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

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diff -urN linux-2.4.24/fs/xfs/xfs_btree.c linux-2.4.25/fs/xfs/xfs_btree.c
@@ -0,0 +1,949 @@
+/*
+ * 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/
+ */
+
+/*
+ * This file contains common code for the space manager's btree implementations.
+ */
+
+#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_dir2.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_attr_sf.h"
+#include "xfs_dir_sf.h"
+#include "xfs_dir2_sf.h"
+#include "xfs_dinode.h"
+#include "xfs_inode.h"
+#include "xfs_bit.h"
+#include "xfs_error.h"
+
+/*
+ * Cursor allocation zone.
+ */
+kmem_zone_t	*xfs_btree_cur_zone;
+
+/*
+ * Btree magic numbers.
+ */
+const __uint32_t xfs_magics[XFS_BTNUM_MAX] =
+{
+	XFS_ABTB_MAGIC, XFS_ABTC_MAGIC, XFS_BMAP_MAGIC, XFS_IBT_MAGIC
+};
+
+/*
+ * Prototypes for internal routines.
+ */
+
+/*
+ * Checking routine: return maxrecs for the block.
+ */
+STATIC int				/* number of records fitting in block */
+xfs_btree_maxrecs(
+	xfs_btree_cur_t		*cur,	/* btree cursor */
+	xfs_btree_block_t	*block);/* generic btree block pointer */
+
+/*
+ * Internal routines.
+ */
+
+/*
+ * Checking routine: return maxrecs for the block.
+ */
+STATIC int				/* number of records fitting in block */
+xfs_btree_maxrecs(
+	xfs_btree_cur_t		*cur,	/* btree cursor */
+	xfs_btree_block_t	*block)	/* generic btree block pointer */
+{
+	switch (cur->bc_btnum) {
+	case XFS_BTNUM_BNO:
+	case XFS_BTNUM_CNT:
+		return (int)XFS_ALLOC_BLOCK_MAXRECS(INT_GET(block->bb_h.bb_level, ARCH_CONVERT), cur);
+	case XFS_BTNUM_BMAP:
+		return (int)XFS_BMAP_BLOCK_IMAXRECS(INT_GET(block->bb_h.bb_level, ARCH_CONVERT), cur);
+	case XFS_BTNUM_INO:
+		return (int)XFS_INOBT_BLOCK_MAXRECS(INT_GET(block->bb_h.bb_level, ARCH_CONVERT), cur);
+	default:
+		ASSERT(0);
+		return 0;
+	}
+}
+
+/*
+ * External routines.
+ */
+
+#ifdef DEBUG
+/*
+ * Debug routine: check that block header is ok.
+ */
+void
+xfs_btree_check_block(
+	xfs_btree_cur_t		*cur,	/* btree cursor */
+	xfs_btree_block_t	*block,	/* generic btree block pointer */
+	int			level,	/* level of the btree block */
+	xfs_buf_t		*bp)	/* buffer containing block, if any */
+{
+	if (XFS_BTREE_LONG_PTRS(cur->bc_btnum))
+		xfs_btree_check_lblock(cur, (xfs_btree_lblock_t *)block, level,
+			bp);
+	else
+		xfs_btree_check_sblock(cur, (xfs_btree_sblock_t *)block, level,
+			bp);
+}
+
+/*
+ * Debug routine: check that keys are in the right order.
+ */
+void
+xfs_btree_check_key(
+	xfs_btnum_t	btnum,		/* btree identifier */
+	void		*ak1,		/* pointer to left (lower) key */
+	void		*ak2)		/* pointer to right (higher) key */
+{
+	switch (btnum) {
+	case XFS_BTNUM_BNO: {
+		xfs_alloc_key_t	*k1;
+		xfs_alloc_key_t	*k2;
+
+		k1 = ak1;
+		k2 = ak2;
+		ASSERT(INT_GET(k1->ar_startblock, ARCH_CONVERT) < INT_GET(k2->ar_startblock, ARCH_CONVERT));
+		break;
+	    }
+	case XFS_BTNUM_CNT: {
+		xfs_alloc_key_t	*k1;
+		xfs_alloc_key_t	*k2;
+
+		k1 = ak1;
+		k2 = ak2;
+		ASSERT(INT_GET(k1->ar_blockcount, ARCH_CONVERT) < INT_GET(k2->ar_blockcount, ARCH_CONVERT) ||
+		       (INT_GET(k1->ar_blockcount, ARCH_CONVERT) == INT_GET(k2->ar_blockcount, ARCH_CONVERT) &&
+			INT_GET(k1->ar_startblock, ARCH_CONVERT) < INT_GET(k2->ar_startblock, ARCH_CONVERT)));
+		break;
+	    }
+	case XFS_BTNUM_BMAP: {
+		xfs_bmbt_key_t	*k1;
+		xfs_bmbt_key_t	*k2;
+
+		k1 = ak1;
+		k2 = ak2;
+		ASSERT(INT_GET(k1->br_startoff, ARCH_CONVERT) < INT_GET(k2->br_startoff, ARCH_CONVERT));
+		break;
+	    }
+	case XFS_BTNUM_INO: {
+		xfs_inobt_key_t	*k1;
+		xfs_inobt_key_t	*k2;
+
+		k1 = ak1;
+		k2 = ak2;
+		ASSERT(INT_GET(k1->ir_startino, ARCH_CONVERT) < INT_GET(k2->ir_startino, ARCH_CONVERT));
+		break;
+	    }
+	default:
+		ASSERT(0);
+	}
+}
+#endif	/* DEBUG */
+
+/*
+ * Checking routine: check that long form block header is ok.
+ */
+/* ARGSUSED */
+int					/* error (0 or EFSCORRUPTED) */
+xfs_btree_check_lblock(
+	xfs_btree_cur_t		*cur,	/* btree cursor */
+	xfs_btree_lblock_t	*block,	/* btree long form block pointer */
+	int			level,	/* level of the btree block */
+	xfs_buf_t		*bp)	/* buffer for block, if any */
+{
+	int			lblock_ok; /* block passes checks */
+	xfs_mount_t		*mp;	/* file system mount point */
+
+	mp = cur->bc_mp;
+	lblock_ok =
+		INT_GET(block->bb_magic, ARCH_CONVERT) == xfs_magics[cur->bc_btnum] &&
+		INT_GET(block->bb_level, ARCH_CONVERT) == level &&
+		INT_GET(block->bb_numrecs, ARCH_CONVERT) <=
+			xfs_btree_maxrecs(cur, (xfs_btree_block_t *)block) &&
+		!INT_ISZERO(block->bb_leftsib, ARCH_CONVERT) &&
+		(INT_GET(block->bb_leftsib, ARCH_CONVERT) == NULLDFSBNO ||
+		 XFS_FSB_SANITY_CHECK(mp, INT_GET(block->bb_leftsib, ARCH_CONVERT))) &&
+		!INT_ISZERO(block->bb_rightsib, ARCH_CONVERT) &&
+		(INT_GET(block->bb_rightsib, ARCH_CONVERT) == NULLDFSBNO ||
+		 XFS_FSB_SANITY_CHECK(mp, INT_GET(block->bb_rightsib, ARCH_CONVERT)));
+	if (unlikely(XFS_TEST_ERROR(!lblock_ok, mp, XFS_ERRTAG_BTREE_CHECK_LBLOCK,
+			XFS_RANDOM_BTREE_CHECK_LBLOCK))) {
+		if (bp)
+			xfs_buftrace("LBTREE ERROR", bp);
+		XFS_ERROR_REPORT("xfs_btree_check_lblock", XFS_ERRLEVEL_LOW,
+				 mp);
+		return XFS_ERROR(EFSCORRUPTED);
+	}
+	return 0;
+}
+
+/*
+ * Checking routine: check that (long) pointer is ok.
+ */
+int					/* error (0 or EFSCORRUPTED) */
+xfs_btree_check_lptr(
+	xfs_btree_cur_t	*cur,		/* btree cursor */
+	xfs_dfsbno_t	ptr,		/* btree block disk address */
+	int		level)		/* btree block level */
+{
+	xfs_mount_t	*mp;		/* file system mount point */
+
+	mp = cur->bc_mp;
+	XFS_WANT_CORRUPTED_RETURN(
+		level > 0 &&
+		ptr != NULLDFSBNO &&
+		XFS_FSB_SANITY_CHECK(mp, ptr));
+	return 0;
+}
+
+#ifdef DEBUG
+/*
+ * Debug routine: check that records are in the right order.
+ */
+void
+xfs_btree_check_rec(
+	xfs_btnum_t	btnum,		/* btree identifier */
+	void		*ar1,		/* pointer to left (lower) record */
+	void		*ar2)		/* pointer to right (higher) record */
+{
+	switch (btnum) {
+	case XFS_BTNUM_BNO: {
+		xfs_alloc_rec_t	*r1;
+		xfs_alloc_rec_t	*r2;
+
+		r1 = ar1;
+		r2 = ar2;
+		ASSERT(INT_GET(r1->ar_startblock, ARCH_CONVERT) + INT_GET(r1->ar_blockcount, ARCH_CONVERT) <=
+		       INT_GET(r2->ar_startblock, ARCH_CONVERT));
+		break;
+	    }
+	case XFS_BTNUM_CNT: {
+		xfs_alloc_rec_t	*r1;
+		xfs_alloc_rec_t	*r2;
+
+		r1 = ar1;
+		r2 = ar2;
+		ASSERT(INT_GET(r1->ar_blockcount, ARCH_CONVERT) < INT_GET(r2->ar_blockcount, ARCH_CONVERT) ||
+		       (INT_GET(r1->ar_blockcount, ARCH_CONVERT) == INT_GET(r2->ar_blockcount, ARCH_CONVERT) &&
+			INT_GET(r1->ar_startblock, ARCH_CONVERT) < INT_GET(r2->ar_startblock, ARCH_CONVERT)));
+		break;
+	    }
+	case XFS_BTNUM_BMAP: {
+		xfs_bmbt_rec_t	*r1;
+		xfs_bmbt_rec_t	*r2;
+
+		r1 = ar1;
+		r2 = ar2;
+		ASSERT(xfs_bmbt_disk_get_startoff(r1) +
+		       xfs_bmbt_disk_get_blockcount(r1) <=
+		       xfs_bmbt_disk_get_startoff(r2));
+		break;
+	    }
+	case XFS_BTNUM_INO: {
+		xfs_inobt_rec_t	*r1;
+		xfs_inobt_rec_t	*r2;
+
+		r1 = ar1;
+		r2 = ar2;
+		ASSERT(INT_GET(r1->ir_startino, ARCH_CONVERT) + XFS_INODES_PER_CHUNK <=
+		       INT_GET(r2->ir_startino, ARCH_CONVERT));
+		break;
+	    }
+	default:
+		ASSERT(0);
+	}
+}
+#endif	/* DEBUG */
+
+/*
+ * Checking routine: check that block header is ok.
+ */
+/* ARGSUSED */
+int					/* error (0 or EFSCORRUPTED) */
+xfs_btree_check_sblock(
+	xfs_btree_cur_t		*cur,	/* btree cursor */
+	xfs_btree_sblock_t	*block,	/* btree short form block pointer */
+	int			level,	/* level of the btree block */
+	xfs_buf_t		*bp)	/* buffer containing block */
+{
+	xfs_buf_t		*agbp;	/* buffer for ag. freespace struct */
+	xfs_agf_t		*agf;	/* ag. freespace structure */
+	xfs_agblock_t		agflen;	/* native ag. freespace length */
+	int			sblock_ok; /* block passes checks */
+
+	agbp = cur->bc_private.a.agbp;
+	agf = XFS_BUF_TO_AGF(agbp);
+	agflen = INT_GET(agf->agf_length, ARCH_CONVERT);
+	sblock_ok =
+		INT_GET(block->bb_magic, ARCH_CONVERT) == xfs_magics[cur->bc_btnum] &&
+		INT_GET(block->bb_level, ARCH_CONVERT) == level &&
+		INT_GET(block->bb_numrecs, ARCH_CONVERT) <=
+			xfs_btree_maxrecs(cur, (xfs_btree_block_t *)block) &&
+		(INT_GET(block->bb_leftsib, ARCH_CONVERT) == NULLAGBLOCK ||
+		 INT_GET(block->bb_leftsib, ARCH_CONVERT) < agflen) &&
+		!INT_ISZERO(block->bb_leftsib, ARCH_CONVERT) &&
+		(INT_GET(block->bb_rightsib, ARCH_CONVERT) == NULLAGBLOCK ||
+		 INT_GET(block->bb_rightsib, ARCH_CONVERT) < agflen) &&
+		!INT_ISZERO(block->bb_rightsib, ARCH_CONVERT);
+	if (unlikely(XFS_TEST_ERROR(!sblock_ok, cur->bc_mp,
+			XFS_ERRTAG_BTREE_CHECK_SBLOCK,
+			XFS_RANDOM_BTREE_CHECK_SBLOCK))) {
+		if (bp)
+			xfs_buftrace("SBTREE ERROR", bp);
+		XFS_ERROR_REPORT("xfs_btree_check_sblock", XFS_ERRLEVEL_LOW,
+				 cur->bc_mp);
+		return XFS_ERROR(EFSCORRUPTED);
+	}
+	return 0;
+}
+
+/*
+ * Checking routine: check that (short) pointer is ok.
+ */
+int					/* error (0 or EFSCORRUPTED) */
+xfs_btree_check_sptr(
+	xfs_btree_cur_t	*cur,		/* btree cursor */
+	xfs_agblock_t	ptr,		/* btree block disk address */
+	int		level)		/* btree block level */
+{
+	xfs_buf_t	*agbp;		/* buffer for ag. freespace struct */
+	xfs_agf_t	*agf;		/* ag. freespace structure */
+
+	agbp = cur->bc_private.a.agbp;
+	agf = XFS_BUF_TO_AGF(agbp);
+	XFS_WANT_CORRUPTED_RETURN(
+		level > 0 &&
+		ptr != NULLAGBLOCK && ptr != 0 &&
+		ptr < INT_GET(agf->agf_length, ARCH_CONVERT));
+	return 0;
+}
+
+/*
+ * Delete the btree cursor.
+ */
+void
+xfs_btree_del_cursor(
+	xfs_btree_cur_t	*cur,		/* btree cursor */
+	int		error)		/* del because of error */
+{
+	int		i;		/* btree level */
+
+	/*
+	 * Clear the buffer pointers, and release the buffers.
+	 * If we're doing this in the face of an error, we
+	 * need to make sure to inspect all of the entries
+	 * in the bc_bufs array for buffers to be unlocked.
+	 * This is because some of the btree code works from
+	 * level n down to 0, and if we get an error along
+	 * the way we won't have initialized all the entries
+	 * down to 0.
+	 */
+	for (i = 0; i < cur->bc_nlevels; i++) {
+		if (cur->bc_bufs[i])
+			xfs_btree_setbuf(cur, i, NULL);
+		else if (!error)
+			break;
+	}
+	/*
+	 * Can't free a bmap cursor without having dealt with the
+	 * allocated indirect blocks' accounting.
+	 */
+	ASSERT(cur->bc_btnum != XFS_BTNUM_BMAP ||
+	       cur->bc_private.b.allocated == 0);
+	/*
+	 * Free the cursor.
+	 */
+	kmem_zone_free(xfs_btree_cur_zone, cur);
+}
+
+/*
+ * Duplicate the btree cursor.
+ * Allocate a new one, copy the record, re-get the buffers.
+ */
+int					/* error */
+xfs_btree_dup_cursor(
+	xfs_btree_cur_t	*cur,		/* input cursor */
+	xfs_btree_cur_t	**ncur)		/* output cursor */
+{
+	xfs_buf_t	*bp;		/* btree block's buffer pointer */
+	int		error;		/* error return value */
+	int		i;		/* level number of btree block */
+	xfs_mount_t	*mp;		/* mount structure for filesystem */
+	xfs_btree_cur_t	*new;		/* new cursor value */
+	xfs_trans_t	*tp;		/* transaction pointer, can be NULL */
+
+	tp = cur->bc_tp;
+	mp = cur->bc_mp;
+	/*
+	 * Allocate a new cursor like the old one.
+	 */
+	new = xfs_btree_init_cursor(mp, tp, cur->bc_private.a.agbp,
+		cur->bc_private.a.agno, cur->bc_btnum, cur->bc_private.b.ip,
+		cur->bc_private.b.whichfork);
+	/*
+	 * Copy the record currently in the cursor.
+	 */
+	new->bc_rec = cur->bc_rec;
+	/*
+	 * For each level current, re-get the buffer and copy the ptr value.
+	 */
+	for (i = 0; i < new->bc_nlevels; i++) {
+		new->bc_ptrs[i] = cur->bc_ptrs[i];
+		new->bc_ra[i] = cur->bc_ra[i];
+		if ((bp = cur->bc_bufs[i])) {
+			if ((error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp,
+				XFS_BUF_ADDR(bp), mp->m_bsize, 0, &bp))) {
+				xfs_btree_del_cursor(new, error);
+				*ncur = NULL;
+				return error;
+			}
+			new->bc_bufs[i] = bp;
+			ASSERT(bp);
+			ASSERT(!XFS_BUF_GETERROR(bp));
+		} else
+			new->bc_bufs[i] = NULL;
+	}
+	/*
+	 * For bmap btrees, copy the firstblock, flist, and flags values,
+	 * since init cursor doesn't get them.
+	 */
+	if (new->bc_btnum == XFS_BTNUM_BMAP) {
+		new->bc_private.b.firstblock = cur->bc_private.b.firstblock;
+		new->bc_private.b.flist = cur->bc_private.b.flist;
+		new->bc_private.b.flags = cur->bc_private.b.flags;
+	}
+	*ncur = new;
+	return 0;
+}
+
+/*
+ * Change the cursor to point to the first record at the given level.
+ * Other levels are unaffected.
+ */
+int					/* success=1, failure=0 */
+xfs_btree_firstrec(
+	xfs_btree_cur_t		*cur,	/* btree cursor */
+	int			level)	/* level to change */
+{
+	xfs_btree_block_t	*block;	/* generic btree block pointer */
+	xfs_buf_t		*bp;	/* buffer containing block */
+
+	/*
+	 * Get the block pointer for this level.
+	 */
+	block = xfs_btree_get_block(cur, level, &bp);
+	xfs_btree_check_block(cur, block, level, bp);
+	/*
+	 * It's empty, there is no such record.
+	 */
+	if (INT_ISZERO(block->bb_h.bb_numrecs, ARCH_CONVERT))
+		return 0;
+	/*
+	 * Set the ptr value to 1, that's the first record/key.
+	 */
+	cur->bc_ptrs[level] = 1;
+	return 1;
+}
+
+/*
+ * Retrieve the block pointer from the cursor at the given level.
+ * This may be a bmap btree root or from a buffer.
+ */
+xfs_btree_block_t *			/* generic btree block pointer */
+xfs_btree_get_block(
+	xfs_btree_cur_t		*cur,	/* btree cursor */
+	int			level,	/* level in btree */
+	xfs_buf_t		**bpp)	/* buffer containing the block */
+{
+	xfs_btree_block_t	*block;	/* return value */
+	xfs_buf_t		*bp;	/* return buffer */
+	xfs_ifork_t		*ifp;	/* inode fork pointer */
+	int			whichfork; /* data or attr fork */
+
+	if (cur->bc_btnum == XFS_BTNUM_BMAP && level == cur->bc_nlevels - 1) {
+		whichfork = cur->bc_private.b.whichfork;
+		ifp = XFS_IFORK_PTR(cur->bc_private.b.ip, whichfork);
+		block = (xfs_btree_block_t *)ifp->if_broot;
+		bp = NULL;
+	} else {
+		bp = cur->bc_bufs[level];
+		block = XFS_BUF_TO_BLOCK(bp);
+	}
+	ASSERT(block != NULL);
+	*bpp = bp;
+	return block;
+}
+
+/*
+ * Get a buffer for the block, return it with no data read.
+ * Long-form addressing.
+ */
+xfs_buf_t *				/* buffer for fsbno */
+xfs_btree_get_bufl(
+	xfs_mount_t	*mp,		/* file system mount point */
+	xfs_trans_t	*tp,		/* transaction pointer */
+	xfs_fsblock_t	fsbno,		/* file system block number */
+	uint		lock)		/* lock flags for get_buf */
+{
+	xfs_buf_t	*bp;		/* buffer pointer (return value) */
+	xfs_daddr_t		d;		/* real disk block address */
+
+	ASSERT(fsbno != NULLFSBLOCK);
+	d = XFS_FSB_TO_DADDR(mp, fsbno);
+	bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, d, mp->m_bsize, lock);
+	ASSERT(bp);
+	ASSERT(!XFS_BUF_GETERROR(bp));
+	return bp;
+}
+
+/*
+ * Get a buffer for the block, return it with no data read.
+ * Short-form addressing.
+ */
+xfs_buf_t *				/* buffer for agno/agbno */
+xfs_btree_get_bufs(
+	xfs_mount_t	*mp,		/* file system mount point */
+	xfs_trans_t	*tp,		/* transaction pointer */
+	xfs_agnumber_t	agno,		/* allocation group number */
+	xfs_agblock_t	agbno,		/* allocation group block number */
+	uint		lock)		/* lock flags for get_buf */
+{
+	xfs_buf_t	*bp;		/* buffer pointer (return value) */
+	xfs_daddr_t		d;		/* real disk block address */
+
+	ASSERT(agno != NULLAGNUMBER);
+	ASSERT(agbno != NULLAGBLOCK);
+	d = XFS_AGB_TO_DADDR(mp, agno, agbno);
+	bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, d, mp->m_bsize, lock);
+	ASSERT(bp);
+	ASSERT(!XFS_BUF_GETERROR(bp));
+	return bp;
+}
+
+/*
+ * Allocate a new btree cursor.
+ * The cursor is either for allocation (A) or bmap (B) or inodes (I).
+ */
+xfs_btree_cur_t *			/* new btree cursor */
+xfs_btree_init_cursor(
+	xfs_mount_t	*mp,		/* file system mount point */
+	xfs_trans_t	*tp,		/* transaction pointer */
+	xfs_buf_t	*agbp,		/* (A only) buffer for agf structure */
+					/* (I only) buffer for agi structure */
+	xfs_agnumber_t	agno,		/* (AI only) allocation group number */
+	xfs_btnum_t	btnum,		/* btree identifier */
+	xfs_inode_t	*ip,		/* (B only) inode owning the btree */
+	int		whichfork)	/* (B only) data or attr fork */
+{
+	xfs_agf_t	*agf;		/* (A) allocation group freespace */
+	xfs_agi_t	*agi;		/* (I) allocation group inodespace */
+	xfs_btree_cur_t	*cur;		/* return value */
+	xfs_ifork_t	*ifp;		/* (I) inode fork pointer */
+	int		nlevels=0;	/* number of levels in the btree */
+
+	ASSERT(xfs_btree_cur_zone != NULL);
+	/*
+	 * Allocate a new cursor.
+	 */
+	cur = kmem_zone_zalloc(xfs_btree_cur_zone, KM_SLEEP);
+	/*
+	 * Deduce the number of btree levels from the arguments.
+	 */
+	switch (btnum) {
+	case XFS_BTNUM_BNO:
+	case XFS_BTNUM_CNT:
+		agf = XFS_BUF_TO_AGF(agbp);
+		nlevels = INT_GET(agf->agf_levels[btnum], ARCH_CONVERT);
+		break;
+	case XFS_BTNUM_BMAP:
+		ifp = XFS_IFORK_PTR(ip, whichfork);
+		nlevels = INT_GET(ifp->if_broot->bb_level, ARCH_CONVERT) + 1;
+		break;
+	case XFS_BTNUM_INO:
+		agi = XFS_BUF_TO_AGI(agbp);
+		nlevels = INT_GET(agi->agi_level, ARCH_CONVERT);
+		break;
+	default:
+		ASSERT(0);
+	}
+	/*
+	 * Fill in the common fields.
+	 */
+	cur->bc_tp = tp;
+	cur->bc_mp = mp;
+	cur->bc_nlevels = nlevels;
+	cur->bc_btnum = btnum;
+	cur->bc_blocklog = mp->m_sb.sb_blocklog;
+	/*
+	 * Fill in private fields.
+	 */
+	switch (btnum) {
+	case XFS_BTNUM_BNO:
+	case XFS_BTNUM_CNT:
+		/*
+		 * Allocation btree fields.
+		 */
+		cur->bc_private.a.agbp = agbp;
+		cur->bc_private.a.agno = agno;
+		break;
+	case XFS_BTNUM_BMAP:
+		/*
+		 * Bmap btree fields.
+		 */
+		cur->bc_private.b.forksize = XFS_IFORK_SIZE(ip, whichfork);
+		cur->bc_private.b.ip = ip;
+		cur->bc_private.b.firstblock = NULLFSBLOCK;
+		cur->bc_private.b.flist = NULL;
+		cur->bc_private.b.allocated = 0;
+		cur->bc_private.b.flags = 0;
+		cur->bc_private.b.whichfork = whichfork;
+		break;
+	case XFS_BTNUM_INO:
+		/*
+		 * Inode allocation btree fields.
+		 */
+		cur->bc_private.i.agbp = agbp;
+		cur->bc_private.i.agno = agno;
+		break;
+	default:
+		ASSERT(0);
+	}
+	return cur;
+}
+
+/*
+ * Check for the cursor referring to the last block at the given level.
+ */
+int					/* 1=is last block, 0=not last block */
+xfs_btree_islastblock(
+	xfs_btree_cur_t		*cur,	/* btree cursor */
+	int			level)	/* level to check */
+{
+	xfs_btree_block_t	*block;	/* generic btree block pointer */
+	xfs_buf_t		*bp;	/* buffer containing block */
+
+	block = xfs_btree_get_block(cur, level, &bp);
+	xfs_btree_check_block(cur, block, level, bp);
+	if (XFS_BTREE_LONG_PTRS(cur->bc_btnum))
+		return INT_GET(block->bb_u.l.bb_rightsib, ARCH_CONVERT) == NULLDFSBNO;
+	else
+		return INT_GET(block->bb_u.s.bb_rightsib, ARCH_CONVERT) == NULLAGBLOCK;
+}
+
+/*
+ * Change the cursor to point to the last record in the current block
+ * at the given level.  Other levels are unaffected.
+ */
+int					/* success=1, failure=0 */
+xfs_btree_lastrec(
+	xfs_btree_cur_t		*cur,	/* btree cursor */
+	int			level)	/* level to change */
+{
+	xfs_btree_block_t	*block;	/* generic btree block pointer */
+	xfs_buf_t		*bp;	/* buffer containing block */
+
+	/*
+	 * Get the block pointer for this level.
+	 */
+	block = xfs_btree_get_block(cur, level, &bp);
+	xfs_btree_check_block(cur, block, level, bp);
+	/*
+	 * It's empty, there is no such record.
+	 */
+	if (INT_ISZERO(block->bb_h.bb_numrecs, ARCH_CONVERT))
+		return 0;
+	/*
+	 * Set the ptr value to numrecs, that's the last record/key.
+	 */
+	cur->bc_ptrs[level] = INT_GET(block->bb_h.bb_numrecs, ARCH_CONVERT);
+	return 1;
+}
+
+/*
+ * Compute first and last byte offsets for the fields given.
+ * Interprets the offsets table, which contains struct field offsets.
+ */
+void
+xfs_btree_offsets(
+	__int64_t	fields,		/* bitmask of fields */
+	const short	*offsets,	/* table of field offsets */
+	int		nbits,		/* number of bits to inspect */
+	int		*first,		/* output: first byte offset */
+	int		*last)		/* output: last byte offset */
+{
+	int		i;		/* current bit number */
+	__int64_t	imask;		/* mask for current bit number */
+
+	ASSERT(fields != 0);
+	/*
+	 * Find the lowest bit, so the first byte offset.
+	 */
+	for (i = 0, imask = 1LL; ; i++, imask <<= 1) {
+		if (imask & fields) {
+			*first = offsets[i];
+			break;
+		}
+	}
+	/*
+	 * Find the highest bit, so the last byte offset.
+	 */
+	for (i = nbits - 1, imask = 1LL << i; ; i--, imask >>= 1) {
+		if (imask & fields) {
+			*last = offsets[i + 1] - 1;
+			break;
+		}
+	}
+}
+
+/*
+ * Get a buffer for the block, return it read in.
+ * Long-form addressing.
+ */
+int					/* error */
+xfs_btree_read_bufl(
+	xfs_mount_t	*mp,		/* file system mount point */
+	xfs_trans_t	*tp,		/* transaction pointer */
+	xfs_fsblock_t	fsbno,		/* file system block number */
+	uint		lock,		/* lock flags for read_buf */
+	xfs_buf_t	**bpp,		/* buffer for fsbno */
+	int		refval)		/* ref count value for buffer */
+{
+	xfs_buf_t	*bp;		/* return value */
+	xfs_daddr_t		d;		/* real disk block address */
+	int		error;
+
+	ASSERT(fsbno != NULLFSBLOCK);
+	d = XFS_FSB_TO_DADDR(mp, fsbno);
+	if ((error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp, d,
+			mp->m_bsize, lock, &bp))) {
+		return error;
+	}
+	ASSERT(!bp || !XFS_BUF_GETERROR(bp));
+	if (bp != NULL) {
+		XFS_BUF_SET_VTYPE_REF(bp, B_FS_MAP, refval);
+	}
+	*bpp = bp;
+	return 0;
+}
+
+/*
+ * Get a buffer for the block, return it read in.
+ * Short-form addressing.
+ */
+int					/* error */
+xfs_btree_read_bufs(
+	xfs_mount_t	*mp,		/* file system mount point */
+	xfs_trans_t	*tp,		/* transaction pointer */
+	xfs_agnumber_t	agno,		/* allocation group number */
+	xfs_agblock_t	agbno,		/* allocation group block number */
+	uint		lock,		/* lock flags for read_buf */
+	xfs_buf_t	**bpp,		/* buffer for agno/agbno */
+	int		refval)		/* ref count value for buffer */
+{
+	xfs_buf_t	*bp;		/* return value */
+	xfs_daddr_t	d;		/* real disk block address */
+	int		error;
+
+	ASSERT(agno != NULLAGNUMBER);
+	ASSERT(agbno != NULLAGBLOCK);
+	d = XFS_AGB_TO_DADDR(mp, agno, agbno);
+	if ((error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp, d,
+					mp->m_bsize, lock, &bp))) {
+		return error;
+	}
+	ASSERT(!bp || !XFS_BUF_GETERROR(bp));
+	if (bp != NULL) {
+		switch (refval) {
+		case XFS_ALLOC_BTREE_REF:
+			XFS_BUF_SET_VTYPE_REF(bp, B_FS_MAP, refval);
+			break;
+		case XFS_INO_BTREE_REF:
+			XFS_BUF_SET_VTYPE_REF(bp, B_FS_INOMAP, refval);
+			break;
+		}
+	}
+	*bpp = bp;
+	return 0;
+}
+
+/*
+ * Read-ahead the block, don't wait for it, don't return a buffer.
+ * Long-form addressing.
+ */
+/* ARGSUSED */
+void
+xfs_btree_reada_bufl(
+	xfs_mount_t	*mp,		/* file system mount point */
+	xfs_fsblock_t	fsbno,		/* file system block number */
+	xfs_extlen_t	count)		/* count of filesystem blocks */
+{
+	xfs_daddr_t		d;
+
+	ASSERT(fsbno != NULLFSBLOCK);
+	d = XFS_FSB_TO_DADDR(mp, fsbno);
+	xfs_baread(mp->m_ddev_targp, d, mp->m_bsize * count);
+}
+
+/*
+ * Read-ahead the block, don't wait for it, don't return a buffer.
+ * Short-form addressing.
+ */
+/* ARGSUSED */
+void
+xfs_btree_reada_bufs(
+	xfs_mount_t	*mp,		/* file system mount point */
+	xfs_agnumber_t	agno,		/* allocation group number */
+	xfs_agblock_t	agbno,		/* allocation group block number */
+	xfs_extlen_t	count)		/* count of filesystem blocks */
+{
+	xfs_daddr_t		d;
+
+	ASSERT(agno != NULLAGNUMBER);
+	ASSERT(agbno != NULLAGBLOCK);
+	d = XFS_AGB_TO_DADDR(mp, agno, agbno);
+	xfs_baread(mp->m_ddev_targp, d, mp->m_bsize * count);
+}
+
+/*
+ * Read-ahead btree blocks, at the given level.
+ * Bits in lr are set from XFS_BTCUR_{LEFT,RIGHT}RA.
+ */
+int
+xfs_btree_readahead_core(
+	xfs_btree_cur_t		*cur,		/* btree cursor */
+	int			lev,		/* level in btree */
+	int			lr)		/* left/right bits */
+{
+	xfs_alloc_block_t	*a;
+	xfs_bmbt_block_t	*b;
+	xfs_inobt_block_t	*i;
+	int			rval = 0;
+
+	ASSERT(cur->bc_bufs[lev] != NULL);
+	cur->bc_ra[lev] |= lr;
+	switch (cur->bc_btnum) {
+	case XFS_BTNUM_BNO:
+	case XFS_BTNUM_CNT:
+		a = XFS_BUF_TO_ALLOC_BLOCK(cur->bc_bufs[lev]);
+		if ((lr & XFS_BTCUR_LEFTRA) && INT_GET(a->bb_leftsib, ARCH_CONVERT) != NULLAGBLOCK) {
+			xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.a.agno,
+				INT_GET(a->bb_leftsib, ARCH_CONVERT), 1);
+			rval++;
+		}
+		if ((lr & XFS_BTCUR_RIGHTRA) && INT_GET(a->bb_rightsib, ARCH_CONVERT) != NULLAGBLOCK) {
+			xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.a.agno,
+				INT_GET(a->bb_rightsib, ARCH_CONVERT), 1);
+			rval++;
+		}
+		break;
+	case XFS_BTNUM_BMAP:
+		b = XFS_BUF_TO_BMBT_BLOCK(cur->bc_bufs[lev]);
+		if ((lr & XFS_BTCUR_LEFTRA) && INT_GET(b->bb_leftsib, ARCH_CONVERT) != NULLDFSBNO) {
+			xfs_btree_reada_bufl(cur->bc_mp, INT_GET(b->bb_leftsib, ARCH_CONVERT), 1);
+			rval++;
+		}
+		if ((lr & XFS_BTCUR_RIGHTRA) && INT_GET(b->bb_rightsib, ARCH_CONVERT) != NULLDFSBNO) {
+			xfs_btree_reada_bufl(cur->bc_mp, INT_GET(b->bb_rightsib, ARCH_CONVERT), 1);
+			rval++;
+		}
+		break;
+	case XFS_BTNUM_INO:
+		i = XFS_BUF_TO_INOBT_BLOCK(cur->bc_bufs[lev]);
+		if ((lr & XFS_BTCUR_LEFTRA) && INT_GET(i->bb_leftsib, ARCH_CONVERT) != NULLAGBLOCK) {
+			xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.i.agno,
+				INT_GET(i->bb_leftsib, ARCH_CONVERT), 1);
+			rval++;
+		}
+		if ((lr & XFS_BTCUR_RIGHTRA) && INT_GET(i->bb_rightsib, ARCH_CONVERT) != NULLAGBLOCK) {
+			xfs_btree_reada_bufs(cur->bc_mp, cur->bc_private.i.agno,
+				INT_GET(i->bb_rightsib, ARCH_CONVERT), 1);
+			rval++;
+		}
+		break;
+	default:
+		ASSERT(0);
+	}
+	return rval;
+}
+
+/*
+ * Set the buffer for level "lev" in the cursor to bp, releasing
+ * any previous buffer.
+ */
+void
+xfs_btree_setbuf(
+	xfs_btree_cur_t		*cur,	/* btree cursor */
+	int			lev,	/* level in btree */
+	xfs_buf_t		*bp)	/* new buffer to set */
+{
+	xfs_btree_block_t	*b;	/* btree block */
+	xfs_buf_t		*obp;	/* old buffer pointer */
+
+	obp = cur->bc_bufs[lev];
+	if (obp)
+		xfs_trans_brelse(cur->bc_tp, obp);
+	cur->bc_bufs[lev] = bp;
+	cur->bc_ra[lev] = 0;
+	if (!bp)
+		return;
+	b = XFS_BUF_TO_BLOCK(bp);
+	if (XFS_BTREE_LONG_PTRS(cur->bc_btnum)) {
+		if (INT_GET(b->bb_u.l.bb_leftsib, ARCH_CONVERT) == NULLDFSBNO)
+			cur->bc_ra[lev] |= XFS_BTCUR_LEFTRA;
+		if (INT_GET(b->bb_u.l.bb_rightsib, ARCH_CONVERT) == NULLDFSBNO)
+			cur->bc_ra[lev] |= XFS_BTCUR_RIGHTRA;
+	} else {
+		if (INT_GET(b->bb_u.s.bb_leftsib, ARCH_CONVERT) == NULLAGBLOCK)
+			cur->bc_ra[lev] |= XFS_BTCUR_LEFTRA;
+		if (INT_GET(b->bb_u.s.bb_rightsib, ARCH_CONVERT) == NULLAGBLOCK)
+			cur->bc_ra[lev] |= XFS_BTCUR_RIGHTRA;
+	}
+}
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)