Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1438 insertions, 0 deletions

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
new file mode 100644
index 0000000000..18c8f168b1
--- /dev/null
+++ b/fs/xfs/xfs_iomap.c
@@ -0,0 +1,1438 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2000-2006 Silicon Graphics, Inc.
+ * Copyright (c) 2016-2018 Christoph Hellwig.
+ * All Rights Reserved.
+ */
+#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_inode.h"
+#include "xfs_btree.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_bmap.h"
+#include "xfs_bmap_util.h"
+#include "xfs_errortag.h"
+#include "xfs_error.h"
+#include "xfs_trans.h"
+#include "xfs_trans_space.h"
+#include "xfs_inode_item.h"
+#include "xfs_iomap.h"
+#include "xfs_trace.h"
+#include "xfs_quota.h"
+#include "xfs_dquot_item.h"
+#include "xfs_dquot.h"
+#include "xfs_reflink.h"
+
+#define XFS_ALLOC_ALIGN(mp, off) \
+	(((off) >> mp->m_allocsize_log) << mp->m_allocsize_log)
+
+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;
+}
+
+u64
+xfs_iomap_inode_sequence(
+	struct xfs_inode	*ip,
+	u16			iomap_flags)
+{
+	u64			cookie = 0;
+
+	if (iomap_flags & IOMAP_F_XATTR)
+		return READ_ONCE(ip->i_af.if_seq);
+	if ((iomap_flags & IOMAP_F_SHARED) && ip->i_cowfp)
+		cookie = (u64)READ_ONCE(ip->i_cowfp->if_seq) << 32;
+	return cookie | READ_ONCE(ip->i_df.if_seq);
+}
+
+/*
+ * Check that the iomap passed to us is still valid for the given offset and
+ * length.
+ */
+static bool
+xfs_iomap_valid(
+	struct inode		*inode,
+	const struct iomap	*iomap)
+{
+	struct xfs_inode	*ip = XFS_I(inode);
+
+	if (iomap->validity_cookie !=
+			xfs_iomap_inode_sequence(ip, iomap->flags)) {
+		trace_xfs_iomap_invalid(ip, iomap);
+		return false;
+	}
+
+	XFS_ERRORTAG_DELAY(ip->i_mount, XFS_ERRTAG_WRITE_DELAY_MS);
+	return true;
+}
+
+static const struct iomap_folio_ops xfs_iomap_folio_ops = {
+	.iomap_valid		= xfs_iomap_valid,
+};
+
+int
+xfs_bmbt_to_iomap(
+	struct xfs_inode	*ip,
+	struct iomap		*iomap,
+	struct xfs_bmbt_irec	*imap,
+	unsigned int		mapping_flags,
+	u16			iomap_flags,
+	u64			sequence_cookie)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_buftarg	*target = xfs_inode_buftarg(ip);
+
+	if (unlikely(!xfs_valid_startblock(ip, imap->br_startblock)))
+		return xfs_alert_fsblock_zero(ip, imap);
+
+	if (imap->br_startblock == HOLESTARTBLOCK) {
+		iomap->addr = IOMAP_NULL_ADDR;
+		iomap->type = IOMAP_HOLE;
+	} else if (imap->br_startblock == DELAYSTARTBLOCK ||
+		   isnullstartblock(imap->br_startblock)) {
+		iomap->addr = IOMAP_NULL_ADDR;
+		iomap->type = IOMAP_DELALLOC;
+	} else {
+		iomap->addr = BBTOB(xfs_fsb_to_db(ip, imap->br_startblock));
+		if (mapping_flags & IOMAP_DAX)
+			iomap->addr += target->bt_dax_part_off;
+
+		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);
+	if (mapping_flags & IOMAP_DAX)
+		iomap->dax_dev = target->bt_daxdev;
+	else
+		iomap->bdev = target->bt_bdev;
+	iomap->flags = iomap_flags;
+
+	if (xfs_ipincount(ip) &&
+	    (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
+		iomap->flags |= IOMAP_F_DIRTY;
+
+	iomap->validity_cookie = sequence_cookie;
+	iomap->folio_ops = &xfs_iomap_folio_ops;
+	return 0;
+}
+
+static void
+xfs_hole_to_iomap(
+	struct xfs_inode	*ip,
+	struct iomap		*iomap,
+	xfs_fileoff_t		offset_fsb,
+	xfs_fileoff_t		end_fsb)
+{
+	struct xfs_buftarg	*target = xfs_inode_buftarg(ip);
+
+	iomap->addr = IOMAP_NULL_ADDR;
+	iomap->type = IOMAP_HOLE;
+	iomap->offset = XFS_FSB_TO_B(ip->i_mount, offset_fsb);
+	iomap->length = XFS_FSB_TO_B(ip->i_mount, end_fsb - offset_fsb);
+	iomap->bdev = target->bt_bdev;
+	iomap->dax_dev = target->bt_daxdev;
+}
+
+static inline xfs_fileoff_t
+xfs_iomap_end_fsb(
+	struct xfs_mount	*mp,
+	loff_t			offset,
+	loff_t			count)
+{
+	ASSERT(offset <= mp->m_super->s_maxbytes);
+	return min(XFS_B_TO_FSB(mp, offset + count),
+		   XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes));
+}
+
+static xfs_extlen_t
+xfs_eof_alignment(
+	struct xfs_inode	*ip)
+{
+	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 && xfs_has_swalloc(mp))
+			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;
+	}
+
+	return align;
+}
+
+/*
+ * Check if last_fsb is outside the last extent, and if so grow it to the next
+ * stripe unit boundary.
+ */
+xfs_fileoff_t
+xfs_iomap_eof_align_last_fsb(
+	struct xfs_inode	*ip,
+	xfs_fileoff_t		end_fsb)
+{
+	struct xfs_ifork	*ifp = xfs_ifork_ptr(ip, XFS_DATA_FORK);
+	xfs_extlen_t		extsz = xfs_get_extsz_hint(ip);
+	xfs_extlen_t		align = xfs_eof_alignment(ip);
+	struct xfs_bmbt_irec	irec;
+	struct xfs_iext_cursor	icur;
+
+	ASSERT(!xfs_need_iread_extents(ifp));
+
+	/*
+	 * Always round up the allocation request to the extent hint boundary.
+	 */
+	if (extsz) {
+		if (align)
+			align = roundup_64(align, extsz);
+		else
+			align = extsz;
+	}
+
+	if (align) {
+		xfs_fileoff_t	aligned_end_fsb = roundup_64(end_fsb, align);
+
+		xfs_iext_last(ifp, &icur);
+		if (!xfs_iext_get_extent(ifp, &icur, &irec) ||
+		    aligned_end_fsb >= irec.br_startoff + irec.br_blockcount)
+			return aligned_end_fsb;
+	}
+
+	return end_fsb;
+}
+
+int
+xfs_iomap_write_direct(
+	struct xfs_inode	*ip,
+	xfs_fileoff_t		offset_fsb,
+	xfs_fileoff_t		count_fsb,
+	unsigned int		flags,
+	struct xfs_bmbt_irec	*imap,
+	u64			*seq)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_trans	*tp;
+	xfs_filblks_t		resaligned;
+	int			nimaps;
+	unsigned int		dblocks, rblocks;
+	bool			force = false;
+	int			error;
+	int			bmapi_flags = XFS_BMAPI_PREALLOC;
+	int			nr_exts = XFS_IEXT_ADD_NOSPLIT_CNT;
+
+	ASSERT(count_fsb > 0);
+
+	resaligned = xfs_aligned_fsb_count(offset_fsb, count_fsb,
+					   xfs_get_extsz_hint(ip));
+	if (unlikely(XFS_IS_REALTIME_INODE(ip))) {
+		dblocks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
+		rblocks = resaligned;
+	} else {
+		dblocks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
+		rblocks = 0;
+	}
+
+	error = xfs_qm_dqattach(ip);
+	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 (flags & IOMAP_DAX) {
+		bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;
+		if (imap->br_state == XFS_EXT_UNWRITTEN) {
+			force = true;
+			nr_exts = XFS_IEXT_WRITE_UNWRITTEN_CNT;
+			dblocks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
+		}
+	}
+
+	error = xfs_trans_alloc_inode(ip, &M_RES(mp)->tr_write, dblocks,
+			rblocks, force, &tp);
+	if (error)
+		return error;
+
+	error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK, nr_exts);
+	if (error == -EFBIG)
+		error = xfs_iext_count_upgrade(tp, ip, nr_exts);
+	if (error)
+		goto out_trans_cancel;
+
+	/*
+	 * From this point onwards we overwrite the imap pointer that the
+	 * caller gave to us.
+	 */
+	nimaps = 1;
+	error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb, bmapi_flags, 0,
+				imap, &nimaps);
+	if (error)
+		goto out_trans_cancel;
+
+	/*
+	 * Complete the transaction
+	 */
+	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 (unlikely(!xfs_valid_startblock(ip, imap->br_startblock)))
+		error = xfs_alert_fsblock_zero(ip, imap);
+
+out_unlock:
+	*seq = xfs_iomap_inode_sequence(ip, 0);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return error;
+
+out_trans_cancel:
+	xfs_trans_cancel(tp);
+	goto out_unlock;
+}
+
+STATIC bool
+xfs_quota_need_throttle(
+	struct xfs_inode	*ip,
+	xfs_dqtype_t		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_blk.reserved + alloc_blocks < dq->q_prealloc_lo_wmark)
+		return false;
+
+	return true;
+}
+
+STATIC void
+xfs_quota_calc_throttle(
+	struct xfs_inode	*ip,
+	xfs_dqtype_t		type,
+	xfs_fsblock_t		*qblocks,
+	int			*qshift,
+	int64_t			*qfreesp)
+{
+	struct xfs_dquot	*dq = xfs_inode_dquot(ip, type);
+	int64_t			freesp;
+	int			shift = 0;
+
+	/* no dq, or over hi wmark, squash the prealloc completely */
+	if (!dq || dq->q_blk.reserved >= dq->q_prealloc_hi_wmark) {
+		*qblocks = 0;
+		*qfreesp = 0;
+		return;
+	}
+
+	freesp = dq->q_prealloc_hi_wmark - dq->q_blk.reserved;
+	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 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 being full, the smaller the maximum preallocation.
+ */
+STATIC xfs_fsblock_t
+xfs_iomap_prealloc_size(
+	struct xfs_inode	*ip,
+	int			whichfork,
+	loff_t			offset,
+	loff_t			count,
+	struct xfs_iext_cursor	*icur)
+{
+	struct xfs_iext_cursor	ncur = *icur;
+	struct xfs_bmbt_irec	prev, got;
+	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_ifork	*ifp = xfs_ifork_ptr(ip, whichfork);
+	xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);
+	int64_t			freesp;
+	xfs_fsblock_t		qblocks;
+	xfs_fsblock_t		alloc_blocks = 0;
+	xfs_extlen_t		plen;
+	int			shift = 0;
+	int			qshift = 0;
+
+	/*
+	 * 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.
+	 */
+	if (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_allocsize_blocks))
+		return 0;
+
+	/*
+	 * Use the minimum preallocation size for small files or if we are
+	 * writing right after a hole.
+	 */
+	if (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign) ||
+	    !xfs_iext_prev_extent(ifp, &ncur, &prev) ||
+	    prev.br_startoff + prev.br_blockcount < offset_fsb)
+		return mp->m_allocsize_blocks;
+
+	/*
+	 * Take the size of the preceding data extents as the basis for the
+	 * preallocation size. Note that we don't care if the previous extents
+	 * are written or not.
+	 */
+	plen = prev.br_blockcount;
+	while (xfs_iext_prev_extent(ifp, &ncur, &got)) {
+		if (plen > XFS_MAX_BMBT_EXTLEN / 2 ||
+		    isnullstartblock(got.br_startblock) ||
+		    got.br_startoff + got.br_blockcount != prev.br_startoff ||
+		    got.br_startblock + got.br_blockcount != prev.br_startblock)
+			break;
+		plen += got.br_blockcount;
+		prev = got;
+	}
+
+	/*
+	 * If the size of the extents 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
+	 * XFS_BMBT_MAX_EXTLEN rather than falling short due to things like stripe
+	 * unit/width alignment of real extents.
+	 */
+	alloc_blocks = plen * 2;
+	if (alloc_blocks > XFS_MAX_BMBT_EXTLEN)
+		alloc_blocks = XFS_B_TO_FSB(mp, offset);
+	qblocks = alloc_blocks;
+
+	/*
+	 * XFS_BMBT_MAX_EXTLEN 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 XFS_BMBT_MAX_EXTLEN.
+	 */
+	alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(XFS_MAX_BMBT_EXTLEN),
+				       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_DQTYPE_USER, alloc_blocks))
+		xfs_quota_calc_throttle(ip, XFS_DQTYPE_USER, &qblocks, &qshift,
+					&freesp);
+	if (xfs_quota_need_throttle(ip, XFS_DQTYPE_GROUP, alloc_blocks))
+		xfs_quota_calc_throttle(ip, XFS_DQTYPE_GROUP, &qblocks, &qshift,
+					&freesp);
+	if (xfs_quota_need_throttle(ip, XFS_DQTYPE_PROJ, alloc_blocks))
+		xfs_quota_calc_throttle(ip, XFS_DQTYPE_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 > XFS_MAX_BMBT_EXTLEN)
+		alloc_blocks = XFS_MAX_BMBT_EXTLEN;
+
+	/*
+	 * 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 XFS_BMBT_MAX_EXTLEN.
+	 */
+	while (alloc_blocks && alloc_blocks >= freesp)
+		alloc_blocks >>= 4;
+	if (alloc_blocks < mp->m_allocsize_blocks)
+		alloc_blocks = mp->m_allocsize_blocks;
+	trace_xfs_iomap_prealloc_size(ip, alloc_blocks, shift,
+				      mp->m_allocsize_blocks);
+	return alloc_blocks;
+}
+
+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;
+	int		nimaps;
+	xfs_trans_t	*tp;
+	xfs_bmbt_irec_t imap;
+	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;
+
+	/* Attach dquots so that bmbt splits are accounted correctly. */
+	error = xfs_qm_dqattach(ip);
+	if (error)
+		return error;
+
+	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_inode(ip, &M_RES(mp)->tr_write, resblks,
+				0, true, &tp);
+		if (error)
+			return error;
+
+		error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
+				XFS_IEXT_WRITE_UNWRITTEN_CNT);
+		if (error == -EFBIG)
+			error = xfs_iext_count_upgrade(tp, ip,
+					XFS_IEXT_WRITE_UNWRITTEN_CNT);
+		if (error)
+			goto error_on_bmapi_transaction;
+
+		/*
+		 * Modify the unwritten extent state of the buffer.
+		 */
+		nimaps = 1;
+		error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,
+					XFS_BMAPI_CONVERT, resblks, &imap,
+					&nimaps);
+		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_disk_size = i_size;
+			xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
+		}
+
+		error = xfs_trans_commit(tp);
+		xfs_iunlock(ip, XFS_ILOCK_EXCL);
+		if (error)
+			return error;
+
+		if (unlikely(!xfs_valid_startblock(ip, imap.br_startblock)))
+			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_trans_cancel(tp);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return error;
+}
+
+static inline bool
+imap_needs_alloc(
+	struct inode		*inode,
+	unsigned		flags,
+	struct xfs_bmbt_irec	*imap,
+	int			nimaps)
+{
+	/* don't allocate blocks when just zeroing */
+	if (flags & IOMAP_ZERO)
+		return false;
+	if (!nimaps ||
+	    imap->br_startblock == HOLESTARTBLOCK ||
+	    imap->br_startblock == DELAYSTARTBLOCK)
+		return true;
+	/* we convert unwritten extents before copying the data for DAX */
+	if ((flags & IOMAP_DAX) && imap->br_state == XFS_EXT_UNWRITTEN)
+		return true;
+	return false;
+}
+
+static inline bool
+imap_needs_cow(
+	struct xfs_inode	*ip,
+	unsigned int		flags,
+	struct xfs_bmbt_irec	*imap,
+	int			nimaps)
+{
+	if (!xfs_is_cow_inode(ip))
+		return false;
+
+	/* when zeroing we don't have to COW holes or unwritten extents */
+	if (flags & IOMAP_ZERO) {
+		if (!nimaps ||
+		    imap->br_startblock == HOLESTARTBLOCK ||
+		    imap->br_state == XFS_EXT_UNWRITTEN)
+			return false;
+	}
+
+	return true;
+}
+
+static int
+xfs_ilock_for_iomap(
+	struct xfs_inode	*ip,
+	unsigned		flags,
+	unsigned		*lockmode)
+{
+	unsigned int		mode = *lockmode;
+	bool			is_write = flags & (IOMAP_WRITE | IOMAP_ZERO);
+
+	/*
+	 * COW writes may allocate delalloc space or convert unwritten COW
+	 * extents, so we need to make sure to take the lock exclusively here.
+	 */
+	if (xfs_is_cow_inode(ip) && is_write)
+		mode = XFS_ILOCK_EXCL;
+
+	/*
+	 * Extents not yet cached requires exclusive access, don't block.  This
+	 * is an opencoded xfs_ilock_data_map_shared() call but with
+	 * non-blocking behaviour.
+	 */
+	if (xfs_need_iread_extents(&ip->i_df)) {
+		if (flags & IOMAP_NOWAIT)
+			return -EAGAIN;
+		mode = XFS_ILOCK_EXCL;
+	}
+
+relock:
+	if (flags & IOMAP_NOWAIT) {
+		if (!xfs_ilock_nowait(ip, mode))
+			return -EAGAIN;
+	} else {
+		xfs_ilock(ip, mode);
+	}
+
+	/*
+	 * The reflink iflag could have changed since the earlier unlocked
+	 * check, so if we got ILOCK_SHARED for a write and but we're now a
+	 * reflink inode we have to switch to ILOCK_EXCL and relock.
+	 */
+	if (mode == XFS_ILOCK_SHARED && is_write && xfs_is_cow_inode(ip)) {
+		xfs_iunlock(ip, mode);
+		mode = XFS_ILOCK_EXCL;
+		goto relock;
+	}
+
+	*lockmode = mode;
+	return 0;
+}
+
+/*
+ * Check that the imap we are going to return to the caller spans the entire
+ * range that the caller requested for the IO.
+ */
+static bool
+imap_spans_range(
+	struct xfs_bmbt_irec	*imap,
+	xfs_fileoff_t		offset_fsb,
+	xfs_fileoff_t		end_fsb)
+{
+	if (imap->br_startoff > offset_fsb)
+		return false;
+	if (imap->br_startoff + imap->br_blockcount < end_fsb)
+		return false;
+	return true;
+}
+
+static int
+xfs_direct_write_iomap_begin(
+	struct inode		*inode,
+	loff_t			offset,
+	loff_t			length,
+	unsigned		flags,
+	struct iomap		*iomap,
+	struct iomap		*srcmap)
+{
+	struct xfs_inode	*ip = XFS_I(inode);
+	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_bmbt_irec	imap, cmap;
+	xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);
+	xfs_fileoff_t		end_fsb = xfs_iomap_end_fsb(mp, offset, length);
+	int			nimaps = 1, error = 0;
+	bool			shared = false;
+	u16			iomap_flags = 0;
+	unsigned int		lockmode = XFS_ILOCK_SHARED;
+	u64			seq;
+
+	ASSERT(flags & (IOMAP_WRITE | IOMAP_ZERO));
+
+	if (xfs_is_shutdown(mp))
+		return -EIO;
+
+	/*
+	 * Writes that span EOF might trigger an IO size update on completion,
+	 * so consider them to be dirty for the purposes of O_DSYNC even if
+	 * there is no other metadata changes pending or have been made here.
+	 */
+	if (offset + length > i_size_read(inode))
+		iomap_flags |= IOMAP_F_DIRTY;
+
+	error = xfs_ilock_for_iomap(ip, flags, &lockmode);
+	if (error)
+		return error;
+
+	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
+			       &nimaps, 0);
+	if (error)
+		goto out_unlock;
+
+	if (imap_needs_cow(ip, flags, &imap, nimaps)) {
+		error = -EAGAIN;
+		if (flags & IOMAP_NOWAIT)
+			goto out_unlock;
+
+		/* may drop and re-acquire the ilock */
+		error = xfs_reflink_allocate_cow(ip, &imap, &cmap, &shared,
+				&lockmode,
+				(flags & IOMAP_DIRECT) || IS_DAX(inode));
+		if (error)
+			goto out_unlock;
+		if (shared)
+			goto out_found_cow;
+		end_fsb = imap.br_startoff + imap.br_blockcount;
+		length = XFS_FSB_TO_B(mp, end_fsb) - offset;
+	}
+
+	if (imap_needs_alloc(inode, flags, &imap, nimaps))
+		goto allocate_blocks;
+
+	/*
+	 * NOWAIT and OVERWRITE I/O needs to span the entire requested I/O with
+	 * a single map so that we avoid partial IO failures due to the rest of
+	 * the I/O range not covered by this map triggering an EAGAIN condition
+	 * when it is subsequently mapped and aborting the I/O.
+	 */
+	if (flags & (IOMAP_NOWAIT | IOMAP_OVERWRITE_ONLY)) {
+		error = -EAGAIN;
+		if (!imap_spans_range(&imap, offset_fsb, end_fsb))
+			goto out_unlock;
+	}
+
+	/*
+	 * For overwrite only I/O, we cannot convert unwritten extents without
+	 * requiring sub-block zeroing.  This can only be done under an
+	 * exclusive IOLOCK, hence return -EAGAIN if this is not a written
+	 * extent to tell the caller to try again.
+	 */
+	if (flags & IOMAP_OVERWRITE_ONLY) {
+		error = -EAGAIN;
+		if (imap.br_state != XFS_EXT_NORM &&
+	            ((offset | length) & mp->m_blockmask))
+			goto out_unlock;
+	}
+
+	seq = xfs_iomap_inode_sequence(ip, iomap_flags);
+	xfs_iunlock(ip, lockmode);
+	trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap);
+	return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, iomap_flags, seq);
+
+allocate_blocks:
+	error = -EAGAIN;
+	if (flags & (IOMAP_NOWAIT | IOMAP_OVERWRITE_ONLY))
+		goto out_unlock;
+
+	/*
+	 * We cap the maximum length we map to a sane size  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);
+	end_fsb = xfs_iomap_end_fsb(mp, offset, length);
+
+	if (offset + length > XFS_ISIZE(ip))
+		end_fsb = xfs_iomap_eof_align_last_fsb(ip, end_fsb);
+	else if (nimaps && imap.br_startblock == HOLESTARTBLOCK)
+		end_fsb = min(end_fsb, imap.br_startoff + imap.br_blockcount);
+	xfs_iunlock(ip, lockmode);
+
+	error = xfs_iomap_write_direct(ip, offset_fsb, end_fsb - offset_fsb,
+			flags, &imap, &seq);
+	if (error)
+		return error;
+
+	trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap);
+	return xfs_bmbt_to_iomap(ip, iomap, &imap, flags,
+				 iomap_flags | IOMAP_F_NEW, seq);
+
+out_found_cow:
+	length = XFS_FSB_TO_B(mp, cmap.br_startoff + cmap.br_blockcount);
+	trace_xfs_iomap_found(ip, offset, length - offset, XFS_COW_FORK, &cmap);
+	if (imap.br_startblock != HOLESTARTBLOCK) {
+		seq = xfs_iomap_inode_sequence(ip, 0);
+		error = xfs_bmbt_to_iomap(ip, srcmap, &imap, flags, 0, seq);
+		if (error)
+			goto out_unlock;
+	}
+	seq = xfs_iomap_inode_sequence(ip, IOMAP_F_SHARED);
+	xfs_iunlock(ip, lockmode);
+	return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, IOMAP_F_SHARED, seq);
+
+out_unlock:
+	if (lockmode)
+		xfs_iunlock(ip, lockmode);
+	return error;
+}
+
+const struct iomap_ops xfs_direct_write_iomap_ops = {
+	.iomap_begin		= xfs_direct_write_iomap_begin,
+};
+
+static int
+xfs_dax_write_iomap_end(
+	struct inode		*inode,
+	loff_t			pos,
+	loff_t			length,
+	ssize_t			written,
+	unsigned		flags,
+	struct iomap		*iomap)
+{
+	struct xfs_inode	*ip = XFS_I(inode);
+
+	if (!xfs_is_cow_inode(ip))
+		return 0;
+
+	if (!written) {
+		xfs_reflink_cancel_cow_range(ip, pos, length, true);
+		return 0;
+	}
+
+	return xfs_reflink_end_cow(ip, pos, written);
+}
+
+const struct iomap_ops xfs_dax_write_iomap_ops = {
+	.iomap_begin	= xfs_direct_write_iomap_begin,
+	.iomap_end	= xfs_dax_write_iomap_end,
+};
+
+static int
+xfs_buffered_write_iomap_begin(
+	struct inode		*inode,
+	loff_t			offset,
+	loff_t			count,
+	unsigned		flags,
+	struct iomap		*iomap,
+	struct iomap		*srcmap)
+{
+	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_iomap_end_fsb(mp, offset, count);
+	struct xfs_bmbt_irec	imap, cmap;
+	struct xfs_iext_cursor	icur, ccur;
+	xfs_fsblock_t		prealloc_blocks = 0;
+	bool			eof = false, cow_eof = false, shared = false;
+	int			allocfork = XFS_DATA_FORK;
+	int			error = 0;
+	unsigned int		lockmode = XFS_ILOCK_EXCL;
+	u64			seq;
+
+	if (xfs_is_shutdown(mp))
+		return -EIO;
+
+	/* we can't use delayed allocations when using extent size hints */
+	if (xfs_get_extsz_hint(ip))
+		return xfs_direct_write_iomap_begin(inode, offset, count,
+				flags, iomap, srcmap);
+
+	ASSERT(!XFS_IS_REALTIME_INODE(ip));
+
+	error = xfs_qm_dqattach(ip);
+	if (error)
+		return error;
+
+	error = xfs_ilock_for_iomap(ip, flags, &lockmode);
+	if (error)
+		return error;
+
+	if (XFS_IS_CORRUPT(mp, !xfs_ifork_has_extents(&ip->i_df)) ||
+	    XFS_TEST_ERROR(false, mp, XFS_ERRTAG_BMAPIFORMAT)) {
+		error = -EFSCORRUPTED;
+		goto out_unlock;
+	}
+
+	XFS_STATS_INC(mp, xs_blk_mapw);
+
+	error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
+	if (error)
+		goto out_unlock;
+
+	/*
+	 * Search the data fork first to look up our source mapping.  We
+	 * always need the data fork map, as we have to return it to the
+	 * iomap code so that the higher level write code can read data in to
+	 * perform read-modify-write cycles for unaligned writes.
+	 */
+	eof = !xfs_iext_lookup_extent(ip, &ip->i_df, offset_fsb, &icur, &imap);
+	if (eof)
+		imap.br_startoff = end_fsb; /* fake hole until the end */
+
+	/* We never need to allocate blocks for zeroing or unsharing a hole. */
+	if ((flags & (IOMAP_UNSHARE | IOMAP_ZERO)) &&
+	    imap.br_startoff > offset_fsb) {
+		xfs_hole_to_iomap(ip, iomap, offset_fsb, imap.br_startoff);
+		goto out_unlock;
+	}
+
+	/*
+	 * Search the COW fork extent list even if we did not find a data fork
+	 * extent.  This serves two purposes: first this implements the
+	 * speculative preallocation using cowextsize, so that we also unshare
+	 * block adjacent to shared blocks instead of just the shared blocks
+	 * themselves.  Second the lookup in the extent list is generally faster
+	 * than going out to the shared extent tree.
+	 */
+	if (xfs_is_cow_inode(ip)) {
+		if (!ip->i_cowfp) {
+			ASSERT(!xfs_is_reflink_inode(ip));
+			xfs_ifork_init_cow(ip);
+		}
+		cow_eof = !xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb,
+				&ccur, &cmap);
+		if (!cow_eof && cmap.br_startoff <= offset_fsb) {
+			trace_xfs_reflink_cow_found(ip, &cmap);
+			goto found_cow;
+		}
+	}
+
+	if (imap.br_startoff <= offset_fsb) {
+		/*
+		 * For reflink files we may need a delalloc reservation when
+		 * overwriting shared extents.   This includes zeroing of
+		 * existing extents that contain data.
+		 */
+		if (!xfs_is_cow_inode(ip) ||
+		    ((flags & IOMAP_ZERO) && imap.br_state != XFS_EXT_NORM)) {
+			trace_xfs_iomap_found(ip, offset, count, XFS_DATA_FORK,
+					&imap);
+			goto found_imap;
+		}
+
+		xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb);
+
+		/* Trim the mapping to the nearest shared extent boundary. */
+		error = xfs_bmap_trim_cow(ip, &imap, &shared);
+		if (error)
+			goto out_unlock;
+
+		/* Not shared?  Just report the (potentially capped) extent. */
+		if (!shared) {
+			trace_xfs_iomap_found(ip, offset, count, XFS_DATA_FORK,
+					&imap);
+			goto found_imap;
+		}
+
+		/*
+		 * Fork all the shared blocks from our write offset until the
+		 * end of the extent.
+		 */
+		allocfork = XFS_COW_FORK;
+		end_fsb = imap.br_startoff + imap.br_blockcount;
+	} else {
+		/*
+		 * 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.
+		 *
+		 * 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 = xfs_iomap_end_fsb(mp, offset, count);
+
+		if (xfs_is_always_cow_inode(ip))
+			allocfork = XFS_COW_FORK;
+	}
+
+	if (eof && offset + count > XFS_ISIZE(ip)) {
+		/*
+		 * Determine the initial size of the preallocation.
+		 * We clean up any extra preallocation when the file is closed.
+		 */
+		if (xfs_has_allocsize(mp))
+			prealloc_blocks = mp->m_allocsize_blocks;
+		else if (allocfork == XFS_DATA_FORK)
+			prealloc_blocks = xfs_iomap_prealloc_size(ip, allocfork,
+						offset, count, &icur);
+		else
+			prealloc_blocks = xfs_iomap_prealloc_size(ip, allocfork,
+						offset, count, &ccur);
+		if (prealloc_blocks) {
+			xfs_extlen_t	align;
+			xfs_off_t	end_offset;
+			xfs_fileoff_t	p_end_fsb;
+
+			end_offset = XFS_ALLOC_ALIGN(mp, offset + count - 1);
+			p_end_fsb = XFS_B_TO_FSBT(mp, end_offset) +
+					prealloc_blocks;
+
+			align = xfs_eof_alignment(ip);
+			if (align)
+				p_end_fsb = roundup_64(p_end_fsb, align);
+
+			p_end_fsb = min(p_end_fsb,
+				XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes));
+			ASSERT(p_end_fsb > offset_fsb);
+			prealloc_blocks = p_end_fsb - end_fsb;
+		}
+	}
+
+retry:
+	error = xfs_bmapi_reserve_delalloc(ip, allocfork, offset_fsb,
+			end_fsb - offset_fsb, prealloc_blocks,
+			allocfork == XFS_DATA_FORK ? &imap : &cmap,
+			allocfork == XFS_DATA_FORK ? &icur : &ccur,
+			allocfork == XFS_DATA_FORK ? eof : cow_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;
+		}
+		fallthrough;
+	default:
+		goto out_unlock;
+	}
+
+	if (allocfork == XFS_COW_FORK) {
+		trace_xfs_iomap_alloc(ip, offset, count, allocfork, &cmap);
+		goto found_cow;
+	}
+
+	/*
+	 * Flag newly allocated delalloc blocks with IOMAP_F_NEW so we punch
+	 * them out if the write happens to fail.
+	 */
+	seq = xfs_iomap_inode_sequence(ip, IOMAP_F_NEW);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	trace_xfs_iomap_alloc(ip, offset, count, allocfork, &imap);
+	return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, IOMAP_F_NEW, seq);
+
+found_imap:
+	seq = xfs_iomap_inode_sequence(ip, 0);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0, seq);
+
+found_cow:
+	seq = xfs_iomap_inode_sequence(ip, 0);
+	if (imap.br_startoff <= offset_fsb) {
+		error = xfs_bmbt_to_iomap(ip, srcmap, &imap, flags, 0, seq);
+		if (error)
+			goto out_unlock;
+		seq = xfs_iomap_inode_sequence(ip, IOMAP_F_SHARED);
+		xfs_iunlock(ip, XFS_ILOCK_EXCL);
+		return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags,
+					 IOMAP_F_SHARED, seq);
+	}
+
+	xfs_trim_extent(&cmap, offset_fsb, imap.br_startoff - offset_fsb);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return xfs_bmbt_to_iomap(ip, iomap, &cmap, flags, 0, seq);
+
+out_unlock:
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return error;
+}
+
+static int
+xfs_buffered_write_delalloc_punch(
+	struct inode		*inode,
+	loff_t			offset,
+	loff_t			length)
+{
+	return xfs_bmap_punch_delalloc_range(XFS_I(inode), offset,
+			offset + length);
+}
+
+static int
+xfs_buffered_write_iomap_end(
+	struct inode		*inode,
+	loff_t			offset,
+	loff_t			length,
+	ssize_t			written,
+	unsigned		flags,
+	struct iomap		*iomap)
+{
+
+	struct xfs_mount	*mp = XFS_M(inode->i_sb);
+	int			error;
+
+	error = iomap_file_buffered_write_punch_delalloc(inode, iomap, offset,
+			length, written, &xfs_buffered_write_delalloc_punch);
+	if (error && !xfs_is_shutdown(mp)) {
+		xfs_alert(mp, "%s: unable to clean up ino 0x%llx",
+			__func__, XFS_I(inode)->i_ino);
+		return error;
+	}
+	return 0;
+}
+
+const struct iomap_ops xfs_buffered_write_iomap_ops = {
+	.iomap_begin		= xfs_buffered_write_iomap_begin,
+	.iomap_end		= xfs_buffered_write_iomap_end,
+};
+
+/*
+ * iomap_page_mkwrite() will never fail in a way that requires delalloc extents
+ * that it allocated to be revoked. Hence we do not need an .iomap_end method
+ * for this operation.
+ */
+const struct iomap_ops xfs_page_mkwrite_iomap_ops = {
+	.iomap_begin		= xfs_buffered_write_iomap_begin,
+};
+
+static int
+xfs_read_iomap_begin(
+	struct inode		*inode,
+	loff_t			offset,
+	loff_t			length,
+	unsigned		flags,
+	struct iomap		*iomap,
+	struct iomap		*srcmap)
+{
+	struct xfs_inode	*ip = XFS_I(inode);
+	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_bmbt_irec	imap;
+	xfs_fileoff_t		offset_fsb = XFS_B_TO_FSBT(mp, offset);
+	xfs_fileoff_t		end_fsb = xfs_iomap_end_fsb(mp, offset, length);
+	int			nimaps = 1, error = 0;
+	bool			shared = false;
+	unsigned int		lockmode = XFS_ILOCK_SHARED;
+	u64			seq;
+
+	ASSERT(!(flags & (IOMAP_WRITE | IOMAP_ZERO)));
+
+	if (xfs_is_shutdown(mp))
+		return -EIO;
+
+	error = xfs_ilock_for_iomap(ip, flags, &lockmode);
+	if (error)
+		return error;
+	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
+			       &nimaps, 0);
+	if (!error && ((flags & IOMAP_REPORT) || IS_DAX(inode)))
+		error = xfs_reflink_trim_around_shared(ip, &imap, &shared);
+	seq = xfs_iomap_inode_sequence(ip, shared ? IOMAP_F_SHARED : 0);
+	xfs_iunlock(ip, lockmode);
+
+	if (error)
+		return error;
+	trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap);
+	return xfs_bmbt_to_iomap(ip, iomap, &imap, flags,
+				 shared ? IOMAP_F_SHARED : 0, seq);
+}
+
+const struct iomap_ops xfs_read_iomap_ops = {
+	.iomap_begin		= xfs_read_iomap_begin,
+};
+
+static int
+xfs_seek_iomap_begin(
+	struct inode		*inode,
+	loff_t			offset,
+	loff_t			length,
+	unsigned		flags,
+	struct iomap		*iomap,
+	struct iomap		*srcmap)
+{
+	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);
+	xfs_fileoff_t		cow_fsb = NULLFILEOFF, data_fsb = NULLFILEOFF;
+	struct xfs_iext_cursor	icur;
+	struct xfs_bmbt_irec	imap, cmap;
+	int			error = 0;
+	unsigned		lockmode;
+	u64			seq;
+
+	if (xfs_is_shutdown(mp))
+		return -EIO;
+
+	lockmode = xfs_ilock_data_map_shared(ip);
+	error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
+	if (error)
+		goto out_unlock;
+
+	if (xfs_iext_lookup_extent(ip, &ip->i_df, offset_fsb, &icur, &imap)) {
+		/*
+		 * If we found a data extent we are done.
+		 */
+		if (imap.br_startoff <= offset_fsb)
+			goto done;
+		data_fsb = imap.br_startoff;
+	} else {
+		/*
+		 * Fake a hole until the end of the file.
+		 */
+		data_fsb = xfs_iomap_end_fsb(mp, offset, length);
+	}
+
+	/*
+	 * If a COW fork extent covers the hole, report it - capped to the next
+	 * data fork extent:
+	 */
+	if (xfs_inode_has_cow_data(ip) &&
+	    xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &cmap))
+		cow_fsb = cmap.br_startoff;
+	if (cow_fsb != NULLFILEOFF && cow_fsb <= offset_fsb) {
+		if (data_fsb < cow_fsb + cmap.br_blockcount)
+			end_fsb = min(end_fsb, data_fsb);
+		xfs_trim_extent(&cmap, offset_fsb, end_fsb);
+		seq = xfs_iomap_inode_sequence(ip, IOMAP_F_SHARED);
+		error = xfs_bmbt_to_iomap(ip, iomap, &cmap, flags,
+				IOMAP_F_SHARED, seq);
+		/*
+		 * This is a COW extent, so we must probe the page cache
+		 * because there could be dirty page cache being backed
+		 * by this extent.
+		 */
+		iomap->type = IOMAP_UNWRITTEN;
+		goto out_unlock;
+	}
+
+	/*
+	 * Else report a hole, capped to the next found data or COW extent.
+	 */
+	if (cow_fsb != NULLFILEOFF && cow_fsb < data_fsb)
+		imap.br_blockcount = cow_fsb - offset_fsb;
+	else
+		imap.br_blockcount = data_fsb - offset_fsb;
+	imap.br_startoff = offset_fsb;
+	imap.br_startblock = HOLESTARTBLOCK;
+	imap.br_state = XFS_EXT_NORM;
+done:
+	seq = xfs_iomap_inode_sequence(ip, 0);
+	xfs_trim_extent(&imap, offset_fsb, end_fsb);
+	error = xfs_bmbt_to_iomap(ip, iomap, &imap, flags, 0, seq);
+out_unlock:
+	xfs_iunlock(ip, lockmode);
+	return error;
+}
+
+const struct iomap_ops xfs_seek_iomap_ops = {
+	.iomap_begin		= xfs_seek_iomap_begin,
+};
+
+static int
+xfs_xattr_iomap_begin(
+	struct inode		*inode,
+	loff_t			offset,
+	loff_t			length,
+	unsigned		flags,
+	struct iomap		*iomap,
+	struct iomap		*srcmap)
+{
+	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;
+	int			seq;
+
+	if (xfs_is_shutdown(mp))
+		return -EIO;
+
+	lockmode = xfs_ilock_attr_map_shared(ip);
+
+	/* if there are no attribute fork or extents, return ENOENT */
+	if (!xfs_inode_has_attr_fork(ip) || !ip->i_af.if_nextents) {
+		error = -ENOENT;
+		goto out_unlock;
+	}
+
+	ASSERT(ip->i_af.if_format != XFS_DINODE_FMT_LOCAL);
+	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
+			       &nimaps, XFS_BMAPI_ATTRFORK);
+out_unlock:
+
+	seq = xfs_iomap_inode_sequence(ip, IOMAP_F_XATTR);
+	xfs_iunlock(ip, lockmode);
+
+	if (error)
+		return error;
+	ASSERT(nimaps);
+	return xfs_bmbt_to_iomap(ip, iomap, &imap, flags, IOMAP_F_XATTR, seq);
+}
+
+const struct iomap_ops xfs_xattr_iomap_ops = {
+	.iomap_begin		= xfs_xattr_iomap_begin,
+};
+
+int
+xfs_zero_range(
+	struct xfs_inode	*ip,
+	loff_t			pos,
+	loff_t			len,
+	bool			*did_zero)
+{
+	struct inode		*inode = VFS_I(ip);
+
+	if (IS_DAX(inode))
+		return dax_zero_range(inode, pos, len, did_zero,
+				      &xfs_dax_write_iomap_ops);
+	return iomap_zero_range(inode, pos, len, did_zero,
+				&xfs_buffered_write_iomap_ops);
+}
+
+int
+xfs_truncate_page(
+	struct xfs_inode	*ip,
+	loff_t			pos,
+	bool			*did_zero)
+{
+	struct inode		*inode = VFS_I(ip);
+
+	if (IS_DAX(inode))
+		return dax_truncate_page(inode, pos, did_zero,
+					&xfs_dax_write_iomap_ops);
+	return iomap_truncate_page(inode, pos, did_zero,
+				   &xfs_buffered_write_iomap_ops);
+}