ext4: online defrag -- Add EXT4_IOC_MOVE_EXT ioctl

The EXT4_IOC_MOVE_EXT exchanges the blocks between orig_fd and donor_fd,
and then write the file data of orig_fd to donor_fd.
ext4_mext_move_extent() is the main fucntion of ext4 online defrag,
and this patch includes all functions related to ext4 online defrag.

Signed-off-by: Akira Fujita <a-fujita@rs.jp.nec.com>
Signed-off-by: Takashi Sato <t-sato@yk.jp.nec.com>
Signed-off-by: Kazuya Mio <k-mio@sx.jp.nec.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

6 files changed, 1378 insertions, 3 deletions

diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
index 8a34710ecf40..8867b2a1e5fe 100644
--- a/fs/ext4/Makefile
+++ b/fs/ext4/Makefile
@@ -6,7 +6,7 @@ obj-$(CONFIG_EXT4_FS) += ext4.o
 
 ext4-y	:= balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o \
 		ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \
-		ext4_jbd2.o migrate.o mballoc.o block_validity.o
+		ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o
 
 ext4-$(CONFIG_EXT4_FS_XATTR)		+= xattr.o xattr_user.o xattr_trusted.o
 ext4-$(CONFIG_EXT4_FS_POSIX_ACL)	+= acl.o
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index cc7d5edc38c9..276a26f117e6 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -352,6 +352,7 @@ struct ext4_new_group_data {
  /* note ioctl 10 reserved for an early version of the FIEMAP ioctl */
  /* note ioctl 11 reserved for filesystem-independent FIEMAP ioctl */
 #define EXT4_IOC_ALLOC_DA_BLKS		_IO('f', 12)
+#define EXT4_IOC_MOVE_EXT		_IOWR('f', 15, struct move_extent)
 
 /*
  * ioctl commands in 32 bit emulation
@@ -447,6 +448,15 @@ struct ext4_inode {
 	__le32  i_version_hi;	/* high 32 bits for 64-bit version */
 };
 
+struct move_extent {
+	__u32 reserved;		/* should be zero */
+	__u32 donor_fd;		/* donor file descriptor */
+	__u64 orig_start;	/* logical start offset in block for orig */
+	__u64 donor_start;	/* logical start offset in block for donor */
+	__u64 len;		/* block length to be moved */
+	__u64 moved_len;	/* moved block length */
+};
+#define MAX_DEFRAG_SIZE         ((1UL<<31) - 1)
 
 #define EXT4_EPOCH_BITS 2
 #define EXT4_EPOCH_MASK ((1 << EXT4_EPOCH_BITS) - 1)
@@ -1647,6 +1657,11 @@ extern int ext4_get_blocks(handle_t *handle, struct inode *inode,
 			   struct buffer_head *bh, int flags);
 extern int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 			__u64 start, __u64 len);
+/* move_extent.c */
+extern int ext4_move_extents(struct file *o_filp, struct file *d_filp,
+			     __u64 start_orig, __u64 start_donor,
+			     __u64 len, __u64 *moved_len);
+
 
 /*
  * Add new method to test wether block and inode bitmaps are properly
diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
index f0c3ec85bd48..20a84105a10b 100644
--- a/fs/ext4/ext4_extents.h
+++ b/fs/ext4/ext4_extents.h
@@ -221,12 +221,16 @@ static inline int ext4_ext_get_actual_len(struct ext4_extent *ext)
 }
 
 extern int ext4_ext_calc_metadata_amount(struct inode *inode, int blocks);
+extern ext4_fsblk_t ext_pblock(struct ext4_extent *ex);
 extern ext4_fsblk_t idx_pblock(struct ext4_extent_idx *);
 extern void ext4_ext_store_pblock(struct ext4_extent *, ext4_fsblk_t);
 extern int ext4_extent_tree_init(handle_t *, struct inode *);
 extern int ext4_ext_calc_credits_for_single_extent(struct inode *inode,
 						   int num,
 						   struct ext4_ext_path *path);
+extern int ext4_can_extents_be_merged(struct inode *inode,
+				      struct ext4_extent *ex1,
+				      struct ext4_extent *ex2);
 extern int ext4_ext_try_to_merge(struct inode *inode,
 				 struct ext4_ext_path *path,
 				 struct ext4_extent *);
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 2593f748c3a4..50322a09bd01 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -49,7 +49,7 @@
  * ext_pblock:
  * combine low and high parts of physical block number into ext4_fsblk_t
  */
-static ext4_fsblk_t ext_pblock(struct ext4_extent *ex)
+ext4_fsblk_t ext_pblock(struct ext4_extent *ex)
 {
 	ext4_fsblk_t block;
 
@@ -1417,7 +1417,7 @@ static int ext4_ext_correct_indexes(handle_t *handle, struct inode *inode,
 	return err;
 }
 
-static int
+int
 ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
 				struct ext4_extent *ex2)
 {
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 91e75f7a9e73..bb415408fdb6 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -14,6 +14,7 @@
 #include <linux/compat.h>
 #include <linux/smp_lock.h>
 #include <linux/mount.h>
+#include <linux/file.h>
 #include <asm/uaccess.h>
 #include "ext4_jbd2.h"
 #include "ext4.h"
@@ -213,6 +214,41 @@ setversion_out:
 
 		return err;
 	}
+
+	case EXT4_IOC_MOVE_EXT: {
+		struct move_extent me;
+		struct file *donor_filp;
+		int err;
+
+		if (copy_from_user(&me,
+			(struct move_extent __user *)arg, sizeof(me)))
+			return -EFAULT;
+
+		donor_filp = fget(me.donor_fd);
+		if (!donor_filp)
+			return -EBADF;
+
+		if (!capable(CAP_DAC_OVERRIDE)) {
+			if ((current->real_cred->fsuid != inode->i_uid) ||
+				!(inode->i_mode & S_IRUSR) ||
+				!(donor_filp->f_dentry->d_inode->i_mode &
+				S_IRUSR)) {
+				fput(donor_filp);
+				return -EACCES;
+			}
+		}
+
+		err = ext4_move_extents(filp, donor_filp, me.orig_start,
+					me.donor_start, me.len, &me.moved_len);
+		fput(donor_filp);
+
+		if (!err)
+			if (copy_to_user((struct move_extent *)arg,
+				&me, sizeof(me)))
+				return -EFAULT;
+		return err;
+	}
+
 	case EXT4_IOC_GROUP_ADD: {
 		struct ext4_new_group_data input;
 		struct super_block *sb = inode->i_sb;
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
new file mode 100644
index 000000000000..bbf2dd9404dc
--- /dev/null
+++ b/fs/ext4/move_extent.c
@@ -0,0 +1,1320 @@
+/*
+ * Copyright (c) 2008,2009 NEC Software Tohoku, Ltd.
+ * Written by Takashi Sato <t-sato@yk.jp.nec.com>
+ *            Akira Fujita <a-fujita@rs.jp.nec.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/fs.h>
+#include <linux/quotaops.h>
+#include "ext4_jbd2.h"
+#include "ext4_extents.h"
+#include "ext4.h"
+
+#define get_ext_path(path, inode, block, ret)		\
+	do {								\
+		path = ext4_ext_find_extent(inode, block, path);	\
+		if (IS_ERR(path)) {					\
+			ret = PTR_ERR(path);				\
+			path = NULL;					\
+		}							\
+	} while (0)
+
+/**
+ * copy_extent_status - Copy the extent's initialization status
+ *
+ * @src:	an extent for getting initialize status
+ * @dest:	an extent to be set the status
+ */
+static void
+copy_extent_status(struct ext4_extent *src, struct ext4_extent *dest)
+{
+	if (ext4_ext_is_uninitialized(src))
+		ext4_ext_mark_uninitialized(dest);
+	else
+		dest->ee_len = cpu_to_le16(ext4_ext_get_actual_len(dest));
+}
+
+/**
+ * mext_next_extent - Search for the next extent and set it to "extent"
+ *
+ * @inode:	inode which is searched
+ * @path:	this will obtain data for the next extent
+ * @extent:	pointer to the next extent we have just gotten
+ *
+ * Search the next extent in the array of ext4_ext_path structure (@path)
+ * and set it to ext4_extent structure (@extent). In addition, the member of
+ * @path (->p_ext) also points the next extent. Return 0 on success, 1 if
+ * ext4_ext_path structure refers to the last extent, or a negative error
+ * value on failure.
+ */
+static int
+mext_next_extent(struct inode *inode, struct ext4_ext_path *path,
+		      struct ext4_extent **extent)
+{
+	int ppos, leaf_ppos = path->p_depth;
+
+	ppos = leaf_ppos;
+	if (EXT_LAST_EXTENT(path[ppos].p_hdr) > path[ppos].p_ext) {
+		/* leaf block */
+		*extent = ++path[ppos].p_ext;
+		return 0;
+	}
+
+	while (--ppos >= 0) {
+		if (EXT_LAST_INDEX(path[ppos].p_hdr) >
+		    path[ppos].p_idx) {
+			int cur_ppos = ppos;
+
+			/* index block */
+			path[ppos].p_idx++;
+			path[ppos].p_block = idx_pblock(path[ppos].p_idx);
+			if (path[ppos+1].p_bh)
+				brelse(path[ppos+1].p_bh);
+			path[ppos+1].p_bh =
+				sb_bread(inode->i_sb, path[ppos].p_block);
+			if (!path[ppos+1].p_bh)
+				return -EIO;
+			path[ppos+1].p_hdr =
+				ext_block_hdr(path[ppos+1].p_bh);
+
+			/* Halfway index block */
+			while (++cur_ppos < leaf_ppos) {
+				path[cur_ppos].p_idx =
+					EXT_FIRST_INDEX(path[cur_ppos].p_hdr);
+				path[cur_ppos].p_block =
+					idx_pblock(path[cur_ppos].p_idx);
+				if (path[cur_ppos+1].p_bh)
+					brelse(path[cur_ppos+1].p_bh);
+				path[cur_ppos+1].p_bh = sb_bread(inode->i_sb,
+					path[cur_ppos].p_block);
+				if (!path[cur_ppos+1].p_bh)
+					return -EIO;
+				path[cur_ppos+1].p_hdr =
+					ext_block_hdr(path[cur_ppos+1].p_bh);
+			}
+
+			/* leaf block */
+			path[leaf_ppos].p_ext = *extent =
+				EXT_FIRST_EXTENT(path[leaf_ppos].p_hdr);
+			return 0;
+		}
+	}
+	/* We found the last extent */
+	return 1;
+}
+
+/**
+ * mext_double_down_read - Acquire two inodes' read semaphore
+ *
+ * @orig_inode:		original inode structure
+ * @donor_inode:	donor inode structure
+ * Acquire read semaphore of the two inodes (orig and donor) by i_ino order.
+ */
+static void
+mext_double_down_read(struct inode *orig_inode, struct inode *donor_inode)
+{
+	struct inode *first = orig_inode, *second = donor_inode;
+
+	BUG_ON(orig_inode == NULL || donor_inode == NULL);
+
+	/*
+	 * Use the inode number to provide the stable locking order instead
+	 * of its address, because the C language doesn't guarantee you can
+	 * compare pointers that don't come from the same array.
+	 */
+	if (donor_inode->i_ino < orig_inode->i_ino) {
+		first = donor_inode;
+		second = orig_inode;
+	}
+
+	down_read(&EXT4_I(first)->i_data_sem);
+	down_read(&EXT4_I(second)->i_data_sem);
+}
+
+/**
+ * mext_double_down_write - Acquire two inodes' write semaphore
+ *
+ * @orig_inode:		original inode structure
+ * @donor_inode:	donor inode structure
+ * Acquire write semaphore of the two inodes (orig and donor) by i_ino order.
+ */
+static void
+mext_double_down_write(struct inode *orig_inode, struct inode *donor_inode)
+{
+	struct inode *first = orig_inode, *second = donor_inode;
+
+	BUG_ON(orig_inode == NULL || donor_inode == NULL);
+
+	/*
+	 * Use the inode number to provide the stable locking order instead
+	 * of its address, because the C language doesn't guarantee you can
+	 * compare pointers that don't come from the same array.
+	 */
+	if (donor_inode->i_ino < orig_inode->i_ino) {
+		first = donor_inode;
+		second = orig_inode;
+	}
+
+	down_write(&EXT4_I(first)->i_data_sem);
+	down_write(&EXT4_I(second)->i_data_sem);
+}
+
+/**
+ * mext_double_up_read - Release two inodes' read semaphore
+ *
+ * @orig_inode:		original inode structure to be released its lock first
+ * @donor_inode:	donor inode structure to be released its lock second
+ * Release read semaphore of two inodes (orig and donor).
+ */
+static void
+mext_double_up_read(struct inode *orig_inode, struct inode *donor_inode)
+{
+	BUG_ON(orig_inode == NULL || donor_inode == NULL);
+
+	up_read(&EXT4_I(orig_inode)->i_data_sem);
+	up_read(&EXT4_I(donor_inode)->i_data_sem);
+}
+
+/**
+ * mext_double_up_write - Release two inodes' write semaphore
+ *
+ * @orig_inode:		original inode structure to be released its lock first
+ * @donor_inode:	donor inode structure to be released its lock second
+ * Release write semaphore of two inodes (orig and donor).
+ */
+static void
+mext_double_up_write(struct inode *orig_inode, struct inode *donor_inode)
+{
+	BUG_ON(orig_inode == NULL || donor_inode == NULL);
+
+	up_write(&EXT4_I(orig_inode)->i_data_sem);
+	up_write(&EXT4_I(donor_inode)->i_data_sem);
+}
+
+/**
+ * mext_insert_across_blocks - Insert extents across leaf block
+ *
+ * @handle:		journal handle
+ * @orig_inode:		original inode
+ * @o_start:		first original extent to be changed
+ * @o_end:		last original extent to be changed
+ * @start_ext:		first new extent to be inserted
+ * @new_ext:		middle of new extent to be inserted
+ * @end_ext:		last new extent to be inserted
+ *
+ * Allocate a new leaf block and insert extents into it. Return 0 on success,
+ * or a negative error value on failure.
+ */
+static int
+mext_insert_across_blocks(handle_t *handle, struct inode *orig_inode,
+		struct ext4_extent *o_start, struct ext4_extent *o_end,
+		struct ext4_extent *start_ext, struct ext4_extent *new_ext,
+		struct ext4_extent *end_ext)
+{
+	struct ext4_ext_path *orig_path = NULL;
+	ext4_lblk_t eblock = 0;
+	int new_flag = 0;
+	int end_flag = 0;
+	int err = 0;
+
+	if (start_ext->ee_len && new_ext->ee_len && end_ext->ee_len) {
+		if (o_start == o_end) {
+
+			/*       start_ext   new_ext    end_ext
+			 * donor |---------|-----------|--------|
+			 * orig  |------------------------------|
+			 */
+			end_flag = 1;
+		} else {
+
+			/*       start_ext   new_ext   end_ext
+			 * donor |---------|----------|---------|
+			 * orig  |---------------|--------------|
+			 */
+			o_end->ee_block = end_ext->ee_block;
+			o_end->ee_len = end_ext->ee_len;
+			ext4_ext_store_pblock(o_end, ext_pblock(end_ext));
+		}
+
+		o_start->ee_len = start_ext->ee_len;
+		new_flag = 1;
+
+	} else if (start_ext->ee_len && new_ext->ee_len &&
+		   !end_ext->ee_len && o_start == o_end) {
+
+		/*	 start_ext	new_ext
+		 * donor |--------------|---------------|
+		 * orig  |------------------------------|
+		 */
+		o_start->ee_len = start_ext->ee_len;
+		new_flag = 1;
+
+	} else if (!start_ext->ee_len && new_ext->ee_len &&
+		   end_ext->ee_len && o_start == o_end) {
+
+		/*	  new_ext	end_ext
+		 * donor |--------------|---------------|
+		 * orig  |------------------------------|
+		 */
+		o_end->ee_block = end_ext->ee_block;
+		o_end->ee_len = end_ext->ee_len;
+		ext4_ext_store_pblock(o_end, ext_pblock(end_ext));
+
+		/*
+		 * Set 0 to the extent block if new_ext was
+		 * the first block.
+		 */
+		if (new_ext->ee_block)
+			eblock = le32_to_cpu(new_ext->ee_block);
+
+		new_flag = 1;
+	} else {
+		ext4_debug("ext4 move extent: Unexpected insert case\n");
+		return -EIO;
+	}
+
+	if (new_flag) {
+		get_ext_path(orig_path, orig_inode, eblock, err);
+		if (orig_path == NULL)
+			goto out;
+
+		if (ext4_ext_insert_extent(handle, orig_inode,
+					orig_path, new_ext))
+			goto out;
+	}
+
+	if (end_flag) {
+		get_ext_path(orig_path, orig_inode,
+				      le32_to_cpu(end_ext->ee_block) - 1, err);
+		if (orig_path == NULL)
+			goto out;
+
+		if (ext4_ext_insert_extent(handle, orig_inode,
+					   orig_path, end_ext))
+			goto out;
+	}
+out:
+	if (orig_path) {
+		ext4_ext_drop_refs(orig_path);
+		kfree(orig_path);
+	}
+
+	return err;
+
+}
+
+/**
+ * mext_insert_inside_block - Insert new extent to the extent block
+ *
+ * @o_start:		first original extent to be moved
+ * @o_end:		last original extent to be moved
+ * @start_ext:		first new extent to be inserted
+ * @new_ext:		middle of new extent to be inserted
+ * @end_ext:		last new extent to be inserted
+ * @eh:			extent header of target leaf block
+ * @range_to_move:	used to decide how to insert extent
+ *
+ * Insert extents into the leaf block. The extent (@o_start) is overwritten
+ * by inserted extents.
+ */
+static void
+mext_insert_inside_block(struct ext4_extent *o_start,
+			      struct ext4_extent *o_end,
+			      struct ext4_extent *start_ext,
+			      struct ext4_extent *new_ext,
+			      struct ext4_extent *end_ext,
+			      struct ext4_extent_header *eh,
+			      int range_to_move)
+{
+	int i = 0;
+	unsigned long len;
+
+	/* Move the existing extents */
+	if (range_to_move && o_end < EXT_LAST_EXTENT(eh)) {
+		len = (unsigned long)(EXT_LAST_EXTENT(eh) + 1) -
+			(unsigned long)(o_end + 1);
+		memmove(o_end + 1 + range_to_move, o_end + 1, len);
+	}
+
+	/* Insert start entry */
+	if (start_ext->ee_len)
+		o_start[i++].ee_len = start_ext->ee_len;
+
+	/* Insert new entry */
+	if (new_ext->ee_len) {
+		o_start[i] = *new_ext;
+		ext4_ext_store_pblock(&o_start[i++], ext_pblock(new_ext));
+	}
+
+	/* Insert end entry */
+	if (end_ext->ee_len)
+		o_start[i] = *end_ext;
+
+	/* Increment the total entries counter on the extent block */
+	le16_add_cpu(&eh->eh_entries, range_to_move);
+}
+
+/**
+ * mext_insert_extents - Insert new extent
+ *
+ * @handle:	journal handle
+ * @orig_inode:	original inode
+ * @orig_path:	path indicates first extent to be changed
+ * @o_start:	first original extent to be changed
+ * @o_end:	last original extent to be changed
+ * @start_ext:	first new extent to be inserted
+ * @new_ext:	middle of new extent to be inserted
+ * @end_ext:	last new extent to be inserted
+ *
+ * Call the function to insert extents. If we cannot add more extents into
+ * the leaf block, we call mext_insert_across_blocks() to create a
+ * new leaf block. Otherwise call mext_insert_inside_block(). Return 0
+ * on success, or a negative error value on failure.
+ */
+static int
+mext_insert_extents(handle_t *handle, struct inode *orig_inode,
+			 struct ext4_ext_path *orig_path,
+			 struct ext4_extent *o_start,
+			 struct ext4_extent *o_end,
+			 struct ext4_extent *start_ext,
+			 struct ext4_extent *new_ext,
+			 struct ext4_extent *end_ext)
+{
+	struct  ext4_extent_header *eh;
+	unsigned long need_slots, slots_range;
+	int	range_to_move, depth, ret;
+
+	/*
+	 * The extents need to be inserted
+	 * start_extent + new_extent + end_extent.
+	 */
+	need_slots = (start_ext->ee_len ? 1 : 0) + (end_ext->ee_len ? 1 : 0) +
+		(new_ext->ee_len ? 1 : 0);
+
+	/* The number of slots between start and end */
+	slots_range = ((unsigned long)(o_end + 1) - (unsigned long)o_start + 1)
+		/ sizeof(struct ext4_extent);
+
+	/* Range to move the end of extent */
+	range_to_move = need_slots - slots_range;
+	depth = orig_path->p_depth;
+	orig_path += depth;
+	eh = orig_path->p_hdr;
+
+	if (depth) {
+		/* Register to journal */
+		ret = ext4_journal_get_write_access(handle, orig_path->p_bh);
+		if (ret)
+			return ret;
+	}
+
+	/* Expansion */
+	if (range_to_move > 0 &&
+		(range_to_move > le16_to_cpu(eh->eh_max)
+			- le16_to_cpu(eh->eh_entries))) {
+
+		ret = mext_insert_across_blocks(handle, orig_inode, o_start,
+					o_end, start_ext, new_ext, end_ext);
+		if (ret < 0)
+			return ret;
+	} else
+		mext_insert_inside_block(o_start, o_end, start_ext, new_ext,
+						end_ext, eh, range_to_move);
+
+	if (depth) {
+		ret = ext4_handle_dirty_metadata(handle, orig_inode,
+						 orig_path->p_bh);
+		if (ret)
+			return ret;
+	} else {
+		ret = ext4_mark_inode_dirty(handle, orig_inode);
+		if (ret < 0)
+			return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * mext_leaf_block - Move one leaf extent block into the inode.
+ *
+ * @handle:		journal handle
+ * @orig_inode:		original inode
+ * @orig_path:		path indicates first extent to be changed
+ * @dext:		donor extent
+ * @from:		start offset on the target file
+ *
+ * In order to insert extents into the leaf block, we must divide the extent
+ * in the leaf block into three extents. The one is located to be inserted
+ * extents, and the others are located around it.
+ *
+ * Therefore, this function creates structures to save extents of the leaf
+ * block, and inserts extents by calling mext_insert_extents() with
+ * created extents. Return 0 on success, or a negative error value on failure.
+ */
+static int
+mext_leaf_block(handle_t *handle, struct inode *orig_inode,
+		     struct ext4_ext_path *orig_path, struct ext4_extent *dext,
+		     ext4_lblk_t *from)
+{
+	struct ext4_extent *oext, *o_start, *o_end, *prev_ext;
+	struct ext4_extent new_ext, start_ext, end_ext;
+	ext4_lblk_t new_ext_end;
+	ext4_fsblk_t new_phys_end;
+	int oext_alen, new_ext_alen, end_ext_alen;
+	int depth = ext_depth(orig_inode);
+	int ret;
+
+	o_start = o_end = oext = orig_path[depth].p_ext;
+	oext_alen = ext4_ext_get_actual_len(oext);
+	start_ext.ee_len = end_ext.ee_len = 0;
+
+	new_ext.ee_block = cpu_to_le32(*from);
+	ext4_ext_store_pblock(&new_ext, ext_pblock(dext));
+	new_ext.ee_len = dext->ee_len;
+	new_ext_alen = ext4_ext_get_actual_len(&new_ext);
+	new_ext_end = le32_to_cpu(new_ext.ee_block) + new_ext_alen - 1;
+	new_phys_end = ext_pblock(&new_ext) + new_ext_alen - 1;
+
+	/*
+	 * Case: original extent is first
+	 * oext      |--------|
+	 * new_ext      |--|
+	 * start_ext |--|
+	 */
+	if (le32_to_cpu(oext->ee_block) < le32_to_cpu(new_ext.ee_block) &&
+		le32_to_cpu(new_ext.ee_block) <
+		le32_to_cpu(oext->ee_block) + oext_alen) {
+		start_ext.ee_len = cpu_to_le16(le32_to_cpu(new_ext.ee_block) -
+					       le32_to_cpu(oext->ee_block));
+		copy_extent_status(oext, &start_ext);
+	} else if (oext > EXT_FIRST_EXTENT(orig_path[depth].p_hdr)) {
+		prev_ext = oext - 1;
+		/*
+		 * We can merge new_ext into previous extent,
+		 * if these are contiguous and same extent type.
+		 */
+		if (ext4_can_extents_be_merged(orig_inode, prev_ext,
+					       &new_ext)) {
+			o_start = prev_ext;
+			start_ext.ee_len = cpu_to_le16(
+				ext4_ext_get_actual_len(prev_ext) +
+				new_ext_alen);
+			copy_extent_status(prev_ext, &start_ext);
+			new_ext.ee_len = 0;
+		}
+	}
+
+	/*
+	 * Case: new_ext_end must be less than oext
+	 * oext      |-----------|
+	 * new_ext       |-------|
+	 */
+	BUG_ON(le32_to_cpu(oext->ee_block) + oext_alen - 1 < new_ext_end);
+
+	/*
+	 * Case: new_ext is smaller than original extent
+	 * oext    |---------------|
+	 * new_ext |-----------|
+	 * end_ext             |---|
+	 */
+	if (le32_to_cpu(oext->ee_block) <= new_ext_end &&
+		new_ext_end < le32_to_cpu(oext->ee_block) + oext_alen - 1) {
+		end_ext.ee_len =
+			cpu_to_le16(le32_to_cpu(oext->ee_block) +
+			oext_alen - 1 - new_ext_end);
+		copy_extent_status(oext, &end_ext);
+		end_ext_alen = ext4_ext_get_actual_len(&end_ext);
+		ext4_ext_store_pblock(&end_ext,
+			(ext_pblock(o_end) + oext_alen - end_ext_alen));
+		end_ext.ee_block =
+			cpu_to_le32(le32_to_cpu(o_end->ee_block) +
+			oext_alen - end_ext_alen);
+	}
+
+	ret = mext_insert_extents(handle, orig_inode, orig_path, o_start,
+				o_end, &start_ext, &new_ext, &end_ext);
+	return ret;
+}
+
+/**
+ * mext_calc_swap_extents - Calculate extents for extent swapping.
+ *
+ * @tmp_dext:		the extent that will belong to the original inode
+ * @tmp_oext:		the extent that will belong to the donor inode
+ * @orig_off:		block offset of original inode
+ * @donor_off:		block offset of donor inode
+ * @max_count:		the maximun length of extents
+ */
+static void
+mext_calc_swap_extents(struct ext4_extent *tmp_dext,
+			      struct ext4_extent *tmp_oext,
+			      ext4_lblk_t orig_off, ext4_lblk_t donor_off,
+			      ext4_lblk_t max_count)
+{
+	ext4_lblk_t diff, orig_diff;
+	struct ext4_extent dext_old, oext_old;
+
+	dext_old = *tmp_dext;
+	oext_old = *tmp_oext;
+
+	/* When tmp_dext is too large, pick up the target range. */
+	diff = donor_off - le32_to_cpu(tmp_dext->ee_block);
+
+	ext4_ext_store_pblock(tmp_dext, ext_pblock(tmp_dext) + diff);
+	tmp_dext->ee_block =
+			cpu_to_le32(le32_to_cpu(tmp_dext->ee_block) + diff);
+	tmp_dext->ee_len = cpu_to_le16(le16_to_cpu(tmp_dext->ee_len) - diff);
+
+	if (max_count < ext4_ext_get_actual_len(tmp_dext))
+		tmp_dext->ee_len = cpu_to_le16(max_count);
+
+	orig_diff = orig_off - le32_to_cpu(tmp_oext->ee_block);
+	ext4_ext_store_pblock(tmp_oext, ext_pblock(tmp_oext) + orig_diff);
+
+	/* Adjust extent length if donor extent is larger than orig */
+	if (ext4_ext_get_actual_len(tmp_dext) >
+	    ext4_ext_get_actual_len(tmp_oext) - orig_diff)
+		tmp_dext->ee_len = cpu_to_le16(le16_to_cpu(tmp_oext->ee_len) -
+						orig_diff);
+
+	tmp_oext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(tmp_dext));
+
+	copy_extent_status(&oext_old, tmp_dext);
+	copy_extent_status(&dext_old, tmp_oext);
+}
+
+/**
+ * mext_replace_branches - Replace original extents with new extents
+ *
+ * @handle:		journal handle
+ * @orig_inode:		original inode
+ * @donor_inode:	donor inode
+ * @from:		block offset of orig_inode
+ * @count:		block count to be replaced
+ *
+ * Replace original inode extents and donor inode extents page by page.
+ * We implement this replacement in the following three steps:
+ * 1. Save the block information of original and donor inodes into
+ *    dummy extents.
+ * 2. Change the block information of original inode to point at the
+ *    donor inode blocks.
+ * 3. Change the block information of donor inode to point at the saved
+ *    original inode blocks in the dummy extents.
+ *
+ * Return 0 on success, or a negative error value on failure.
+ */
+static int
+mext_replace_branches(handle_t *handle, struct inode *orig_inode,
+			   struct inode *donor_inode, ext4_lblk_t from,
+			   ext4_lblk_t count)
+{
+	struct ext4_ext_path *orig_path = NULL;
+	struct ext4_ext_path *donor_path = NULL;
+	struct ext4_extent *oext, *dext;
+	struct ext4_extent tmp_dext, tmp_oext;
+	ext4_lblk_t orig_off = from, donor_off = from;
+	int err = 0;
+	int depth;
+	int replaced_count = 0;
+	int dext_alen;
+
+	mext_double_down_write(orig_inode, donor_inode);
+
+	/* Get the original extent for the block "orig_off" */
+	get_ext_path(orig_path, orig_inode, orig_off, err);
+	if (orig_path == NULL)
+		goto out;
+
+	/* Get the donor extent for the head */
+	get_ext_path(donor_path, donor_inode, donor_off, err);
+	if (donor_path == NULL)
+		goto out;
+	depth = ext_depth(orig_inode);
+	oext = orig_path[depth].p_ext;
+	tmp_oext = *oext;
+
+	depth = ext_depth(donor_inode);
+	dext = donor_path[depth].p_ext;
+	tmp_dext = *dext;
+
+	mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
+				      donor_off, count);
+
+	/* Loop for the donor extents */
+	while (1) {
+		/* The extent for donor must be found. */
+		BUG_ON(!dext || donor_off != le32_to_cpu(tmp_dext.ee_block));
+
+		/* Set donor extent to orig extent */
+		err = mext_leaf_block(handle, orig_inode,
+					   orig_path, &tmp_dext, &orig_off);
+		if (err < 0)
+			goto out;
+
+		/* Set orig extent to donor extent */
+		err = mext_leaf_block(handle, donor_inode,
+					   donor_path, &tmp_oext, &donor_off);
+		if (err < 0)
+			goto out;
+
+		dext_alen = ext4_ext_get_actual_len(&tmp_dext);
+		replaced_count += dext_alen;
+		donor_off += dext_alen;
+		orig_off += dext_alen;
+
+		/* Already moved the expected blocks */
+		if (replaced_count >= count)
+			break;
+
+		if (orig_path)
+			ext4_ext_drop_refs(orig_path);
+		get_ext_path(orig_path, orig_inode, orig_off, err);
+		if (orig_path == NULL)
+			goto out;
+		depth = ext_depth(orig_inode);
+		oext = orig_path[depth].p_ext;
+		if (le32_to_cpu(oext->ee_block) +
+				ext4_ext_get_actual_len(oext) <= orig_off) {
+			err = 0;
+			goto out;
+		}
+		tmp_oext = *oext;
+
+		if (donor_path)
+			ext4_ext_drop_refs(donor_path);
+		get_ext_path(donor_path, donor_inode,
+				      donor_off, err);
+		if (donor_path == NULL)
+			goto out;
+		depth = ext_depth(donor_inode);
+		dext = donor_path[depth].p_ext;
+		if (le32_to_cpu(dext->ee_block) +
+				ext4_ext_get_actual_len(dext) <= donor_off) {
+			err = 0;
+			goto out;
+		}
+		tmp_dext = *dext;
+
+		mext_calc_swap_extents(&tmp_dext, &tmp_oext, orig_off,
+					      donor_off,
+					      count - replaced_count);
+	}
+
+out:
+	if (orig_path) {
+		ext4_ext_drop_refs(orig_path);
+		kfree(orig_path);
+	}
+	if (donor_path) {
+		ext4_ext_drop_refs(donor_path);
+		kfree(donor_path);
+	}
+
+	mext_double_up_write(orig_inode, donor_inode);
+	return err;
+}
+
+/**
+ * move_extent_per_page - Move extent data per page
+ *
+ * @o_filp:			file structure of original file
+ * @donor_inode:		donor inode
+ * @orig_page_offset:		page index on original file
+ * @data_offset_in_page:	block index where data swapping starts
+ * @block_len_in_page:		the number of blocks to be swapped
+ * @uninit:			orig extent is uninitialized or not
+ *
+ * Save the data in original inode blocks and replace original inode extents
+ * with donor inode extents by calling mext_replace_branches().
+ * Finally, write out the saved data in new original inode blocks. Return 0
+ * on success, or a negative error value on failure.
+ */
+static int
+move_extent_par_page(struct file *o_filp, struct inode *donor_inode,
+		  pgoff_t orig_page_offset, int data_offset_in_page,
+		  int block_len_in_page, int uninit)
+{
+	struct inode *orig_inode = o_filp->f_dentry->d_inode;
+	struct address_space *mapping = orig_inode->i_mapping;
+	struct buffer_head *bh;
+	struct page *page = NULL;
+	const struct address_space_operations *a_ops = mapping->a_ops;
+	handle_t *handle;
+	ext4_lblk_t orig_blk_offset;
+	long long offs = orig_page_offset << PAGE_CACHE_SHIFT;
+	unsigned long blocksize = orig_inode->i_sb->s_blocksize;
+	unsigned int w_flags = 0;
+	unsigned int tmp_data_len, data_len;
+	void *fsdata;
+	int ret, i, jblocks;
+	int blocks_per_page = PAGE_CACHE_SIZE >> orig_inode->i_blkbits;
+
+	/*
+	 * It needs twice the amount of ordinary journal buffers because
+	 * inode and donor_inode may change each different metadata blocks.
+	 */
+	jblocks = ext4_writepage_trans_blocks(orig_inode) * 2;
+	handle = ext4_journal_start(orig_inode, jblocks);
+	if (IS_ERR(handle)) {
+		ret = PTR_ERR(handle);
+		return ret;
+	}
+
+	if (segment_eq(get_fs(), KERNEL_DS))
+		w_flags |= AOP_FLAG_UNINTERRUPTIBLE;
+
+	orig_blk_offset = orig_page_offset * blocks_per_page +
+		data_offset_in_page;
+
+	/*
+	 * If orig extent is uninitialized one,
+	 * it's not necessary force the page into memory
+	 * and then force it to be written out again.
+	 * Just swap data blocks between orig and donor.
+	 */
+	if (uninit) {
+		ret = mext_replace_branches(handle, orig_inode,
+						 donor_inode, orig_blk_offset,
+						 block_len_in_page);
+
+		/* Clear the inode cache not to refer to the old data */
+		ext4_ext_invalidate_cache(orig_inode);
+		ext4_ext_invalidate_cache(donor_inode);
+		goto out2;
+	}
+
+	offs = (long long)orig_blk_offset << orig_inode->i_blkbits;
+
+	/* Calculate data_len */
+	if ((orig_blk_offset + block_len_in_page - 1) ==
+	    ((orig_inode->i_size - 1) >> orig_inode->i_blkbits)) {
+		/* Replace the last block */
+		tmp_data_len = orig_inode->i_size & (blocksize - 1);
+		/*
+		 * If data_len equal zero, it shows data_len is multiples of
+		 * blocksize. So we set appropriate value.
+		 */
+		if (tmp_data_len == 0)
+			tmp_data_len = blocksize;
+
+		data_len = tmp_data_len +
+			((block_len_in_page - 1) << orig_inode->i_blkbits);
+	} else {
+		data_len = block_len_in_page << orig_inode->i_blkbits;
+	}
+
+	ret = a_ops->write_begin(o_filp, mapping, offs, data_len, w_flags,
+				 &page, &fsdata);
+	if (unlikely(ret < 0))
+		goto out;
+
+	if (!PageUptodate(page)) {
+		mapping->a_ops->readpage(o_filp, page);
+		lock_page(page);
+	}
+
+	/*
+	 * try_to_release_page() doesn't call releasepage in writeback mode.
+	 * We should care about the order of writing to the same file
+	 * by multiple move extent processes.
+	 * It needs to call wait_on_page_writeback() to wait for the
+	 * writeback of the page.
+	 */
+	if (PageWriteback(page))
+		wait_on_page_writeback(page);
+
+	/* Release old bh and drop refs */
+	try_to_release_page(page, 0);
+
+	ret = mext_replace_branches(handle, orig_inode, donor_inode,
+					 orig_blk_offset, block_len_in_page);
+	if (ret < 0)
+		goto out;
+
+	/* Clear the inode cache not to refer to the old data */
+	ext4_ext_invalidate_cache(orig_inode);
+	ext4_ext_invalidate_cache(donor_inode);
+
+	if (!page_has_buffers(page))
+		create_empty_buffers(page, 1 << orig_inode->i_blkbits, 0);
+
+	bh = page_buffers(page);
+	for (i = 0; i < data_offset_in_page; i++)
+		bh = bh->b_this_page;
+
+	for (i = 0; i < block_len_in_page; i++) {
+		ret = ext4_get_block(orig_inode,
+				(sector_t)(orig_blk_offset + i), bh, 0);
+		if (ret < 0)
+			goto out;
+
+		if (bh->b_this_page != NULL)
+			bh = bh->b_this_page;
+	}
+
+	ret = a_ops->write_end(o_filp, mapping, offs, data_len, data_len,
+			       page, fsdata);
+	page = NULL;
+
+out:
+	if (unlikely(page)) {
+		if (PageLocked(page))
+			unlock_page(page);
+		page_cache_release(page);
+	}
+out2:
+	ext4_journal_stop(handle);
+
+	return ret < 0 ? ret : 0;
+}
+
+/**
+ * mext_check_argumants - Check whether move extent can be done
+ *
+ * @orig_inode:		original inode
+ * @donor_inode:	donor inode
+ * @orig_start:		logical start offset in block for orig
+ * @donor_start:	logical start offset in block for donor
+ * @len:		the number of blocks to be moved
+ * @moved_len:		moved block length
+ *
+ * Check the arguments of ext4_move_extents() whether the files can be
+ * exchanged with each other.
+ * Return 0 on success, or a negative error value on failure.
+ */
+static int
+mext_check_arguments(struct inode *orig_inode,
+			  struct inode *donor_inode, __u64 orig_start,
+			  __u64 donor_start, __u64 *len, __u64 moved_len)
+{
+	/* Regular file check */
+	if (!S_ISREG(orig_inode->i_mode) || !S_ISREG(donor_inode->i_mode)) {
+		ext4_debug("ext4 move extent: The argument files should be "
+			"regular file [ino:orig %lu, donor %lu]\n",
+			orig_inode->i_ino, donor_inode->i_ino);
+		return -EINVAL;
+	}
+
+	/* Ext4 move extent does not support swapfile */
+	if (IS_SWAPFILE(orig_inode) || IS_SWAPFILE(donor_inode)) {
+		ext4_debug("ext4 move extent: The argument files should "
+			"not be swapfile [ino:orig %lu, donor %lu]\n",
+			orig_inode->i_ino, donor_inode->i_ino);
+		return -EINVAL;
+	}
+
+	/* Files should be in the same ext4 FS */
+	if (orig_inode->i_sb != donor_inode->i_sb) {
+		ext4_debug("ext4 move extent: The argument files "
+			"should be in same FS [ino:orig %lu, donor %lu]\n",
+			orig_inode->i_ino, donor_inode->i_ino);
+		return -EINVAL;
+	}
+
+	/* orig and donor should be different file */
+	if (orig_inode->i_ino == donor_inode->i_ino) {
+		ext4_debug("ext4 move extent: The argument files should not "
+			"be same file [ino:orig %lu, donor %lu]\n",
+			orig_inode->i_ino, donor_inode->i_ino);
+		return -EINVAL;
+	}
+
+	/* Ext4 move extent supports only extent based file */
+	if (!(EXT4_I(orig_inode)->i_flags & EXT4_EXTENTS_FL)) {
+		ext4_debug("ext4 move extent: orig file is not extents "
+			"based file [ino:orig %lu]\n", orig_inode->i_ino);
+		return -EOPNOTSUPP;
+	} else if (!(EXT4_I(donor_inode)->i_flags & EXT4_EXTENTS_FL)) {
+		ext4_debug("ext4 move extent: donor file is not extents "
+			"based file [ino:donor %lu]\n", donor_inode->i_ino);
+		return -EOPNOTSUPP;
+	}
+
+	if ((!orig_inode->i_size) || (!donor_inode->i_size)) {
+		ext4_debug("ext4 move extent: File size is 0 byte\n");
+		return -EINVAL;
+	}
+
+	/* Start offset should be same */
+	if (orig_start != donor_start) {
+		ext4_debug("ext4 move extent: orig and donor's start "
+			"offset are not same [ino:orig %lu, donor %lu]\n",
+			orig_inode->i_ino, donor_inode->i_ino);
+		return -EINVAL;
+	}
+
+	if (moved_len) {
+		ext4_debug("ext4 move extent: moved_len should be 0 "
+			"[ino:orig %lu, donor %lu]\n", orig_inode->i_ino,
+			donor_inode->i_ino);
+		return -EINVAL;
+	}
+
+	if ((orig_start > MAX_DEFRAG_SIZE) ||
+	    (donor_start > MAX_DEFRAG_SIZE) ||
+	    (*len > MAX_DEFRAG_SIZE) ||
+	    (orig_start + *len > MAX_DEFRAG_SIZE))  {
+		ext4_debug("ext4 move extent: Can't handle over [%lu] blocks "
+			"[ino:orig %lu, donor %lu]\n", MAX_DEFRAG_SIZE,
+			orig_inode->i_ino, donor_inode->i_ino);
+		return -EINVAL;
+	}
+
+	if (orig_inode->i_size > donor_inode->i_size) {
+		if (orig_start >= donor_inode->i_size) {
+			ext4_debug("ext4 move extent: orig start offset "
+			"[%llu] should be less than donor file size "
+			"[%lld] [ino:orig %lu, donor_inode %lu]\n",
+			orig_start, donor_inode->i_size,
+			orig_inode->i_ino, donor_inode->i_ino);
+			return -EINVAL;
+		}
+
+		if (orig_start + *len > donor_inode->i_size) {
+			ext4_debug("ext4 move extent: End offset [%llu] should "
+				"be less than donor file size [%lld]."
+				"So adjust length from %llu to %lld "
+				"[ino:orig %lu, donor %lu]\n",
+				orig_start + *len, donor_inode->i_size,
+				*len, donor_inode->i_size - orig_start,
+				orig_inode->i_ino, donor_inode->i_ino);
+			*len = donor_inode->i_size - orig_start;
+		}
+	} else {
+		if (orig_start >= orig_inode->i_size) {
+			ext4_debug("ext4 move extent: start offset [%llu] "
+				"should be less than original file size "
+				"[%lld] [inode:orig %lu, donor %lu]\n",
+				 orig_start, orig_inode->i_size,
+				orig_inode->i_ino, donor_inode->i_ino);
+			return -EINVAL;
+		}
+
+		if (orig_start + *len > orig_inode->i_size) {
+			ext4_debug("ext4 move extent: Adjust length "
+				"from %llu to %lld. Because it should be "
+				"less than original file size "
+				"[ino:orig %lu, donor %lu]\n",
+				*len, orig_inode->i_size - orig_start,
+				orig_inode->i_ino, donor_inode->i_ino);
+			*len = orig_inode->i_size - orig_start;
+		}
+	}
+
+	if (!*len) {
+		ext4_debug("ext4 move extent: len shoudld not be 0 "
+			"[ino:orig %lu, donor %lu]\n", orig_inode->i_ino,
+			donor_inode->i_ino);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * mext_inode_double_lock - Lock i_mutex on both @inode1 and @inode2
+ *
+ * @inode1:	the inode structure
+ * @inode2:	the inode structure
+ *
+ * Lock two inodes' i_mutex by i_ino order. This function is moved from
+ * fs/inode.c.
+ */
+static void
+mext_inode_double_lock(struct inode *inode1, struct inode *inode2)
+{
+	if (inode1 == NULL || inode2 == NULL || inode1 == inode2) {
+		if (inode1)
+			mutex_lock(&inode1->i_mutex);
+		else if (inode2)
+			mutex_lock(&inode2->i_mutex);
+		return;
+	}
+
+	if (inode1->i_ino < inode2->i_ino) {
+		mutex_lock_nested(&inode1->i_mutex, I_MUTEX_PARENT);
+		mutex_lock_nested(&inode2->i_mutex, I_MUTEX_CHILD);
+	} else {
+		mutex_lock_nested(&inode2->i_mutex, I_MUTEX_PARENT);
+		mutex_lock_nested(&inode1->i_mutex, I_MUTEX_CHILD);
+	}
+}
+
+/**
+ * mext_inode_double_unlock - Release i_mutex on both @inode1 and @inode2
+ *
+ * @inode1:     the inode that is released first
+ * @inode2:     the inode that is released second
+ *
+ * This function is moved from fs/inode.c.
+ */
+
+static void
+mext_inode_double_unlock(struct inode *inode1, struct inode *inode2)
+{
+	if (inode1)
+		mutex_unlock(&inode1->i_mutex);
+
+	if (inode2 && inode2 != inode1)
+		mutex_unlock(&inode2->i_mutex);
+}
+
+/**
+ * ext4_move_extents - Exchange the specified range of a file
+ *
+ * @o_filp:		file structure of the original file
+ * @d_filp:		file structure of the donor file
+ * @orig_start:		start offset in block for orig
+ * @donor_start:	start offset in block for donor
+ * @len:		the number of blocks to be moved
+ * @moved_len:		moved block length
+ *
+ * This function returns 0 and moved block length is set in moved_len
+ * if succeed, otherwise returns error value.
+ *
+ * Note: ext4_move_extents() proceeds the following order.
+ * 1:ext4_move_extents() calculates the last block number of moving extent
+ *   function by the start block number (orig_start) and the number of blocks
+ *   to be moved (len) specified as arguments.
+ *   If the {orig, donor}_start points a hole, the extent's start offset
+ *   pointed by ext_cur (current extent), holecheck_path, orig_path are set
+ *   after hole behind.
+ * 2:Continue step 3 to step 5, until the holecheck_path points to last_extent
+ *   or the ext_cur exceeds the block_end which is last logical block number.
+ * 3:To get the length of continues area, call mext_next_extent()
+ *   specified with the ext_cur (initial value is holecheck_path) re-cursive,
+ *   until find un-continuous extent, the start logical block number exceeds
+ *   the block_end or the extent points to the last extent.
+ * 4:Exchange the original inode data with donor inode data
+ *   from orig_page_offset to seq_end_page.
+ *   The start indexes of data are specified as arguments.
+ *   That of the original inode is orig_page_offset,
+ *   and the donor inode is also orig_page_offset
+ *   (To easily handle blocksize != pagesize case, the offset for the
+ *   donor inode is block unit).
+ * 5:Update holecheck_path and orig_path to points a next proceeding extent,
+ *   then returns to step 2.
+ * 6:Release holecheck_path, orig_path and set the len to moved_len
+ *   which shows the number of moved blocks.
+ *   The moved_len is useful for the command to calculate the file offset
+ *   for starting next move extent ioctl.
+ * 7:Return 0 on success, or a negative error value on failure.
+ */
+int
+ext4_move_extents(struct file *o_filp, struct file *d_filp,
+		 __u64 orig_start, __u64 donor_start, __u64 len,
+		 __u64 *moved_len)
+{
+	struct inode *orig_inode = o_filp->f_dentry->d_inode;
+	struct inode *donor_inode = d_filp->f_dentry->d_inode;
+	struct ext4_ext_path *orig_path = NULL, *holecheck_path = NULL;
+	struct ext4_extent *ext_prev, *ext_cur, *ext_dummy;
+	ext4_lblk_t block_start = orig_start;
+	ext4_lblk_t block_end, seq_start, add_blocks, file_end, seq_blocks = 0;
+	ext4_lblk_t rest_blocks;
+	pgoff_t orig_page_offset = 0, seq_end_page;
+	int ret, depth, last_extent = 0;
+	int blocks_per_page = PAGE_CACHE_SIZE >> orig_inode->i_blkbits;
+	int data_offset_in_page;
+	int block_len_in_page;
+	int uninit;
+
+	/* protect orig and donor against a truncate */
+	mext_inode_double_lock(orig_inode, donor_inode);
+
+	mext_double_down_read(orig_inode, donor_inode);
+	/* Check the filesystem environment whether move_extent can be done */
+	ret = mext_check_arguments(orig_inode, donor_inode, orig_start,
+					donor_start, &len, *moved_len);
+	mext_double_up_read(orig_inode, donor_inode);
+	if (ret)
+		goto out2;
+
+	file_end = (i_size_read(orig_inode) - 1) >> orig_inode->i_blkbits;
+	block_end = block_start + len - 1;
+	if (file_end < block_end)
+		len -= block_end - file_end;
+
+	get_ext_path(orig_path, orig_inode, block_start, ret);
+	if (orig_path == NULL)
+		goto out2;
+
+	/* Get path structure to check the hole */
+	get_ext_path(holecheck_path, orig_inode, block_start, ret);
+	if (holecheck_path == NULL)
+		goto out;
+
+	depth = ext_depth(orig_inode);
+	ext_cur = holecheck_path[depth].p_ext;
+	if (ext_cur == NULL) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/*
+	 * Get proper extent whose ee_block is beyond block_start
+	 * if block_start was within the hole.
+	 */
+	if (le32_to_cpu(ext_cur->ee_block) +
+		ext4_ext_get_actual_len(ext_cur) - 1 < block_start) {
+		last_extent = mext_next_extent(orig_inode,
+					holecheck_path, &ext_cur);
+		if (last_extent < 0) {
+			ret = last_extent;
+			goto out;
+		}
+		last_extent = mext_next_extent(orig_inode, orig_path,
+							&ext_dummy);
+		if (last_extent < 0) {
+			ret = last_extent;
+			goto out;
+		}
+	}
+	seq_start = block_start;
+
+	/* No blocks within the specified range. */
+	if (le32_to_cpu(ext_cur->ee_block) > block_end) {
+		ext4_debug("ext4 move extent: The specified range of file "
+							"may be the hole\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* Adjust start blocks */
+	add_blocks = min(le32_to_cpu(ext_cur->ee_block) +
+			 ext4_ext_get_actual_len(ext_cur), block_end + 1) -
+		     max(le32_to_cpu(ext_cur->ee_block), block_start);
+
+	while (!last_extent && le32_to_cpu(ext_cur->ee_block) <= block_end) {
+		seq_blocks += add_blocks;
+
+		/* Adjust tail blocks */
+		if (seq_start + seq_blocks - 1 > block_end)
+			seq_blocks = block_end - seq_start + 1;
+
+		ext_prev = ext_cur;
+		last_extent = mext_next_extent(orig_inode, holecheck_path,
+						&ext_cur);
+		if (last_extent < 0) {
+			ret = last_extent;
+			break;
+		}
+		add_blocks = ext4_ext_get_actual_len(ext_cur);
+
+		/*
+		 * Extend the length of contiguous block (seq_blocks)
+		 * if extents are contiguous.
+		 */
+		if (ext4_can_extents_be_merged(orig_inode,
+					       ext_prev, ext_cur) &&
+		    block_end >= le32_to_cpu(ext_cur->ee_block) &&
+		    !last_extent)
+			continue;
+
+		/* Is original extent is uninitialized */
+		uninit = ext4_ext_is_uninitialized(ext_prev);
+
+		data_offset_in_page = seq_start % blocks_per_page;
+
+		/*
+		 * Calculate data blocks count that should be swapped
+		 * at the first page.
+		 */
+		if (data_offset_in_page + seq_blocks > blocks_per_page) {
+			/* Swapped blocks are across pages */
+			block_len_in_page =
+					blocks_per_page - data_offset_in_page;
+		} else {
+			/* Swapped blocks are in a page */
+			block_len_in_page = seq_blocks;
+		}
+
+		orig_page_offset = seq_start >>
+				(PAGE_CACHE_SHIFT - orig_inode->i_blkbits);
+		seq_end_page = (seq_start + seq_blocks - 1) >>
+				(PAGE_CACHE_SHIFT - orig_inode->i_blkbits);
+		seq_start = le32_to_cpu(ext_cur->ee_block);
+		rest_blocks = seq_blocks;
+
+		/* Discard preallocations of two inodes */
+		down_write(&EXT4_I(orig_inode)->i_data_sem);
+		ext4_discard_preallocations(orig_inode);
+		up_write(&EXT4_I(orig_inode)->i_data_sem);
+
+		down_write(&EXT4_I(donor_inode)->i_data_sem);
+		ext4_discard_preallocations(donor_inode);
+		up_write(&EXT4_I(donor_inode)->i_data_sem);
+
+		while (orig_page_offset <= seq_end_page) {
+
+			/* Swap original branches with new branches */
+			ret = move_extent_par_page(o_filp, donor_inode,
+						orig_page_offset,
+						data_offset_in_page,
+						block_len_in_page, uninit);
+			if (ret < 0)
+				goto out;
+			orig_page_offset++;
+			/* Count how many blocks we have exchanged */
+			*moved_len += block_len_in_page;
+			BUG_ON(*moved_len > len);
+
+			data_offset_in_page = 0;
+			rest_blocks -= block_len_in_page;
+			if (rest_blocks > blocks_per_page)
+				block_len_in_page = blocks_per_page;
+			else
+				block_len_in_page = rest_blocks;
+		}
+
+		/* Decrease buffer counter */
+		if (holecheck_path)
+			ext4_ext_drop_refs(holecheck_path);
+		get_ext_path(holecheck_path, orig_inode,
+				      seq_start, ret);
+		if (holecheck_path == NULL)
+			break;
+		depth = holecheck_path->p_depth;
+
+		/* Decrease buffer counter */
+		if (orig_path)
+			ext4_ext_drop_refs(orig_path);
+		get_ext_path(orig_path, orig_inode, seq_start, ret);
+		if (orig_path == NULL)
+			break;
+
+		ext_cur = holecheck_path[depth].p_ext;
+		add_blocks = ext4_ext_get_actual_len(ext_cur);
+		seq_blocks = 0;
+
+	}
+out:
+	if (orig_path) {
+		ext4_ext_drop_refs(orig_path);
+		kfree(orig_path);
+	}
+	if (holecheck_path) {
+		ext4_ext_drop_refs(holecheck_path);
+		kfree(holecheck_path);
+	}
+out2:
+	mext_inode_double_unlock(orig_inode, donor_inode);
+
+	if (ret)
+		return ret;
+
+	/* All of the specified blocks must be exchanged in succeed */
+	BUG_ON(*moved_len != len);
+
+	return 0;
+}