufs(args->mp, args->tp,
                                        args->agno, fbno, 0);
                                xfs_trans_binval(args->tp, bp);
                        }
                        args->len = 1;
                        args->agbno = fbno;
                        XFS_WANT_CORRUPTED_GOTO(
                                args->agbno + args->len <=
                                be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length),
                                error0);
                        args->wasfromfl = 1;
                        TRACE_ALLOC("freelist", args);
                        *stat = 0;
                        return 0;
                }
                /*
                 * Nothing in the freelist.
                 */
                else
                        flen = 0;
        }
        /*
         * Can't allocate from the freelist for some reason.
         */
        else {
                fbno = NULLAGBLOCK;
                flen = 0;
        }
        /*
         * Can't do the allocation, give up.
         */
        if (flen < args->minlen) {
                args->agbno = NULLAGBLOCK;
                TRACE_ALLOC("notenough", args);
                flen = 0;
        }
        *fbnop = fbno;
        *flenp = flen;
        *stat = 1;
        TRACE_ALLOC("normal", args);
        return 0;

error0:
        TRACE_ALLOC("error", args);
        return error;
}

/*
 * Free the extent starting at agno/bno for length.
 */
STATIC int                      /* error */
xfs_free_ag_extent(
        xfs_trans_t     *tp,    /* transaction pointer */
        xfs_buf_t       *agbp,  /* buffer for a.g. freelist header */
        xfs_agnumber_t  agno,   /* allocation group number */
        xfs_agblock_t   bno,    /* starting block number */
        xfs_extlen_t    len,    /* length of extent */
        int             isfl)   /* set if is freelist blocks - no sb acctg */
{
        xfs_btree_cur_t *bno_cur;       /* cursor for by-block btree */
        xfs_btree_cur_t *cnt_cur;       /* cursor for by-size btree */
        int             error;          /* error return value */
        xfs_agblock_t   gtbno;          /* start of right neighbor block */
        xfs_extlen_t    gtlen;          /* length of right neighbor block */
        int             haveleft;       /* have a left neighbor block */
        int             haveright;      /* have a right neighbor block */
        int             i;              /* temp, result code */
        xfs_agblock_t   ltbno;          /* start of left neighbor block */
        xfs_extlen_t    ltlen;          /* length of left neighbor block */
        xfs_mount_t     *mp;            /* mount point struct for filesystem */
        xfs_agblock_t   nbno;           /* new starting block of freespace */
        xfs_extlen_t    nlen;           /* new length of freespace */

        mp = tp->t_mountp;
        /*
         * Allocate and initialize a cursor for the by-block btree.
         */
        bno_cur = xfs_allocbt_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_BNO);
        cnt_cur = NULL;
        /*
         * Look for a neighboring block on the left (lower block numbers)
         * that is contiguous with this space.
         */
        if ((error = xfs_alloc_lookup_le(bno_cur, bno, len, &haveleft)))
                goto error0;
        if (haveleft) {
                /*
                 * There is a block to our left.
                 */
                if ((error = xfs_alloc_get_rec(bno_cur, &ltbno, &ltlen, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                /*
                 * It's not contiguous, though.
                 */
                if (ltbno + ltlen < bno)
                        haveleft = 0;
                else {
                        /*
                         * If this failure happens the request to free this
                         * space was invalid, it's (partly) already free.
                         * Very bad.
                         */
                        XFS_WANT_CORRUPTED_GOTO(ltbno + ltlen <= bno, error0);
                }
        }
        /*
         * Look for a neighboring block on the right (higher block numbers)
         * that is contiguous with this space.
         */
        if ((error = xfs_btree_increment(bno_cur, 0, &haveright)))
                goto error0;
        if (haveright) {
                /*
                 * There is a block to our right.
                 */
                if ((error = xfs_alloc_get_rec(bno_cur, &gtbno, &gtlen, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                /*
                 * It's not contiguous, though.
                 */
                if (bno + len < gtbno)
                        haveright = 0;
                else {
                        /*
                         * If this failure happens the request to free this
                         * space was invalid, it's (partly) already free.
                         * Very bad.
                         */
                        XFS_WANT_CORRUPTED_GOTO(gtbno >= bno + len, error0);
                }
        }
        /*
         * Now allocate and initialize a cursor for the by-size tree.
         */
        cnt_cur = xfs_allocbt_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_CNT);
        /*
         * Have both left and right contiguous neighbors.
         * Merge all three into a single free block.
         */
        if (haveleft && haveright) {
                /*
                 * Delete the old by-size entry on the left.
                 */
                if ((error = xfs_alloc_lookup_eq(cnt_cur, ltbno, ltlen, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                if ((error = xfs_alloc_delete(cnt_cur, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                /*
                 * Delete the old by-size entry on the right.
                 */
                if ((error = xfs_alloc_lookup_eq(cnt_cur, gtbno, gtlen, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                if ((error = xfs_alloc_delete(cnt_cur, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                /*
                 * Delete the old by-block entry for the right block.
                 */
                if ((error = xfs_alloc_delete(bno_cur, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                /*
                 * Move the by-block cursor back to the left neighbor.
                 */
                if ((error = xfs_btree_decrement(bno_cur, 0, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
#ifdef DEBUG
                /*
                 * Check that this is the right record: delete didn't
                 * mangle the cursor.
                 */
                {
                        xfs_agblock_t   xxbno;
                        xfs_extlen_t    xxlen;

                        if ((error = xfs_alloc_get_rec(bno_cur, &xxbno, &xxlen,
                                        &i)))
                                goto error0;
                        XFS_WANT_CORRUPTED_GOTO(
                                i == 1 && xxbno == ltbno && xxlen == ltlen,
                                error0);
                }
#endif
                /*
                 * Update remaining by-block entry to the new, joined block.
                 */
                nbno = ltbno;
                nlen = len + ltlen + gtlen;
                if ((error = xfs_alloc_update(bno_cur, nbno, nlen)))
                        goto error0;
        }
        /*
         * Have only a left contiguous neighbor.
         * Merge it together with the new freespace.
         */
        else if (haveleft) {
                /*
                 * Delete the old by-size entry on the left.
                 */
                if ((error = xfs_alloc_lookup_eq(cnt_cur, ltbno, ltlen, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                if ((error = xfs_alloc_delete(cnt_cur, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                /*
                 * Back up the by-block cursor to the left neighbor, and
                 * update its length.
                 */
                if ((error = xfs_btree_decrement(bno_cur, 0, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                nbno = ltbno;
                nlen = len + ltlen;
                if ((error = xfs_alloc_update(bno_cur, nbno, nlen)))
                        goto error0;
        }
        /*
         * Have only a right contiguous neighbor.
         * Merge it together with the new freespace.
         */
        else if (haveright) {
                /*
                 * Delete the old by-size entry on the right.
                 */
                if ((error = xfs_alloc_lookup_eq(cnt_cur, gtbno, gtlen, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                if ((error = xfs_alloc_delete(cnt_cur, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                /*
                 * Update the starting block and length of the right
                 * neighbor in the by-block tree.
                 */
                nbno = bno;
                nlen = len + gtlen;
                if ((error = xfs_alloc_update(bno_cur, nbno, nlen)))
                        goto error0;
        }
        /*
         * No contiguous neighbors.
         * Insert the new freespace into the by-block tree.
         */
        else {
                nbno = bno;
                nlen = len;
                if ((error = xfs_alloc_insert(bno_cur, &i)))
                        goto error0;
                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
        }
        xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
        bno_cur = NULL;
        /*
         * In all cases we need to insert the new freespace in the by-size tree.
         */
        if ((error = xfs_alloc_lookup_eq(cnt_cur, nbno, nlen, &i)))
                goto error0;
        XFS_WANT_CORRUPTED_GOTO(i == 0, error0);
        if ((error = xfs_alloc_insert(cnt_cur, &i)))
                goto error0;
        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
        xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
        cnt_cur = NULL;
        /*
         * Update the freespace totals in the ag and superblock.
         */
        {
                xfs_agf_t       *agf;
                xfs_perag_t     *pag;           /* per allocation group data */

                agf = XFS_BUF_TO_AGF(agbp);
                pag = &mp->m_perag[agno];
                be32_add_cpu(&agf->agf_freeblks, len);
                xfs_trans_agblocks_delta(tp, len);
                pag->pagf_freeblks += len;
                XFS_WANT_CORRUPTED_GOTO(
                        be32_to_cpu(agf->agf_freeblks) <=
                        be32_to_cpu(agf->agf_length),
                        error0);
                TRACE_MODAGF(NULL, agf, XFS_AGF_FREEBLKS);
                xfs_alloc_log_agf(tp, agbp, XFS_AGF_FREEBLKS);
                if (!isfl)
                        xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, (long)len);
                XFS_STATS_INC(xs_freex);
                XFS_STATS_ADD(xs_freeb, len);
        }
        TRACE_FREE(haveleft ?
                        (haveright ? "both" : "left") :
                        (haveright ? "right" : "none"),
                agno, bno, len, isfl);

        /*
         * Since blocks move to the free list without the coordination
         * used in xfs_bmap_finish, we can't allow block to be available
         * for reallocation and non-transaction writing (user data)
         * until we know that the transaction that moved it to the free
         * list is permanently on disk.  We track the blocks by declaring
         * these blocks as "busy"; the busy list is maintained on a per-ag
         * basis and each transaction records which entries should be removed
         * when the iclog commits to disk.  If a busy block is allocated,
         * the iclog is pushed up to the LSN that freed the block.
         */
        xfs_alloc_mark_busy(tp, agno, bno, len);
        return 0;

 error0:
        TRACE_FREE("error", agno, bno, len, isfl);
        if (bno_cur)
                xfs_btree_del_cursor(bno_cur, XFS_BTREE_ERROR);
        if (cnt_cur)
                xfs_btree_del_cursor(cnt_cur, XFS_BTREE_ERROR);
        return error;
}

/*
 * Visible (exported) allocation/free functions.
 * Some of these are used just by xfs_alloc_btree.c and this file.
 */

/*
 * Compute and fill in value of m_ag_maxlevels.
 */
void
xfs_alloc_compute_maxlevels(
        xfs_mount_t     *mp)    /* file system mount structure */
{
        int             level;
        uint            maxblocks;
        uint            maxleafents;
        int             minleafrecs;
        int             minnoderecs;

        maxleafents = (mp->m_sb.sb_agblocks + 1) / 2;
        minleafrecs = mp->m_alloc_mnr[0];
        minnoderecs = mp->m_alloc_mnr[1];
        maxblocks = (maxleafents + minleafrecs - 1) / minleafrecs;
        for (level = 1; maxblocks > 1; level++)
                maxblocks = (maxblocks + minnoderecs - 1) / minnoderecs;
        mp->m_ag_maxlevels = level;
}

/*
 * Decide whether to use this allocation group for this allocation.
 * If so, fix up the btree freelist's size.
 */
STATIC int                      /* error */
xfs_alloc_fix_freelist(
        xfs_alloc_arg_t *args,  /* allocation argument structure */
        int             flags)  /* XFS_ALLOC_FLAG_... */
{
        xfs_buf_t       *agbp;  /* agf buffer pointer */
        xfs_agf_t       *agf;   /* a.g. freespace structure pointer */
        xfs_buf_t       *agflbp;/* agfl buffer pointer */
        xfs_agblock_t   bno;    /* freelist block */
        xfs_extlen_t    delta;  /* new blocks needed in freelist */
        int             error;  /* error result code */
        xfs_extlen_t    longest;/* longest extent in allocation group */
        xfs_mount_t     *mp;    /* file system mount point structure */
        xfs_extlen_t    need;   /* total blocks needed in freelist */
        xfs_perag_t     *pag;   /* per-ag information structure */
        xfs_alloc_arg_t targs;  /* local allocation arguments */
        xfs_trans_t     *tp;    /* transaction pointer */

        mp = args->mp;

        pag = args->pag;
        tp = args->tp;
        if (!pag->pagf_init) {
                if ((error = xfs_alloc_read_agf(mp, tp, args->agno, flags,
                                &agbp)))
                        return error;
                if (!pag->pagf_init) {
                        ASSERT(flags & XFS_ALLOC_FLAG_TRYLOCK);
                        ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING));
                        args->agbp = NULL;
                        return 0;
                }
        } else
                agbp = NULL;

        /*
         * If this is a metadata preferred pag and we are user data
         * then try somewhere else if we are not being asked to
         * try harder at this point
         */
        if (pag->pagf_metadata && args->userdata &&
            (flags & XFS_ALLOC_FLAG_TRYLOCK)) {
                ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING));
                args->agbp = NULL;
                return 0;
        }

        if (!(flags & XFS_ALLOC_FLAG_FREEING)) {
                need = XFS_MIN_FREELIST_PAG(pag, mp);
                delta = need > pag->pagf_flcount ? need - pag->pagf_flcount : 0;
                /*
                 * If it looks like there isn't a long enough extent, or enough
                 * total blocks, reject it.
                 */
                longest = (pag->pagf_longest > delta) ?
                        (pag->pagf_longest - delta) :
                        (pag->pagf_flcount > 0 || pag->pagf_longest > 0);
                if ((args->minlen + args->alignment + args->minalignslop - 1) >
                                longest ||
                    ((int)(pag->pagf_freeblks + pag->pagf_flcount -
                           need - args->total) < (int)args->minleft)) {
                        if (agbp)
                                xfs_trans_brelse(tp, agbp);
                        args->agbp = NULL;
                        return 0;
                }
        }

        /*
         * Get the a.g. freespace buffer.
         * Can fail if we're not blocking on locks, and it's held.
         */
        if (agbp == NULL) {
                if ((error = xfs_alloc_read_agf(mp, tp, args->agno, flags,
                                &agbp)))
                        return error;
                if (agbp == NULL) {
                        ASSERT(flags & XFS_ALLOC_FLAG_TRYLOCK);
                        ASSERT(!(flags & XFS_ALLOC_FLAG_FREEING));
                        args->agbp = NULL;
                        return 0;
                }
        }
        /*
         * Figure out how many blocks we should have in the freelist.
         */
        agf = XFS_BUF_TO_AGF(agbp);
        need = XFS_MIN_FREELIST(agf, mp);
        /*
         * If there isn't enough total or single-extent, reject it.
         */
        if (!(flags & XFS_ALLOC_FLAG_FREEING)) {
                delta = need > be32_to_cpu(agf->agf_flcount) ?
                        (need - be32_to_cpu(agf->agf_flcount)) : 0;
                longest = be32_to_cpu(agf->agf_longest);
                longest = (longest > delta) ? (longest - delta) :
                        (be32_to_cpu(agf->agf_flcount) > 0 || longest > 0);
                if ((args->minlen + args->alignment + args->minalignslop - 1) >
                                longest ||
                    ((int)(be32_to_cpu(agf->agf_freeblks) +
                     be32_to_cpu(agf->agf_flcount) - need - args->total) <
                                (int)args->minleft)) {
                        xfs_trans_brelse(tp, agbp);
                        args->agbp = NULL;
                        return 0;
                }
        }
        /*
         * Make the freelist shorter if it's too long.
         */
        while (be32_to_cpu(agf->agf_flcount) > need) {
                xfs_buf_t       *bp;

                error = xfs_alloc_get_freelist(tp, agbp, &bno, 0);
                if (error)
                        return error;
                if ((error = xfs_free_ag_extent(tp, agbp, args->agno, bno, 1, 1)))
                        return error;
                bp = xfs_btree_get_bufs(mp, tp, args->agno, bno, 0);
                xfs_trans_binval(tp, bp);
        }
        /*
         * Initialize the args structure.
         */
        targs.tp = tp;
        targs.mp = mp;
        targs.agbp = agbp;
        targs.agno = args->agno;
        targs.mod = targs.minleft = targs.wasdel = targs.userdata =
                targs.minalignslop = 0;
        targs.alignment = targs.minlen = targs.prod = targs.isfl = 1;
        targs.type = XFS_ALLOCTYPE_THIS_AG;
        targs.pag = pag;
        if ((error = xfs_alloc_read_agfl(mp, tp, targs.agno, &agflbp)))
                return error;
        /*
         * Make the freelist longer if it's too short.
         */
        while (be32_to_cpu(agf->agf_flcount) < need) {
                targs.agbno = 0;
                targs.maxlen = need - be32_to_cpu(agf->agf_flcount);
                /*
                 * Allocate as many blocks as possible at once.
                 */
                if ((error = xfs_alloc_ag_vextent(&targs))) {
                        xfs_trans_brelse(tp, agflbp);
                        return error;
                }
                /*
                 * Stop if we run out.  Won't happen if callers are obeying
                 * the restrictions correctly.  Can happen for free calls
                 * on a completely full ag.
                 */
                if (targs.agbno == NULLAGBLOCK) {
                        if (flags & XFS_ALLOC_FLAG_FREEING)
                                break;
                        xfs_trans_brelse(tp, agflbp);
                        args->agbp = NULL;
                        return 0;
                }
                /*
                 * Put each allocated block on the list.
                 */
                for (bno = targs.agbno; bno < targs.agbno + targs.len; bno++) {
                        error = xfs_alloc_put_freelist(tp, agbp,
                                                        agflbp, bno, 0);
                        if (error)
                                return error;
                }
        }
        xfs_trans_brelse(tp, agflbp);
        args->agbp = agbp;
        return 0;
}

/*
 * Get a block from the freelist.
 * Returns with the buffer for the block gotten.
 */
int                             /* error */
xfs_alloc_get_freelist(
        xfs_trans_t     *tp,    /* transaction pointer */
        xfs_buf_t       *agbp,  /* buffer containing the agf structure */
        xfs_agblock_t   *bnop,  /* block address retrieved from freelist */
        int             btreeblk) /* destination is a AGF btree */
{
        xfs_agf_t       *agf;   /* a.g. freespace structure */
        xfs_agfl_t      *agfl;  /* a.g. freelist structure */
        xfs_buf_t       *agflbp;/* buffer for a.g. freelist structure */
        xfs_agblock_t   bno;    /* block number returned */
        int             error;
        int             logflags;
        xfs_mount_t     *mp;    /* mount structure */
        xfs_perag_t     *pag;   /* per allocation group data */

        agf = XFS_BUF_TO_AGF(agbp);
        /*
         * Freelist is empty, give up.
         */
        if (!agf->agf_flcount) {
                *bnop = NULLAGBLOCK;
                return 0;
        }
        /*
         * Read the array of free blocks.
         */
        mp = tp->t_mountp;
        if ((error = xfs_alloc_read_agfl(mp, tp,
                        be32_to_cpu(agf->agf_seqno), &agflbp)))
                return error;
        agfl = XFS_BUF_TO_AGFL(agflbp);
        /*
         * Get the block number and update the data structures.
         */
        bno = be32_to_cpu(agfl->agfl_bno[be32_to_cpu(agf->agf_flfirst)]);
        be32_add_cpu(&agf->agf_flfirst, 1);
        xfs_trans_brelse(tp, agflbp);
        if (be32_to_cpu(agf->agf_flfirst) == XFS_AGFL_SIZE(mp))
                agf->agf_flfirst = 0;
        pag = &mp->m_perag[be32_to_cpu(agf->agf_seqno)];
        be32_add_cpu(&agf->agf_flcount, -1);
        xfs_trans_agflist_delta(tp, -1);
        pag->pagf_flcount--;

        logflags = XFS_AGF_FLFIRST | XFS_AGF_FLCOUNT;
        if (btreeblk) {
                be32_add_cpu(&agf->agf_btreeblks, 1);
                pag->pagf_btreeblks++;
                logflags |= XFS_AGF_BTREEBLKS;
        }

        TRACE_MODAGF(NULL, agf, logflags);
        xfs_alloc_log_agf(tp, agbp, logflags);
        *bnop = bno;

        /*
         * As blocks are freed, they are added to the per-ag busy list
         * and remain there until the freeing transaction is committed to
         * disk.  Now that we have allocated blocks, this list must be
         * searched to see if a block is being reused.  If one is, then
         * the freeing transaction must be pushed to disk NOW by forcing
         * to disk all iclogs up that transaction's LSN.
         */
        xfs_alloc_search_busy(tp, be32_to_cpu(agf->agf_seqno), bno, 1);
        return 0;
}

/*
 * Log the given fields from the agf structure.
 */
void
xfs_alloc_log_agf(
        xfs_trans_t     *tp,    /* transaction pointer */
        xfs_buf_t       *bp,    /* buffer for a.g. freelist header */
        int             fields) /* mask of fields to be logged (XFS_AGF_...) */
{
        int     first;          /* first byte offset */
        int     last;           /* last byte offset */
        static const short      offsets[] = {
                offsetof(xfs_agf_t, agf_magicnum),
                offsetof(xfs_agf_t, agf_versionnum),
                offsetof(xfs_agf_t, agf_seqno),
                offsetof(xfs_agf_t, agf_length),
                offsetof(xfs_agf_t, agf_roots[0]),
                offsetof(xfs_agf_t, agf_levels[0]),
                offsetof(xfs_agf_t, agf_flfirst),
                offsetof(xfs_agf_t, agf_fllast),
                offsetof(xfs_agf_t, agf_flcount),
                offsetof(xfs_agf_t, agf_freeblks),
                offsetof(xfs_agf_t, agf_longest),
                offsetof(xfs_agf_t, agf_btreeblks),
                sizeof(xfs_agf_t)
        };

        xfs_btree_offsets(fields, offsets, XFS_AGF_NUM_BITS, &first, &last);
        xfs_trans_log_buf(tp, bp, (uint)first, (uint)last);
}

/*
 * Interface for inode allocation to force the pag data to be initialized.
 */
int                                     /* error */
xfs_alloc_pagf_init(
        xfs_mount_t             *mp,    /* file system mount structure */
        xfs_trans_t             *tp,    /* transaction pointer */
        xfs_agnumber_t          agno,   /* allocation group number */
        int                     flags)  /* XFS_ALLOC_FLAGS_... */
{
        xfs_buf_t               *bp;
        int                     error;

        if ((error = xfs_alloc_read_agf(mp, tp, agno, flags, &bp)))
                return error;
        if (bp)
                xfs_trans_brelse(tp, bp);
        return 0;
}

/*
 * Put the block on the freelist for the allocation group.
 */
int                                     /* error */
xfs_alloc_put_freelist(
        xfs_trans_t             *tp,    /* transaction pointer */
        xfs_buf_t               *agbp,  /* buffer for a.g. freelist header */
        xfs_buf_t               *agflbp,/* buffer for a.g. free block array */
        xfs_agblock_t           bno,    /* block being freed */
        int                     btreeblk) /* block came from a AGF btree */
{
        xfs_agf_t               *agf;   /* a.g. freespace structure */
        xfs_agfl_t              *agfl;  /* a.g. free block array */
        __be32                  *blockp;/* pointer to array entry */
        int                     error;
        int                     logflags;
        xfs_mount_t             *mp;    /* mount structure */
        xfs_perag_t             *pag;   /* per allocation group data */

        agf = XFS_BUF_TO_AGF(agbp);
        mp = tp->t_mountp;

        if (!agflbp && (error = xfs_alloc_read_agfl(mp, tp,
                        be32_to_cpu(agf->agf_seqno), &agflbp)))
                return error;
        agfl = XFS_BUF_TO_AGFL(agflbp);
        be32_add_cpu(&agf->agf_fllast, 1);
        if (be32_to_cpu(agf->agf_fllast) == XFS_AGFL_SIZE(mp))
                agf->agf_fllast = 0;
        pag = &mp->m_perag[be32_to_cpu(agf->agf_seqno)];
        be32_add_cpu(&agf->agf_flcount, 1);
        xfs_trans_agflist_delta(tp, 1);
        pag->pagf_flcount++;

        logflags = XFS_AGF_FLLAST | XFS_AGF_FLCOUNT;
        if (btreeblk) {
                be32_add_cpu(&agf->agf_btreeblks, -1);
                pag->pagf_btreeblks--;
                logflags |= XFS_AGF_BTREEBLKS;
        }

        TRACE_MODAGF(NULL, agf, logflags);
        xfs_alloc_log_agf(tp, agbp, logflags);

        ASSERT(be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp));
        blockp = &agfl->agfl_bno[be32_to_cpu(agf->agf_fllast)];
        *blockp = cpu_to_be32(bno);
        TRACE_MODAGF(NULL, agf, logflags);
        xfs_alloc_log_agf(tp, agbp, logflags);
        xfs_trans_log_buf(tp, agflbp,
                (int)((xfs_caddr_t)blockp - (xfs_caddr_t)agfl),
                (int)((xfs_caddr_t)blockp - (xfs_caddr_t)agfl +
                        sizeof(xfs_agblock_t) - 1));
        return 0;
}

/*
 * Read in the allocation group header (free/alloc section).
 */
int                                     /* error */
xfs_alloc_read_agf(
        xfs_mount_t     *mp,            /* mount point structure */
        xfs_trans_t     *tp,            /* transaction pointer */
        xfs_agnumber_t  agno,           /* allocation group number */
        int             flags,          /* XFS_ALLOC_FLAG_... */
        xfs_buf_t       **bpp)          /* buffer for the ag freelist header */
{
        xfs_agf_t       *agf;           /* ag freelist header */
        int             agf_ok;         /* set if agf is consistent */
        xfs_buf_t       *bp;            /* return value */
        xfs_perag_t     *pag;           /* per allocation group data */
        int             error;

        ASSERT(agno != NULLAGNUMBER);
        error = xfs_trans_read_buf(
                        mp, tp, mp->m_ddev_targp,
                        XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
                        XFS_FSS_TO_BB(mp, 1),
                        (flags & XFS_ALLOC_FLAG_TRYLOCK) ? XFS_BUF_TRYLOCK : 0U,
                        &bp);
        if (error)
                return error;
        ASSERT(!bp || !XFS_BUF_GETERROR(bp));
        if (!bp) {
                *bpp = NULL;
                return 0;
        }
        /*
         * Validate the magic number of the agf block.
         */
        agf = XFS_BUF_TO_AGF(bp);
        agf_ok =
                be32_to_cpu(agf->agf_magicnum) == XFS_AGF_MAGIC &&
                XFS_AGF_GOOD_VERSION(be32_to_cpu(agf->agf_versionnum)) &&
                be32_to_cpu(agf->agf_freeblks) <= be32_to_cpu(agf->agf_length) &&
                be32_to_cpu(agf->agf_flfirst) < XFS_AGFL_SIZE(mp) &&
                be32_to_cpu(agf->agf_fllast) < XFS_AGFL_SIZE(mp) &&
                be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp);
        if (unlikely(XFS_TEST_ERROR(!agf_ok, mp, XFS_ERRTAG_ALLOC_READ_AGF,
                        XFS_RANDOM_ALLOC_READ_AGF))) {
                XFS_CORRUPTION_ERROR("xfs_alloc_read_agf",
                                     XFS_ERRLEVEL_LOW, mp, agf);
                xfs_trans_brelse(tp, bp);
                return XFS_ERROR(EFSCORRUPTED);
        }
        pag = &mp->m_perag[agno];
        if (!pag->pagf_init) {
                pag->pagf_freeblks = be32_to_cpu(agf->agf_freeblks);
                pag->pagf_btreeblks = be32_to_cpu(agf->agf_btreeblks);
                pag->pagf_flcount = be32_to_cpu(agf->agf_flcount);
                pag->pagf_longest = be32_to_cpu(agf->agf_longest);
                pag->pagf_levels[XFS_BTNUM_BNOi] =
                        be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNOi]);
                pag->pagf_levels[XFS_BTNUM_CNTi] =
                        be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNTi]);
                spin_lock_init(&pag->pagb_lock);
                pag->pagb_list = kmem_zalloc(XFS_PAGB_NUM_SLOTS *
                                        sizeof(xfs_perag_busy_t), KM_SLEEP);
                pag->pagf_init = 1;
        }
#ifdef DEBUG
        else if (!XFS_FORCED_SHUTDOWN(mp)) {
                ASSERT(pag->pagf_freeblks == be32_to_cpu(agf->agf_freeblks));
                ASSERT(pag->pagf_flcount == be32_to_cpu(agf->agf_flcount));
                ASSERT(pag->pagf_longest == be32_to_cpu(agf->agf_longest));
                ASSERT(pag->pagf_levels[XFS_BTNUM_BNOi] ==
                       be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNOi]));
                ASSERT(pag->pagf_levels[XFS_BTNUM_CNTi] ==
                       be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNTi]));
        }
#endif
        XFS_BUF_SET_VTYPE_REF(bp, B_FS_AGF, XFS_AGF_REF);
        *bpp = bp;
        return 0;
}

/*
 * Allocate an extent (variable-size).
 * Depending on the allocation type, we either look in a single allocation
 * group or loop over the allocation groups to find the result.
 */
int                             /* error */
xfs_alloc_vextent(
        xfs_alloc_arg_t *args)  /* allocation argument structure */
{
        xfs_agblock_t   agsize; /* allocation group size */
        int             error;
        int             flags;  /* XFS_ALLOC_FLAG_... locking flags */
        xfs_extlen_t    minleft;/* minimum left value, temp copy */
        xfs_mount_t     *mp;    /* mount structure pointer */
        xfs_agnumber_t  sagno;  /* starting allocation group number */
        xfs_alloctype_t type;   /* input allocation type */
        int             bump_rotor = 0;
        int             no_min = 0;
        xfs_agnumber_t  rotorstep = xfs_rotorstep; /* inode32 agf stepper */

        mp = args->mp;
        type = args->otype = args->type;
        args->agbno = NULLAGBLOCK;
        /*
         * Just fix this up, for the case where the last a.g. is shorter
         * (or there's only one a.g.) and the caller couldn't easily figure
         * that out (xfs_bmap_alloc).
         */
        agsize = mp->m_sb.sb_agblocks;
        if (args->maxlen > agsize)
                args->maxlen = agsize;
        if (args->alignment == 0)
                args->alignment = 1;
        ASSERT(XFS_FSB_TO_AGNO(mp, args->fsbno) < mp->m_sb.sb_agcount);
        ASSERT(XFS_FSB_TO_AGBNO(mp, args->fsbno) < agsize);
        ASSERT(args->minlen <= args->maxlen);
        ASSERT(args->minlen <= agsize);
        ASSERT(args->mod < args->prod);
        if (XFS_FSB_TO_AGNO(mp, args->fsbno) >= mp->m_sb.sb_agcount ||
            XFS_FSB_TO_AGBNO(mp, args->fsbno) >= agsize ||
            args->minlen > args->maxlen || args->minlen > agsize ||
            args->mod >= args->prod) {
                args->fsbno = NULLFSBLOCK;
                TRACE_ALLOC("badargs", args);
                return 0;
        }
        minleft = args->minleft;

        switch (type) {
        case XFS_ALLOCTYPE_THIS_AG:
        case XFS_ALLOCTYPE_NEAR_BNO:
        case XFS_ALLOCTYPE_THIS_BNO:
                /*
                 * These three force us into a single a.g.
                 */
                args->agno = XFS_FSB_TO_AGNO(mp, args->fsbno);
                down_read(&mp->m_peraglock);
                args->pag = &mp->m_perag[args->agno];
                args->minleft = 0;
                error = xfs_alloc_fix_freelist(args, 0);
                args->minleft = minleft;
                if (error) {
                        TRACE_ALLOC("nofix", args);
                        goto error0;
                }
                if (!args->agbp) {
                        up_read(&mp->m_peraglock);
                        TRACE_ALLOC("noagbp", args);
                        break;
                }
                args->agbno = XFS_FSB_TO_AGBNO(mp, args->fsbno);
                if ((error = xfs_alloc_ag_vextent(args)))
                        goto error0;
                up_read(&mp->m_peraglock);
                break;
        case XFS_ALLOCTYPE_START_BNO:
                /*
                 * Try near allocation first, then anywhere-in-ag after
                 * the first a.g. fails.
                 */
                if ((args->userdata  == XFS_ALLOC_INITIAL_USER_DATA) &&
                    (mp->m_flags & XFS_MOUNT_32BITINODES)) {
                        args->fsbno = XFS_AGB_TO_FSB(mp,
                                        ((mp->m_agfrotor / rotorstep) %
                                        mp->m_sb.sb_agcount), 0);
                        bump_rotor = 1;
                }
                args->agbno = XFS_FSB_TO_AGBNO(mp, args->fsbno);
                args->type = XFS_ALLOCTYPE_NEAR_BNO;
                /* FALLTHROUGH */
        case XFS_ALLOCTYPE_ANY_AG:
        case XFS_ALLOCTYPE_START_AG:
        case XFS_ALLOCTYPE_FIRST_AG:
                /*
                 * Rotate through the allocation groups looking for a winner.
                 */
                if (type == XFS_ALLOCTYPE_ANY_AG) {
                        /*
                         * Start with the last place we left off.
                         */
                        args->agno = sagno = (mp->m_agfrotor / rotorstep) %
                                        mp->m_sb.sb_agcount;
                        args->type = XFS_ALLOCTYPE_THIS_AG;
                        flags = XFS_ALLOC_FLAG_TRYLOCK;
                } else if (type == XFS_ALLOCTYPE_FIRST_AG) {
                        /*
                         * Start with allocation group given by bno.
                         */
                        args->agno = XFS_FSB_TO_AGNO(mp, args->fsbno);
                        args->type = XFS_ALLOCTYPE_THIS_AG;
                        sagno = 0;
                        flags = 0;
                } else {
                        if (type == XFS_ALLOCTYPE_START_AG)
                                args->type = XFS_ALLOCTYPE_THIS_AG;
                        /*
                         * Start with the given allocation group.
                         */
                        args->agno = sagno = XFS_FSB_TO_AGNO(mp, args->fsbno);
                        flags = XFS_ALLOC_FLAG_TRYLOCK;
                }
                /*
                 * Loop over allocation groups twice; first time with
                 * trylock set, second time without.
                 */
                down_read(&mp->m_peraglock);
                for (;;) {
                        args->pag = &mp->m_perag[args->agno];
                        if (no_min) args->minleft = 0;
                        error = xfs_alloc_fix_freelist(args, flags);
                        args->minleft = minleft;
                        if (error) {
                                TRACE_ALLOC("nofix", args);
                                goto error0;
                        }
                        /*
                         * If we get a buffer back then the allocation will fly.
                         */
                        if (args->agbp) {
                                if ((error = xfs_alloc_ag_vextent(args)))
                                        goto error0;
                                break;
                        }
                        TRACE_ALLOC("loopfailed", args);
                        /*
                         * Didn't work, figure out the next iteration.
                         */
                        if (args->agno == sagno &&
                            type == XFS_ALLOCTYPE_START_BNO)
                                args->type = XFS_ALLOCTYPE_THIS_AG;
                        /*
                        * For the first allocation, we can try any AG to get
                        * space.  However, if we already have allocated a
                        * block, we don't want to try AGs whose number is below
                        * sagno. Otherwise, we may end up with out-of-order
                        * locking of AGF, which might cause deadlock.
                        */
                        if (++(args->agno) == mp->m_sb.sb_agcount) {
                                if (args->firstblock != NULLFSBLOCK)
                                        args->agno = sagno;
                                else
                                        args->agno = 0;
                        }
                        /*
                         * Reached the starting a.g., must either be done
                         * or switch to non-trylock mode.
                         */
                        if (args->agno == sagno) {
                                if (no_min == 1) {
                                        args->agbno = NULLAGBLOCK;
                                        TRACE_ALLOC("allfailed", args);
                                        break;
                                }
                                if (flags == 0) {
                                        no_min = 1;
                                } else {
                                        flags = 0;
                                        if (type == XFS_ALLOCTYPE_START_BNO) {
                                                args->agbno = XFS_FSB_TO_AGBNO(mp,
                                                        args->fsbno);
                                                args->type = XFS_ALLOCTYPE_NEAR_BNO;
                                        }
                                }
                        }
                }
                up_read(&mp->m_peraglock);
                if (bump_rotor || (type == XFS_ALLOCTYPE_ANY_AG)) {
                        if (args->agno == sagno)
                                mp->m_agfrotor = (mp->m_agfrotor + 1) %
                                        (mp->m_sb.sb_agcount * rotorstep);
                        else
                                mp->m_agfrotor = (args->agno * rotorstep + 1) %
                                        (mp->m_sb.sb_agcount * rotorstep);
                }
                break;
        default:
                ASSERT(0);
                /* NOTREACHED */
        }
        if (args->agbno == NULLAGBLOCK)
                args->fsbno = NULLFSBLOCK;
        else {
                args->fsbno = XFS_AGB_TO_FSB(mp, args->agno, args->agbno);
#ifdef DEBUG
                ASSERT(args->len >= args->minlen);
                ASSERT(args->len <= args->maxlen);
                ASSERT(args->agbno % args->alignment == 0);
                XFS_AG_CHECK_DADDR(mp, XFS_FSB_TO_DADDR(mp, args->fsbno),
                        args->len);
#endif
        }
        return 0;
error0:
        up_read(&mp->m_peraglock);
        return error;
}

/*
 * Free an extent.
 * Just break up the extent address and hand off to xfs_free_ag_extent
 * after fixing up the freelist.
 */
int                             /* error */
xfs_free_extent(
        xfs_trans_t     *tp,    /* transaction pointer */
        xfs_fsblock_t   bno,    /* starting block number of extent */
        xfs_extlen_t    len)    /* length of extent */
{
        xfs_alloc_arg_t args;
        int             error;

        ASSERT(len != 0);
        memset(&args, 0, sizeof(xfs_alloc_arg_t));
        args.tp = tp;
        args.mp = tp->t_mountp;
        args.agno = XFS_FSB_TO_AGNO(args.mp, bno);
        ASSERT(args.agno < args.mp->m_sb.sb_agcount);
        args.agbno = XFS_FSB_TO_AGBNO(args.mp, bno);
        down_read(&args.mp->m_peraglock);
        args.pag = &args.mp->m_perag[args.agno];
        if ((error = xfs_alloc_fix_freelist(&args, XFS_ALLOC_FLAG_FREEING)))
                goto error0;
#ifdef DEBUG
        ASSERT(args.agbp != NULL);
        ASSERT((args.agbno + len) <=
                be32_to_cpu(XFS_BUF_TO_AGF(args.agbp)->agf_length));
#endif
        error = xfs_free_ag_extent(tp, args.agbp, args.agno, args.agbno, len, 0);
error0:
        up_read(&args.mp->m_peraglock);
        return error;
}


/*
 * AG Busy list management
 * The busy list contains block ranges that have been freed but whose
 * transactions have not yet hit disk.  If any block listed in a busy
 * list is reused, the transaction that freed it must be forced to disk
 * before continuing to use the block.
 *
 * xfs_alloc_mark_busy - add to the per-ag busy list
 * xfs_alloc_clear_busy - remove an item from the per-ag busy list
 */
void
xfs_alloc_mark_busy(xfs_trans_t *tp,
                    xfs_agnumber_t agno,
                    xfs_agblock_t bno,
                    xfs_extlen_t len)
{
        xfs_mount_t             *mp;
        xfs_perag_busy_t        *bsy;
        int                     n;

        mp = tp->t_mountp;
        spin_lock(&mp->m_perag[agno].pagb_lock);

        /* search pagb_list for an open slot */
        for (bsy = mp->m_perag[agno].pagb_list, n = 0;
             n < XFS_PAGB_NUM_SLOTS;
             bsy++, n++) {
                if (bsy->busy_tp == NULL) {
                        break;
                }
        }

        if (n < XFS_PAGB_NUM_SLOTS) {
                bsy = &mp->m_perag[agno].pagb_list[n];
                mp->m_perag[agno].pagb_count++;
                TRACE_BUSY("xfs_alloc_mark_busy", "got", agno, bno, len, n, tp);
                bsy->busy_start = bno;
                bsy->busy_length = len;
                bsy->busy_tp = tp;
                xfs_trans_add_busy(tp, agno, n);
        } else {
                TRACE_BUSY("xfs_alloc_mark_busy", "FULL", agno, bno, len, -1, tp);
                /*
                 * The busy list is full!  Since it is now not possible to
                 * track the free block, make this a synchronous transaction
                 * to insure that the block is not reused before this
                 * transaction commits.
                 */
                xfs_trans_set_sync(tp);
        }

        spin_unlock(&mp->m_perag[agno].pagb_lock);
}

void
xfs_alloc_clear_busy(xfs_trans_t *tp,
                     xfs_agnumber_t agno,
                     int idx)
{
        xfs_mount_t             *mp;
        xfs_perag_busy_t        *list;

        mp = tp->t_mountp;

        spin_lock(&mp->m_perag[agno].pagb_lock);
        list = mp->m_perag[agno].pagb_list;

        ASSERT(idx < XFS_PAGB_NUM_SLOTS);
        if (list[idx].busy_tp == tp) {
                TRACE_UNBUSY("xfs_alloc_clear_busy", "found", agno, idx, tp);
                list[idx].busy_tp = NULL;
                mp->m_perag[agno].pagb_count--;
        } else {
                TRACE_UNBUSY("xfs_alloc_clear_busy", "missing", agno, idx, tp);
        }

        spin_unlock(&mp->m_perag[agno].pagb_lock);
}


/*
 * If we find the extent in the busy list, force the log out to get the
 * extent out of the busy list so the caller can use it straight away.
 */
STATIC void
xfs_alloc_search_busy(xfs_trans_t *tp,
                    xfs_agnumber_t agno,
                    xfs_agblock_t bno,
                    xfs_extlen_t len)
{
        xfs_mount_t             *mp;
        xfs_perag_busy_t        *bsy;
        xfs_agblock_t           uend, bend;
        xfs_lsn_t               lsn;
        int                     cnt;

        mp = tp->t_mountp;

        spin_lock(&mp->m_perag[agno].pagb_lock);
        cnt = mp->m_perag[agno].pagb_count;

        uend = bno + len - 1;

        /* search pagb_list for this slot, skipping open slots */
        for (bsy = mp->m_perag[agno].pagb_list; cnt; bsy++) {

                /*
                 * (start1,length1) within (start2, length2)
                 */
                if (bsy->busy_tp != NULL) {
                        bend = bsy->busy_start + bsy->busy_length - 1;
                        if ((bno > bend) || (uend < bsy->busy_start)) {
                                cnt--;
                        } else {
                                TRACE_BUSYSEARCH("xfs_alloc_search_busy",
                                         "found1", agno, bno, len, tp);
                                break;
                        }
                }
        }

        /*
         * If a block was found, force the log through the LSN of the
         * transaction that freed the block
         */
        if (cnt) {
                TRACE_BUSYSEARCH("xfs_alloc_search_busy", "found", agno, bno, len, tp);
                lsn = bsy->busy_tp->t_commit_lsn;
                spin_unlock(&mp->m_perag[agno].pagb_lock);
                xfs_log_force(mp, lsn, XFS_LOG_FORCE|XFS_LOG_SYNC);
        } else {
                TRACE_BUSYSEARCH("xfs_alloc_search_busy", "not-found", agno, bno, len, tp);
                spin_unlock(&mp->m_perag[agno].pagb_lock);
        }
}