Message-id: <003801cf6aa7$f1f87b70$d5e97250$@samsung.com>
Date:	Thu, 08 May 2014 19:26:16 +0900
From:	Namjae Jeon <namjae.jeon@...sung.com>
To:	'Dave Chinner' <david@...morbit.com>,
	'Theodore Ts'o' <tytso@....edu>
Cc:	'linux-ext4' <linux-ext4@...r.kernel.org>, xfs@....sgi.com,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	'Ashish Sangwan' <a.sangwan@...sung.com>
Subject: [PATCH v2 2/10] xfs: Add support FALLOC_FL_INSERT_RANGE for fallocate

This patch implements fallocate's FALLOC_FL_INSERT_RANGE for XFS.

1) Make sure that both offset and len are block size aligned.
2) Update the i_size of inode by len bytes.
3) Compute the file's logical block number against offset. If the computed
   block number is not the starting block of the extent, split the extent
   such that the block number is the starting block of the extent.
4) Shift all the extents which are lying bewteen [offset, last allocated extent]
   towards right by len bytes. This step will make a hole of len bytes
   at offset.
5) Allocate unwritten extents for the hole created in step 4.

Signed-off-by: Namjae Jeon <namjae.jeon@...sung.com>
Signed-off-by: Ashish Sangwan <a.sangwan@...sung.com>
---
 fs/xfs/xfs_bmap.c      | 372 ++++++++++++++++++++++++++++++++++++++++++++++++-
 fs/xfs/xfs_bmap.h      |   9 +-
 fs/xfs/xfs_bmap_util.c | 129 ++++++++++++++++-
 fs/xfs/xfs_bmap_util.h |   2 +
 fs/xfs/xfs_file.c      |  37 ++++-
 fs/xfs/xfs_trace.h     |   1 +
 6 files changed, 545 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index 1ff0da6..e24aa14 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -5419,7 +5419,7 @@ error0:
  * into, this will be considered invalid operation and we abort immediately.
  */
 int
-xfs_bmap_shift_extents(
+xfs_bmap_shift_extents_left(
 	struct xfs_trans	*tp,
 	struct xfs_inode	*ip,
 	int			*done,
@@ -5449,7 +5449,7 @@ xfs_bmap_shift_extents(
 	    (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
 	     XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
 	     mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
-		XFS_ERROR_REPORT("xfs_bmap_shift_extents",
+		XFS_ERROR_REPORT("xfs_bmap_shift_extents_left",
 				 XFS_ERRLEVEL_LOW, mp);
 		return XFS_ERROR(EFSCORRUPTED);
 	}
@@ -5606,3 +5606,371 @@ del_cursor:
 	xfs_trans_log_inode(tp, ip, logflags);
 	return error;
 }
+
+/*
+ * Splits an extent into two extents at split_fsb block that it is
+ * the first block of the current_ext. @current_ext is a target extent
+ * to be splitted. @split_fsb is a block where the extents is spliited.
+ * If split_fsb lies in a hole or the first block of extents, just return 0.
+ */
+STATIC int
+xfs_bmap_split_extent_at(
+	struct xfs_trans	*tp,
+	struct xfs_inode	*ip,
+	xfs_fileoff_t		split_fsb,
+	xfs_extnum_t		*current_ext,
+	xfs_fsblock_t		*firstfsb,
+	struct xfs_bmap_free	*free_list)
+{
+	int				whichfork = XFS_DATA_FORK;
+	struct xfs_btree_cur		*cur;
+	struct xfs_bmbt_rec_host	*gotp;
+	struct xfs_bmbt_irec		got;
+	struct xfs_bmbt_irec		new; /* splitted extent */
+	struct xfs_mount		*mp = ip->i_mount;
+	struct xfs_ifork		*ifp;
+	xfs_fsblock_t			gotblkcnt; /* new block count for got */
+	int				error = 0;
+	int				logflags;
+	int				i = 0;
+
+	if (unlikely(XFS_TEST_ERROR(
+	    (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
+	     XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
+	     mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
+		XFS_ERROR_REPORT("xfs_bmap_split_extent_at",
+				 XFS_ERRLEVEL_LOW, mp);
+		return XFS_ERROR(EFSCORRUPTED);
+	}
+
+	if (XFS_FORCED_SHUTDOWN(mp))
+		return XFS_ERROR(EIO);
+
+	ASSERT(current_ext != NULL);
+
+	ifp = XFS_IFORK_PTR(ip, whichfork);
+	if (!(ifp->if_flags & XFS_IFEXTENTS)) {
+		/* Read in all the extents */
+		error = xfs_iread_extents(tp, ip, whichfork);
+		if (error)
+			return error;
+	}
+
+	gotp = xfs_iext_bno_to_ext(ifp, split_fsb, current_ext);
+	/*
+	 * gotp can be null in 2 cases: 1) if there are no extents
+	 * or 2) split_fsb lies in a hole beyond which there are
+	 * no extents. Either way, we are done.
+	 */
+	if (!gotp)
+		return 0;
+
+	xfs_bmbt_get_all(gotp, &got);
+
+	/*
+	 * Check split_fsb lies in a hole or the start boundary offset
+	 * of the extent.
+	 */
+	if (got.br_startoff >= split_fsb)
+		return 0;
+
+	gotblkcnt = split_fsb - got.br_startoff;
+	new.br_startoff = split_fsb;
+	new.br_startblock = got.br_startblock + gotblkcnt;
+	new.br_blockcount = got.br_blockcount - gotblkcnt;
+	new.br_state = got.br_state;
+
+	/* We are going to change core inode */
+	logflags = XFS_ILOG_CORE;
+
+	if (ifp->if_flags & XFS_IFBROOT) {
+		cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
+		cur->bc_private.b.firstblock = *firstfsb;
+		cur->bc_private.b.flist = free_list;
+		cur->bc_private.b.flags = 0;
+	} else {
+		cur = NULL;
+		logflags |= XFS_ILOG_DEXT;
+	}
+
+	if (cur) {
+		error = xfs_bmbt_lookup_eq(cur, got.br_startoff,
+					   got.br_startblock,
+					   got.br_blockcount,
+					   &i);
+		if (error)
+			goto del_cursor;
+		XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
+	}
+
+	xfs_bmbt_set_blockcount(gotp, gotblkcnt);
+	got.br_blockcount = gotblkcnt;
+	if (cur) {
+		error = xfs_bmbt_update(cur, got.br_startoff,
+					got.br_startblock,
+					got.br_blockcount,
+					got.br_state);
+		if (error)
+			goto del_cursor;
+	}
+
+	/* Add new extent */
+	(*current_ext)++;
+	xfs_iext_insert(ip, *current_ext, 1, &new, 0);
+	XFS_IFORK_NEXT_SET(ip, whichfork,
+		XFS_IFORK_NEXTENTS(ip, whichfork) + 1);
+
+	if (cur) {
+		error = xfs_bmbt_lookup_eq(cur, new.br_startoff,
+					   new.br_startblock, new.br_blockcount,
+					   &i);
+		if (error)
+			goto del_cursor;
+		XFS_WANT_CORRUPTED_GOTO(i == 0, del_cursor);
+		cur->bc_rec.b.br_state = new.br_state;
+
+		error = xfs_btree_insert(cur, &i);
+		if (error)
+			goto del_cursor;
+		XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
+	}
+
+	/*
+	 * Convert to a btree if necessary.
+	 */
+	if (xfs_bmap_needs_btree(ip, whichfork)) {
+		int tmp_logflags; /* partial log flag return val */
+
+		ASSERT(cur == NULL);
+		error = xfs_bmap_extents_to_btree(tp, ip, firstfsb, free_list,
+				&cur, 0, &tmp_logflags, whichfork);
+		logflags |= tmp_logflags;
+	}
+
+del_cursor:
+	if (cur)
+		xfs_btree_del_cursor(cur,
+			error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
+	xfs_trans_log_inode(tp, ip, logflags);
+	return error;
+}
+
+int
+xfs_bmap_split_extent(
+	struct xfs_inode	*ip,
+	xfs_fileoff_t		split_fsb,
+	xfs_extnum_t		*split_ext)
+{
+	struct xfs_mount        *mp = ip->i_mount;
+	struct xfs_trans	*tp;
+	struct xfs_bmap_free	free_list;
+	xfs_fsblock_t		firstfsb;
+	int			committed;
+	int			error;
+
+	tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);
+	error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write,
+			XFS_DIOSTRAT_SPACE_RES(mp, 0), 0);
+
+	if (error) {
+		/*
+		 * Free the transaction structure.
+		 */
+		ASSERT(XFS_FORCED_SHUTDOWN(mp));
+		xfs_trans_cancel(tp, 0);
+		return error;
+	}
+
+	xfs_ilock(ip, XFS_ILOCK_EXCL);
+	error = xfs_trans_reserve_quota(tp, mp, ip->i_udquot,
+			ip->i_gdquot, ip->i_pdquot,
+			XFS_DIOSTRAT_SPACE_RES(mp, 0), 0,
+			XFS_QMOPT_RES_REGBLKS);
+	if (error)
+		goto error1;
+
+	xfs_trans_ijoin(tp, ip, 0);
+	xfs_bmap_init(&free_list, &firstfsb);
+
+	error = xfs_bmap_split_extent_at(tp, ip, split_fsb, split_ext,
+					 &firstfsb, &free_list);
+	if (error)
+		goto error0;
+
+	error = xfs_bmap_finish(&tp, &free_list, &committed);
+	if (error)
+		goto error0;
+
+	error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+
+	return error;
+error0:
+	xfs_bmap_cancel(&free_list);
+error1:
+	xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return error;
+}
+
+/*
+ * Shift extent records to the right to make a hole.
+ * The maximum number of extents to be shifted in a single operation
+ * is @num_exts, and @current_ext keeps track of the current extent
+ * index we have shifted. @offset_shift_fsb is the length by which each
+ * extent is shifted. @end_ext is the last extent to be shifted.
+ */
+int
+xfs_bmap_shift_extents_right(
+	struct xfs_trans	*tp,
+	struct xfs_inode	*ip,
+	int			*done,
+	xfs_fileoff_t		offset_shift_fsb,
+	xfs_extnum_t		*current_ext,
+	xfs_extnum_t		end_ext,
+	xfs_fsblock_t		*firstblock,
+	struct xfs_bmap_free	*flist,
+	int			num_exts)
+{
+	struct xfs_mount		*mp = ip->i_mount;
+	struct xfs_btree_cur		*cur;
+	struct xfs_bmbt_rec_host	*gotp;
+	struct xfs_bmbt_irec		got;
+	struct xfs_bmbt_irec            right;
+	xfs_ifork_t			*ifp;
+	xfs_fileoff_t			startoff;
+	xfs_filblks_t			blockcount = 0;
+	xfs_extnum_t			last_extent;
+	int				error = 0;
+	int				i;
+	int				whichfork = XFS_DATA_FORK;
+	int				logflags;
+
+	if (unlikely(XFS_TEST_ERROR(
+	    (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
+	     XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
+	     mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
+		XFS_ERROR_REPORT("xfs_bmap_shift_extents_right",
+				 XFS_ERRLEVEL_LOW, mp);
+		return XFS_ERROR(EFSCORRUPTED);
+	}
+
+	if (XFS_FORCED_SHUTDOWN(mp))
+		return XFS_ERROR(EIO);
+
+	ASSERT(current_ext != NULL);
+
+	/* We are going to change core inode */
+	logflags = XFS_ILOG_CORE;
+	ifp = XFS_IFORK_PTR(ip, whichfork);
+
+	if (ifp->if_flags & XFS_IFBROOT) {
+		cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
+		cur->bc_private.b.firstblock = *firstblock;
+		cur->bc_private.b.flist = flist;
+		cur->bc_private.b.flags = 0;
+	} else {
+		cur = NULL;
+		logflags |= XFS_ILOG_DEXT;
+	}
+
+	/* start shifting extents to right */
+	while (num_exts-- > 0) {
+		blockcount = 0;
+
+		if (*current_ext < end_ext) {
+			*done = 1;
+			break;
+		}
+
+		gotp = xfs_iext_get_ext(ifp, *current_ext);
+		xfs_bmbt_get_all(gotp, &got);
+		startoff = got.br_startoff + offset_shift_fsb;
+
+		/*
+		 * Before shifting extent into hole, make sure that the hole
+		 * is large enough to accomodate the shift. This checking has
+		 * to be performed for all except the last extent.
+		 */
+		last_extent = (ifp->if_bytes / sizeof(xfs_bmbt_rec_t)) - 1;
+		if (last_extent != *current_ext) {
+			xfs_bmbt_get_all(xfs_iext_get_ext(ifp,
+						*current_ext + 1), &right);
+			if (startoff + got.br_blockcount > right.br_startoff) {
+				error = XFS_ERROR(EINVAL);
+				if (error)
+					goto del_cursor;
+			}
+		}
+
+		/* Check if we can merge 2 adjacent extents */
+		if (last_extent != *current_ext &&
+		    right.br_startoff == startoff + got.br_blockcount &&
+		    right.br_startblock ==
+				got.br_startblock + got.br_blockcount &&
+		    right.br_state == got.br_state &&
+		    right.br_blockcount + got.br_blockcount <= MAXEXTLEN) {
+			blockcount = right.br_blockcount + got.br_blockcount;
+
+			/* Make cursor point to the extent we will update */
+			if (cur) {
+				error = xfs_bmbt_lookup_eq(cur,
+							   right.br_startoff,
+							   right.br_startblock,
+							   right.br_blockcount,
+							   &i);
+				if (error)
+					goto del_cursor;
+				XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
+			}
+
+			xfs_iext_remove(ip, *current_ext + 1, 1, 0);
+			if (cur) {
+				error = xfs_btree_delete(cur, &i);
+				if (error)
+					goto del_cursor;
+				XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
+			}
+			XFS_IFORK_NEXT_SET(ip, whichfork,
+					XFS_IFORK_NEXTENTS(ip, whichfork) - 1);
+
+		}
+
+		if (cur) {
+			error = xfs_bmbt_lookup_eq(cur, got.br_startoff,
+						   got.br_startblock,
+						   got.br_blockcount,
+						   &i);
+			if (error)
+				goto del_cursor;
+			XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
+		}
+
+		if (got.br_blockcount < blockcount) {
+			xfs_bmbt_set_blockcount(gotp, blockcount);
+			got.br_blockcount = blockcount;
+		}
+
+
+		xfs_bmbt_set_startoff(gotp, startoff);
+		got.br_startoff = startoff;
+
+		if (cur) {
+			error = xfs_bmbt_update(cur, got.br_startoff,
+						got.br_startblock,
+						got.br_blockcount,
+						got.br_state);
+			if (error)
+				goto del_cursor;
+		}
+
+		(*current_ext)--;
+	}
+
+del_cursor:
+	if (cur)
+		xfs_btree_del_cursor(cur,
+			error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
+	xfs_trans_log_inode(tp, ip, logflags);
+	return error;
+}
diff --git a/fs/xfs/xfs_bmap.h b/fs/xfs/xfs_bmap.h
index 38ba36e..af05899 100644
--- a/fs/xfs/xfs_bmap.h
+++ b/fs/xfs/xfs_bmap.h
@@ -179,10 +179,17 @@ int	xfs_bunmapi(struct xfs_trans *tp, struct xfs_inode *ip,
 int	xfs_check_nostate_extents(struct xfs_ifork *ifp, xfs_extnum_t idx,
 		xfs_extnum_t num);
 uint	xfs_default_attroffset(struct xfs_inode *ip);
-int	xfs_bmap_shift_extents(struct xfs_trans *tp, struct xfs_inode *ip,
+int	xfs_bmap_shift_extents_left(struct xfs_trans *tp, struct xfs_inode *ip,
 		int *done, xfs_fileoff_t start_fsb,
 		xfs_fileoff_t offset_shift_fsb, xfs_extnum_t *current_ext,
 		xfs_fsblock_t *firstblock, struct xfs_bmap_free	*flist,
 		int num_exts);
+int	xfs_bmap_split_extent(struct xfs_inode *ip, xfs_fileoff_t split_offset,
+		xfs_extnum_t *split_ext);
+int	xfs_bmap_shift_extents_right(struct xfs_trans *tp, struct xfs_inode *ip,
+		int *done, xfs_fsblock_t offset_shift_fsb,
+		xfs_extnum_t *current_ext, xfs_extnum_t end_ext,
+		xfs_fsblock_t *firstblock, struct xfs_bmap_free *flist,
+		int num_exts);
 
 #endif	/* __XFS_BMAP_H__ */
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 296160b..5a56f5b 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -1550,7 +1550,7 @@ xfs_collapse_file_space(
 		 * We are using the write transaction in which max 2 bmbt
 		 * updates are allowed
 		 */
-		error = xfs_bmap_shift_extents(tp, ip, &done, start_fsb,
+		error = xfs_bmap_shift_extents_left(tp, ip, &done, start_fsb,
 					       shift_fsb, &current_ext,
 					       &first_block, &free_list,
 					       XFS_BMAP_MAX_SHIFT_EXTENTS);
@@ -1574,6 +1574,133 @@ out:
 }
 
 /*
+ * xfs_insert_file_space()
+ *	This routine allocate disk space and shift extent for the given file.
+ *	The first thing we do is to sync dirty data and invalidate page cache
+ *	over the region on which insert range is working. And split an extent
+ *	to two extents at given offset by calling xfs_bmap_split_extent.
+ *	And shift all extent records which are laying between [offset,
+ *	last allocated extent] to the right to reserve hole range. Lastly
+ *	allocate an unwritten extent in hole range created by shifting extents.
+ *
+ * RETURNS:
+ *	0 on success
+ *	errno on error
+ *
+ */
+int
+xfs_insert_file_space(
+	struct xfs_inode	*ip,
+	loff_t			offset,
+	loff_t			len)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+	struct xfs_trans	*tp;
+	struct xfs_bmap_free	free_list;
+	xfs_fsblock_t		first_block;
+	xfs_ifork_t		*ifp;
+	int			done = 0;
+	int			committed;
+	int			error;
+	uint			rounding;
+	xfs_fileoff_t		start_fsb;
+	xfs_fileoff_t		shift_fsb;
+	xfs_extnum_t		split_ext;
+	xfs_extnum_t		current_ext = 0;
+	xfs_off_t		ioffset;
+
+	ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
+	trace_xfs_insert_file_space(ip);
+
+	error = xfs_qm_dqattach(ip, 0);
+	if (error)
+		return error;
+
+	/* wait for the completion of any pending DIOs */
+	inode_dio_wait(VFS_I(ip));
+
+	rounding = max_t(uint, 1 << mp->m_sb.sb_blocklog, PAGE_CACHE_SIZE);
+	ioffset = offset & ~(rounding - 1);
+	error = -filemap_write_and_wait_range(VFS_I(ip)->i_mapping,
+			ioffset, -1);
+	if (error)
+		return error;
+
+	truncate_pagecache_range(VFS_I(ip), ioffset, -1);
+
+	start_fsb = XFS_B_TO_FSB(mp, offset);
+	shift_fsb = XFS_B_TO_FSB(mp, len);
+
+	error = xfs_bmap_split_extent(ip, start_fsb, &split_ext);
+	if (error)
+		return error;
+
+	ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
+	current_ext = (ifp->if_bytes / sizeof(xfs_bmbt_rec_t)) - 1;
+	while (!error && !done) {
+		tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);
+		/*
+		 * We would need to reserve permanent block for transaction.
+		 * This will come into picture when after shifting extent into
+		 * hole we found that adjacent extents can be merged which
+		 * may lead to freeing of a block during record update.
+		 */
+		error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write,
+				XFS_DIOSTRAT_SPACE_RES(mp, 0), 0);
+		if (error) {
+			ASSERT(error == ENOSPC || XFS_FORCED_SHUTDOWN(mp));
+			xfs_trans_cancel(tp, 0);
+			break;
+		}
+
+		xfs_ilock(ip, XFS_ILOCK_EXCL);
+		error = xfs_trans_reserve_quota(tp, mp, ip->i_udquot,
+				ip->i_gdquot, ip->i_pdquot,
+				XFS_DIOSTRAT_SPACE_RES(mp, 0), 0,
+				XFS_QMOPT_RES_REGBLKS);
+		if (error)
+			goto error1;
+
+		xfs_trans_ijoin(tp, ip, 0);
+
+		xfs_bmap_init(&free_list, &first_block);
+
+		/*
+		 * We are using the write transaction in which max 2 bmbt
+		 * updates are allowed
+		 */
+		error = xfs_bmap_shift_extents_right(tp, ip, &done, shift_fsb,
+						&current_ext, split_ext,
+						&first_block, &free_list,
+						XFS_BMAP_MAX_SHIFT_EXTENTS);
+		if (error)
+			goto error0;
+
+		error = xfs_bmap_finish(&tp, &free_list, &committed);
+		if (error)
+			goto error0;
+
+		error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
+		xfs_iunlock(ip, XFS_ILOCK_EXCL);
+		if (error)
+			goto out;
+	}
+
+	/* Add unwritten extent in a hole range. */
+	error = xfs_alloc_file_space(ip, offset, len, XFS_BMAPI_PREALLOC);
+
+out:
+	return error;
+
+error0:
+	xfs_bmap_cancel(&free_list);
+error1:
+	xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT);
+	xfs_iunlock(ip, XFS_ILOCK_EXCL);
+	return error;
+}
+
+/*
  * We need to check that the format of the data fork in the temporary inode is
  * valid for the target inode before doing the swap. This is not a problem with
  * attr1 because of the fixed fork offset, but attr2 has a dynamically sized
diff --git a/fs/xfs/xfs_bmap_util.h b/fs/xfs/xfs_bmap_util.h
index 935ed2b..d62ab4b 100644
--- a/fs/xfs/xfs_bmap_util.h
+++ b/fs/xfs/xfs_bmap_util.h
@@ -101,6 +101,8 @@ int	xfs_zero_file_space(struct xfs_inode *ip, xfs_off_t offset,
 			    xfs_off_t len);
 int	xfs_collapse_file_space(struct xfs_inode *, xfs_off_t offset,
 				xfs_off_t len);
+int	xfs_insert_file_space(struct xfs_inode *, xfs_off_t offset,
+				xfs_off_t len);
 
 /* EOF block manipulation functions */
 bool	xfs_can_free_eofblocks(struct xfs_inode *ip, bool force);
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 97855c5..392b029 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -760,7 +760,8 @@ xfs_file_fallocate(
 	if (!S_ISREG(inode->i_mode))
 		return -EINVAL;
 	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
-		     FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE))
+		     FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |
+		     FALLOC_FL_INSERT_RANGE))
 		return -EOPNOTSUPP;
 
 	xfs_ilock(ip, XFS_IOLOCK_EXCL);
@@ -790,6 +791,40 @@ xfs_file_fallocate(
 		error = xfs_collapse_file_space(ip, offset, len);
 		if (error)
 			goto out_unlock;
+	} else if (mode & FALLOC_FL_INSERT_RANGE) {
+		unsigned blksize_mask = (1 << inode->i_blkbits) - 1;
+		struct iattr iattr;
+
+		if (offset & blksize_mask || len & blksize_mask) {
+			error = -EINVAL;
+			goto out_unlock;
+		}
+
+		/* Check for wrap through zero */
+		if (inode->i_size + len > inode->i_sb->s_maxbytes) {
+			error = -EFBIG;
+			goto out_unlock;
+		}
+
+		/* Offset should be less than i_size */
+		if (offset >= i_size_read(inode)) {
+			error = -EINVAL;
+			goto out_unlock;
+		}
+
+		/*
+		 * The first thing we do is to expand file to
+		 * avoid data loss if there is error while shifting
+		 */
+		iattr.ia_valid = ATTR_SIZE;
+		iattr.ia_size = i_size_read(inode) + len;
+		error = xfs_setattr_size(ip, &iattr);
+		if (error)
+			goto out_unlock;
+
+		error = xfs_insert_file_space(ip, offset, len);
+		if (error)
+			goto out_unlock;
 	} else {
 		if (!(mode & FALLOC_FL_KEEP_SIZE) &&
 		    offset + len > i_size_read(inode)) {
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 152f827..8943c9f 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -663,6 +663,7 @@ DEFINE_INODE_EVENT(xfs_alloc_file_space);
 DEFINE_INODE_EVENT(xfs_free_file_space);
 DEFINE_INODE_EVENT(xfs_zero_file_space);
 DEFINE_INODE_EVENT(xfs_collapse_file_space);
+DEFINE_INODE_EVENT(xfs_insert_file_space);
 DEFINE_INODE_EVENT(xfs_readdir);
 #ifdef CONFIG_XFS_POSIX_ACL
 DEFINE_INODE_EVENT(xfs_get_acl);
-- 
1.7.11-rc0

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