text: /*
   * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
   * All Rights Reserved.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it would be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write the Free Software Foundation,
   * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
   */
  #include "xfs.h"
  #include "xfs_fs.h"
  #include "xfs_types.h"
  #include "xfs_log.h"
  #include "xfs_trans.h"
  #include "xfs_sb.h"
  #include "xfs_ag.h"
  #include "xfs_mount.h"
  #include "xfs_da_btree.h"
  #include "xfs_bmap_btree.h"
  #include "xfs_dinode.h"
  #include "xfs_inode.h"
  #include "xfs_dir2_format.h"
  #include "xfs_dir2_priv.h"
  #include "xfs_error.h"
  
  STATIC xfs_dir2_data_free_t *
  xfs_dir2_data_freefind(xfs_dir2_data_hdr_t *hdr, xfs_dir2_data_unused_t *dup);
  
  #ifdef DEBUG
  /*
   * Check the consistency of the data block.
   * The input can also be a block-format directory.
   * Pop an assert if we find anything bad.
   */
  void
  xfs_dir2_data_check(
  	struct xfs_inode	*dp,		/* incore inode pointer */
  	struct xfs_buf		*bp)		/* data block's buffer */
  {
  	xfs_dir2_dataptr_t	addr;		/* addr for leaf lookup */
  	xfs_dir2_data_free_t	*bf;		/* bestfree table */
  	xfs_dir2_block_tail_t	*btp=NULL;	/* block tail */
  	int			count;		/* count of entries found */
  	xfs_dir2_data_hdr_t	*hdr;		/* data block header */
  	xfs_dir2_data_entry_t	*dep;		/* data entry */
  	xfs_dir2_data_free_t	*dfp;		/* bestfree entry */
  	xfs_dir2_data_unused_t	*dup;		/* unused entry */
  	char			*endp;		/* end of useful data */
  	int			freeseen;	/* mask of bestfrees seen */
  	xfs_dahash_t		hash;		/* hash of current name */
  	int			i;		/* leaf index */
  	int			lastfree;	/* last entry was unused */
  	xfs_dir2_leaf_entry_t	*lep=NULL;	/* block leaf entries */
  	xfs_mount_t		*mp;		/* filesystem mount point */
  	char			*p;		/* current data position */
  	int			stale;		/* count of stale leaves */
  	struct xfs_name		name;
  
  	mp = dp->i_mount;
  	hdr = bp->b_addr;
  	bf = hdr->bestfree;
  	p = (char *)(hdr + 1);
  
  	if (hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC)) {
  		btp = xfs_dir2_block_tail_p(mp, hdr);
  		lep = xfs_dir2_block_leaf_p(btp);
  		endp = (char *)lep;
  	} else {
  		ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC));
  		endp = (char *)hdr + mp->m_dirblksize;
  	}
  
  	count = lastfree = freeseen = 0;
  	/*
  	 * Account for zero bestfree entries.
  	 */
  	if (!bf[0].length) {
  		ASSERT(!bf[0].offset);
  		freeseen |= 1 << 0;
  	}
  	if (!bf[1].length) {
  		ASSERT(!bf[1].offset);
  		freeseen |= 1 << 1;
  	}
  	if (!bf[2].length) {
  		ASSERT(!bf[2].offset);
  		freeseen |= 1 << 2;
  	}
  	ASSERT(be16_to_cpu(bf[0].length) >= be16_to_cpu(bf[1].length));
  	ASSERT(be16_to_cpu(bf[1].length) >= be16_to_cpu(bf[2].length));
  	/*
  	 * Loop over the data/unused entries.
  	 */
  	while (p < endp) {
  		dup = (xfs_dir2_data_unused_t *)p;
  		/*
  		 * If it's unused, look for the space in the bestfree table.
  		 * If we find it, account for that, else make sure it
  		 * doesn't need to be there.
  		 */
  		if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
  			ASSERT(lastfree == 0);
  			ASSERT(be16_to_cpu(*xfs_dir2_data_unused_tag_p(dup)) ==
  			       (char *)dup - (char *)hdr);
  			dfp = xfs_dir2_data_freefind(hdr, dup);
  			if (dfp) {
  				i = (int)(dfp - bf);
  				ASSERT((freeseen & (1 << i)) == 0);
  				freeseen |= 1 << i;
  			} else {
  				ASSERT(be16_to_cpu(dup->length) <=
  				       be16_to_cpu(bf[2].length));
  			}
  			p += be16_to_cpu(dup->length);
  			lastfree = 1;
  			continue;
  		}
  		/*
  		 * It's a real entry.  Validate the fields.
  		 * If this is a block directory then make sure it's
  		 * in the leaf section of the block.
  		 * The linear search is crude but this is DEBUG code.
  		 */
  		dep = (xfs_dir2_data_entry_t *)p;
  		ASSERT(dep->namelen != 0);
  		ASSERT(xfs_dir_ino_validate(mp, be64_to_cpu(dep->inumber)) == 0);
  		ASSERT(be16_to_cpu(*xfs_dir2_data_entry_tag_p(dep)) ==
  		       (char *)dep - (char *)hdr);
  		count++;
  		lastfree = 0;
  		if (hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC)) {
  			addr = xfs_dir2_db_off_to_dataptr(mp, mp->m_dirdatablk,
  				(xfs_dir2_data_aoff_t)
  				((char *)dep - (char *)hdr));
  			name.name = dep->name;
  			name.len = dep->namelen;
  			hash = mp->m_dirnameops->hashname(&name);
  			for (i = 0; i < be32_to_cpu(btp->count); i++) {
  				if (be32_to_cpu(lep[i].address) == addr &&
  				    be32_to_cpu(lep[i].hashval) == hash)
  					break;
  			}
  			ASSERT(i < be32_to_cpu(btp->count));
  		}
  		p += xfs_dir2_data_entsize(dep->namelen);
  	}
  	/*
  	 * Need to have seen all the entries and all the bestfree slots.
  	 */
  	ASSERT(freeseen == 7);
  	if (hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC)) {
  		for (i = stale = 0; i < be32_to_cpu(btp->count); i++) {
  			if (lep[i].address ==
  			    cpu_to_be32(XFS_DIR2_NULL_DATAPTR))
  				stale++;
  			if (i > 0)
  				ASSERT(be32_to_cpu(lep[i].hashval) >= be32_to_cpu(lep[i - 1].hashval));
  		}
  		ASSERT(count == be32_to_cpu(btp->count) - be32_to_cpu(btp->stale));
  		ASSERT(stale == be32_to_cpu(btp->stale));
  	}
  }
  #endif
  
  /*
   * Given a data block and an unused entry from that block,
   * return the bestfree entry if any that corresponds to it.
   */
  STATIC xfs_dir2_data_free_t *
  xfs_dir2_data_freefind(
  	xfs_dir2_data_hdr_t	*hdr,		/* data block */
  	xfs_dir2_data_unused_t	*dup)		/* data unused entry */
  {
  	xfs_dir2_data_free_t	*dfp;		/* bestfree entry */
  	xfs_dir2_data_aoff_t	off;		/* offset value needed */
  #if defined(DEBUG) && defined(__KERNEL__)
  	int			matched;	/* matched the value */
  	int			seenzero;	/* saw a 0 bestfree entry */
  #endif
  
  	off = (xfs_dir2_data_aoff_t)((char *)dup - (char *)hdr);
  #if defined(DEBUG) && defined(__KERNEL__)
  	/*
  	 * Validate some consistency in the bestfree table.
  	 * Check order, non-overlapping entries, and if we find the
  	 * one we're looking for it has to be exact.
  	 */
  	ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
  	       hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
  	for (dfp = &hdr->bestfree[0], seenzero = matched = 0;
  	     dfp < &hdr->bestfree[XFS_DIR2_DATA_FD_COUNT];
  	     dfp++) {
  		if (!dfp->offset) {
  			ASSERT(!dfp->length);
  			seenzero = 1;
  			continue;
  		}
  		ASSERT(seenzero == 0);
  		if (be16_to_cpu(dfp->offset) == off) {
  			matched = 1;
  			ASSERT(dfp->length == dup->length);
  		} else if (off < be16_to_cpu(dfp->offset))
  			ASSERT(off + be16_to_cpu(dup->length) <= be16_to_cpu(dfp->offset));
  		else
  			ASSERT(be16_to_cpu(dfp->offset) + be16_to_cpu(dfp->length) <= off);
  		ASSERT(matched || be16_to_cpu(dfp->length) >= be16_to_cpu(dup->length));
  		if (dfp > &hdr->bestfree[0])
  			ASSERT(be16_to_cpu(dfp[-1].length) >= be16_to_cpu(dfp[0].length));
  	}
  #endif
  	/*
  	 * If this is smaller than the smallest bestfree entry,
  	 * it can't be there since they're sorted.
  	 */
  	if (be16_to_cpu(dup->length) <
  	    be16_to_cpu(hdr->bestfree[XFS_DIR2_DATA_FD_COUNT - 1].length))
  		return NULL;
  	/*
  	 * Look at the three bestfree entries for our guy.
  	 */
  	for (dfp = &hdr->bestfree[0];
  	     dfp < &hdr->bestfree[XFS_DIR2_DATA_FD_COUNT];
  	     dfp++) {
  		if (!dfp->offset)
  			return NULL;
  		if (be16_to_cpu(dfp->offset) == off)
  			return dfp;
  	}
  	/*
  	 * Didn't find it.  This only happens if there are duplicate lengths.
  	 */
  	return NULL;
  }
  
  /*
   * Insert an unused-space entry into the bestfree table.
   */
  xfs_dir2_data_free_t *				/* entry inserted */
  xfs_dir2_data_freeinsert(
  	xfs_dir2_data_hdr_t	*hdr,		/* data block pointer */
  	xfs_dir2_data_unused_t	*dup,		/* unused space */
  	int			*loghead)	/* log the data header (out) */
  {
  	xfs_dir2_data_free_t	*dfp;		/* bestfree table pointer */
  	xfs_dir2_data_free_t	new;		/* new bestfree entry */
  
  #ifdef __KERNEL__
  	ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
  	       hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
  #endif
  	dfp = hdr->bestfree;
  	new.length = dup->length;
  	new.offset = cpu_to_be16((char *)dup - (char *)hdr);
  
  	/*
  	 * Insert at position 0, 1, or 2; or not at all.
  	 */
  	if (be16_to_cpu(new.length) > be16_to_cpu(dfp[0].length)) {
  		dfp[2] = dfp[1];
  		dfp[1] = dfp[0];
  		dfp[0] = new;
  		*loghead = 1;
  		return &dfp[0];
  	}
  	if (be16_to_cpu(new.length) > be16_to_cpu(dfp[1].length)) {
  		dfp[2] = dfp[1];
  		dfp[1] = new;
  		*loghead = 1;
  		return &dfp[1];
  	}
  	if (be16_to_cpu(new.length) > be16_to_cpu(dfp[2].length)) {
  		dfp[2] = new;
  		*loghead = 1;
  		return &dfp[2];
  	}
  	return NULL;
  }
  
  /*
   * Remove a bestfree entry from the table.
   */
  STATIC void
  xfs_dir2_data_freeremove(
  	xfs_dir2_data_hdr_t	*hdr,		/* data block header */
  	xfs_dir2_data_free_t	*dfp,		/* bestfree entry pointer */
  	int			*loghead)	/* out: log data header */
  {
  #ifdef __KERNEL__
  	ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
  	       hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
  #endif
  	/*
  	 * It's the first entry, slide the next 2 up.
  	 */
  	if (dfp == &hdr->bestfree[0]) {
  		hdr->bestfree[0] = hdr->bestfree[1];
  		hdr->bestfree[1] = hdr->bestfree[2];
  	}
  	/*
  	 * It's the second entry, slide the 3rd entry up.
  	 */
  	else if (dfp == &hdr->bestfree[1])
  		hdr->bestfree[1] = hdr->bestfree[2];
  	/*
  	 * Must be the last entry.
  	 */
  	else
  		ASSERT(dfp == &hdr->bestfree[2]);
  	/*
  	 * Clear the 3rd entry, must be zero now.
  	 */
  	hdr->bestfree[2].length = 0;
  	hdr->bestfree[2].offset = 0;
  	*loghead = 1;
  }
  
  /*
   * Given a data block, reconstruct its bestfree map.
   */
  void
  xfs_dir2_data_freescan(
  	xfs_mount_t		*mp,		/* filesystem mount point */
  	xfs_dir2_data_hdr_t	*hdr,		/* data block header */
  	int			*loghead)	/* out: log data header */
  {
  	xfs_dir2_block_tail_t	*btp;		/* block tail */
  	xfs_dir2_data_entry_t	*dep;		/* active data entry */
  	xfs_dir2_data_unused_t	*dup;		/* unused data entry */
  	char			*endp;		/* end of block's data */
  	char			*p;		/* current entry pointer */
  
  #ifdef __KERNEL__
  	ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
  	       hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
  #endif
  	/*
  	 * Start by clearing the table.
  	 */
  	memset(hdr->bestfree, 0, sizeof(hdr->bestfree));
  	*loghead = 1;
  	/*
  	 * Set up pointers.
  	 */
  	p = (char *)(hdr + 1);
  	if (hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC)) {
  		btp = xfs_dir2_block_tail_p(mp, hdr);
  		endp = (char *)xfs_dir2_block_leaf_p(btp);
  	} else
  		endp = (char *)hdr + mp->m_dirblksize;
  	/*
  	 * Loop over the block's entries.
  	 */
  	while (p < endp) {
  		dup = (xfs_dir2_data_unused_t *)p;
  		/*
  		 * If it's a free entry, insert it.
  		 */
  		if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
  			ASSERT((char *)dup - (char *)hdr ==
  			       be16_to_cpu(*xfs_dir2_data_unused_tag_p(dup)));
  			xfs_dir2_data_freeinsert(hdr, dup, loghead);
  			p += be16_to_cpu(dup->length);
  		}
  		/*
  		 * For active entries, check their tags and skip them.
  		 */
  		else {
  			dep = (xfs_dir2_data_entry_t *)p;
  			ASSERT((char *)dep - (char *)hdr ==
  			       be16_to_cpu(*xfs_dir2_data_entry_tag_p(dep)));
  			p += xfs_dir2_data_entsize(dep->namelen);
  		}
  	}
  }
  
  /*
   * Initialize a data block at the given block number in the directory.
   * Give back the buffer for the created block.
   */
  int						/* error */
  xfs_dir2_data_init(
  	xfs_da_args_t		*args,		/* directory operation args */
  	xfs_dir2_db_t		blkno,		/* logical dir block number */
  	struct xfs_buf		**bpp)		/* output block buffer */
  {
  	struct xfs_buf		*bp;		/* block buffer */
  	xfs_dir2_data_hdr_t	*hdr;		/* data block header */
  	xfs_inode_t		*dp;		/* incore directory inode */
  	xfs_dir2_data_unused_t	*dup;		/* unused entry pointer */
  	int			error;		/* error return value */
  	int			i;		/* bestfree index */
  	xfs_mount_t		*mp;		/* filesystem mount point */
  	xfs_trans_t		*tp;		/* transaction pointer */
  	int                     t;              /* temp */
  
  	dp = args->dp;
  	mp = dp->i_mount;
  	tp = args->trans;
  	/*
  	 * Get the buffer set up for the block.
  	 */
  	error = xfs_da_get_buf(tp, dp, xfs_dir2_db_to_da(mp, blkno), -1, &bp,
  		XFS_DATA_FORK);
  	if (error) {
  		return error;
  	}
  	ASSERT(bp != NULL);
  
  	/*
  	 * Initialize the header.
  	 */
  	hdr = bp->b_addr;
  	hdr->magic = cpu_to_be32(XFS_DIR2_DATA_MAGIC);
  	hdr->bestfree[0].offset = cpu_to_be16(sizeof(*hdr));
  	for (i = 1; i < XFS_DIR2_DATA_FD_COUNT; i++) {
  		hdr->bestfree[i].length = 0;
  		hdr->bestfree[i].offset = 0;
  	}
  
  	/*
  	 * Set up an unused entry for the block's body.
  	 */
  	dup = (xfs_dir2_data_unused_t *)(hdr + 1);
  	dup->freetag = cpu_to_be16(XFS_DIR2_DATA_FREE_TAG);
  
  	t = mp->m_dirblksize - (uint)sizeof(*hdr);
  	hdr->bestfree[0].length = cpu_to_be16(t);
  	dup->length = cpu_to_be16(t);
  	*xfs_dir2_data_unused_tag_p(dup) = cpu_to_be16((char *)dup - (char *)hdr);
  	/*
  	 * Log it and return it.
  	 */
  	xfs_dir2_data_log_header(tp, bp);
  	xfs_dir2_data_log_unused(tp, bp, dup);
  	*bpp = bp;
  	return 0;
  }
  
  /*
   * Log an active data entry from the block.
   */
  void
  xfs_dir2_data_log_entry(
  	struct xfs_trans	*tp,
  	struct xfs_buf		*bp,
  	xfs_dir2_data_entry_t	*dep)		/* data entry pointer */
  {
  	xfs_dir2_data_hdr_t	*hdr = bp->b_addr;
  
  	ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
  	       hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
  
  	xfs_trans_log_buf(tp, bp, (uint)((char *)dep - (char *)hdr),
  		(uint)((char *)(xfs_dir2_data_entry_tag_p(dep) + 1) -
  		       (char *)hdr - 1));
  }
  
  /*
   * Log a data block header.
   */
  void
  xfs_dir2_data_log_header(
  	struct xfs_trans	*tp,
  	struct xfs_buf		*bp)
  {
  	xfs_dir2_data_hdr_t	*hdr = bp->b_addr;
  
  	ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
  	       hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
  
  	xfs_trans_log_buf(tp, bp, 0, sizeof(*hdr) - 1);
  }
  
  /*
   * Log a data unused entry.
   */
  void
  xfs_dir2_data_log_unused(
  	struct xfs_trans	*tp,
  	struct xfs_buf		*bp,
  	xfs_dir2_data_unused_t	*dup)		/* data unused pointer */
  {
  	xfs_dir2_data_hdr_t	*hdr = bp->b_addr;
  
  	ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
  	       hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
  
  	/*
  	 * Log the first part of the unused entry.
  	 */
  	xfs_trans_log_buf(tp, bp, (uint)((char *)dup - (char *)hdr),
  		(uint)((char *)&dup->length + sizeof(dup->length) -
  		       1 - (char *)hdr));
  	/*
  	 * Log the end (tag) of the unused entry.
  	 */
  	xfs_trans_log_buf(tp, bp,
  		(uint)((char *)xfs_dir2_data_unused_tag_p(dup) - (char *)hdr),
  		(uint)((char *)xfs_dir2_data_unused_tag_p(dup) - (char *)hdr +
  		       sizeof(xfs_dir2_data_off_t) - 1));
  }
  
  /*
   * Make a byte range in the data block unused.
   * Its current contents are unimportant.
   */
  void
  xfs_dir2_data_make_free(
  	struct xfs_trans	*tp,
  	struct xfs_buf		*bp,
  	xfs_dir2_data_aoff_t	offset,		/* starting byte offset */
  	xfs_dir2_data_aoff_t	len,		/* length in bytes */
  	int			*needlogp,	/* out: log header */
  	int			*needscanp)	/* out: regen bestfree */
  {
  	xfs_dir2_data_hdr_t	*hdr;		/* data block pointer */
  	xfs_dir2_data_free_t	*dfp;		/* bestfree pointer */
  	char			*endptr;	/* end of data area */
  	xfs_mount_t		*mp;		/* filesystem mount point */
  	int			needscan;	/* need to regen bestfree */
  	xfs_dir2_data_unused_t	*newdup;	/* new unused entry */
  	xfs_dir2_data_unused_t	*postdup;	/* unused entry after us */
  	xfs_dir2_data_unused_t	*prevdup;	/* unused entry before us */
  
  	mp = tp->t_mountp;
  	hdr = bp->b_addr;
  
  	/*
  	 * Figure out where the end of the data area is.
  	 */
  	if (hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC))
  		endptr = (char *)hdr + mp->m_dirblksize;
  	else {
  		xfs_dir2_block_tail_t	*btp;	/* block tail */
  
  		ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
  		btp = xfs_dir2_block_tail_p(mp, hdr);
  		endptr = (char *)xfs_dir2_block_leaf_p(btp);
  	}
  	/*
  	 * If this isn't the start of the block, then back up to
  	 * the previous entry and see if it's free.
  	 */
  	if (offset > sizeof(*hdr)) {
  		__be16			*tagp;	/* tag just before us */
  
  		tagp = (__be16 *)((char *)hdr + offset) - 1;
  		prevdup = (xfs_dir2_data_unused_t *)((char *)hdr + be16_to_cpu(*tagp));
  		if (be16_to_cpu(prevdup->freetag) != XFS_DIR2_DATA_FREE_TAG)
  			prevdup = NULL;
  	} else
  		prevdup = NULL;
  	/*
  	 * If this isn't the end of the block, see if the entry after
  	 * us is free.
  	 */
  	if ((char *)hdr + offset + len < endptr) {
  		postdup =
  			(xfs_dir2_data_unused_t *)((char *)hdr + offset + len);
  		if (be16_to_cpu(postdup->freetag) != XFS_DIR2_DATA_FREE_TAG)
  			postdup = NULL;
  	} else
  		postdup = NULL;
  	ASSERT(*needscanp == 0);
  	needscan = 0;
  	/*
  	 * Previous and following entries are both free,
  	 * merge everything into a single free entry.
  	 */
  	if (prevdup && postdup) {
  		xfs_dir2_data_free_t	*dfp2;	/* another bestfree pointer */
  
  		/*
  		 * See if prevdup and/or postdup are in bestfree table.
  		 */
  		dfp = xfs_dir2_data_freefind(hdr, prevdup);
  		dfp2 = xfs_dir2_data_freefind(hdr, postdup);
  		/*
  		 * We need a rescan unless there are exactly 2 free entries
  		 * namely our two.  Then we know what's happening, otherwise
  		 * since the third bestfree is there, there might be more
  		 * entries.
  		 */
  		needscan = (hdr->bestfree[2].length != 0);
  		/*
  		 * Fix up the new big freespace.
  		 */
  		be16_add_cpu(&prevdup->length, len + be16_to_cpu(postdup->length));
  		*xfs_dir2_data_unused_tag_p(prevdup) =
  			cpu_to_be16((char *)prevdup - (char *)hdr);
  		xfs_dir2_data_log_unused(tp, bp, prevdup);
  		if (!needscan) {
  			/*
  			 * Has to be the case that entries 0 and 1 are
  			 * dfp and dfp2 (don't know which is which), and
  			 * entry 2 is empty.
  			 * Remove entry 1 first then entry 0.
  			 */
  			ASSERT(dfp && dfp2);
  			if (dfp == &hdr->bestfree[1]) {
  				dfp = &hdr->bestfree[0];
  				ASSERT(dfp2 == dfp);
  				dfp2 = &hdr->bestfree[1];
  			}
  			xfs_dir2_data_freeremove(hdr, dfp2, needlogp);
  			xfs_dir2_data_freeremove(hdr, dfp, needlogp);
  			/*
  			 * Now insert the new entry.
  			 */
  			dfp = xfs_dir2_data_freeinsert(hdr, prevdup, needlogp);
  			ASSERT(dfp == &hdr->bestfree[0]);
  			ASSERT(dfp->length == prevdup->length);
  			ASSERT(!dfp[1].length);
  			ASSERT(!dfp[2].length);
  		}
  	}
  	/*
  	 * The entry before us is free, merge with it.
  	 */
  	else if (prevdup) {
  		dfp = xfs_dir2_data_freefind(hdr, prevdup);
  		be16_add_cpu(&prevdup->length, len);
  		*xfs_dir2_data_unused_tag_p(prevdup) =
  			cpu_to_be16((char *)prevdup - (char *)hdr);
  		xfs_dir2_data_log_unused(tp, bp, prevdup);
  		/*
  		 * If the previous entry was in the table, the new entry
  		 * is longer, so it will be in the table too.  Remove
  		 * the old one and add the new one.
  		 */
  		if (dfp) {
  			xfs_dir2_data_freeremove(hdr, dfp, needlogp);
  			xfs_dir2_data_freeinsert(hdr, prevdup, needlogp);
  		}
  		/*
  		 * Otherwise we need a scan if the new entry is big enough.
  		 */
  		else {
  			needscan = be16_to_cpu(prevdup->length) >
  				   be16_to_cpu(hdr->bestfree[2].length);
  		}
  	}
  	/*
  	 * The following entry is free, merge with it.
  	 */
  	else if (postdup) {
  		dfp = xfs_dir2_data_freefind(hdr, postdup);
  		newdup = (xfs_dir2_data_unused_t *)((char *)hdr + offset);
  		newdup->freetag = cpu_to_be16(XFS_DIR2_DATA_FREE_TAG);
  		newdup->length = cpu_to_be16(len + be16_to_cpu(postdup->length));
  		*xfs_dir2_data_unused_tag_p(newdup) =
  			cpu_to_be16((char *)newdup - (char *)hdr);
  		xfs_dir2_data_log_unused(tp, bp, newdup);
  		/*
  		 * If the following entry was in the table, the new entry
  		 * is longer, so it will be in the table too.  Remove
  		 * the old one and add the new one.
  		 */
  		if (dfp) {
  			xfs_dir2_data_freeremove(hdr, dfp, needlogp);
  			xfs_dir2_data_freeinsert(hdr, newdup, needlogp);
  		}
  		/*
  		 * Otherwise we need a scan if the new entry is big enough.
  		 */
  		else {
  			needscan = be16_to_cpu(newdup->length) >
  				   be16_to_cpu(hdr->bestfree[2].length);
  		}
  	}
  	/*
  	 * Neither neighbor is free.  Make a new entry.
  	 */
  	else {
  		newdup = (xfs_dir2_data_unused_t *)((char *)hdr + offset);
  		newdup->freetag = cpu_to_be16(XFS_DIR2_DATA_FREE_TAG);
  		newdup->length = cpu_to_be16(len);
  		*xfs_dir2_data_unused_tag_p(newdup) =
  			cpu_to_be16((char *)newdup - (char *)hdr);
  		xfs_dir2_data_log_unused(tp, bp, newdup);
  		xfs_dir2_data_freeinsert(hdr, newdup, needlogp);
  	}
  	*needscanp = needscan;
  }
  
  /*
   * Take a byte range out of an existing unused space and make it un-free.
   */
  void
  xfs_dir2_data_use_free(
  	struct xfs_trans	*tp,
  	struct xfs_buf		*bp,
  	xfs_dir2_data_unused_t	*dup,		/* unused entry */
  	xfs_dir2_data_aoff_t	offset,		/* starting offset to use */
  	xfs_dir2_data_aoff_t	len,		/* length to use */
  	int			*needlogp,	/* out: need to log header */
  	int			*needscanp)	/* out: need regen bestfree */
  {
  	xfs_dir2_data_hdr_t	*hdr;		/* data block header */
  	xfs_dir2_data_free_t	*dfp;		/* bestfree pointer */
  	int			matchback;	/* matches end of freespace */
  	int			matchfront;	/* matches start of freespace */
  	int			needscan;	/* need to regen bestfree */
  	xfs_dir2_data_unused_t	*newdup;	/* new unused entry */
  	xfs_dir2_data_unused_t	*newdup2;	/* another new unused entry */
  	int			oldlen;		/* old unused entry's length */
  
  	hdr = bp->b_addr;
  	ASSERT(hdr->magic == cpu_to_be32(XFS_DIR2_DATA_MAGIC) ||
  	       hdr->magic == cpu_to_be32(XFS_DIR2_BLOCK_MAGIC));
  	ASSERT(be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG);
  	ASSERT(offset >= (char *)dup - (char *)hdr);
  	ASSERT(offset + len <= (char *)dup + be16_to_cpu(dup->length) - (char *)hdr);
  	ASSERT((char *)dup - (char *)hdr == be16_to_cpu(*xfs_dir2_data_unused_tag_p(dup)));
  	/*
  	 * Look up the entry in the bestfree table.
  	 */
  	dfp = xfs_dir2_data_freefind(hdr, dup);
  	oldlen = be16_to_cpu(dup->length);
  	ASSERT(dfp || oldlen <= be16_to_cpu(hdr->bestfree[2].length));
  	/*
  	 * Check for alignment with front and back of the entry.
  	 */
  	matchfront = (char *)dup - (char *)hdr == offset;
  	matchback = (char *)dup + oldlen - (char *)hdr == offset + len;
  	ASSERT(*needscanp == 0);
  	needscan = 0;
  	/*
  	 * If we matched it exactly we just need to get rid of it from
  	 * the bestfree table.
  	 */
  	if (matchfront && matchback) {
  		if (dfp) {
  			needscan = (hdr->bestfree[2].offset != 0);
  			if (!needscan)
  				xfs_dir2_data_freeremove(hdr, dfp, needlogp);
  		}
  	}
  	/*
  	 * We match the first part of the entry.
  	 * Make a new entry with the remaining freespace.
  	 */
  	else if (matchfront) {
  		newdup = (xfs_dir2_data_unused_t *)((char *)hdr + offset + len);
  		newdup->freetag = cpu_to_be16(XFS_DIR2_DATA_FREE_TAG);
  		newdup->length = cpu_to_be16(oldlen - len);
  		*xfs_dir2_data_unused_tag_p(newdup) =
  			cpu_to_be16((char *)newdup - (char *)hdr);
  		xfs_dir2_data_log_unused(tp, bp, newdup);
  		/*
  		 * If it was in the table, remove it and add the new one.
  		 */
  		if (dfp) {
  			xfs_dir2_data_freeremove(hdr, dfp, needlogp);
  			dfp = xfs_dir2_data_freeinsert(hdr, newdup, needlogp);
  			ASSERT(dfp != NULL);
  			ASSERT(dfp->length == newdup->length);
  			ASSERT(be16_to_cpu(dfp->offset) == (char *)newdup - (char *)hdr);
  			/*
  			 * If we got inserted at the last slot,
  			 * that means we don't know if there was a better
  			 * choice for the last slot, or not.  Rescan.
  			 */
  			needscan = dfp == &hdr->bestfree[2];
  		}
  	}
  	/*
  	 * We match the last part of the entry.
  	 * Trim the allocated space off the tail of the entry.
  	 */
  	else if (matchback) {
  		newdup = dup;
  		newdup->length = cpu_to_be16(((char *)hdr + offset) - (char *)newdup);
  		*xfs_dir2_data_unused_tag_p(newdup) =
  			cpu_to_be16((char *)newdup - (char *)hdr);
  		xfs_dir2_data_log_unused(tp, bp, newdup);
  		/*
  		 * If it was in the table, remove it and add the new one.
  		 */
  		if (dfp) {
  			xfs_dir2_data_freeremove(hdr, dfp, needlogp);
  			dfp = xfs_dir2_data_freeinsert(hdr, newdup, needlogp);
  			ASSERT(dfp != NULL);
  			ASSERT(dfp->length == newdup->length);
  			ASSERT(be16_to_cpu(dfp->offset) == (char *)newdup - (char *)hdr);
  			/*
  			 * If we got inserted at the last slot,
  			 * that means we don't know if there was a better
  			 * choice for the last slot, or not.  Rescan.
  			 */
  			needscan = dfp == &hdr->bestfree[2];
  		}
  	}
  	/*
  	 * Poking out the middle of an entry.
  	 * Make two new entries.
  	 */
  	else {
  		newdup = dup;
  		newdup->length = cpu_to_be16(((char *)hdr + offset) - (char *)newdup);
  		*xfs_dir2_data_unused_tag_p(newdup) =
  			cpu_to_be16((char *)newdup - (char *)hdr);
  		xfs_dir2_data_log_unused(tp, bp, newdup);
  		newdup2 = (xfs_dir2_data_unused_t *)((char *)hdr + offset + len);
  		newdup2->freetag = cpu_to_be16(XFS_DIR2_DATA_FREE_TAG);
  		newdup2->length = cpu_to_be16(oldlen - len - be16_to_cpu(newdup->length));
  		*xfs_dir2_data_unused_tag_p(newdup2) =
  			cpu_to_be16((char *)newdup2 - (char *)hdr);
  		xfs_dir2_data_log_unused(tp, bp, newdup2);
  		/*
  		 * If the old entry was in the table, we need to scan
  		 * if the 3rd entry was valid, since these entries
  		 * are smaller than the old one.
  		 * If we don't need to scan that means there were 1 or 2
  		 * entries in the table, and removing the old and adding
  		 * the 2 new will work.
  		 */
  		if (dfp) {
  			needscan = (hdr->bestfree[2].length != 0);
  			if (!needscan) {
  				xfs_dir2_data_freeremove(hdr, dfp, needlogp);
  				xfs_dir2_data_freeinsert(hdr, newdup, needlogp);
  				xfs_dir2_data_freeinsert(hdr, newdup2,
  							 needlogp);
  			}
  		}
  	}
  	*needscanp = needscan;
  }
  