patch-2.4.25 linux-2.4.25/fs/xfs/xfs_alloc.c

• Lines: 2620
• Date: 2004-02-18 05:36:32.000000000 -0800
• Orig file: linux-2.4.24/fs/xfs/xfs_alloc.c
• Orig date: 1969-12-31 16:00:00.000000000 -0800

diff -urN linux-2.4.24/fs/xfs/xfs_alloc.c linux-2.4.25/fs/xfs/xfs_alloc.c
@@ -0,0 +1,2619 @@
+/*
+ * Copyright (c) 2000-2002 Silicon Graphics, Inc.  All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2 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.
+ *
+ * Further, this software is distributed without any warranty that it is
+ * free of the rightful claim of any third person regarding infringement
+ * or the like.  Any license provided herein, whether implied or
+ * otherwise, applies only to this software file.  Patent licenses, if
+ * any, provided herein do not apply to combinations of this program with
+ * other software, or any other product whatsoever.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write the Free Software Foundation, Inc., 59
+ * Temple Place - Suite 330, Boston MA 02111-1307, USA.
+ *
+ * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
+ * Mountain View, CA  94043, or:
+ *
+ * http://www.sgi.com
+ *
+ * For further information regarding this notice, see:
+ *
+ * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
+ */
+
+/*
+ * Free space allocation for XFS.
+ */
+#include "xfs.h"
+#include "xfs_macros.h"
+#include "xfs_types.h"
+#include "xfs_inum.h"
+#include "xfs_log.h"
+#include "xfs_trans.h"
+#include "xfs_sb.h"
+#include "xfs_ag.h"
+#include "xfs_dir.h"
+#include "xfs_dmapi.h"
+#include "xfs_mount.h"
+#include "xfs_alloc_btree.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_ialloc_btree.h"
+#include "xfs_btree.h"
+#include "xfs_ialloc.h"
+#include "xfs_alloc.h"
+#include "xfs_bit.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
+
+int
+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(fname, s, a, __LINE__)
+#define	TRACE_FREE(s,a,b,x,f)	\
+	xfs_alloc_trace_free(fname, s, mp, a, b, x, f, __LINE__)
+#define	TRACE_MODAGF(s,a,f)	\
+	xfs_alloc_trace_modagf(fname, s, mp, a, f, __LINE__)
+#define	TRACE_BUSY(fname,s,ag,agb,l,sl,tp)	\
+	xfs_alloc_trace_busy(fname, s, mp, ag, agb, l, sl, tp, XFS_ALLOC_KTRACE_BUSY, __LINE__)
+#define	TRACE_UNBUSY(fname,s,ag,sl,tp)	\
+	xfs_alloc_trace_busy(fname, s, mp, ag, -1, -1, sl, tp, XFS_ALLOC_KTRACE_UNBUSY, __LINE__)
+#define	TRACE_BUSYSEARCH(fname,s,ag,agb,l,sl,tp)	\
+	xfs_alloc_trace_busy(fname, s, mp, ag, agb, l, sl, 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,sl,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.
+ */
+
+/*
+ * Compute aligned version of the found extent.
+ * Takes alignment and min length into account.
+ */
+STATIC int				/* success (>= minlen) */
+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;
+	return len >= minlen;
+}
+
+/*
+ * 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 = INT_GET(agf->agf_freeblks, ARCH_CONVERT)
+		+ INT_GET(agf->agf_flcount, ARCH_CONVERT)
+		- 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(
+				INT_GET(bnoblock->bb_numrecs, ARCH_CONVERT) == INT_GET(cntblock->bb_numrecs, ARCH_CONVERT));
+		}
+	}
+#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(
+	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(
+	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(
+	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)INT_GET(agf->agf_seqno, ARCH_CONVERT),
+		(void *)(__psunsigned_t)INT_GET(agf->agf_length, ARCH_CONVERT),
+		(void *)(__psunsigned_t)INT_GET(agf->agf_roots[XFS_BTNUM_BNO],
+						ARCH_CONVERT),
+		(void *)(__psunsigned_t)INT_GET(agf->agf_roots[XFS_BTNUM_CNT],
+						ARCH_CONVERT),
+		(void *)(__psunsigned_t)INT_GET(agf->agf_levels[XFS_BTNUM_BNO],
+						ARCH_CONVERT),
+		(void *)(__psunsigned_t)INT_GET(agf->agf_levels[XFS_BTNUM_CNT],
+						ARCH_CONVERT),
+		(void *)(__psunsigned_t)INT_GET(agf->agf_flfirst, ARCH_CONVERT),
+		(void *)(__psunsigned_t)INT_GET(agf->agf_fllast, ARCH_CONVERT),
+		(void *)(__psunsigned_t)INT_GET(agf->agf_flcount, ARCH_CONVERT),
+		(void *)(__psunsigned_t)INT_GET(agf->agf_freeblks, ARCH_CONVERT),
+		(void *)(__psunsigned_t)INT_GET(agf->agf_longest, ARCH_CONVERT));
+}
+
+STATIC void
+xfs_alloc_trace_busy(
+	char		*name,		/* function tag string */
+	char		*str,		/* additional string */
+	xfs_mount_t	*mp,		/* file system mount poing */
+	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;
+#ifdef XFS_ALLOC_TRACE
+	static char	fname[] = "xfs_alloc_ag_vextent";
+#endif
+
+	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);
+			INT_MOD(agf->agf_freeblks, ARCH_CONVERT, -(args->len));
+			xfs_trans_agblocks_delta(args->tp,
+						 -((long)(args->len)));
+			args->pag->pagf_freeblks -= args->len;
+			ASSERT(INT_GET(agf->agf_freeblks, ARCH_CONVERT)
+				<= INT_GET(agf->agf_length, ARCH_CONVERT));
+			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 */
+#ifdef XFS_ALLOC_TRACE
+	static char	fname[] = "xfs_alloc_ag_vextent_exact";
+#endif
+	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_btree_init_cursor(args->mp, args->tp, args->agbp,
+		args->agno, XFS_BTNUM_BNO, 0, 0);
+	/*
+	 * 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_btree_init_cursor(args->mp, args->tp, args->agbp,
+		args->agno, XFS_BTNUM_CNT, 0, 0);
+	ASSERT(args->agbno + args->len <=
+		INT_GET(XFS_BUF_TO_AGF(args->agbp)->agf_length,
+			ARCH_CONVERT));
+	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 */
+#ifdef XFS_ALLOC_TRACE
+	static char	fname[] = "xfs_alloc_ag_vextent_near";
+#endif
+	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.
+	 */
+	static int	seed;		/* randomizing seed value */
+	int		dofirst;	/* set to do first algorithm */
+	timespec_t	now;		/* current time */
+
+	if (!seed) {
+		nanotime(&now);
+		seed = (int)now.tv_sec ^ (int)now.tv_nsec;
+	}
+	dofirst = random() & 1;
+#endif
+	/*
+	 * Get a cursor for the by-size btree.
+	 */
+	cnt_cur = xfs_btree_init_cursor(args->mp, args->tp, args->agbp,
+		args->agno, XFS_BTNUM_CNT, 0, 0);
+	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_alloc_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_alloc_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);
+			if (!xfs_alloc_compute_aligned(ltbno, ltlen,
+					args->alignment, args->minlen,
+					&ltbnoa, &ltlena))
+				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 <= INT_GET(XFS_BUF_TO_AGF(args->agbp)->agf_length,
+				ARCH_CONVERT));
+		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_btree_init_cursor(args->mp, args->tp,
+			args->agbp, args->agno, XFS_BTNUM_BNO, 0, 0);
+		/*
+		 * 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_btree_init_cursor(args->mp, args->tp, args->agbp,
+		args->agno, XFS_BTNUM_BNO, 0, 0);
+	/*
+	 * 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 = 0;
+	}
+	/*
+	 * 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_alloc_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);
+			if (xfs_alloc_compute_aligned(ltbno, ltlen,
+					args->alignment, args->minlen,
+					&ltbnoa, &ltlena))
+				break;
+			if ((error = xfs_alloc_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);
+			if (xfs_alloc_compute_aligned(gtbno, gtlen,
+					args->alignment, args->minlen,
+					&gtbnoa, &gtlena))
+				break;
+			if ((error = xfs_alloc_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_alloc_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_alloc_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 <= INT_GET(XFS_BUF_TO_AGF(args->agbp)->agf_length,
+		ARCH_CONVERT));
+	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 */
+#ifdef XFS_ALLOC_TRACE
+	static char	fname[] = "xfs_alloc_ag_vextent_size";
+#endif
+	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_btree_init_cursor(args->mp, args->tp, args->agbp,
+		args->agno, XFS_BTNUM_CNT, 0, 0);
+	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_alloc_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_btree_init_cursor(args->mp, args->tp, args->agbp,
+		args->agno, XFS_BTNUM_BNO, 0, 0);
+	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 <=
+			INT_GET(XFS_BUF_TO_AGF(args->agbp)->agf_length,
+			ARCH_CONVERT),
+		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;
+#ifdef XFS_ALLOC_TRACE
+	static char	fname[] = "xfs_alloc_ag_vextent_small";
+#endif
+	int		i;
+
+	if ((error = xfs_alloc_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 &&
+		 (INT_GET(XFS_BUF_TO_AGF(args->agbp)->agf_flcount,
+			ARCH_CONVERT) > args->minleft)) {
+		if ((error = xfs_alloc_get_freelist(args->tp, args->agbp, &fbno)))
+			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 <=
+				INT_GET(XFS_BUF_TO_AGF(args->agbp)->agf_length,
+					ARCH_CONVERT),
+				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
+		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 */
+#ifdef XFS_ALLOC_TRACE
+	static char	fname[] = "xfs_free_ag_extent";
+#endif
+	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_btree_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_BNO, 0,
+		0);
+	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_alloc_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_btree_init_cursor(mp, tp, agbp, agno, XFS_BTNUM_CNT, 0,
+		0);
+	/*
+	 * 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_alloc_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_alloc_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];
+		INT_MOD(agf->agf_freeblks, ARCH_CONVERT, len);
+		xfs_trans_agblocks_delta(tp, len);
+		pag->pagf_freeblks += len;
+		XFS_WANT_CORRUPTED_GOTO(
+			INT_GET(agf->agf_freeblks, ARCH_CONVERT)
+				<= INT_GET(agf->agf_length, ARCH_CONVERT),
+			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) {
+			args->agbp = NULL;
+			return 0;
+		}
+	} else
+		agbp = NULL;
+
+	/* If this is a metadata prefered 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) {
+		args->agbp = NULL;
+		return 0;
+	}
+
+	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 ||
+	    (args->minleft &&
+	     (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) {
+			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);
+	delta = need > INT_GET(agf->agf_flcount, ARCH_CONVERT) ?
+		(need - INT_GET(agf->agf_flcount, ARCH_CONVERT)) : 0;
+	/*
+	 * If there isn't enough total or single-extent, reject it.
+	 */
+	longest = INT_GET(agf->agf_longest, ARCH_CONVERT);
+	longest = (longest > delta) ? (longest - delta) :
+		(INT_GET(agf->agf_flcount, ARCH_CONVERT) > 0 || longest > 0);
+	if (args->minlen + args->alignment + args->minalignslop - 1 > longest ||
+	     (args->minleft &&
+		(int)(INT_GET(agf->agf_freeblks, ARCH_CONVERT) +
+		   INT_GET(agf->agf_flcount, ARCH_CONVERT) - 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 (INT_GET(agf->agf_flcount, ARCH_CONVERT) > need) {
+		xfs_buf_t	*bp;
+
+		if ((error = xfs_alloc_get_freelist(tp, agbp, &bno)))
+			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 (INT_GET(agf->agf_flcount, ARCH_CONVERT) < need) {
+		targs.agbno = 0;
+		targs.maxlen = need - INT_GET(agf->agf_flcount, ARCH_CONVERT);
+		/*
+		 * Allocate as many blocks as possible at once.
+		 */
+		if ((error = xfs_alloc_ag_vextent(&targs)))
+			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)
+			break;
+		/*
+		 * Put each allocated block on the list.
+		 */
+		for (bno = targs.agbno; bno < targs.agbno + targs.len; bno++) {
+			if ((error = xfs_alloc_put_freelist(tp, agbp, agflbp,
+					bno)))
+				return error;
+		}
+	}
+	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 */
+{
+	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;
+#ifdef XFS_ALLOC_TRACE
+	static char	fname[] = "xfs_alloc_get_freelist";
+#endif
+	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 (INT_ISZERO(agf->agf_flcount, ARCH_CONVERT)) {
+		*bnop = NULLAGBLOCK;
+		return 0;
+	}
+	/*
+	 * Read the array of free blocks.
+	 */
+	mp = tp->t_mountp;
+	if ((error = xfs_alloc_read_agfl(mp, tp,
+			INT_GET(agf->agf_seqno, ARCH_CONVERT), &agflbp)))
+		return error;
+	agfl = XFS_BUF_TO_AGFL(agflbp);
+	/*
+	 * Get the block number and update the data structures.
+	 */
+	bno = INT_GET(agfl->agfl_bno[INT_GET(agf->agf_flfirst, ARCH_CONVERT)], ARCH_CONVERT);
+	INT_MOD(agf->agf_flfirst, ARCH_CONVERT, 1);
+	xfs_trans_brelse(tp, agflbp);
+	if (INT_GET(agf->agf_flfirst, ARCH_CONVERT) == XFS_AGFL_SIZE(mp))
+		INT_ZERO(agf->agf_flfirst, ARCH_CONVERT);
+	pag = &mp->m_perag[INT_GET(agf->agf_seqno, ARCH_CONVERT)];
+	INT_MOD(agf->agf_flcount, ARCH_CONVERT, -1);
+	xfs_trans_agflist_delta(tp, -1);
+	pag->pagf_flcount--;
+	TRACE_MODAGF(NULL, agf, XFS_AGF_FLFIRST | XFS_AGF_FLCOUNT);
+	xfs_alloc_log_agf(tp, agbp, XFS_AGF_FLFIRST | XFS_AGF_FLCOUNT);
+	*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, INT_GET(agf->agf_seqno, ARCH_CONVERT), 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),
+		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 */
+{
+	xfs_agf_t		*agf;	/* a.g. freespace structure */
+	xfs_agfl_t		*agfl;	/* a.g. free block array */
+	xfs_agblock_t		*blockp;/* pointer to array entry */
+	int			error;
+#ifdef XFS_ALLOC_TRACE
+	static char		fname[] = "xfs_alloc_put_freelist";
+#endif
+	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,
+			INT_GET(agf->agf_seqno, ARCH_CONVERT), &agflbp)))
+		return error;
+	agfl = XFS_BUF_TO_AGFL(agflbp);
+	INT_MOD(agf->agf_fllast, ARCH_CONVERT, 1);
+	if (INT_GET(agf->agf_fllast, ARCH_CONVERT) == XFS_AGFL_SIZE(mp))
+		INT_ZERO(agf->agf_fllast, ARCH_CONVERT);
+	pag = &mp->m_perag[INT_GET(agf->agf_seqno, ARCH_CONVERT)];
+	INT_MOD(agf->agf_flcount, ARCH_CONVERT, 1);
+	xfs_trans_agflist_delta(tp, 1);
+	pag->pagf_flcount++;
+	ASSERT(INT_GET(agf->agf_flcount, ARCH_CONVERT) <= XFS_AGFL_SIZE(mp));
+	blockp = &agfl->agfl_bno[INT_GET(agf->agf_fllast, ARCH_CONVERT)];
+	INT_SET(*blockp, ARCH_CONVERT, bno);
+	TRACE_MODAGF(NULL, agf, XFS_AGF_FLLAST | XFS_AGF_FLCOUNT);
+	xfs_alloc_log_agf(tp, agbp, XFS_AGF_FLLAST | XFS_AGF_FLCOUNT);
+	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 =
+		INT_GET(agf->agf_magicnum, ARCH_CONVERT) == XFS_AGF_MAGIC &&
+		XFS_AGF_GOOD_VERSION(
+			INT_GET(agf->agf_versionnum, ARCH_CONVERT)) &&
+		INT_GET(agf->agf_freeblks, ARCH_CONVERT) <=
+				INT_GET(agf->agf_length, ARCH_CONVERT) &&
+		INT_GET(agf->agf_flfirst, ARCH_CONVERT) < XFS_AGFL_SIZE(mp) &&
+		INT_GET(agf->agf_fllast,  ARCH_CONVERT) < XFS_AGFL_SIZE(mp) &&
+		INT_GET(agf->agf_flcount, ARCH_CONVERT) <= 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 = INT_GET(agf->agf_freeblks, ARCH_CONVERT);
+		pag->pagf_flcount = INT_GET(agf->agf_flcount, ARCH_CONVERT);
+		pag->pagf_longest = INT_GET(agf->agf_longest, ARCH_CONVERT);
+		pag->pagf_levels[XFS_BTNUM_BNOi] =
+			INT_GET(agf->agf_levels[XFS_BTNUM_BNOi], ARCH_CONVERT);
+		pag->pagf_levels[XFS_BTNUM_CNTi] =
+			INT_GET(agf->agf_levels[XFS_BTNUM_CNTi], ARCH_CONVERT);
+		spinlock_init(&pag->pagb_lock, "xfspagb");
+		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 == INT_GET(agf->agf_freeblks, ARCH_CONVERT));
+		ASSERT(pag->pagf_flcount == INT_GET(agf->agf_flcount, ARCH_CONVERT));
+		ASSERT(pag->pagf_longest == INT_GET(agf->agf_longest, ARCH_CONVERT));
+		ASSERT(pag->pagf_levels[XFS_BTNUM_BNOi] ==
+		       INT_GET(agf->agf_levels[XFS_BTNUM_BNOi], ARCH_CONVERT));
+		ASSERT(pag->pagf_levels[XFS_BTNUM_CNTi] ==
+		       INT_GET(agf->agf_levels[XFS_BTNUM_CNTi], ARCH_CONVERT));
+	}
+#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 */
+#ifdef XFS_ALLOC_TRACE
+	static char	fname[] = "xfs_alloc_vextent";
+#endif
+	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;
+
+	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, 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;
+			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;
+			if (++(args->agno) == mp->m_sb.sb_agcount)
+				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))
+			mp->m_agfrotor = (args->agno + 1) % mp->m_sb.sb_agcount;
+		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 */
+{
+#ifdef DEBUG
+	xfs_agf_t	*agf;	/* a.g. freespace header */
+#endif
+	xfs_alloc_arg_t	args;	/* allocation argument structure */
+	int		error;
+
+	ASSERT(len != 0);
+	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);
+	args.alignment = 1;
+	args.minlen = args.minleft = args.minalignslop = 0;
+	down_read(&args.mp->m_peraglock);
+	args.pag = &args.mp->m_perag[args.agno];
+	if ((error = xfs_alloc_fix_freelist(&args, 0)))
+		goto error0;
+#ifdef DEBUG
+	ASSERT(args.agbp != NULL);
+	agf = XFS_BUF_TO_AGF(args.agbp);
+	ASSERT(args.agbno + len <= INT_GET(agf->agf_length, ARCH_CONVERT));
+#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
+ * transacations 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;
+	SPLDECL(s);
+
+	mp = tp->t_mountp;
+	s = mutex_spinlock(&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);
+	}
+
+	mutex_spinunlock(&mp->m_perag[agno].pagb_lock, s);
+}
+
+void
+xfs_alloc_clear_busy(xfs_trans_t *tp,
+		     xfs_agnumber_t agno,
+		     int idx)
+{
+	xfs_mount_t		*mp;
+	xfs_perag_busy_t	*list;
+	SPLDECL(s);
+
+	mp = tp->t_mountp;
+
+	s = mutex_spinlock(&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);
+	}
+
+	mutex_spinunlock(&mp->m_perag[agno].pagb_lock, s);
+}
+
+
+/*
+ * returns non-zero if any of (agno,bno):len is in a busy list
+ */
+int
+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;
+	int			n;
+	xfs_agblock_t		uend, bend;
+	xfs_lsn_t		lsn;
+	int			cnt;
+	SPLDECL(s);
+
+	mp = tp->t_mountp;
+
+	s = mutex_spinlock(&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, n = 0;
+	     cnt; bsy++, n++) {
+
+		/*
+		 * (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, n,
+						 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, n, tp);
+		lsn = bsy->busy_tp->t_commit_lsn;
+		mutex_spinunlock(&mp->m_perag[agno].pagb_lock, s);
+		xfs_log_force(mp, lsn, XFS_LOG_FORCE|XFS_LOG_SYNC);
+	} else {
+		TRACE_BUSYSEARCH("xfs_alloc_search_busy", "not-found", agno, bno, len, n, tp);
+		n = -1;
+		mutex_spinunlock(&mp->m_perag[agno].pagb_lock, s);
+	}
+
+	return n;
+}