Initial import

1 files changed, 2639 insertions, 0 deletions

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
new file mode 100644
index 000000000..516162be1
--- /dev/null
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -0,0 +1,2639 @@
+/*
+ * 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_format.h"
+#include "xfs_log_format.h"
+#include "xfs_shared.h"
+#include "xfs_trans_resv.h"
+#include "xfs_bit.h"
+#include "xfs_sb.h"
+#include "xfs_mount.h"
+#include "xfs_inode.h"
+#include "xfs_btree.h"
+#include "xfs_alloc_btree.h"
+#include "xfs_alloc.h"
+#include "xfs_extent_busy.h"
+#include "xfs_error.h"
+#include "xfs_cksum.h"
+#include "xfs_trace.h"
+#include "xfs_trans.h"
+#include "xfs_buf_item.h"
+#include "xfs_log.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 *);
+
+/*
+ * 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_extent_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 */
+	char		userdata,	/* are we allocating data? */
+	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;
+	/*
+	 * We want to allocate from the start of a free extent if it is past
+	 * the desired block or if we are allocating user data and the free
+	 * extent is before desired block. The second case is there to allow
+	 * for contiguous allocation from the remaining free space if the file
+	 * grows in the short term.
+	 */
+	if (freebno >= wantbno || (userdata && freeend < wantend)) {
+		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)
+		rlen = rlen - (k - args->mod);
+	else
+		rlen = rlen - args->prod + (args->mod - k);
+	/* casts to (int) catch length underflows */
+	if ((int)rlen < (int)args->minlen)
+		return;
+	ASSERT(rlen >= args->minlen && rlen <= args->maxlen);
+	ASSERT(rlen % args->prod == args->mod);
+	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 */
+	/* casts to (int) catch length underflows */
+	if ((int)args->len >= (int)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 */
+	struct xfs_mount *mp;
+
+	mp = cnt_cur->bc_mp;
+
+	/*
+	 * 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(mp,
+			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(mp, 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(mp,
+			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(mp, 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(mp,
+			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(mp, 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(mp, i == 0);
+		if ((error = xfs_btree_insert(cnt_cur, &i)))
+			return error;
+		XFS_WANT_CORRUPTED_RETURN(mp, i == 1);
+	}
+	if (nfbno2 != NULLAGBLOCK) {
+		if ((error = xfs_alloc_lookup_eq(cnt_cur, nfbno2, nflen2, &i)))
+			return error;
+		XFS_WANT_CORRUPTED_RETURN(mp, i == 0);
+		if ((error = xfs_btree_insert(cnt_cur, &i)))
+			return error;
+		XFS_WANT_CORRUPTED_RETURN(mp, 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(mp, 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(mp, i == 0);
+		if ((error = xfs_btree_insert(bno_cur, &i)))
+			return error;
+		XFS_WANT_CORRUPTED_RETURN(mp, i == 1);
+	}
+	return 0;
+}
+
+static bool
+xfs_agfl_verify(
+	struct xfs_buf	*bp)
+{
+	struct xfs_mount *mp = bp->b_target->bt_mount;
+	struct xfs_agfl	*agfl = XFS_BUF_TO_AGFL(bp);
+	int		i;
+
+	if (!uuid_equal(&agfl->agfl_uuid, &mp->m_sb.sb_uuid))
+		return false;
+	if (be32_to_cpu(agfl->agfl_magicnum) != XFS_AGFL_MAGIC)
+		return false;
+	/*
+	 * during growfs operations, the perag is not fully initialised,
+	 * so we can't use it for any useful checking. growfs ensures we can't
+	 * use it by using uncached buffers that don't have the perag attached
+	 * so we can detect and avoid this problem.
+	 */
+	if (bp->b_pag && be32_to_cpu(agfl->agfl_seqno) != bp->b_pag->pag_agno)
+		return false;
+
+	for (i = 0; i < XFS_AGFL_SIZE(mp); i++) {
+		if (be32_to_cpu(agfl->agfl_bno[i]) != NULLAGBLOCK &&
+		    be32_to_cpu(agfl->agfl_bno[i]) >= mp->m_sb.sb_agblocks)
+			return false;
+	}
+	return true;
+}
+
+static void
+xfs_agfl_read_verify(
+	struct xfs_buf	*bp)
+{
+	struct xfs_mount *mp = bp->b_target->bt_mount;
+
+	/*
+	 * There is no verification of non-crc AGFLs because mkfs does not
+	 * initialise the AGFL to zero or NULL. Hence the only valid part of the
+	 * AGFL is what the AGF says is active. We can't get to the AGF, so we
+	 * can't verify just those entries are valid.
+	 */
+	if (!xfs_sb_version_hascrc(&mp->m_sb))
+		return;
+
+	if (!xfs_buf_verify_cksum(bp, XFS_AGFL_CRC_OFF))
+		xfs_buf_ioerror(bp, -EFSBADCRC);
+	else if (!xfs_agfl_verify(bp))
+		xfs_buf_ioerror(bp, -EFSCORRUPTED);
+
+	if (bp->b_error)
+		xfs_verifier_error(bp);
+}
+
+static void
+xfs_agfl_write_verify(
+	struct xfs_buf	*bp)
+{
+	struct xfs_mount *mp = bp->b_target->bt_mount;
+	struct xfs_buf_log_item	*bip = bp->b_fspriv;
+
+	/* no verification of non-crc AGFLs */
+	if (!xfs_sb_version_hascrc(&mp->m_sb))
+		return;
+
+	if (!xfs_agfl_verify(bp)) {
+		xfs_buf_ioerror(bp, -EFSCORRUPTED);
+		xfs_verifier_error(bp);
+		return;
+	}
+
+	if (bip)
+		XFS_BUF_TO_AGFL(bp)->agfl_lsn = cpu_to_be64(bip->bli_item.li_lsn);
+
+	xfs_buf_update_cksum(bp, XFS_AGFL_CRC_OFF);
+}
+
+const struct xfs_buf_ops xfs_agfl_buf_ops = {
+	.verify_read = xfs_agfl_read_verify,
+	.verify_write = xfs_agfl_write_verify,
+};
+
+/*
+ * 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, &xfs_agfl_buf_ops);
+	if (error)
+		return error;
+	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_extent_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(args->mp, i == 1, error0);
+	ASSERT(fbno <= args->agbno);
+
+	/*
+	 * Check for overlapping busy extents.
+	 */
+	xfs_extent_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(args->mp, 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,
+						       args->userdata, *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;
+#ifdef DEBUG
+	/*
+	 * Randomly don't execute the first algorithm.
+	 */
+	int		dofirst;	/* set to do first algorithm */
+
+	dofirst = prandom_u32() & 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;
+
+#ifdef DEBUG
+		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(args->mp, 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(args->mp, 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, args->userdata, 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(args->mp, 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(args->mp, 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(args->mp, 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, args->userdata, 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, args->userdata, 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) {
+		xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
+
+		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,
+				     args->userdata, 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(args->mp, 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(args->mp, 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(args->mp, 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(args->mp, 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(args->mp, 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(args->mp, 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->mp,
+		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(args->mp, 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_extent_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->mp,
+				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(mp, 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(mp,
+						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(mp, 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(mp, 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(mp, i == 1, error0);
+		if ((error = xfs_btree_delete(cnt_cur, &i)))
+			goto error0;
+		XFS_WANT_CORRUPTED_GOTO(mp, 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(mp, i == 1, error0);
+		if ((error = xfs_btree_delete(cnt_cur, &i)))
+			goto error0;
+		XFS_WANT_CORRUPTED_GOTO(mp, 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(mp, 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(mp, 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(mp,
+				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(mp, i == 1, error0);
+		if ((error = xfs_btree_delete(cnt_cur, &i)))
+			goto error0;
+		XFS_WANT_CORRUPTED_GOTO(mp, 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(mp, 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(mp, i == 1, error0);
+		if ((error = xfs_btree_delete(cnt_cur, &i)))
+			goto error0;
+		XFS_WANT_CORRUPTED_GOTO(mp, 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(mp, 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(mp, i == 0, error0);
+	if ((error = xfs_btree_insert(cnt_cur, &i)))
+		goto error0;
+	XFS_WANT_CORRUPTED_GOTO(mp, 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.
+	 */
+	memset(&targs, 0, sizeof(targs));
+	targs.tp = tp;
+	targs.mp = mp;
+	targs.agbp = agbp;
+	targs.agno = args->agno;
+	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_buf_t	*agflbp;/* buffer for a.g. freelist structure */
+	xfs_agblock_t	bno;	/* block number returned */
+	__be32		*agfl_bno;
+	int		error;
+	int		logflags;
+	xfs_mount_t	*mp = tp->t_mountp;
+	xfs_perag_t	*pag;	/* per allocation group data */
+
+	/*
+	 * Freelist is empty, give up.
+	 */
+	agf = XFS_BUF_TO_AGF(agbp);
+	if (!agf->agf_flcount) {
+		*bnop = NULLAGBLOCK;
+		return 0;
+	}
+	/*
+	 * Read the array of free blocks.
+	 */
+	error = xfs_alloc_read_agfl(mp, tp, be32_to_cpu(agf->agf_seqno),
+				    &agflbp);
+	if (error)
+		return error;
+
+
+	/*
+	 * Get the block number and update the data structures.
+	 */
+	agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp);
+	bno = be32_to_cpu(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),
+		offsetof(xfs_agf_t, agf_uuid),
+		sizeof(xfs_agf_t)
+	};
+
+	trace_xfs_agf(tp->t_mountp, XFS_BUF_TO_AGF(bp), fields, _RET_IP_);
+
+	xfs_trans_buf_set_type(tp, bp, XFS_BLFT_AGF_BUF);
+
+	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 */
+	__be32			*blockp;/* pointer to array entry */
+	int			error;
+	int			logflags;
+	xfs_mount_t		*mp;	/* mount structure */
+	xfs_perag_t		*pag;	/* per allocation group data */
+	__be32			*agfl_bno;
+	int			startoff;
+
+	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;
+	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));
+
+	agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp);
+	blockp = &agfl_bno[be32_to_cpu(agf->agf_fllast)];
+	*blockp = cpu_to_be32(bno);
+	startoff = (char *)blockp - (char *)agflbp->b_addr;
+
+	xfs_alloc_log_agf(tp, agbp, logflags);
+
+	xfs_trans_buf_set_type(tp, agflbp, XFS_BLFT_AGFL_BUF);
+	xfs_trans_log_buf(tp, agflbp, startoff,
+			  startoff + sizeof(xfs_agblock_t) - 1);
+	return 0;
+}
+
+static bool
+xfs_agf_verify(
+	struct xfs_mount *mp,
+	struct xfs_buf	*bp)
+ {
+	struct xfs_agf	*agf = XFS_BUF_TO_AGF(bp);
+
+	if (xfs_sb_version_hascrc(&mp->m_sb) &&
+	    !uuid_equal(&agf->agf_uuid, &mp->m_sb.sb_uuid))
+			return false;
+
+	if (!(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)))
+		return false;
+
+	if (be32_to_cpu(agf->agf_levels[XFS_BTNUM_BNO]) > XFS_BTREE_MAXLEVELS ||
+	    be32_to_cpu(agf->agf_levels[XFS_BTNUM_CNT]) > XFS_BTREE_MAXLEVELS)
+		return false;
+
+	/*
+	 * during growfs operations, the perag is not fully initialised,
+	 * so we can't use it for any useful checking. growfs ensures we can't
+	 * use it by using uncached buffers that don't have the perag attached
+	 * so we can detect and avoid this problem.
+	 */
+	if (bp->b_pag && be32_to_cpu(agf->agf_seqno) != bp->b_pag->pag_agno)
+		return false;
+
+	if (xfs_sb_version_haslazysbcount(&mp->m_sb) &&
+	    be32_to_cpu(agf->agf_btreeblks) > be32_to_cpu(agf->agf_length))
+		return false;
+
+	return true;;
+
+}
+
+static void
+xfs_agf_read_verify(
+	struct xfs_buf	*bp)
+{
+	struct xfs_mount *mp = bp->b_target->bt_mount;
+
+	if (xfs_sb_version_hascrc(&mp->m_sb) &&
+	    !xfs_buf_verify_cksum(bp, XFS_AGF_CRC_OFF))
+		xfs_buf_ioerror(bp, -EFSBADCRC);
+	else if (XFS_TEST_ERROR(!xfs_agf_verify(mp, bp), mp,
+				XFS_ERRTAG_ALLOC_READ_AGF,
+				XFS_RANDOM_ALLOC_READ_AGF))
+		xfs_buf_ioerror(bp, -EFSCORRUPTED);
+
+	if (bp->b_error)
+		xfs_verifier_error(bp);
+}
+
+static void
+xfs_agf_write_verify(
+	struct xfs_buf	*bp)
+{
+	struct xfs_mount *mp = bp->b_target->bt_mount;
+	struct xfs_buf_log_item	*bip = bp->b_fspriv;
+
+	if (!xfs_agf_verify(mp, bp)) {
+		xfs_buf_ioerror(bp, -EFSCORRUPTED);
+		xfs_verifier_error(bp);
+		return;
+	}
+
+	if (!xfs_sb_version_hascrc(&mp->m_sb))
+		return;
+
+	if (bip)
+		XFS_BUF_TO_AGF(bp)->agf_lsn = cpu_to_be64(bip->bli_item.li_lsn);
+
+	xfs_buf_update_cksum(bp, XFS_AGF_CRC_OFF);
+}
+
+const struct xfs_buf_ops xfs_agf_buf_ops = {
+	.verify_read = xfs_agf_read_verify,
+	.verify_write = xfs_agf_write_verify,
+};
+
+/*
+ * 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 */
+{
+	int		error;
+
+	trace_xfs_read_agf(mp, agno);
+
+	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, &xfs_agf_buf_ops);
+	if (error)
+		return error;
+	if (!*bpp)
+		return 0;
+
+	ASSERT(!(*bpp)->b_error);
+	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;
+
+	trace_xfs_alloc_read_agf(mp, agno);
+
+	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;
+}
+
+/*
+ * 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_extent_busy_insert(tp, args.agno, args.agbno, len, 0);
+error0:
+	xfs_perag_put(args.pag);
+	return error;
+}