/*

   * Copyright (c) 2000-2006 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_bit.h"

  #include "xfs_log.h"

  #include "xfs_inum.h"

  #include "xfs_trans.h"
  #include "xfs_sb.h"
  #include "xfs_ag.h"

  #include "xfs_alloc.h"

  #include "xfs_quota.h"
  #include "xfs_mount.h"

  #include "xfs_bmap_btree.h"

  #include "xfs_alloc_btree.h"

  #include "xfs_ialloc_btree.h"

  #include "xfs_dinode.h"
  #include "xfs_inode.h"

  #include "xfs_btree.h"

  #include "xfs_bmap.h"

  #include "xfs_rtalloc.h"
  #include "xfs_error.h"
  #include "xfs_itable.h"
  #include "xfs_rw.h"

  #include "xfs_attr.h"
  #include "xfs_buf_item.h"
  #include "xfs_trans_space.h"
  #include "xfs_utils.h"
  #include "xfs_iomap.h"

  #include "xfs_trace.h"

  
  #define XFS_WRITEIO_ALIGN(mp,off)	(((off) >> mp->m_writeio_log) \
  						<< mp->m_writeio_log)

  #define XFS_WRITE_IMAPS		XFS_BMAP_MAX_NMAP

  STATIC int

  xfs_iomap_eof_align_last_fsb(
  	xfs_mount_t	*mp,

  	xfs_inode_t	*ip,

  	xfs_extlen_t	extsize,
  	xfs_fileoff_t	*last_fsb)
  {
  	xfs_fileoff_t	new_last_fsb = 0;
  	xfs_extlen_t	align;
  	int		eof, error;

  	if (XFS_IS_REALTIME_INODE(ip))

  		;
  	/*
  	 * If mounted with the "-o swalloc" option, roundup the allocation
  	 * request to a stripe width boundary if the file size is >=
  	 * stripe width and we are allocating past the allocation eof.
  	 */
  	else if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC) &&

  	        (ip->i_size >= XFS_FSB_TO_B(mp, mp->m_swidth)))

  		new_last_fsb = roundup_64(*last_fsb, mp->m_swidth);
  	/*
  	 * Roundup the allocation request to a stripe unit (m_dalign) boundary
  	 * if the file size is >= stripe unit size, and we are allocating past
  	 * the allocation eof.
  	 */

  	else if (mp->m_dalign && (ip->i_size >= XFS_FSB_TO_B(mp, mp->m_dalign)))

  		new_last_fsb = roundup_64(*last_fsb, mp->m_dalign);
  
  	/*
  	 * Always round up the allocation request to an extent boundary
  	 * (when file on a real-time subvolume or has di_extsize hint).
  	 */
  	if (extsize) {
  		if (new_last_fsb)
  			align = roundup_64(new_last_fsb, extsize);
  		else
  			align = extsize;
  		new_last_fsb = roundup_64(*last_fsb, align);
  	}
  
  	if (new_last_fsb) {

  		error = xfs_bmap_eof(ip, new_last_fsb, XFS_DATA_FORK, &eof);

  		if (error)
  			return error;
  		if (eof)
  			*last_fsb = new_last_fsb;
  	}
  	return 0;
  }
  
  STATIC int

  xfs_alert_fsblock_zero(

  	xfs_inode_t	*ip,
  	xfs_bmbt_irec_t	*imap)
  {

  	xfs_alert_tag(ip->i_mount, XFS_PTAG_FSBLOCK_ZERO,

  			"Access to block zero in inode %llu "
  			"start_block: %llx start_off: %llx "
  			"blkcnt: %llx extent-state: %x
  ",
  		(unsigned long long)ip->i_ino,
  		(unsigned long long)imap->br_startblock,
  		(unsigned long long)imap->br_startoff,
  		(unsigned long long)imap->br_blockcount,
  		imap->br_state);
  	return EFSCORRUPTED;
  }

  int

  xfs_iomap_write_direct(
  	xfs_inode_t	*ip,

  	xfs_off_t	offset,

  	size_t		count,

  	xfs_bmbt_irec_t *imap,

  	int		nmaps)

  {
  	xfs_mount_t	*mp = ip->i_mount;

  	xfs_fileoff_t	offset_fsb;
  	xfs_fileoff_t	last_fsb;

  	xfs_filblks_t	count_fsb, resaligned;

  	xfs_fsblock_t	firstfsb;

  	xfs_extlen_t	extsz, temp;

  	int		nimaps;

  	int		bmapi_flag;

  	int		quota_flag;

  	int		rt;
  	xfs_trans_t	*tp;

  	xfs_bmap_free_t free_list;

  	uint		qblocks, resblks, resrtextents;

  	int		committed;

  	int		error;

  
  	/*
  	 * Make sure that the dquots are there. This doesn't hold
  	 * the ilock across a disk read.
  	 */

  	error = xfs_qm_dqattach_locked(ip, 0);

  	if (error)
  		return XFS_ERROR(error);

  	rt = XFS_IS_REALTIME_INODE(ip);

  	extsz = xfs_get_extsz_hint(ip);

  	offset_fsb = XFS_B_TO_FSBT(mp, offset);
  	last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));

  	if ((offset + count) > ip->i_size) {
  		error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);

  		if (error)
  			goto error_out;

  	} else {

  		if (nmaps && (imap->br_startblock == HOLESTARTBLOCK))

  			last_fsb = MIN(last_fsb, (xfs_fileoff_t)

  					imap->br_blockcount +
  					imap->br_startoff);

  	}

  	count_fsb = last_fsb - offset_fsb;
  	ASSERT(count_fsb > 0);
  
  	resaligned = count_fsb;
  	if (unlikely(extsz)) {
  		if ((temp = do_mod(offset_fsb, extsz)))
  			resaligned += temp;
  		if ((temp = do_mod(resaligned, extsz)))
  			resaligned += extsz - temp;
  	}
  
  	if (unlikely(rt)) {
  		resrtextents = qblocks = resaligned;
  		resrtextents /= mp->m_sb.sb_rextsize;

  		resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
  		quota_flag = XFS_QMOPT_RES_RTBLKS;
  	} else {
  		resrtextents = 0;

  		resblks = qblocks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);

  		quota_flag = XFS_QMOPT_RES_REGBLKS;
  	}

  
  	/*

  	 * Allocate and setup the transaction

  	 */
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);
  	tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);

  	error = xfs_trans_reserve(tp, resblks,

  			XFS_WRITE_LOG_RES(mp), resrtextents,

  			XFS_TRANS_PERM_LOG_RES,
  			XFS_WRITE_LOG_COUNT);

  	/*

  	 * Check for running out of space, note: need lock to return

  	 */
  	if (error)

  		xfs_trans_cancel(tp, 0);

  	xfs_ilock(ip, XFS_ILOCK_EXCL);

  	if (error)

  		goto error_out;

  	error = xfs_trans_reserve_quota_nblks(tp, ip, qblocks, 0, quota_flag);

  	if (error)

  		goto error1;

  	xfs_trans_ijoin(tp, ip, 0);

  	bmapi_flag = 0;

  	if (offset < ip->i_size || extsz)

  		bmapi_flag |= XFS_BMAPI_PREALLOC;
  
  	/*

  	 * From this point onwards we overwrite the imap pointer that the
  	 * caller gave to us.

  	 */

  	xfs_bmap_init(&free_list, &firstfsb);

  	nimaps = 1;

  	error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb, bmapi_flag,
  				&firstfsb, 0, imap, &nimaps, &free_list);

  	if (error)

  		goto error0;

  
  	/*

  	 * Complete the transaction

  	 */

  	error = xfs_bmap_finish(&tp, &free_list, &committed);

  	if (error)

  		goto error0;

  	error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);

  	if (error)

  		goto error_out;

  	/*
  	 * Copy any maps to caller's array and return any error.
  	 */

  	if (nimaps == 0) {

  		error = ENOSPC;
  		goto error_out;
  	}

  	if (!(imap->br_startblock || XFS_IS_REALTIME_INODE(ip))) {

  		error = xfs_alert_fsblock_zero(ip, imap);

  		goto error_out;
  	}

  	return 0;

  error0:	/* Cancel bmap, unlock inode, unreserve quota blocks, cancel trans */

  	xfs_bmap_cancel(&free_list);

  	xfs_trans_unreserve_quota_nblks(tp, ip, qblocks, 0, quota_flag);

  error1:	/* Just cancel transaction */

  	xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT);

  
  error_out:
  	return XFS_ERROR(error);
  }

  /*

   * If the caller is doing a write at the end of the file, then extend the
   * allocation out to the file system's write iosize.  We clean up any extra
   * space left over when the file is closed in xfs_inactive().

   *
   * If we find we already have delalloc preallocation beyond EOF, don't do more
   * preallocation as it it not needed.

   */
  STATIC int
  xfs_iomap_eof_want_preallocate(
  	xfs_mount_t	*mp,

  	xfs_inode_t	*ip,

  	xfs_off_t	offset,
  	size_t		count,

  	xfs_bmbt_irec_t *imap,
  	int		nimaps,
  	int		*prealloc)
  {
  	xfs_fileoff_t   start_fsb;
  	xfs_filblks_t   count_fsb;
  	xfs_fsblock_t	firstblock;
  	int		n, error, imaps;

  	int		found_delalloc = 0;

  
  	*prealloc = 0;

  	if ((offset + count) <= ip->i_size)

  		return 0;
  
  	/*
  	 * If there are any real blocks past eof, then don't
  	 * do any speculative allocation.
  	 */
  	start_fsb = XFS_B_TO_FSBT(mp, ((xfs_ufsize_t)(offset + count - 1)));
  	count_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)XFS_MAXIOFFSET(mp));
  	while (count_fsb > 0) {
  		imaps = nimaps;

  		firstblock = NULLFSBLOCK;

  		error = xfs_bmapi_read(ip, start_fsb, count_fsb, imap, &imaps,
  				       0);

  		if (error)
  			return error;
  		for (n = 0; n < imaps; n++) {
  			if ((imap[n].br_startblock != HOLESTARTBLOCK) &&
  			    (imap[n].br_startblock != DELAYSTARTBLOCK))
  				return 0;
  			start_fsb += imap[n].br_blockcount;
  			count_fsb -= imap[n].br_blockcount;

  
  			if (imap[n].br_startblock == DELAYSTARTBLOCK)
  				found_delalloc = 1;

  		}
  	}

  	if (!found_delalloc)
  		*prealloc = 1;

  	return 0;
  }

  /*
   * If we don't have a user specified preallocation size, dynamically increase
   * the preallocation size as the size of the file grows. Cap the maximum size
   * at a single extent or less if the filesystem is near full. The closer the
   * filesystem is to full, the smaller the maximum prealocation.
   */
  STATIC xfs_fsblock_t
  xfs_iomap_prealloc_size(
  	struct xfs_mount	*mp,
  	struct xfs_inode	*ip)
  {
  	xfs_fsblock_t		alloc_blocks = 0;
  
  	if (!(mp->m_flags & XFS_MOUNT_DFLT_IOSIZE)) {
  		int shift = 0;
  		int64_t freesp;

  		/*
  		 * rounddown_pow_of_two() returns an undefined result
  		 * if we pass in alloc_blocks = 0. Hence the "+ 1" to
  		 * ensure we always pass in a non-zero value.
  		 */
  		alloc_blocks = XFS_B_TO_FSB(mp, ip->i_size) + 1;

  		alloc_blocks = XFS_FILEOFF_MIN(MAXEXTLEN,
  					rounddown_pow_of_two(alloc_blocks));
  
  		xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
  		freesp = mp->m_sb.sb_fdblocks;
  		if (freesp < mp->m_low_space[XFS_LOWSP_5_PCNT]) {
  			shift = 2;
  			if (freesp < mp->m_low_space[XFS_LOWSP_4_PCNT])
  				shift++;
  			if (freesp < mp->m_low_space[XFS_LOWSP_3_PCNT])
  				shift++;
  			if (freesp < mp->m_low_space[XFS_LOWSP_2_PCNT])
  				shift++;
  			if (freesp < mp->m_low_space[XFS_LOWSP_1_PCNT])
  				shift++;
  		}
  		if (shift)
  			alloc_blocks >>= shift;
  	}
  
  	if (alloc_blocks < mp->m_writeio_blocks)
  		alloc_blocks = mp->m_writeio_blocks;
  
  	return alloc_blocks;
  }

  int

  xfs_iomap_write_delay(
  	xfs_inode_t	*ip,

  	xfs_off_t	offset,

  	size_t		count,

  	xfs_bmbt_irec_t *ret_imap)

  {
  	xfs_mount_t	*mp = ip->i_mount;

  	xfs_fileoff_t	offset_fsb;
  	xfs_fileoff_t	last_fsb;

  	xfs_off_t	aligned_offset;
  	xfs_fileoff_t	ioalign;

  	xfs_extlen_t	extsz;

  	int		nimaps;

  	xfs_bmbt_irec_t imap[XFS_WRITE_IMAPS];

  	int		prealloc, flushed = 0;

  	int		error;

  	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));

  
  	/*
  	 * Make sure that the dquots are there. This doesn't hold
  	 * the ilock across a disk read.
  	 */

  	error = xfs_qm_dqattach_locked(ip, 0);

  	if (error)
  		return XFS_ERROR(error);

  	extsz = xfs_get_extsz_hint(ip);

  	offset_fsb = XFS_B_TO_FSBT(mp, offset);

  	error = xfs_iomap_eof_want_preallocate(mp, ip, offset, count,

  				imap, XFS_WRITE_IMAPS, &prealloc);

  	if (error)
  		return error;

  retry:

  	if (prealloc) {

  		xfs_fsblock_t	alloc_blocks = xfs_iomap_prealloc_size(mp, ip);

  		aligned_offset = XFS_WRITEIO_ALIGN(mp, (offset + count - 1));
  		ioalign = XFS_B_TO_FSBT(mp, aligned_offset);

  		last_fsb = ioalign + alloc_blocks;

  	} else {
  		last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));

  	}

  	if (prealloc || extsz) {

  		error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);

  		if (error)

  			return error;

  	}

  
  	nimaps = XFS_WRITE_IMAPS;

  	error = xfs_bmapi_delay(ip, offset_fsb, last_fsb - offset_fsb,
  				imap, &nimaps, XFS_BMAPI_ENTIRE);

  	switch (error) {
  	case 0:
  	case ENOSPC:
  	case EDQUOT:
  		break;
  	default:

  		return XFS_ERROR(error);

  	}

  	/*

  	 * If bmapi returned us nothing, we got either ENOSPC or EDQUOT.  For
  	 * ENOSPC, * flush all other inodes with delalloc blocks to free up
  	 * some of the excess reserved metadata space. For both cases, retry
  	 * without EOF preallocation.

  	 */
  	if (nimaps == 0) {

  		trace_xfs_delalloc_enospc(ip, offset, count);

  		if (flushed)

  			return XFS_ERROR(error ? error : ENOSPC);

  		if (error == ENOSPC) {
  			xfs_iunlock(ip, XFS_ILOCK_EXCL);
  			xfs_flush_inodes(ip);
  			xfs_ilock(ip, XFS_ILOCK_EXCL);
  		}

  
  		flushed = 1;

  		error = 0;

  		prealloc = 0;

  		goto retry;
  	}

  	if (!(imap[0].br_startblock || XFS_IS_REALTIME_INODE(ip)))

  		return xfs_alert_fsblock_zero(ip, &imap[0]);

  
  	*ret_imap = imap[0];

  	return 0;
  }
  
  /*
   * Pass in a delayed allocate extent, convert it to real extents;
   * return to the caller the extent we create which maps on top of
   * the originating callers request.
   *
   * Called without a lock on the inode.

   *
   * We no longer bother to look at the incoming map - all we have to
   * guarantee is that whatever we allocate fills the required range.

   */

  int

  xfs_iomap_write_allocate(
  	xfs_inode_t	*ip,

  	xfs_off_t	offset,

  	size_t		count,

  	xfs_bmbt_irec_t *imap)

  {
  	xfs_mount_t	*mp = ip->i_mount;

  	xfs_fileoff_t	offset_fsb, last_block;
  	xfs_fileoff_t	end_fsb, map_start_fsb;
  	xfs_fsblock_t	first_block;
  	xfs_bmap_free_t	free_list;
  	xfs_filblks_t	count_fsb;

  	xfs_trans_t	*tp;

  	int		nimaps, committed;

  	int		error = 0;
  	int		nres;

  	/*
  	 * Make sure that the dquots are there.
  	 */

  	error = xfs_qm_dqattach(ip, 0);
  	if (error)

  		return XFS_ERROR(error);

  	offset_fsb = XFS_B_TO_FSBT(mp, offset);

  	count_fsb = imap->br_blockcount;
  	map_start_fsb = imap->br_startoff;

  
  	XFS_STATS_ADD(xs_xstrat_bytes, XFS_FSB_TO_B(mp, count_fsb));
  
  	while (count_fsb != 0) {
  		/*
  		 * Set up a transaction with which to allocate the
  		 * backing store for the file.  Do allocations in a
  		 * loop until we get some space in the range we are
  		 * interested in.  The other space that might be allocated
  		 * is in the delayed allocation extent on which we sit
  		 * but before our buffer starts.
  		 */
  
  		nimaps = 0;
  		while (nimaps == 0) {
  			tp = xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE);

  			tp->t_flags |= XFS_TRANS_RESERVE;

  			nres = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
  			error = xfs_trans_reserve(tp, nres,
  					XFS_WRITE_LOG_RES(mp),
  					0, XFS_TRANS_PERM_LOG_RES,
  					XFS_WRITE_LOG_COUNT);

  			if (error) {
  				xfs_trans_cancel(tp, 0);
  				return XFS_ERROR(error);
  			}
  			xfs_ilock(ip, XFS_ILOCK_EXCL);

  			xfs_trans_ijoin(tp, ip, 0);

  			xfs_bmap_init(&free_list, &first_block);

  			/*

  			 * it is possible that the extents have changed since
  			 * we did the read call as we dropped the ilock for a
  			 * while. We have to be careful about truncates or hole
  			 * punchs here - we are not allowed to allocate
  			 * non-delalloc blocks here.
  			 *
  			 * The only protection against truncation is the pages
  			 * for the range we are being asked to convert are
  			 * locked and hence a truncate will block on them
  			 * first.
  			 *
  			 * As a result, if we go beyond the range we really
  			 * need and hit an delalloc extent boundary followed by
  			 * a hole while we have excess blocks in the map, we
  			 * will fill the hole incorrectly and overrun the
  			 * transaction reservation.
  			 *
  			 * Using a single map prevents this as we are forced to
  			 * check each map we look for overlap with the desired
  			 * range and abort as soon as we find it. Also, given
  			 * that we only return a single map, having one beyond
  			 * what we can return is probably a bit silly.
  			 *
  			 * We also need to check that we don't go beyond EOF;
  			 * this is a truncate optimisation as a truncate sets
  			 * the new file size before block on the pages we
  			 * currently have locked under writeback. Because they
  			 * are about to be tossed, we don't need to write them
  			 * back....

  			 */

  			nimaps = 1;

  			end_fsb = XFS_B_TO_FSB(mp, ip->i_size);

  			error = xfs_bmap_last_offset(NULL, ip, &last_block,
  							XFS_DATA_FORK);
  			if (error)
  				goto trans_cancel;

  			last_block = XFS_FILEOFF_MAX(last_block, end_fsb);
  			if ((map_start_fsb + count_fsb) > last_block) {
  				count_fsb = last_block - map_start_fsb;
  				if (count_fsb == 0) {
  					error = EAGAIN;
  					goto trans_cancel;
  				}
  			}

  			/*

  			 * From this point onwards we overwrite the imap
  			 * pointer that the caller gave to us.
  			 */

  			error = xfs_bmapi_write(tp, ip, map_start_fsb,
  						count_fsb, 0, &first_block, 1,
  						imap, &nimaps, &free_list);

  			if (error)
  				goto trans_cancel;

  			error = xfs_bmap_finish(&tp, &free_list, &committed);

  			if (error)
  				goto trans_cancel;

  			error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);

  			if (error)
  				goto error0;
  
  			xfs_iunlock(ip, XFS_ILOCK_EXCL);
  		}
  
  		/*
  		 * See if we were able to allocate an extent that
  		 * covers at least part of the callers request
  		 */

  		if (!(imap->br_startblock || XFS_IS_REALTIME_INODE(ip)))

  			return xfs_alert_fsblock_zero(ip, imap);

  		if ((offset_fsb >= imap->br_startoff) &&
  		    (offset_fsb < (imap->br_startoff +
  				   imap->br_blockcount))) {

  			XFS_STATS_INC(xs_xstrat_quick);
  			return 0;

  		}

  		/*
  		 * So far we have not mapped the requested part of the

  		 * file, just surrounding data, try again.
  		 */

  		count_fsb -= imap->br_blockcount;
  		map_start_fsb = imap->br_startoff + imap->br_blockcount;

  	}
  
  trans_cancel:
  	xfs_bmap_cancel(&free_list);
  	xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT);
  error0:
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);
  	return XFS_ERROR(error);
  }
  
  int
  xfs_iomap_write_unwritten(
  	xfs_inode_t	*ip,

  	xfs_off_t	offset,

  	size_t		count)
  {
  	xfs_mount_t	*mp = ip->i_mount;

  	xfs_fileoff_t	offset_fsb;
  	xfs_filblks_t	count_fsb;
  	xfs_filblks_t	numblks_fsb;

  	xfs_fsblock_t	firstfsb;
  	int		nimaps;
  	xfs_trans_t	*tp;
  	xfs_bmbt_irec_t imap;
  	xfs_bmap_free_t free_list;
  	uint		resblks;

  	int		committed;
  	int		error;

  	trace_xfs_unwritten_convert(ip, offset, count);

  
  	offset_fsb = XFS_B_TO_FSBT(mp, offset);
  	count_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
  	count_fsb = (xfs_filblks_t)(count_fsb - offset_fsb);

  	/*
  	 * Reserve enough blocks in this transaction for two complete extent
  	 * btree splits.  We may be converting the middle part of an unwritten
  	 * extent and in this case we will insert two new extents in the btree
  	 * each of which could cause a full split.
  	 *
  	 * This reservation amount will be used in the first call to
  	 * xfs_bmbt_split() to select an AG with enough space to satisfy the
  	 * rest of the operation.
  	 */

  	resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;

  	do {

  		/*
  		 * set up a transaction to convert the range of extents
  		 * from unwritten to real. Do allocations in a loop until
  		 * we have covered the range passed in.

  		 *
  		 * Note that we open code the transaction allocation here
  		 * to pass KM_NOFS--we can't risk to recursing back into
  		 * the filesystem here as we might be asked to write out
  		 * the same inode that we complete here and might deadlock
  		 * on the iolock.

  		 */

  		xfs_wait_for_freeze(mp, SB_FREEZE_TRANS);
  		tp = _xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE, KM_NOFS);

  		tp->t_flags |= XFS_TRANS_RESERVE;

  		error = xfs_trans_reserve(tp, resblks,

  				XFS_WRITE_LOG_RES(mp), 0,
  				XFS_TRANS_PERM_LOG_RES,
  				XFS_WRITE_LOG_COUNT);
  		if (error) {
  			xfs_trans_cancel(tp, 0);

  			return XFS_ERROR(error);

  		}
  
  		xfs_ilock(ip, XFS_ILOCK_EXCL);

  		xfs_trans_ijoin(tp, ip, 0);

  
  		/*
  		 * Modify the unwritten extent state of the buffer.
  		 */

  		xfs_bmap_init(&free_list, &firstfsb);

  		nimaps = 1;

  		error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,
  				  XFS_BMAPI_CONVERT, &firstfsb,

  				  1, &imap, &nimaps, &free_list);

  		if (error)
  			goto error_on_bmapi_transaction;

  		error = xfs_bmap_finish(&(tp), &(free_list), &committed);

  		if (error)
  			goto error_on_bmapi_transaction;

  		error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);

  		xfs_iunlock(ip, XFS_ILOCK_EXCL);
  		if (error)

  			return XFS_ERROR(error);

  		if (!(imap.br_startblock || XFS_IS_REALTIME_INODE(ip)))

  			return xfs_alert_fsblock_zero(ip, &imap);

  
  		if ((numblks_fsb = imap.br_blockcount) == 0) {
  			/*
  			 * The numblks_fsb value should always get
  			 * smaller, otherwise the loop is stuck.
  			 */
  			ASSERT(imap.br_blockcount);
  			break;
  		}
  		offset_fsb += numblks_fsb;
  		count_fsb -= numblks_fsb;
  	} while (count_fsb > 0);
  
  	return 0;
  
  error_on_bmapi_transaction:
  	xfs_bmap_cancel(&free_list);
  	xfs_trans_cancel(tp, (XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT));
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);

  	return XFS_ERROR(error);
  }