Adding upstream version 4.19.249.upstream/4.19.249upstream

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

1 files changed, 1257 insertions, 0 deletions

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
new file mode 100644
index 000000000..6320aca39
--- /dev/null
+++ b/fs/xfs/xfs_iomap.c
@@ -0,0 +1,1257 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2000-2006 Silicon Graphics, Inc.
+ * Copyright (c) 2016-2018 Christoph Hellwig.
+ * All Rights Reserved.
+ */
+#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_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_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->addr = IOMAP_NULL_ADDR;
+		iomap->type = IOMAP_HOLE;
+	} else if (imap->br_startblock == DELAYSTARTBLOCK) {
+		iomap->addr = IOMAP_NULL_ADDR;
+		iomap->type = IOMAP_DELALLOC;
+	} else {
+		iomap->addr = BBTOB(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_extlen_t	extsz;
+	int		nimaps;
+	int		quota_flag;
+	int		rt;
+	xfs_trans_t	*tp;
+	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);
+	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.
+	 */
+	nimaps = 1;
+	error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,
+				bmapi_flags, resblks, imap, &nimaps);
+	if (error)
+		goto out_res_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 (!(imap->br_startblock || XFS_IS_REALTIME_INODE(ip)))
+		error = xfs_alert_fsblock_zero(ip, imap);
+
+out_unlock:
+	xfs_iunlock(ip, lockmode);
+	return error;
+
+out_res_cancel:
+	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,
+	struct xfs_iext_cursor	*icur)
+{
+	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_peek_prev_extent(ifp, icur, &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;
+	struct xfs_iext_cursor	icur;
+	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, &icur, &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, false);
+	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,
+				&icur);
+		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, &icur,
+			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,
+	unsigned int	*cow_seq)
+{
+	xfs_mount_t	*mp = ip->i_mount;
+	struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, whichfork);
+	xfs_fileoff_t	offset_fsb, last_block;
+	xfs_fileoff_t	end_fsb, map_start_fsb;
+	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);
+	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);
+
+			/*
+			 * 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, nres, imap,
+						&nimaps);
+			if (error)
+				goto trans_cancel;
+
+			error = xfs_trans_commit(tp);
+			if (error)
+				goto error0;
+
+			if (whichfork == XFS_COW_FORK)
+				*cow_seq = READ_ONCE(ifp->if_seq);
+			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_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;
+	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;
+
+	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.
+		 */
+		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_d.di_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 (!(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_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
+needs_cow_for_zeroing(
+	struct xfs_bmbt_irec	*imap,
+	int			nimaps)
+{
+	return nimaps &&
+		imap->br_startblock != HOLESTARTBLOCK &&
+		imap->br_state != XFS_EXT_UNWRITTEN;
+}
+
+static int
+xfs_ilock_for_iomap(
+	struct xfs_inode	*ip,
+	unsigned		flags,
+	unsigned		*lockmode)
+{
+	unsigned		mode = XFS_ILOCK_SHARED;
+	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_reflink_inode(ip) && is_write) {
+		/*
+		 * FIXME: It could still overwrite on unshared extents and not
+		 * need allocation.
+		 */
+		if (flags & IOMAP_NOWAIT)
+			return -EAGAIN;
+		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 (!(ip->i_df.if_flags & XFS_IFEXTENTS)) {
+		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_reflink_inode(ip)) {
+		xfs_iunlock(ip, mode);
+		mode = XFS_ILOCK_EXCL;
+		goto relock;
+	}
+
+	*lockmode = mode;
+	return 0;
+}
+
+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);
+	}
+
+	/*
+	 * Lock the inode in the manner required for the specified operation and
+	 * check for as many conditions that would result in blocking as
+	 * possible. This removes most of the non-blocking checks from the
+	 * mapping code below.
+	 */
+	error = xfs_ilock_for_iomap(ip, flags, &lockmode);
+	if (error)
+		return error;
+
+	ASSERT(offset <= mp->m_super->s_maxbytes);
+	if (offset > mp->m_super->s_maxbytes - length)
+		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;
+	}
+
+	/* Non-modifying mapping requested, so we are done */
+	if (!(flags & (IOMAP_WRITE | IOMAP_ZERO)))
+		goto out_found;
+
+	/*
+	 * Break shared extents if necessary. Checks for non-blocking IO have
+	 * been done up front, so we don't need to do them here.
+	 */
+	if (xfs_is_reflink_inode(ip)) {
+		/* if zeroing doesn't need COW allocation, then we are done. */
+		if ((flags & IOMAP_ZERO) &&
+		    !needs_cow_for_zeroing(&imap, nimaps))
+			goto out_found;
+
+		if (flags & IOMAP_DIRECT) {
+			/* 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;
+	}
+
+	/* Don't need to allocate over holes when doing zeroing operations. */
+	if (flags & IOMAP_ZERO)
+		goto out_found;
+
+	if (!imap_needs_alloc(inode, &imap, nimaps))
+		goto out_found;
+
+	/* 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 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);
+
+	/*
+	 * 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);
+
+out_finish:
+	if (xfs_ipincount(ip) && (ip->i_itemp->ili_fsync_fields
+				& ~XFS_ILOG_TIMESTAMP))
+		iomap->flags |= IOMAP_F_DIRTY;
+
+	xfs_bmbt_to_iomap(ip, iomap, &imap);
+
+	if (shared)
+		iomap->flags |= IOMAP_F_SHARED;
+	return 0;
+
+out_found:
+	ASSERT(nimaps);
+	xfs_iunlock(ip, lockmode);
+	trace_xfs_iomap_found(ip, offset, length, 0, &imap);
+	goto out_finish;
+
+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);
+
+		error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
+					       end_fsb - start_fsb);
+		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_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,
+};