/*

   * Copyright (c) 2000-2006 Silicon Graphics, Inc.

   * Copyright (c) 2016 Christoph Hellwig.

   * 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 <linux/iomap.h>

  #include "xfs.h"

  #include "xfs_fs.h"

  #include "xfs_shared.h"

  #include "xfs_format.h"
  #include "xfs_log_format.h"
  #include "xfs_trans_resv.h"

  #include "xfs_mount.h"

  #include "xfs_defer.h"

  #include "xfs_inode.h"

  #include "xfs_btree.h"

  #include "xfs_bmap_btree.h"

  #include "xfs_bmap.h"

  #include "xfs_bmap_util.h"

  #include "xfs_error.h"

  #include "xfs_trans.h"

  #include "xfs_trans_space.h"

  #include "xfs_iomap.h"

  #include "xfs_trace.h"

  #include "xfs_icache.h"

  #include "xfs_quota.h"

  #include "xfs_dquot_item.h"
  #include "xfs_dquot.h"

  #include "xfs_reflink.h"

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

  void
  xfs_bmbt_to_iomap(
  	struct xfs_inode	*ip,
  	struct iomap		*iomap,
  	struct xfs_bmbt_irec	*imap)
  {
  	struct xfs_mount	*mp = ip->i_mount;
  
  	if (imap->br_startblock == HOLESTARTBLOCK) {
  		iomap->blkno = IOMAP_NULL_BLOCK;
  		iomap->type = IOMAP_HOLE;
  	} else if (imap->br_startblock == DELAYSTARTBLOCK) {
  		iomap->blkno = IOMAP_NULL_BLOCK;
  		iomap->type = IOMAP_DELALLOC;
  	} else {
  		iomap->blkno = xfs_fsb_to_db(ip, imap->br_startblock);
  		if (imap->br_state == XFS_EXT_UNWRITTEN)
  			iomap->type = IOMAP_UNWRITTEN;
  		else
  			iomap->type = IOMAP_MAPPED;
  	}
  	iomap->offset = XFS_FSB_TO_B(mp, imap->br_startoff);
  	iomap->length = XFS_FSB_TO_B(mp, imap->br_blockcount);
  	iomap->bdev = xfs_find_bdev_for_inode(VFS_I(ip));

  	iomap->dax_dev = xfs_find_daxdev_for_inode(VFS_I(ip));

  }

  xfs_extlen_t

  xfs_eof_alignment(
  	struct xfs_inode	*ip,
  	xfs_extlen_t		extsize)

  {

  	struct xfs_mount	*mp = ip->i_mount;
  	xfs_extlen_t		align = 0;

  	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))
  			align = 0;

  	}

  
  	/*
  	 * 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 (align)
  			align = roundup_64(align, extsize);

  		else
  			align = extsize;

  	}

  	return align;
  }
  
  STATIC int
  xfs_iomap_eof_align_last_fsb(
  	struct xfs_inode	*ip,
  	xfs_extlen_t		extsize,
  	xfs_fileoff_t		*last_fsb)
  {
  	xfs_extlen_t		align = xfs_eof_alignment(ip, extsize);

  	if (align) {
  		xfs_fileoff_t	new_last_fsb = roundup_64(*last_fsb, align);

  		int		eof, error;

  		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;

  	int		nimaps;

  	int		quota_flag;

  	int		rt;
  	xfs_trans_t	*tp;

  	struct xfs_defer_ops dfops;

  	uint		qblocks, resblks, resrtextents;

  	int		error;

  	int		lockmode;

  	int		bmapi_flags = XFS_BMAPI_PREALLOC;

  	uint		tflags = 0;

  	rt = XFS_IS_REALTIME_INODE(ip);

  	extsz = xfs_get_extsz_hint(ip);

  	lockmode = XFS_ILOCK_SHARED;	/* locked by caller */
  
  	ASSERT(xfs_isilocked(ip, lockmode));

  	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)) {

  		/*
  		 * Assert that the in-core extent list is present since this can
  		 * call xfs_iread_extents() and we only have the ilock shared.
  		 * This should be safe because the lock was held around a bmapi
  		 * call in the caller and we only need it to access the in-core
  		 * list.
  		 */
  		ASSERT(XFS_IFORK_PTR(ip, XFS_DATA_FORK)->if_flags &
  								XFS_IFEXTENTS);

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

  		if (error)

  			goto out_unlock;

  	} 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 = xfs_aligned_fsb_count(offset_fsb, count_fsb, extsz);

  
  	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;
  	}

  
  	/*

  	 * Drop the shared lock acquired by the caller, attach the dquot if
  	 * necessary and move on to transaction setup.
  	 */
  	xfs_iunlock(ip, lockmode);
  	error = xfs_qm_dqattach(ip, 0);
  	if (error)
  		return error;
  
  	/*

  	 * For DAX, we do not allocate unwritten extents, but instead we zero
  	 * the block before we commit the transaction.  Ideally we'd like to do
  	 * this outside the transaction context, but if we commit and then crash
  	 * we may not have zeroed the blocks and this will be exposed on
  	 * recovery of the allocation. Hence we must zero before commit.

  	 *

  	 * Further, if we are mapping unwritten extents here, we need to zero
  	 * and convert them to written so that we don't need an unwritten extent
  	 * callback for DAX. This also means that we need to be able to dip into

  	 * the reserve block pool for bmbt block allocation if there is no space
  	 * left but we need to do unwritten extent conversion.

  	 */
  	if (IS_DAX(VFS_I(ip))) {
  		bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;

  		if (imap->br_state == XFS_EXT_UNWRITTEN) {

  			tflags |= XFS_TRANS_RESERVE;

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

  	}

  	error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, resrtextents,
  			tflags, &tp);
  	if (error)

  		return error;

  	lockmode = XFS_ILOCK_EXCL;
  	xfs_ilock(ip, lockmode);

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

  	if (error)

  		goto out_trans_cancel;

  	xfs_trans_ijoin(tp, ip, 0);

  	/*

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

  	 */

  	xfs_defer_init(&dfops, &firstfsb);

  	nimaps = 1;

  	error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,

  				bmapi_flags, &firstfsb, resblks, imap,

  				&nimaps, &dfops);

  	if (error)

  		goto out_bmap_cancel;

  
  	/*

  	 * Complete the transaction

  	 */

  	error = xfs_defer_finish(&tp, &dfops);

  	if (error)

  		goto out_bmap_cancel;

  	error = xfs_trans_commit(tp);

  	if (error)

  		goto out_unlock;

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

  	if (nimaps == 0) {

  		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, lockmode);

  	return error;

  out_bmap_cancel:

  	xfs_defer_cancel(&dfops);

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

  out_trans_cancel:

  	xfs_trans_cancel(tp);

  	goto out_unlock;

  }

  STATIC bool
  xfs_quota_need_throttle(
  	struct xfs_inode *ip,
  	int type,
  	xfs_fsblock_t alloc_blocks)
  {
  	struct xfs_dquot *dq = xfs_inode_dquot(ip, type);
  
  	if (!dq || !xfs_this_quota_on(ip->i_mount, type))
  		return false;
  
  	/* no hi watermark, no throttle */
  	if (!dq->q_prealloc_hi_wmark)
  		return false;
  
  	/* under the lo watermark, no throttle */
  	if (dq->q_res_bcount + alloc_blocks < dq->q_prealloc_lo_wmark)
  		return false;
  
  	return true;
  }
  
  STATIC void
  xfs_quota_calc_throttle(
  	struct xfs_inode *ip,
  	int type,
  	xfs_fsblock_t *qblocks,

  	int *qshift,
  	int64_t	*qfreesp)

  {
  	int64_t freesp;
  	int shift = 0;
  	struct xfs_dquot *dq = xfs_inode_dquot(ip, type);

  	/* no dq, or over hi wmark, squash the prealloc completely */
  	if (!dq || dq->q_res_bcount >= dq->q_prealloc_hi_wmark) {

  		*qblocks = 0;

  		*qfreesp = 0;

  		return;
  	}
  
  	freesp = dq->q_prealloc_hi_wmark - dq->q_res_bcount;
  	if (freesp < dq->q_low_space[XFS_QLOWSP_5_PCNT]) {
  		shift = 2;
  		if (freesp < dq->q_low_space[XFS_QLOWSP_3_PCNT])
  			shift += 2;
  		if (freesp < dq->q_low_space[XFS_QLOWSP_1_PCNT])
  			shift += 2;
  	}

  	if (freesp < *qfreesp)
  		*qfreesp = freesp;

  	/* only overwrite the throttle values if we are more aggressive */
  	if ((freesp >> shift) < (*qblocks >> *qshift)) {
  		*qblocks = freesp;
  		*qshift = shift;
  	}
  }

  /*

   * If we are doing a write at the end of the file and there are no allocations
   * past this one, then extend the allocation out to the file system's write
   * iosize.
   *

   * 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.

   *
   * As an exception we don't do any preallocation at all if the file is smaller
   * than the minimum preallocation and we are using the default dynamic
   * preallocation scheme, as it is likely this is the only write to the file that
   * is going to be done.
   *
   * We clean up any extra space left over when the file is closed in
   * xfs_inactive().

   */
  STATIC xfs_fsblock_t
  xfs_iomap_prealloc_size(

  	struct xfs_inode	*ip,

  	loff_t			offset,
  	loff_t			count,

  	xfs_extnum_t		idx)

  {

  	struct xfs_mount	*mp = ip->i_mount;

  	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);

  	xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);

  	struct xfs_bmbt_irec	prev;

  	int			shift = 0;
  	int64_t			freesp;

  	xfs_fsblock_t		qblocks;
  	int			qshift = 0;

  	xfs_fsblock_t		alloc_blocks = 0;
  
  	if (offset + count <= XFS_ISIZE(ip))
  		return 0;
  
  	if (!(mp->m_flags & XFS_MOUNT_DFLT_IOSIZE) &&
  	    (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_writeio_blocks)))
  		return 0;
  
  	/*
  	 * If an explicit allocsize is set, the file is small, or we
  	 * are writing behind a hole, then use the minimum prealloc:
  	 */
  	if ((mp->m_flags & XFS_MOUNT_DFLT_IOSIZE) ||
  	    XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign) ||

  	    !xfs_iext_get_extent(ifp, idx - 1, &prev) ||
  	    prev.br_startoff + prev.br_blockcount < offset_fsb)

  		return mp->m_writeio_blocks;

  	/*
  	 * Determine the initial size of the preallocation. We are beyond the
  	 * current EOF here, but we need to take into account whether this is
  	 * a sparse write or an extending write when determining the
  	 * preallocation size.  Hence we need to look up the extent that ends
  	 * at the current write offset and use the result to determine the
  	 * preallocation size.
  	 *
  	 * If the extent is a hole, then preallocation is essentially disabled.
  	 * Otherwise we take the size of the preceding data extent as the basis
  	 * for the preallocation size. If the size of the extent is greater than
  	 * half the maximum extent length, then use the current offset as the
  	 * basis. This ensures that for large files the preallocation size
  	 * always extends to MAXEXTLEN rather than falling short due to things
  	 * like stripe unit/width alignment of real extents.
  	 */

  	if (prev.br_blockcount <= (MAXEXTLEN >> 1))
  		alloc_blocks = prev.br_blockcount << 1;

  	else
  		alloc_blocks = XFS_B_TO_FSB(mp, offset);

  	if (!alloc_blocks)
  		goto check_writeio;

  	qblocks = alloc_blocks;

  	/*
  	 * MAXEXTLEN is not a power of two value but we round the prealloc down
  	 * to the nearest power of two value after throttling. To prevent the
  	 * round down from unconditionally reducing the maximum supported prealloc
  	 * size, we round up first, apply appropriate throttling, round down and
  	 * cap the value to MAXEXTLEN.
  	 */
  	alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(MAXEXTLEN),
  				       alloc_blocks);

  	freesp = percpu_counter_read_positive(&mp->m_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++;

  	}

  
  	/*

  	 * Check each quota to cap the prealloc size, provide a shift value to
  	 * throttle with and adjust amount of available space.

  	 */
  	if (xfs_quota_need_throttle(ip, XFS_DQ_USER, alloc_blocks))

  		xfs_quota_calc_throttle(ip, XFS_DQ_USER, &qblocks, &qshift,
  					&freesp);

  	if (xfs_quota_need_throttle(ip, XFS_DQ_GROUP, alloc_blocks))

  		xfs_quota_calc_throttle(ip, XFS_DQ_GROUP, &qblocks, &qshift,
  					&freesp);

  	if (xfs_quota_need_throttle(ip, XFS_DQ_PROJ, alloc_blocks))

  		xfs_quota_calc_throttle(ip, XFS_DQ_PROJ, &qblocks, &qshift,
  					&freesp);

  
  	/*
  	 * The final prealloc size is set to the minimum of free space available
  	 * in each of the quotas and the overall filesystem.
  	 *
  	 * The shift throttle value is set to the maximum value as determined by
  	 * the global low free space values and per-quota low free space values.
  	 */
  	alloc_blocks = MIN(alloc_blocks, qblocks);
  	shift = MAX(shift, qshift);

  	if (shift)
  		alloc_blocks >>= shift;

  	/*
  	 * rounddown_pow_of_two() returns an undefined result if we pass in
  	 * alloc_blocks = 0.
  	 */
  	if (alloc_blocks)
  		alloc_blocks = rounddown_pow_of_two(alloc_blocks);
  	if (alloc_blocks > MAXEXTLEN)
  		alloc_blocks = MAXEXTLEN;

  
  	/*
  	 * If we are still trying to allocate more space than is
  	 * available, squash the prealloc hard. This can happen if we
  	 * have a large file on a small filesystem and the above
  	 * lowspace thresholds are smaller than MAXEXTLEN.
  	 */
  	while (alloc_blocks && alloc_blocks >= freesp)
  		alloc_blocks >>= 4;

  check_writeio:

  	if (alloc_blocks < mp->m_writeio_blocks)
  		alloc_blocks = mp->m_writeio_blocks;

  	trace_xfs_iomap_prealloc_size(ip, alloc_blocks, shift,
  				      mp->m_writeio_blocks);

  	return alloc_blocks;
  }

  static int
  xfs_file_iomap_begin_delay(
  	struct inode		*inode,
  	loff_t			offset,
  	loff_t			count,

  	struct iomap		*iomap)

  {

  	struct xfs_inode	*ip = XFS_I(inode);
  	struct xfs_mount	*mp = ip->i_mount;
  	struct xfs_ifork	*ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
  	xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);
  	xfs_fileoff_t		maxbytes_fsb =
  		XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);

  	xfs_fileoff_t		end_fsb;

  	int			error = 0, eof = 0;
  	struct xfs_bmbt_irec	got;

  	xfs_extnum_t		idx;

  	xfs_fsblock_t		prealloc_blocks = 0;

  
  	ASSERT(!XFS_IS_REALTIME_INODE(ip));
  	ASSERT(!xfs_get_extsz_hint(ip));

  	xfs_ilock(ip, XFS_ILOCK_EXCL);

  	if (unlikely(XFS_TEST_ERROR(
  	    (XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_EXTENTS &&
  	     XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_BTREE),

  	     mp, XFS_ERRTAG_BMAPIFORMAT))) {

  		XFS_ERROR_REPORT(__func__, XFS_ERRLEVEL_LOW, mp);
  		error = -EFSCORRUPTED;
  		goto out_unlock;
  	}

  	XFS_STATS_INC(mp, xs_blk_mapw);

  	if (!(ifp->if_flags & XFS_IFEXTENTS)) {
  		error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
  		if (error)
  			goto out_unlock;

  	}

  	eof = !xfs_iext_lookup_extent(ip, ifp, offset_fsb, &idx, &got);

  	if (!eof && got.br_startoff <= offset_fsb) {

  		if (xfs_is_reflink_inode(ip)) {
  			bool		shared;
  
  			end_fsb = min(XFS_B_TO_FSB(mp, offset + count),
  					maxbytes_fsb);
  			xfs_trim_extent(&got, offset_fsb, end_fsb - offset_fsb);
  			error = xfs_reflink_reserve_cow(ip, &got, &shared);
  			if (error)
  				goto out_unlock;
  		}

  		trace_xfs_iomap_found(ip, offset, count, 0, &got);
  		goto done;

  	}

  	error = xfs_qm_dqattach_locked(ip, 0);
  	if (error)
  		goto out_unlock;

  	/*

  	 * We cap the maximum length we map here to MAX_WRITEBACK_PAGES pages
  	 * to keep the chunks of work done where somewhat symmetric with the
  	 * work writeback does. This is a completely arbitrary number pulled
  	 * out of thin air as a best guess for initial testing.
  	 *
  	 * Note that the values needs to be less than 32-bits wide until
  	 * the lower level functions are updated.

  	 */

  	count = min_t(loff_t, count, 1024 * PAGE_SIZE);

  	end_fsb = min(XFS_B_TO_FSB(mp, offset + count), maxbytes_fsb);

  
  	if (eof) {

  		prealloc_blocks = xfs_iomap_prealloc_size(ip, offset, count, idx);

  		if (prealloc_blocks) {
  			xfs_extlen_t	align;
  			xfs_off_t	end_offset;

  			xfs_fileoff_t	p_end_fsb;

  			end_offset = XFS_WRITEIO_ALIGN(mp, offset + count - 1);

  			p_end_fsb = XFS_B_TO_FSBT(mp, end_offset) +
  					prealloc_blocks;

  
  			align = xfs_eof_alignment(ip, 0);
  			if (align)

  				p_end_fsb = roundup_64(p_end_fsb, align);

  			p_end_fsb = min(p_end_fsb, maxbytes_fsb);
  			ASSERT(p_end_fsb > offset_fsb);
  			prealloc_blocks = p_end_fsb - end_fsb;

  		}
  	}
  
  retry:

  	error = xfs_bmapi_reserve_delalloc(ip, XFS_DATA_FORK, offset_fsb,

  			end_fsb - offset_fsb, prealloc_blocks, &got, &idx, eof);

  	switch (error) {
  	case 0:

  		break;

  	case -ENOSPC:
  	case -EDQUOT:

  		/* retry without any preallocation */

  		trace_xfs_delalloc_enospc(ip, offset, count);

  		if (prealloc_blocks) {
  			prealloc_blocks = 0;

  			goto retry;

  		}

  		/*FALLTHRU*/
  	default:
  		goto out_unlock;

  	}

  	/*
  	 * Flag newly allocated delalloc blocks with IOMAP_F_NEW so we punch
  	 * them out if the write happens to fail.
  	 */
  	iomap->flags = IOMAP_F_NEW;

  	trace_xfs_iomap_alloc(ip, offset, count, 0, &got);
  done:
  	if (isnullstartblock(got.br_startblock))
  		got.br_startblock = DELAYSTARTBLOCK;
  
  	if (!got.br_startblock) {
  		error = xfs_alert_fsblock_zero(ip, &got);
  		if (error)
  			goto out_unlock;
  	}
  
  	xfs_bmbt_to_iomap(ip, iomap, &got);
  
  out_unlock:
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);
  	return error;

  }
  
  /*
   * 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,

  	int		whichfork,

  	xfs_off_t	offset,

  	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;

  	struct xfs_defer_ops	dfops;

  	xfs_filblks_t	count_fsb;

  	xfs_trans_t	*tp;

  	int		nimaps;

  	int		error = 0;

  	int		flags = XFS_BMAPI_DELALLOC;

  	int		nres;

  	if (whichfork == XFS_COW_FORK)

  		flags |= XFS_BMAPI_COWFORK | XFS_BMAPI_PREALLOC;

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

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

  		return error;

  	offset_fsb = XFS_B_TO_FSBT(mp, offset);

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

  	XFS_STATS_ADD(mp, 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) {

  			nres = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);

  			/*
  			 * We have already reserved space for the extent and any
  			 * indirect blocks when creating the delalloc extent,
  			 * there is no need to reserve space in this transaction
  			 * again.
  			 */
  			error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, 0,

  					0, XFS_TRANS_RESERVE, &tp);
  			if (error)

  				return error;

  			xfs_ilock(ip, XFS_ILOCK_EXCL);

  			xfs_trans_ijoin(tp, ip, 0);

  			xfs_defer_init(&dfops, &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(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, flags, &first_block,

  						nres, imap, &nimaps,

  						&dfops);

  			if (error)
  				goto trans_cancel;

  			error = xfs_defer_finish(&tp, &dfops);

  			if (error)
  				goto trans_cancel;

  			error = xfs_trans_commit(tp);

  			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(mp, 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_defer_cancel(&dfops);

  	xfs_trans_cancel(tp);

  error0:
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);

  	return error;

  }
  
  int
  xfs_iomap_write_unwritten(
  	xfs_inode_t	*ip,

  	xfs_off_t	offset,

  	xfs_off_t	count,
  	bool		update_isize)

  {
  	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;

  	struct xfs_defer_ops dfops;

  	struct inode	*inode = VFS_I(ip);

  	xfs_fsize_t	i_size;

  	uint		resblks;

  	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 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.

  		 */

  		error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
  				XFS_TRANS_RESERVE | XFS_TRANS_NOFS, &tp);
  		if (error)

  			return error;

  
  		xfs_ilock(ip, XFS_ILOCK_EXCL);

  		xfs_trans_ijoin(tp, ip, 0);

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

  		xfs_defer_init(&dfops, &firstfsb);

  		nimaps = 1;

  		error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,

  					XFS_BMAPI_CONVERT, &firstfsb, resblks,

  					&imap, &nimaps, &dfops);

  		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;

  		if (update_isize && i_size > i_size_read(inode))
  			i_size_write(inode, i_size);

  		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_defer_finish(&tp, &dfops);

  		if (error)
  			goto error_on_bmapi_transaction;

  		error = xfs_trans_commit(tp);

  		xfs_iunlock(ip, XFS_ILOCK_EXCL);
  		if (error)

  			return 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_defer_cancel(&dfops);

  	xfs_trans_cancel(tp);

  	xfs_iunlock(ip, XFS_ILOCK_EXCL);

  	return error;

  }

  static inline bool imap_needs_alloc(struct inode *inode,
  		struct xfs_bmbt_irec *imap, int nimaps)

  {
  	return !nimaps ||
  		imap->br_startblock == HOLESTARTBLOCK ||

  		imap->br_startblock == DELAYSTARTBLOCK ||

  		(IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN);

  }

  static inline bool need_excl_ilock(struct xfs_inode *ip, unsigned flags)
  {
  	/*
  	 * COW writes will allocate delalloc space, so we need to make sure
  	 * to take the lock exclusively here.
  	 */
  	if (xfs_is_reflink_inode(ip) && (flags & (IOMAP_WRITE | IOMAP_ZERO)))
  		return true;
  	if ((flags & IOMAP_DIRECT) && (flags & IOMAP_WRITE))
  		return true;
  	return false;
  }

  static int
  xfs_file_iomap_begin(
  	struct inode		*inode,
  	loff_t			offset,
  	loff_t			length,
  	unsigned		flags,
  	struct iomap		*iomap)
  {
  	struct xfs_inode	*ip = XFS_I(inode);
  	struct xfs_mount	*mp = ip->i_mount;
  	struct xfs_bmbt_irec	imap;
  	xfs_fileoff_t		offset_fsb, end_fsb;
  	int			nimaps = 1, error = 0;

  	bool			shared = false, trimmed = false;

  	unsigned		lockmode;

  
  	if (XFS_FORCED_SHUTDOWN(mp))
  		return -EIO;

  	if (((flags & (IOMAP_WRITE | IOMAP_DIRECT)) == IOMAP_WRITE) &&
  			!IS_DAX(inode) && !xfs_get_extsz_hint(ip)) {

  		/* Reserve delalloc blocks for regular writeback. */

  		return xfs_file_iomap_begin_delay(inode, offset, length, iomap);

  	}

  	if (need_excl_ilock(ip, flags)) {

  		lockmode = XFS_ILOCK_EXCL;
  		xfs_ilock(ip, XFS_ILOCK_EXCL);
  	} else {
  		lockmode = xfs_ilock_data_map_shared(ip);
  	}

  	if ((flags & IOMAP_NOWAIT) && !(ip->i_df.if_flags & XFS_IFEXTENTS)) {
  		error = -EAGAIN;
  		goto out_unlock;
  	}

  	ASSERT(offset <= mp->m_super->s_maxbytes);
  	if ((xfs_fsize_t)offset + length > mp->m_super->s_maxbytes)
  		length = mp->m_super->s_maxbytes - offset;
  	offset_fsb = XFS_B_TO_FSBT(mp, offset);
  	end_fsb = XFS_B_TO_FSB(mp, offset + length);
  
  	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,

  			       &nimaps, 0);

  	if (error)
  		goto out_unlock;

  	if (flags & IOMAP_REPORT) {

  		/* Trim the mapping to the nearest shared extent boundary. */
  		error = xfs_reflink_trim_around_shared(ip, &imap, &shared,
  				&trimmed);

  		if (error)
  			goto out_unlock;
  	}
  
  	if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && xfs_is_reflink_inode(ip)) {

  		if (flags & IOMAP_DIRECT) {

  			/*
  			 * A reflinked inode will result in CoW alloc.
  			 * FIXME: It could still overwrite on unshared extents
  			 * and not need allocation.
  			 */
  			if (flags & IOMAP_NOWAIT) {
  				error = -EAGAIN;
  				goto out_unlock;
  			}

  			/* may drop and re-acquire the ilock */
  			error = xfs_reflink_allocate_cow(ip, &imap, &shared,
  					&lockmode);
  			if (error)
  				goto out_unlock;
  		} else {
  			error = xfs_reflink_reserve_cow(ip, &imap, &shared);
  			if (error)
  				goto out_unlock;
  		}

  
  		end_fsb = imap.br_startoff + imap.br_blockcount;
  		length = XFS_FSB_TO_B(mp, end_fsb) - offset;

  	}

  	if ((flags & IOMAP_WRITE) && imap_needs_alloc(inode, &imap, nimaps)) {

  		/*

  		 * If nowait is set bail since we are going to make
  		 * allocations.
  		 */
  		if (flags & IOMAP_NOWAIT) {
  			error = -EAGAIN;
  			goto out_unlock;
  		}
  		/*

  		 * We cap the maximum length we map here to MAX_WRITEBACK_PAGES
  		 * pages to keep the chunks of work done where somewhat symmetric
  		 * with the work writeback does. This is a completely arbitrary
  		 * number pulled out of thin air as a best guess for initial
  		 * testing.
  		 *
  		 * Note that the values needs to be less than 32-bits wide until
  		 * the lower level functions are updated.
  		 */
  		length = min_t(loff_t, length, 1024 * PAGE_SIZE);

  		/*
  		 * xfs_iomap_write_direct() expects the shared lock. It
  		 * is unlocked on return.
  		 */

  		if (lockmode == XFS_ILOCK_EXCL)
  			xfs_ilock_demote(ip, lockmode);

  		error = xfs_iomap_write_direct(ip, offset, length, &imap,
  				nimaps);

  		if (error)
  			return error;

  		iomap->flags = IOMAP_F_NEW;

  		trace_xfs_iomap_alloc(ip, offset, length, 0, &imap);

  	} else {

  		ASSERT(nimaps);

  		xfs_iunlock(ip, lockmode);

  		trace_xfs_iomap_found(ip, offset, length, 0, &imap);

  	}

  	xfs_bmbt_to_iomap(ip, iomap, &imap);

  	if (shared)
  		iomap->flags |= IOMAP_F_SHARED;

  	return 0;

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

  }
  
  static int
  xfs_file_iomap_end_delalloc(
  	struct xfs_inode	*ip,
  	loff_t			offset,
  	loff_t			length,

  	ssize_t			written,
  	struct iomap		*iomap)

  {
  	struct xfs_mount	*mp = ip->i_mount;
  	xfs_fileoff_t		start_fsb;
  	xfs_fileoff_t		end_fsb;
  	int			error = 0;

  	/*
  	 * Behave as if the write failed if drop writes is enabled. Set the NEW
  	 * flag to force delalloc cleanup.
  	 */

  	if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_DROP_WRITES)) {

  		iomap->flags |= IOMAP_F_NEW;

  		written = 0;

  	}

  	/*
  	 * start_fsb refers to the first unused block after a short write. If
  	 * nothing was written, round offset down to point at the first block in
  	 * the range.
  	 */
  	if (unlikely(!written))
  		start_fsb = XFS_B_TO_FSBT(mp, offset);
  	else
  		start_fsb = XFS_B_TO_FSB(mp, offset + written);

  	end_fsb = XFS_B_TO_FSB(mp, offset + length);
  
  	/*

  	 * Trim delalloc blocks if they were allocated by this write and we
  	 * didn't manage to write the whole range.

  	 *
  	 * We don't need to care about racing delalloc as we hold i_mutex
  	 * across the reserve/allocate/unreserve calls. If there are delalloc
  	 * blocks in the range, they are ours.
  	 */

  	if ((iomap->flags & IOMAP_F_NEW) && start_fsb < end_fsb) {

  		truncate_pagecache_range(VFS_I(ip), XFS_FSB_TO_B(mp, start_fsb),
  					 XFS_FSB_TO_B(mp, end_fsb) - 1);

  		xfs_ilock(ip, XFS_ILOCK_EXCL);
  		error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
  					       end_fsb - start_fsb);
  		xfs_iunlock(ip, XFS_ILOCK_EXCL);
  
  		if (error && !XFS_FORCED_SHUTDOWN(mp)) {
  			xfs_alert(mp, "%s: unable to clean up ino %lld",
  				__func__, ip->i_ino);
  			return error;
  		}
  	}
  
  	return 0;
  }
  
  static int
  xfs_file_iomap_end(
  	struct inode		*inode,
  	loff_t			offset,
  	loff_t			length,
  	ssize_t			written,
  	unsigned		flags,
  	struct iomap		*iomap)
  {
  	if ((flags & IOMAP_WRITE) && iomap->type == IOMAP_DELALLOC)
  		return xfs_file_iomap_end_delalloc(XFS_I(inode), offset,

  				length, written, iomap);

  	return 0;
  }

  const struct iomap_ops xfs_iomap_ops = {

  	.iomap_begin		= xfs_file_iomap_begin,
  	.iomap_end		= xfs_file_iomap_end,
  };

  
  static int
  xfs_xattr_iomap_begin(
  	struct inode		*inode,
  	loff_t			offset,
  	loff_t			length,
  	unsigned		flags,
  	struct iomap		*iomap)
  {
  	struct xfs_inode	*ip = XFS_I(inode);
  	struct xfs_mount	*mp = ip->i_mount;
  	xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);
  	xfs_fileoff_t		end_fsb = XFS_B_TO_FSB(mp, offset + length);
  	struct xfs_bmbt_irec	imap;
  	int			nimaps = 1, error = 0;
  	unsigned		lockmode;
  
  	if (XFS_FORCED_SHUTDOWN(mp))
  		return -EIO;

  	lockmode = xfs_ilock_attr_map_shared(ip);

  
  	/* if there are no attribute fork or extents, return ENOENT */

  	if (!XFS_IFORK_Q(ip) || !ip->i_d.di_anextents) {

  		error = -ENOENT;
  		goto out_unlock;
  	}
  
  	ASSERT(ip->i_d.di_aformat != XFS_DINODE_FMT_LOCAL);
  	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
  			       &nimaps, XFS_BMAPI_ENTIRE | XFS_BMAPI_ATTRFORK);
  out_unlock:
  	xfs_iunlock(ip, lockmode);
  
  	if (!error) {
  		ASSERT(nimaps);
  		xfs_bmbt_to_iomap(ip, iomap, &imap);
  	}
  
  	return error;
  }

  const struct iomap_ops xfs_xattr_iomap_ops = {

  	.iomap_begin		= xfs_xattr_iomap_begin,
  };