text: /*
   * 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_mount.h"
  #include "xfs_bmap_btree.h"
  #include "xfs_alloc_btree.h"
  #include "xfs_ialloc_btree.h"
  #include "xfs_dinode.h"
  #include "xfs_inode.h"
  #include "xfs_btree.h"
  #include "xfs_alloc.h"
  #include "xfs_error.h"
  #include "xfs_trace.h"
  
  struct workqueue_struct *xfs_alloc_wq;
  
  #define XFS_ABSDIFF(a,b)	(((a) <= (b)) ? ((b) - (a)) : ((a) - (b)))
  
  #define	XFSA_FIXUP_BNO_OK	1
  #define	XFSA_FIXUP_CNT_OK	2
  
  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 *);
  STATIC void xfs_alloc_busy_trim(struct xfs_alloc_arg *,
  		xfs_agblock_t, xfs_extlen_t, xfs_agblock_t *, xfs_extlen_t *);
  
  /*
   * 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.
   */
  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.
   */
  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);
  }
  
  /*
   * Get the data from the pointed-to record.
   */
  int					/* error */
  xfs_alloc_get_rec(
  	struct xfs_btree_cur	*cur,	/* btree cursor */
  	xfs_agblock_t		*bno,	/* output: starting block of extent */
  	xfs_extlen_t		*len,	/* output: length of extent */
  	int			*stat)	/* output: success/failure */
  {
  	union xfs_btree_rec	*rec;
  	int			error;
  
  	error = xfs_btree_get_rec(cur, &rec, stat);
  	if (!error && *stat == 1) {
  		*bno = be32_to_cpu(rec->alloc.ar_startblock);
  		*len = be32_to_cpu(rec->alloc.ar_blockcount);
  	}
  	return error;
  }
  
  /*
   * Compute aligned version of the found extent.
   * Takes alignment and min length into account.
   */
  STATIC void
  xfs_alloc_compute_aligned(
  	xfs_alloc_arg_t	*args,		/* allocation argument structure */
  	xfs_agblock_t	foundbno,	/* starting block in found extent */
  	xfs_extlen_t	foundlen,	/* length in found extent */
  	xfs_agblock_t	*resbno,	/* result block number */
  	xfs_extlen_t	*reslen)	/* result length */
  {
  	xfs_agblock_t	bno;
  	xfs_extlen_t	len;
  
  	/* Trim busy sections out of found extent */
  	xfs_alloc_busy_trim(args, foundbno, foundlen, &bno, &len);
  
  	if (args->alignment > 1 && len >= args->minlen) {
  		xfs_agblock_t	aligned_bno = roundup(bno, args->alignment);
  		xfs_extlen_t	diff = aligned_bno - bno;
  
  		*resbno = aligned_bno;
  		*reslen = diff >= len ? 0 : len - diff;
  	} else {
  		*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)
  		- 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
  	if (bno_cur->bc_nlevels == 1 && cnt_cur->bc_nlevels == 1) {
  		struct xfs_btree_block	*bnoblock;
  		struct xfs_btree_block	*cntblock;
  
  		bnoblock = XFS_BUF_TO_BLOCK(bno_cur->bc_bufs[0]);
  		cntblock = XFS_BUF_TO_BLOCK(cnt_cur->bc_bufs[0]);
  
  		XFS_WANT_CORRUPTED_RETURN(
  			bnoblock->bb_numrecs == 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_btree_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_btree_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_btree_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_btree_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_btree_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(!xfs_buf_geterror(bp));
  	xfs_buf_set_ref(bp, XFS_AGFL_REF);
  	*bpp = bp;
  	return 0;
  }
  
  STATIC int
  xfs_alloc_update_counters(
  	struct xfs_trans	*tp,
  	struct xfs_perag	*pag,
  	struct xfs_buf		*agbp,
  	long			len)
  {
  	struct xfs_agf		*agf = XFS_BUF_TO_AGF(agbp);
  
  	pag->pagf_freeblks += len;
  	be32_add_cpu(&agf->agf_freeblks, len);
  
  	xfs_trans_agblocks_delta(tp, len);
  	if (unlikely(be32_to_cpu(agf->agf_freeblks) >
  		     be32_to_cpu(agf->agf_length)))
  		return EFSCORRUPTED;
  
  	xfs_alloc_log_agf(tp, agbp, XFS_AGF_FREEBLKS);
  	return 0;
  }
  
  /*
   * 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 || args->agbno == NULLAGBLOCK)
  		return error;
  
  	ASSERT(args->len >= args->minlen);
  	ASSERT(args->len <= args->maxlen);
  	ASSERT(!args->wasfromfl || !args->isfl);
  	ASSERT(args->agbno % args->alignment == 0);
  
  	if (!args->wasfromfl) {
  		error = xfs_alloc_update_counters(args->tp, args->pag,
  						  args->agbp,
  						  -((long)(args->len)));
  		if (error)
  			return error;
  
  		ASSERT(!xfs_alloc_busy_search(args->mp, 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,
  				 -((long)(args->len)));
  	}
  
  	XFS_STATS_INC(xs_allocx);
  	XFS_STATS_ADD(xs_allocb, args->len);
  	return error;
  }
  
  /*
   * 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 */
  	int		error;
  	xfs_agblock_t	fbno;	/* start block of found extent */
  	xfs_extlen_t	flen;	/* length of found extent */
  	xfs_agblock_t	tbno;	/* start block of trimmed extent */
  	xfs_extlen_t	tlen;	/* length of trimmed extent */
  	xfs_agblock_t	tend;	/* end block of trimmed extent */
  	int		i;	/* success/failure of operation */
  
  	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.
  	 */
  	error = xfs_alloc_lookup_le(bno_cur, args->agbno, args->minlen, &i);
  	if (error)
  		goto error0;
  	if (!i)
  		goto not_found;
  
  	/*
  	 * Grab the freespace record.
  	 */
  	error = xfs_alloc_get_rec(bno_cur, &fbno, &flen, &i);
  	if (error)
  		goto error0;
  	XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
  	ASSERT(fbno <= args->agbno);
  
  	/*
  	 * Check for overlapping busy extents.
  	 */
  	xfs_alloc_busy_trim(args, fbno, flen, &tbno, &tlen);
  
  	/*
  	 * Give up if the start of the extent is busy, or the freespace isn't
  	 * long enough for the minimum request.
  	 */
  	if (tbno > args->agbno)
  		goto not_found;
  	if (tlen < args->minlen)
  		goto not_found;
  	tend = tbno + tlen;
  	if (tend < args->agbno + args->minlen)
  		goto not_found;
  
  	/*
  	 * End of extent will be smaller of the freespace end and the
  	 * maximal requested end.
  	 *
  	 * Fix the length according to mod and prod if given.
  	 */
  	args->len = XFS_AGBLOCK_MIN(tend, args->agbno + args->maxlen)
  						- args->agbno;
  	xfs_alloc_fix_len(args);
  	if (!xfs_alloc_fix_minleft(args))
  		goto not_found;
  
  	ASSERT(args->agbno + args->len <= tend);
  
  	/*
  	 * We are allocating agbno for args->len
  	 * 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));
  	error = xfs_alloc_fixup_trees(cnt_cur, bno_cur, fbno, flen, args->agbno,
  				      args->len, XFSA_FIXUP_BNO_OK);
  	if (error) {
  		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);
  
  	args->wasfromfl = 0;
  	trace_xfs_alloc_exact_done(args);
  	return 0;
  
  not_found:
  	/* Didn't find it, return null. */
  	xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR);
  	args->agbno = NULLAGBLOCK;
  	trace_xfs_alloc_exact_notfound(args);
  	return 0;
  
  error0:
  	xfs_btree_del_cursor(bno_cur, XFS_BTREE_ERROR);
  	trace_xfs_alloc_exact_error(args);
  	return error;
  }
  
  /*
   * Search the btree in a given direction via the search cursor and compare
   * the records found against the good extent we've already found.
   */
  STATIC int
  xfs_alloc_find_best_extent(
  	struct xfs_alloc_arg	*args,	/* allocation argument structure */
  	struct xfs_btree_cur	**gcur,	/* good cursor */
  	struct xfs_btree_cur	**scur,	/* searching cursor */
  	xfs_agblock_t		gdiff,	/* difference for search comparison */
  	xfs_agblock_t		*sbno,	/* extent found by search */
  	xfs_extlen_t		*slen,	/* extent length */
  	xfs_agblock_t		*sbnoa,	/* aligned extent found by search */
  	xfs_extlen_t		*slena,	/* aligned extent length */
  	int			dir)	/* 0 = search right, 1 = search left */
  {
  	xfs_agblock_t		new;
  	xfs_agblock_t		sdiff;
  	int			error;
  	int			i;
  
  	/* The good extent is perfect, no need to  search. */
  	if (!gdiff)
  		goto out_use_good;
  
  	/*
  	 * Look until we find a better one, run out of space or run off the end.
  	 */
  	do {
  		error = xfs_alloc_get_rec(*scur, sbno, slen, &i);
  		if (error)
  			goto error0;
  		XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
  		xfs_alloc_compute_aligned(args, *sbno, *slen, sbnoa, slena);
  
  		/*
  		 * The good extent is closer than this one.
  		 */
  		if (!dir) {
  			if (*sbnoa >= args->agbno + gdiff)
  				goto out_use_good;
  		} else {
  			if (*sbnoa <= args->agbno - gdiff)
  				goto out_use_good;
  		}
  
  		/*
  		 * Same distance, compare length and pick the best.
  		 */
  		if (*slena >= args->minlen) {
  			args->len = XFS_EXTLEN_MIN(*slena, args->maxlen);
  			xfs_alloc_fix_len(args);
  
  			sdiff = xfs_alloc_compute_diff(args->agbno, args->len,
  						       args->alignment, *sbnoa,
  						       *slena, &new);
  
  			/*
  			 * Choose closer size and invalidate other cursor.
  			 */
  			if (sdiff < gdiff)
  				goto out_use_search;
  			goto out_use_good;
  		}
  
  		if (!dir)
  			error = xfs_btree_increment(*scur, 0, &i);
  		else
  			error = xfs_btree_decrement(*scur, 0, &i);
  		if (error)
  			goto error0;
  	} while (i);
  
  out_use_good:
  	xfs_btree_del_cursor(*scur, XFS_BTREE_NOERROR);
  	*scur = NULL;
  	return 0;
  
  out_use_search:
  	xfs_btree_del_cursor(*gcur, XFS_BTREE_NOERROR);
  	*gcur = NULL;
  	return 0;
  
  error0:
  	/* caller invalidates cursors */
  	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 */
  	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 */
  	int		forced = 0;
  #if defined(DEBUG) && defined(__KERNEL__)
  	/*
  	 * Randomly don't execute the first algorithm.
  	 */
  	int		dofirst;	/* set to do first algorithm */
  
  	dofirst = random32() & 1;
  #endif
  
  restart:
  	bno_cur_lt = NULL;
  	bno_cur_gt = NULL;
  	ltlen = 0;
  	gtlena = 0;
  	ltlena = 0;
  
  	/*
  	 * 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);
  
  	/*
  	 * 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);
  			trace_xfs_alloc_near_noentry(args);
  			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(args, ltbno, ltlen,
  						  &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, ltbnoa, ltlena, &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);
  		ASSERT(ltbno + ltlen <= 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_xfs_alloc_near_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 <= ltbno + ltlen);
  		/*
  		 * 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_xfs_alloc_near_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(args, ltbno, ltlen,
  						  &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(args, gtbno, gtlen,
  						  &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) {
  		if (ltlena >= args->minlen) {
  			/*
  			 * Left side is good, look for a right side entry.
  			 */
  			args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
  			xfs_alloc_fix_len(args);
  			ltdiff = xfs_alloc_compute_diff(args->agbno, args->len,
  				args->alignment, ltbnoa, ltlena, &ltnew);
  
  			error = xfs_alloc_find_best_extent(args,
  						&bno_cur_lt, &bno_cur_gt,
  						ltdiff, &gtbno, &gtlen,
  						&gtbnoa, &gtlena,
  						0 /* search right */);
  		} else {
  			ASSERT(gtlena >= args->minlen);
  
  			/*
  			 * Right side is good, look for a left side entry.
  			 */
  			args->len = XFS_EXTLEN_MIN(gtlena, args->maxlen);
  			xfs_alloc_fix_len(args);
  			gtdiff = xfs_alloc_compute_diff(args->agbno, args->len,
  				args->alignment, gtbnoa, gtlena, &gtnew);
  
  			error = xfs_alloc_find_best_extent(args,
  						&bno_cur_gt, &bno_cur_lt,
  						gtdiff, &ltbno, &ltlen,
  						&ltbnoa, &ltlena,
  						1 /* search left */);
  		}
  
  		if (error)
  			goto error0;
  	}
  
  	/*
  	 * If we couldn't get anything, give up.
  	 */
  	if (bno_cur_lt == NULL && bno_cur_gt == NULL) {
  		if (!forced++) {
  			trace_xfs_alloc_near_busy(args);
  			xfs_log_force(args->mp, XFS_LOG_SYNC);
  			goto restart;
  		}
  
  		trace_xfs_alloc_size_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.
  	 */
  	args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
  	xfs_alloc_fix_len(args);
  	if (!xfs_alloc_fix_minleft(args)) {
  		trace_xfs_alloc_near_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,
  				     ltbnoa, ltlena, &ltnew);
  	ASSERT(ltnew >= ltbno);
  	ASSERT(ltnew + rlen <= ltbnoa + ltlena);
  	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;
  
  	if (j)
  		trace_xfs_alloc_near_greater(args);
  	else
  		trace_xfs_alloc_near_lesser(args);
  
  	xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
  	xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
  	return 0;
  
   error0:
  	trace_xfs_alloc_near_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 */
  	int		forced = 0;
  
  restart:
  	/*
  	 * 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 or we have busy extents that we cannot allocate from, then
  	 * we have to settle for a smaller extent. In the case that there are
  	 * no large extents, this will return the last entry in the tree unless
  	 * the tree is empty. In the case that there are only busy large
  	 * extents, this will return the largest small extent unless there
  	 * are no smaller extents available.
  	 */
  	if (!i || forced > 1) {
  		error = xfs_alloc_ag_vextent_small(args, cnt_cur,
  						   &fbno, &flen, &i);
  		if (error)
  			goto error0;
  		if (i == 0 || flen == 0) {
  			xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
  			trace_xfs_alloc_size_noentry(args);
  			return 0;
  		}
  		ASSERT(i == 1);
  		xfs_alloc_compute_aligned(args, fbno, flen, &rbno, &rlen);
  	} else {
  		/*
  		 * Search for a non-busy extent that is large enough.
  		 * If we are at low space, don't check, or if we fall of
  		 * the end of the btree, turn off the busy check and
  		 * restart.
  		 */
  		for (;;) {
  			error = xfs_alloc_get_rec(cnt_cur, &fbno, &flen, &i);
  			if (error)
  				goto error0;
  			XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
  
  			xfs_alloc_compute_aligned(args, fbno, flen,
  						  &rbno, &rlen);
  
  			if (rlen >= args->maxlen)
  				break;
  
  			error = xfs_btree_increment(cnt_cur, 0, &i);
  			if (error)
  				goto error0;
  			if (i == 0) {
  				/*
  				 * Our only valid extents must have been busy.
  				 * Make it unbusy by forcing the log out and
  				 * retrying. If we've been here before, forcing
  				 * the log isn't making the extents available,
  				 * which means they have probably been freed in
  				 * this transaction.  In that case, we have to
  				 * give up on them and we'll attempt a minlen
  				 * allocation the next time around.
  				 */
  				xfs_btree_del_cursor(cnt_cur,
  						     XFS_BTREE_NOERROR);
  				trace_xfs_alloc_size_busy(args);
  				if (!forced++)
  					xfs_log_force(args->mp, XFS_LOG_SYNC);
  				goto restart;
  			}
  		}
  	}
  
  	/*
  	 * 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.
  	 */
  	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(args, fbno, flen,
  						  &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;
  	if (rlen < args->minlen) {
  		if (!forced++) {
  			xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
  			trace_xfs_alloc_size_busy(args);
  			xfs_log_force(args->mp, XFS_LOG_SYNC);
  			goto restart;
  		}
  		goto out_nominleft;
  	}
  	xfs_alloc_fix_len(args);
  
  	if (!xfs_alloc_fix_minleft(args))
  		goto out_nominleft;
  	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_xfs_alloc_size_done(args);
  	return 0;
  
  error0:
  	trace_xfs_alloc_size_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;
  
  out_nominleft:
  	xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
  	trace_xfs_alloc_size_nominleft(args);
  	args->agbno = NULLAGBLOCK;
  	return 0;
  }
  
  /*
   * 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) {
  			xfs_alloc_busy_reuse(args->mp, args->agno, fbno, 1,
  					     args->userdata);
  
  			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_xfs_alloc_small_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_xfs_alloc_small_notenough(args);
  		flen = 0;
  	}
  	*fbnop = fbno;
  	*flenp = flen;
  	*stat = 1;
  	trace_xfs_alloc_small_done(args);
  	return 0;
  
  error0:
  	trace_xfs_alloc_small_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 */
  	xfs_perag_t	*pag;		/* per allocation group data */
  
  	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_btree_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_btree_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_btree_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_btree_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_btree_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_btree_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_btree_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.
  	 */
  	pag = xfs_perag_get(mp, agno);
  	error = xfs_alloc_update_counters(tp, pag, agbp, len);
  	xfs_perag_put(pag);
  	if (error)
  		goto error0;
  
  	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_xfs_free_extent(mp, agno, bno, len, isfl, haveleft, haveright);
  
  	return 0;
  
   error0:
  	trace_xfs_free_extent(mp, agno, bno, len, isfl, -1, -1);
  	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;
  }
  
  /*
   * Find the length of the longest extent in an AG.
   */
  xfs_extlen_t
  xfs_alloc_longest_free_extent(
  	struct xfs_mount	*mp,
  	struct xfs_perag	*pag)
  {
  	xfs_extlen_t		need, delta = 0;
  
  	need = XFS_MIN_FREELIST_PAG(pag, mp);
  	if (need > pag->pagf_flcount)
  		delta = need - pag->pagf_flcount;
  
  	if (pag->pagf_longest > delta)
  		return pag->pagf_longest - delta;
  	return pag->pagf_flcount > 0 || pag->pagf_longest > 0;
  }
  
  /*
   * 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)) {
  		/*
  		 * If it looks like there isn't a long enough extent, or enough
  		 * total blocks, reject it.
  		 */
  		need = XFS_MIN_FREELIST_PAG(pag, mp);
  		longest = xfs_alloc_longest_free_extent(mp, pag);
  		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 = xfs_perag_get(mp, be32_to_cpu(agf->agf_seqno));
  	be32_add_cpu(&agf->agf_flcount, -1);
  	xfs_trans_agflist_delta(tp, -1);
  	pag->pagf_flcount--;
  	xfs_perag_put(pag);
  
  	logflags = XFS_AGF_FLFIRST | XFS_AGF_FLCOUNT;
  	if (btreeblk) {
  		be32_add_cpu(&agf->agf_btreeblks, 1);
  		pag->pagf_btreeblks++;
  		logflags |= XFS_AGF_BTREEBLKS;
  	}
  
  	xfs_alloc_log_agf(tp, agbp, logflags);
  	*bnop = bno;
  
  	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)
  	};
  
  	trace_xfs_agf(tp->t_mountp, XFS_BUF_TO_AGF(bp), fields, _RET_IP_);
  
  	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 = xfs_perag_get(mp, 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;
  	}
  	xfs_perag_put(pag);
  
  	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);
  	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_read_agf(
  	struct xfs_mount	*mp,	/* mount point structure */
  	struct xfs_trans	*tp,	/* transaction pointer */
  	xfs_agnumber_t		agno,	/* allocation group number */
  	int			flags,	/* XFS_BUF_ */
  	struct xfs_buf		**bpp)	/* buffer for the ag freelist header */
  {
  	struct xfs_agf	*agf;		/* ag freelist header */
  	int		agf_ok;		/* set if agf is consistent */
  	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, bpp);
  	if (error)
  		return error;
  	if (!*bpp)
  		return 0;
  
  	ASSERT(!(*bpp)->b_error);
  	agf = XFS_BUF_TO_AGF(*bpp);
  
  	/*
  	 * Validate the magic number of the agf block.
  	 */
  	agf_ok =
  		agf->agf_magicnum == cpu_to_be32(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) &&
  		be32_to_cpu(agf->agf_seqno) == agno;
  	if (xfs_sb_version_haslazysbcount(&mp->m_sb))
  		agf_ok = agf_ok && be32_to_cpu(agf->agf_btreeblks) <=
  						be32_to_cpu(agf->agf_length);
  	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, *bpp);
  		return XFS_ERROR(EFSCORRUPTED);
  	}
  	xfs_buf_set_ref(*bpp, XFS_AGF_REF);
  	return 0;
  }
  
  /*
   * Read in the allocation group header (free/alloc section).
   */
  int					/* error */
  xfs_alloc_read_agf(
  	struct xfs_mount	*mp,	/* mount point structure */
  	struct xfs_trans	*tp,	/* transaction pointer */
  	xfs_agnumber_t		agno,	/* allocation group number */
  	int			flags,	/* XFS_ALLOC_FLAG_... */
  	struct xfs_buf		**bpp)	/* buffer for the ag freelist header */
  {
  	struct xfs_agf		*agf;		/* ag freelist header */
  	struct xfs_perag	*pag;		/* per allocation group data */
  	int			error;
  
  	ASSERT(agno != NULLAGNUMBER);
  
  	error = xfs_read_agf(mp, tp, agno,
  			(flags & XFS_ALLOC_FLAG_TRYLOCK) ? XBF_TRYLOCK : 0,
  			bpp);
  	if (error)
  		return error;
  	if (!*bpp)
  		return 0;
  	ASSERT(!(*bpp)->b_error);
  
  	agf = XFS_BUF_TO_AGF(*bpp);
  	pag = xfs_perag_get(mp, 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_count = 0;
  		pag->pagb_tree = RB_ROOT;
  		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_btreeblks == be32_to_cpu(agf->agf_btreeblks));
  		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_perag_put(pag);
  	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_xfs_alloc_vextent_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);
  		args->pag = xfs_perag_get(mp, args->agno);
  		args->minleft = 0;
  		error = xfs_alloc_fix_freelist(args, 0);
  		args->minleft = minleft;
  		if (error) {
  			trace_xfs_alloc_vextent_nofix(args);
  			goto error0;
  		}
  		if (!args->agbp) {
  			trace_xfs_alloc_vextent_noagbp(args);
  			break;
  		}
  		args->agbno = XFS_FSB_TO_AGBNO(mp, args->fsbno);
  		if ((error = xfs_alloc_ag_vextent(args)))
  			goto error0;
  		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.
  		 */
  		for (;;) {
  			args->pag = xfs_perag_get(mp, args->agno);
  			if (no_min) args->minleft = 0;
  			error = xfs_alloc_fix_freelist(args, flags);
  			args->minleft = minleft;
  			if (error) {
  				trace_xfs_alloc_vextent_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_xfs_alloc_vextent_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_xfs_alloc_vextent_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;
  					}
  				}
  			}
  			xfs_perag_put(args->pag);
  		}
  		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
  	}
  	xfs_perag_put(args->pag);
  	return 0;
  error0:
  	xfs_perag_put(args->pag);
  	return error;
  }
  
  static void
  xfs_alloc_vextent_worker(
  	struct work_struct	*work)
  {
  	struct xfs_alloc_arg	*args = container_of(work,
  						struct xfs_alloc_arg, work);
  	unsigned long		pflags;
  
  	/* we are in a transaction context here */
  	current_set_flags_nested(&pflags, PF_FSTRANS);
  
  	args->result = __xfs_alloc_vextent(args);
  	complete(args->done);
  
  	current_restore_flags_nested(&pflags, PF_FSTRANS);
  }
  
  
  int				/* error */
  xfs_alloc_vextent(
  	xfs_alloc_arg_t	*args)	/* allocation argument structure */
  {
  	DECLARE_COMPLETION_ONSTACK(done);
  
  	args->done = &done;
  	INIT_WORK(&args->work, xfs_alloc_vextent_worker);
  	queue_work(xfs_alloc_wq, &args->work);
  	wait_for_completion(&done);
  	return args->result;
  }
  
  /*
   * 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;
  
  	/*
  	 * validate that the block number is legal - the enables us to detect
  	 * and handle a silent filesystem corruption rather than crashing.
  	 */
  	args.agno = XFS_FSB_TO_AGNO(args.mp, bno);
  	if (args.agno >= args.mp->m_sb.sb_agcount)
  		return EFSCORRUPTED;
  
  	args.agbno = XFS_FSB_TO_AGBNO(args.mp, bno);
  	if (args.agbno >= args.mp->m_sb.sb_agblocks)
  		return EFSCORRUPTED;
  
  	args.pag = xfs_perag_get(args.mp, args.agno);
  	ASSERT(args.pag);
  
  	error = xfs_alloc_fix_freelist(&args, XFS_ALLOC_FLAG_FREEING);
  	if (error)
  		goto error0;
  
  	/* validate the extent size is legal now we have the agf locked */
  	if (args.agbno + len >
  			be32_to_cpu(XFS_BUF_TO_AGF(args.agbp)->agf_length)) {
  		error = EFSCORRUPTED;
  		goto error0;
  	}
  
  	error = xfs_free_ag_extent(tp, args.agbp, args.agno, args.agbno, len, 0);
  	if (!error)
  		xfs_alloc_busy_insert(tp, args.agno, args.agbno, len, 0);
  error0:
  	xfs_perag_put(args.pag);
  	return error;
  }
  
  void
  xfs_alloc_busy_insert(
  	struct xfs_trans	*tp,
  	xfs_agnumber_t		agno,
  	xfs_agblock_t		bno,
  	xfs_extlen_t		len,
  	unsigned int		flags)
  {
  	struct xfs_busy_extent	*new;
  	struct xfs_busy_extent	*busyp;
  	struct xfs_perag	*pag;
  	struct rb_node		**rbp;
  	struct rb_node		*parent = NULL;
  
  	new = kmem_zalloc(sizeof(struct xfs_busy_extent), KM_MAYFAIL);
  	if (!new) {
  		/*
  		 * No Memory!  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.
  		 */
  		trace_xfs_alloc_busy_enomem(tp->t_mountp, agno, bno, len);
  		xfs_trans_set_sync(tp);
  		return;
  	}
  
  	new->agno = agno;
  	new->bno = bno;
  	new->length = len;
  	INIT_LIST_HEAD(&new->list);
  	new->flags = flags;
  
  	/* trace before insert to be able to see failed inserts */
  	trace_xfs_alloc_busy(tp->t_mountp, agno, bno, len);
  
  	pag = xfs_perag_get(tp->t_mountp, new->agno);
  	spin_lock(&pag->pagb_lock);
  	rbp = &pag->pagb_tree.rb_node;
  	while (*rbp) {
  		parent = *rbp;
  		busyp = rb_entry(parent, struct xfs_busy_extent, rb_node);
  
  		if (new->bno < busyp->bno) {
  			rbp = &(*rbp)->rb_left;
  			ASSERT(new->bno + new->length <= busyp->bno);
  		} else if (new->bno > busyp->bno) {
  			rbp = &(*rbp)->rb_right;
  			ASSERT(bno >= busyp->bno + busyp->length);
  		} else {
  			ASSERT(0);
  		}
  	}
  
  	rb_link_node(&new->rb_node, parent, rbp);
  	rb_insert_color(&new->rb_node, &pag->pagb_tree);
  
  	list_add(&new->list, &tp->t_busy);
  	spin_unlock(&pag->pagb_lock);
  	xfs_perag_put(pag);
  }
  
  /*
   * Search for a busy extent within the range of the extent we are about to
   * allocate.  You need to be holding the busy extent tree lock when calling
   * xfs_alloc_busy_search(). This function returns 0 for no overlapping busy
   * extent, -1 for an overlapping but not exact busy extent, and 1 for an exact
   * match. This is done so that a non-zero return indicates an overlap that
   * will require a synchronous transaction, but it can still be
   * used to distinguish between a partial or exact match.
   */
  int
  xfs_alloc_busy_search(
  	struct xfs_mount	*mp,
  	xfs_agnumber_t		agno,
  	xfs_agblock_t		bno,
  	xfs_extlen_t		len)
  {
  	struct xfs_perag	*pag;
  	struct rb_node		*rbp;
  	struct xfs_busy_extent	*busyp;
  	int			match = 0;
  
  	pag = xfs_perag_get(mp, agno);
  	spin_lock(&pag->pagb_lock);
  
  	rbp = pag->pagb_tree.rb_node;
  
  	/* find closest start bno overlap */
  	while (rbp) {
  		busyp = rb_entry(rbp, struct xfs_busy_extent, rb_node);
  		if (bno < busyp->bno) {
  			/* may overlap, but exact start block is lower */
  			if (bno + len > busyp->bno)
  				match = -1;
  			rbp = rbp->rb_left;
  		} else if (bno > busyp->bno) {
  			/* may overlap, but exact start block is higher */
  			if (bno < busyp->bno + busyp->length)
  				match = -1;
  			rbp = rbp->rb_right;
  		} else {
  			/* bno matches busyp, length determines exact match */
  			match = (busyp->length == len) ? 1 : -1;
  			break;
  		}
  	}
  	spin_unlock(&pag->pagb_lock);
  	xfs_perag_put(pag);
  	return match;
  }
  
  /*
   * The found free extent [fbno, fend] overlaps part or all of the given busy
   * extent.  If the overlap covers the beginning, the end, or all of the busy
   * extent, the overlapping portion can be made unbusy and used for the
   * allocation.  We can't split a busy extent because we can't modify a
   * transaction/CIL context busy list, but we can update an entries block
   * number or length.
   *
   * Returns true if the extent can safely be reused, or false if the search
   * needs to be restarted.
   */
  STATIC bool
  xfs_alloc_busy_update_extent(
  	struct xfs_mount	*mp,
  	struct xfs_perag	*pag,
  	struct xfs_busy_extent	*busyp,
  	xfs_agblock_t		fbno,
  	xfs_extlen_t		flen,
  	bool			userdata)
  {
  	xfs_agblock_t		fend = fbno + flen;
  	xfs_agblock_t		bbno = busyp->bno;
  	xfs_agblock_t		bend = bbno + busyp->length;
  
  	/*
  	 * This extent is currently being discarded.  Give the thread
  	 * performing the discard a chance to mark the extent unbusy
  	 * and retry.
  	 */
  	if (busyp->flags & XFS_ALLOC_BUSY_DISCARDED) {
  		spin_unlock(&pag->pagb_lock);
  		delay(1);
  		spin_lock(&pag->pagb_lock);
  		return false;
  	}
  
  	/*
  	 * If there is a busy extent overlapping a user allocation, we have
  	 * no choice but to force the log and retry the search.
  	 *
  	 * Fortunately this does not happen during normal operation, but
  	 * only if the filesystem is very low on space and has to dip into
  	 * the AGFL for normal allocations.
  	 */
  	if (userdata)
  		goto out_force_log;
  
  	if (bbno < fbno && bend > fend) {
  		/*
  		 * Case 1:
  		 *    bbno           bend
  		 *    +BBBBBBBBBBBBBBBBB+
  		 *        +---------+
  		 *        fbno   fend
  		 */
  
  		/*
  		 * We would have to split the busy extent to be able to track
  		 * it correct, which we cannot do because we would have to
  		 * modify the list of busy extents attached to the transaction
  		 * or CIL context, which is immutable.
  		 *
  		 * Force out the log to clear the busy extent and retry the
  		 * search.
  		 */
  		goto out_force_log;
  	} else if (bbno >= fbno && bend <= fend) {
  		/*
  		 * Case 2:
  		 *    bbno           bend
  		 *    +BBBBBBBBBBBBBBBBB+
  		 *    +-----------------+
  		 *    fbno           fend
  		 *
  		 * Case 3:
  		 *    bbno           bend
  		 *    +BBBBBBBBBBBBBBBBB+
  		 *    +--------------------------+
  		 *    fbno                    fend
  		 *
  		 * Case 4:
  		 *             bbno           bend
  		 *             +BBBBBBBBBBBBBBBBB+
  		 *    +--------------------------+
  		 *    fbno                    fend
  		 *
  		 * Case 5:
  		 *             bbno           bend
  		 *             +BBBBBBBBBBBBBBBBB+
  		 *    +-----------------------------------+
  		 *    fbno                             fend
  		 *
  		 */
  
  		/*
  		 * The busy extent is fully covered by the extent we are
  		 * allocating, and can simply be removed from the rbtree.
  		 * However we cannot remove it from the immutable list
  		 * tracking busy extents in the transaction or CIL context,
  		 * so set the length to zero to mark it invalid.
  		 *
  		 * We also need to restart the busy extent search from the
  		 * tree root, because erasing the node can rearrange the
  		 * tree topology.
  		 */
  		rb_erase(&busyp->rb_node, &pag->pagb_tree);
  		busyp->length = 0;
  		return false;
  	} else if (fend < bend) {
  		/*
  		 * Case 6:
  		 *              bbno           bend
  		 *             +BBBBBBBBBBBBBBBBB+
  		 *             +---------+
  		 *             fbno   fend
  		 *
  		 * Case 7:
  		 *             bbno           bend
  		 *             +BBBBBBBBBBBBBBBBB+
  		 *    +------------------+
  		 *    fbno            fend
  		 *
  		 */
  		busyp->bno = fend;
  	} else if (bbno < fbno) {
  		/*
  		 * Case 8:
  		 *    bbno           bend
  		 *    +BBBBBBBBBBBBBBBBB+
  		 *        +-------------+
  		 *        fbno       fend
  		 *
  		 * Case 9:
  		 *    bbno           bend
  		 *    +BBBBBBBBBBBBBBBBB+
  		 *        +----------------------+
  		 *        fbno                fend
  		 */
  		busyp->length = fbno - busyp->bno;
  	} else {
  		ASSERT(0);
  	}
  
  	trace_xfs_alloc_busy_reuse(mp, pag->pag_agno, fbno, flen);
  	return true;
  
  out_force_log:
  	spin_unlock(&pag->pagb_lock);
  	xfs_log_force(mp, XFS_LOG_SYNC);
  	trace_xfs_alloc_busy_force(mp, pag->pag_agno, fbno, flen);
  	spin_lock(&pag->pagb_lock);
  	return false;
  }
  
  
  /*
   * For a given extent [fbno, flen], make sure we can reuse it safely.
   */
  void
  xfs_alloc_busy_reuse(
  	struct xfs_mount	*mp,
  	xfs_agnumber_t		agno,
  	xfs_agblock_t		fbno,
  	xfs_extlen_t		flen,
  	bool			userdata)
  {
  	struct xfs_perag	*pag;
  	struct rb_node		*rbp;
  
  	ASSERT(flen > 0);
  
  	pag = xfs_perag_get(mp, agno);
  	spin_lock(&pag->pagb_lock);
  restart:
  	rbp = pag->pagb_tree.rb_node;
  	while (rbp) {
  		struct xfs_busy_extent *busyp =
  			rb_entry(rbp, struct xfs_busy_extent, rb_node);
  		xfs_agblock_t	bbno = busyp->bno;
  		xfs_agblock_t	bend = bbno + busyp->length;
  
  		if (fbno + flen <= bbno) {
  			rbp = rbp->rb_left;
  			continue;
  		} else if (fbno >= bend) {
  			rbp = rbp->rb_right;
  			continue;
  		}
  
  		if (!xfs_alloc_busy_update_extent(mp, pag, busyp, fbno, flen,
  						  userdata))
  			goto restart;
  	}
  	spin_unlock(&pag->pagb_lock);
  	xfs_perag_put(pag);
  }
  
  /*
   * For a given extent [fbno, flen], search the busy extent list to find a
   * subset of the extent that is not busy.  If *rlen is smaller than
   * args->minlen no suitable extent could be found, and the higher level
   * code needs to force out the log and retry the allocation.
   */
  STATIC void
  xfs_alloc_busy_trim(
  	struct xfs_alloc_arg	*args,
  	xfs_agblock_t		bno,
  	xfs_extlen_t		len,
  	xfs_agblock_t		*rbno,
  	xfs_extlen_t		*rlen)
  {
  	xfs_agblock_t		fbno;
  	xfs_extlen_t		flen;
  	struct rb_node		*rbp;
  
  	ASSERT(len > 0);
  
  	spin_lock(&args->pag->pagb_lock);
  restart:
  	fbno = bno;
  	flen = len;
  	rbp = args->pag->pagb_tree.rb_node;
  	while (rbp && flen >= args->minlen) {
  		struct xfs_busy_extent *busyp =
  			rb_entry(rbp, struct xfs_busy_extent, rb_node);
  		xfs_agblock_t	fend = fbno + flen;
  		xfs_agblock_t	bbno = busyp->bno;
  		xfs_agblock_t	bend = bbno + busyp->length;
  
  		if (fend <= bbno) {
  			rbp = rbp->rb_left;
  			continue;
  		} else if (fbno >= bend) {
  			rbp = rbp->rb_right;
  			continue;
  		}
  
  		/*
  		 * If this is a metadata allocation, try to reuse the busy
  		 * extent instead of trimming the allocation.
  		 */
  		if (!args->userdata &&
  		    !(busyp->flags & XFS_ALLOC_BUSY_DISCARDED)) {
  			if (!xfs_alloc_busy_update_extent(args->mp, args->pag,
  							  busyp, fbno, flen,
  							  false))
  				goto restart;
  			continue;
  		}
  
  		if (bbno <= fbno) {
  			/* start overlap */
  
  			/*
  			 * Case 1:
  			 *    bbno           bend
  			 *    +BBBBBBBBBBBBBBBBB+
  			 *        +---------+
  			 *        fbno   fend
  			 *
  			 * Case 2:
  			 *    bbno           bend
  			 *    +BBBBBBBBBBBBBBBBB+
  			 *    +-------------+
  			 *    fbno       fend
  			 *
  			 * Case 3:
  			 *    bbno           bend
  			 *    +BBBBBBBBBBBBBBBBB+
  			 *        +-------------+
  			 *        fbno       fend
  			 *
  			 * Case 4:
  			 *    bbno           bend
  			 *    +BBBBBBBBBBBBBBBBB+
  			 *    +-----------------+
  			 *    fbno           fend
  			 *
  			 * No unbusy region in extent, return failure.
  			 */
  			if (fend <= bend)
  				goto fail;
  
  			/*
  			 * Case 5:
  			 *    bbno           bend
  			 *    +BBBBBBBBBBBBBBBBB+
  			 *        +----------------------+
  			 *        fbno                fend
  			 *
  			 * Case 6:
  			 *    bbno           bend
  			 *    +BBBBBBBBBBBBBBBBB+
  			 *    +--------------------------+
  			 *    fbno                    fend
  			 *
  			 * Needs to be trimmed to:
  			 *                       +-------+
  			 *                       fbno fend
  			 */
  			fbno = bend;
  		} else if (bend >= fend) {
  			/* end overlap */
  
  			/*
  			 * Case 7:
  			 *             bbno           bend
  			 *             +BBBBBBBBBBBBBBBBB+
  			 *    +------------------+
  			 *    fbno            fend
  			 *
  			 * Case 8:
  			 *             bbno           bend
  			 *             +BBBBBBBBBBBBBBBBB+
  			 *    +--------------------------+
  			 *    fbno                    fend
  			 *
  			 * Needs to be trimmed to:
  			 *    +-------+
  			 *    fbno fend
  			 */
  			fend = bbno;
  		} else {
  			/* middle overlap */
  
  			/*
  			 * Case 9:
  			 *             bbno           bend
  			 *             +BBBBBBBBBBBBBBBBB+
  			 *    +-----------------------------------+
  			 *    fbno                             fend
  			 *
  			 * Can be trimmed to:
  			 *    +-------+        OR         +-------+
  			 *    fbno fend                   fbno fend
  			 *
  			 * Backward allocation leads to significant
  			 * fragmentation of directories, which degrades
  			 * directory performance, therefore we always want to
  			 * choose the option that produces forward allocation
  			 * patterns.
  			 * Preferring the lower bno extent will make the next
  			 * request use "fend" as the start of the next
  			 * allocation;  if the segment is no longer busy at
  			 * that point, we'll get a contiguous allocation, but
  			 * even if it is still busy, we will get a forward
  			 * allocation.
  			 * We try to avoid choosing the segment at "bend",
  			 * because that can lead to the next allocation
  			 * taking the segment at "fbno", which would be a
  			 * backward allocation.  We only use the segment at
  			 * "fbno" if it is much larger than the current
  			 * requested size, because in that case there's a
  			 * good chance subsequent allocations will be
  			 * contiguous.
  			 */
  			if (bbno - fbno >= args->maxlen) {
  				/* left candidate fits perfect */
  				fend = bbno;
  			} else if (fend - bend >= args->maxlen * 4) {
  				/* right candidate has enough free space */
  				fbno = bend;
  			} else if (bbno - fbno >= args->minlen) {
  				/* left candidate fits minimum requirement */
  				fend = bbno;
  			} else {
  				goto fail;
  			}
  		}
  
  		flen = fend - fbno;
  	}
  	spin_unlock(&args->pag->pagb_lock);
  
  	if (fbno != bno || flen != len) {
  		trace_xfs_alloc_busy_trim(args->mp, args->agno, bno, len,
  					  fbno, flen);
  	}
  	*rbno = fbno;
  	*rlen = flen;
  	return;
  fail:
  	/*
  	 * Return a zero extent length as failure indications.  All callers
  	 * re-check if the trimmed extent satisfies the minlen requirement.
  	 */
  	spin_unlock(&args->pag->pagb_lock);
  	trace_xfs_alloc_busy_trim(args->mp, args->agno, bno, len, fbno, 0);
  	*rbno = fbno;
  	*rlen = 0;
  }
  
  static void
  xfs_alloc_busy_clear_one(
  	struct xfs_mount	*mp,
  	struct xfs_perag	*pag,
  	struct xfs_busy_extent	*busyp)
  {
  	if (busyp->length) {
  		trace_xfs_alloc_busy_clear(mp, busyp->agno, busyp->bno,
  						busyp->length);
  		rb_erase(&busyp->rb_node, &pag->pagb_tree);
  	}
  
  	list_del_init(&busyp->list);
  	kmem_free(busyp);
  }
  
  /*
   * Remove all extents on the passed in list from the busy extents tree.
   * If do_discard is set skip extents that need to be discarded, and mark
   * these as undergoing a discard operation instead.
   */
  void
  xfs_alloc_busy_clear(
  	struct xfs_mount	*mp,
  	struct list_head	*list,
  	bool			do_discard)
  {
  	struct xfs_busy_extent	*busyp, *n;
  	struct xfs_perag	*pag = NULL;
  	xfs_agnumber_t		agno = NULLAGNUMBER;
  
  	list_for_each_entry_safe(busyp, n, list, list) {
  		if (busyp->agno != agno) {
  			if (pag) {
  				spin_unlock(&pag->pagb_lock);
  				xfs_perag_put(pag);
  			}
  			pag = xfs_perag_get(mp, busyp->agno);
  			spin_lock(&pag->pagb_lock);
  			agno = busyp->agno;
  		}
  
  		if (do_discard && busyp->length &&
  		    !(busyp->flags & XFS_ALLOC_BUSY_SKIP_DISCARD))
  			busyp->flags = XFS_ALLOC_BUSY_DISCARDED;
  		else
  			xfs_alloc_busy_clear_one(mp, pag, busyp);
  	}
  
  	if (pag) {
  		spin_unlock(&pag->pagb_lock);
  		xfs_perag_put(pag);
  	}
  }
  
  /*
   * Callback for list_sort to sort busy extents by the AG they reside in.
   */
  int
  xfs_busy_extent_ag_cmp(
  	void			*priv,
  	struct list_head	*a,
  	struct list_head	*b)
  {
  	return container_of(a, struct xfs_busy_extent, list)->agno -
  		container_of(b, struct xfs_busy_extent, list)->agno;
  }
  