fs/xfs/xfs_iomap.c - kernel/msm-4.9 - Gitiles

 /*
  * 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_log.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_inode_item.h"
 #include "xfs_btree.h"
 #include "xfs_bmap.h"
 #include "xfs_rtalloc.h"
 #include "xfs_error.h"
 #include "xfs_itable.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 = 0;
 	int		eof, error;

 	if (!XFS_IS_REALTIME_INODE(ip)) {
 		/*
 		 * Round up 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.
 		 *
 		 * If mounted with the "-o swalloc" option the alignment is
 		 * increased from the strip unit size to the stripe width.
 		 */
 		if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC))
 			align = mp->m_swidth;
 		else if (mp->m_dalign)
 			align = mp->m_dalign;

 		if (align && XFS_ISIZE(ip) >= XFS_FSB_TO_B(mp, align))
 			new_last_fsb = roundup_64(*last_fsb, align);
 	}

 	/*
 	 * 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\n",
 		(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;

 	error = xfs_qm_dqattach(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) > XFS_ISIZE(ip)) {
 		error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
 		if (error)
 			return XFS_ERROR(error);
 	} 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
 	 */
 	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);
 		return XFS_ERROR(error);
 	}

 	xfs_ilock(ip, XFS_ILOCK_EXCL);

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

 	xfs_trans_ijoin(tp, ip, 0);

 	bmapi_flag = 0;
 	if (offset < XFS_ISIZE(ip) || 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 out_bmap_cancel;

 	/*
 	 * Complete the transaction
 	 */
 	error = xfs_bmap_finish(&tp, &free_list, &committed);
 	if (error)
 		goto out_bmap_cancel;
 	error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
 	if (error)
 		goto out_unlock;

 	/*
 	 * Copy any maps to caller's array and return any error.
 	 */
 	if (nimaps == 0) {
 		error = XFS_ERROR(ENOSPC);
 		goto out_unlock;
 	}

 	if (!(imap->br_startblock || XFS_IS_REALTIME_INODE(ip)))
 		error = xfs_alert_fsblock_zero(ip, imap);

 out_unlock:
 	xfs_iunlock(ip, XFS_ILOCK_EXCL);
 	return error;

 out_bmap_cancel:
 	xfs_bmap_cancel(&free_list);
 	xfs_trans_unreserve_quota_nblks(tp, ip, (long)qblocks, 0, quota_flag);
 out_trans_cancel:
 	xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT);
 	goto out_unlock;
 }

 /*
  * 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 <= XFS_ISIZE(ip))
 		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, mp->m_super->s_maxbytes);
 	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, XFS_ISIZE(ip)) + 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;
 	}

 	/*
 	 * Make sure preallocation does not create extents beyond the range we
 	 * actually support in this filesystem.
 	 */
 	if (last_fsb > XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes))
 		last_fsb = XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);

 	ASSERT(last_fsb > offset_fsb);

 	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, XFS_ISIZE(ip));
 			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;
 	xfs_fsize_t	i_size;
 	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.
 		 */
 		sb_start_intwrite(mp->m_super);
 		tp = _xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE, KM_NOFS);
 		tp->t_flags |= XFS_TRANS_RESERVE | XFS_TRANS_FREEZE_PROT;
 		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;

 		/*
 		 * Log the updated inode size as we go.  We have to be careful
 		 * to only log it up to the actual write offset if it is
 		 * halfway into a block.
 		 */
 		i_size = XFS_FSB_TO_B(mp, offset_fsb + count_fsb);
 		if (i_size > offset + count)
 			i_size = offset + count;

 		i_size = xfs_new_eof(ip, i_size);
 		if (i_size) {
 			ip->i_d.di_size = i_size;
 			xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 		}

 		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);
 }
	/*
	* 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_log.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_inode_item.h"
	#include "xfs_btree.h"
	#include "xfs_bmap.h"
	#include "xfs_rtalloc.h"
	#include "xfs_error.h"
	#include "xfs_itable.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 = 0;
	int eof, error;

	if (!XFS_IS_REALTIME_INODE(ip)) {
	/*
	* Round up 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.
	*
	* If mounted with the "-o swalloc" option the alignment is
	* increased from the strip unit size to the stripe width.
	*/
	if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC))
	align = mp->m_swidth;
	else if (mp->m_dalign)
	align = mp->m_dalign;

	if (align && XFS_ISIZE(ip) >= XFS_FSB_TO_B(mp, align))
	new_last_fsb = roundup_64(*last_fsb, align);
	}

	/*
	* 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\n",
	(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;

	error = xfs_qm_dqattach(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) > XFS_ISIZE(ip)) {
	error = xfs_iomap_eof_align_last_fsb(mp, ip, extsz, &last_fsb);
	if (error)
	return XFS_ERROR(error);
	} 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
	*/
	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);
	return XFS_ERROR(error);
	}

	xfs_ilock(ip, XFS_ILOCK_EXCL);

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

	xfs_trans_ijoin(tp, ip, 0);

	bmapi_flag = 0;
	if (offset < XFS_ISIZE(ip) \|\| 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 out_bmap_cancel;

	/*
	* Complete the transaction
	*/
	error = xfs_bmap_finish(&tp, &free_list, &committed);
	if (error)
	goto out_bmap_cancel;
	error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
	if (error)
	goto out_unlock;

	/*
	* Copy any maps to caller's array and return any error.
	*/
	if (nimaps == 0) {
	error = XFS_ERROR(ENOSPC);
	goto out_unlock;
	}

	if (!(imap->br_startblock \|\| XFS_IS_REALTIME_INODE(ip)))
	error = xfs_alert_fsblock_zero(ip, imap);

	out_unlock:
	xfs_iunlock(ip, XFS_ILOCK_EXCL);
	return error;

	out_bmap_cancel:
	xfs_bmap_cancel(&free_list);
	xfs_trans_unreserve_quota_nblks(tp, ip, (long)qblocks, 0, quota_flag);
	out_trans_cancel:
	xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES \| XFS_TRANS_ABORT);
	goto out_unlock;
	}

	/*
	* 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 <= XFS_ISIZE(ip))
	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, mp->m_super->s_maxbytes);
	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, XFS_ISIZE(ip)) + 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;
	}

	/*
	* Make sure preallocation does not create extents beyond the range we
	* actually support in this filesystem.
	*/
	if (last_fsb > XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes))
	last_fsb = XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);

	ASSERT(last_fsb > offset_fsb);

	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, XFS_ISIZE(ip));
	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;
	xfs_fsize_t i_size;
	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.
	*/
	sb_start_intwrite(mp->m_super);
	tp = _xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE, KM_NOFS);
	tp->t_flags \|= XFS_TRANS_RESERVE \| XFS_TRANS_FREEZE_PROT;
	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;

	/*
	* Log the updated inode size as we go. We have to be careful
	* to only log it up to the actual write offset if it is
	* halfway into a block.
	*/
	i_size = XFS_FSB_TO_B(mp, offset_fsb + count_fsb);
	if (i_size > offset + count)
	i_size = offset + count;

	i_size = xfs_new_eof(ip, i_size);
	if (i_size) {
	ip->i_d.di_size = i_size;
	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
	}

	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);
	}