diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 11f7cf9..f04c7aa 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -1111,17 +1111,16 @@
 	return ret;
 }
 
-static int ocfs2_write_remove_suid(struct inode *inode)
+static int __ocfs2_write_remove_suid(struct inode *inode,
+				     struct buffer_head *bh)
 {
 	int ret;
-	struct buffer_head *bh = NULL;
-	struct ocfs2_inode_info *oi = OCFS2_I(inode);
 	handle_t *handle;
 	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
 	struct ocfs2_dinode *di;
 
 	mlog_entry("(Inode %llu, mode 0%o)\n",
-		   (unsigned long long)oi->ip_blkno, inode->i_mode);
+		   (unsigned long long)OCFS2_I(inode)->ip_blkno, inode->i_mode);
 
 	handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
 	if (handle == NULL) {
@@ -1130,17 +1129,11 @@
 		goto out;
 	}
 
-	ret = ocfs2_read_block(osb, oi->ip_blkno, &bh, OCFS2_BH_CACHED, inode);
-	if (ret < 0) {
-		mlog_errno(ret);
-		goto out_trans;
-	}
-
 	ret = ocfs2_journal_access(handle, inode, bh,
 				   OCFS2_JOURNAL_ACCESS_WRITE);
 	if (ret < 0) {
 		mlog_errno(ret);
-		goto out_bh;
+		goto out_trans;
 	}
 
 	inode->i_mode &= ~S_ISUID;
@@ -1153,8 +1146,7 @@
 	ret = ocfs2_journal_dirty(handle, bh);
 	if (ret < 0)
 		mlog_errno(ret);
-out_bh:
-	brelse(bh);
+
 out_trans:
 	ocfs2_commit_trans(osb, handle);
 out:
@@ -1200,6 +1192,25 @@
 	return ret;
 }
 
+static int ocfs2_write_remove_suid(struct inode *inode)
+{
+	int ret;
+	struct buffer_head *bh = NULL;
+	struct ocfs2_inode_info *oi = OCFS2_I(inode);
+
+	ret = ocfs2_read_block(OCFS2_SB(inode->i_sb),
+			       oi->ip_blkno, &bh, OCFS2_BH_CACHED, inode);
+	if (ret < 0) {
+		mlog_errno(ret);
+		goto out;
+	}
+
+	ret =  __ocfs2_write_remove_suid(inode, bh);
+out:
+	brelse(bh);
+	return ret;
+}
+
 /*
  * Allocate enough extents to cover the region starting at byte offset
  * start for len bytes. Existing extents are skipped, any extents
@@ -1490,6 +1501,151 @@
 	return ret;
 }
 
+/*
+ * Parts of this function taken from xfs_change_file_space()
+ */
+int ocfs2_change_file_space(struct file *file, unsigned int cmd,
+			    struct ocfs2_space_resv *sr)
+{
+	int ret;
+	s64 llen;
+	struct inode *inode = file->f_path.dentry->d_inode;
+	struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
+	struct buffer_head *di_bh = NULL;
+	handle_t *handle;
+	unsigned long long max_off = ocfs2_max_file_offset(inode->i_sb->s_blocksize_bits);
+
+	if ((cmd == OCFS2_IOC_RESVSP || cmd == OCFS2_IOC_RESVSP64) &&
+	    !ocfs2_writes_unwritten_extents(osb))
+		return -ENOTTY;
+	else if ((cmd == OCFS2_IOC_UNRESVSP || cmd == OCFS2_IOC_UNRESVSP64) &&
+		 !ocfs2_sparse_alloc(osb))
+		return -ENOTTY;
+
+	if (!S_ISREG(inode->i_mode))
+		return -EINVAL;
+
+	if (!(file->f_mode & FMODE_WRITE))
+		return -EBADF;
+
+	if (ocfs2_is_hard_readonly(osb) || ocfs2_is_soft_readonly(osb))
+		return -EROFS;
+
+	mutex_lock(&inode->i_mutex);
+
+	/*
+	 * This prevents concurrent writes on other nodes
+	 */
+	ret = ocfs2_rw_lock(inode, 1);
+	if (ret) {
+		mlog_errno(ret);
+		goto out;
+	}
+
+	ret = ocfs2_meta_lock(inode, &di_bh, 1);
+	if (ret) {
+		mlog_errno(ret);
+		goto out_rw_unlock;
+	}
+
+	if (inode->i_flags & (S_IMMUTABLE|S_APPEND)) {
+		ret = -EPERM;
+		goto out_meta_unlock;
+	}
+
+	switch (sr->l_whence) {
+	case 0: /*SEEK_SET*/
+		break;
+	case 1: /*SEEK_CUR*/
+		sr->l_start += file->f_pos;
+		break;
+	case 2: /*SEEK_END*/
+		sr->l_start += i_size_read(inode);
+		break;
+	default:
+		ret = -EINVAL;
+		goto out_meta_unlock;
+	}
+	sr->l_whence = 0;
+
+	llen = sr->l_len > 0 ? sr->l_len - 1 : sr->l_len;
+
+	if (sr->l_start < 0
+	    || sr->l_start > max_off
+	    || (sr->l_start + llen) < 0
+	    || (sr->l_start + llen) > max_off) {
+		ret = -EINVAL;
+		goto out_meta_unlock;
+	}
+
+	if (cmd == OCFS2_IOC_RESVSP || cmd == OCFS2_IOC_RESVSP64) {
+		if (sr->l_len <= 0) {
+			ret = -EINVAL;
+			goto out_meta_unlock;
+		}
+	}
+
+	if (should_remove_suid(file->f_path.dentry)) {
+		ret = __ocfs2_write_remove_suid(inode, di_bh);
+		if (ret) {
+			mlog_errno(ret);
+			goto out_meta_unlock;
+		}
+	}
+
+	down_write(&OCFS2_I(inode)->ip_alloc_sem);
+	switch (cmd) {
+	case OCFS2_IOC_RESVSP:
+	case OCFS2_IOC_RESVSP64:
+		/*
+		 * This takes unsigned offsets, but the signed ones we
+		 * pass have been checked against overflow above.
+		 */
+		ret = ocfs2_allocate_unwritten_extents(inode, sr->l_start,
+						       sr->l_len);
+		break;
+	case OCFS2_IOC_UNRESVSP:
+	case OCFS2_IOC_UNRESVSP64:
+		ret = ocfs2_remove_inode_range(inode, di_bh, sr->l_start,
+					       sr->l_len);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+	up_write(&OCFS2_I(inode)->ip_alloc_sem);
+	if (ret) {
+		mlog_errno(ret);
+		goto out_meta_unlock;
+	}
+
+	/*
+	 * We update c/mtime for these changes
+	 */
+	handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
+	if (IS_ERR(handle)) {
+		ret = PTR_ERR(handle);
+		mlog_errno(ret);
+		goto out_meta_unlock;
+	}
+
+	inode->i_ctime = inode->i_mtime = CURRENT_TIME;
+	ret = ocfs2_mark_inode_dirty(handle, inode, di_bh);
+	if (ret < 0)
+		mlog_errno(ret);
+
+	ocfs2_commit_trans(osb, handle);
+
+out_meta_unlock:
+	brelse(di_bh);
+	ocfs2_meta_unlock(inode, 1);
+out_rw_unlock:
+	ocfs2_rw_unlock(inode, 1);
+
+	mutex_unlock(&inode->i_mutex);
+out:
+	return ret;
+}
+
 static int ocfs2_prepare_inode_for_write(struct dentry *dentry,
 					 loff_t *ppos,
 					 size_t count,
diff --git a/fs/ocfs2/file.h b/fs/ocfs2/file.h
index 79115c9..36fe27f 100644
--- a/fs/ocfs2/file.h
+++ b/fs/ocfs2/file.h
@@ -62,4 +62,7 @@
 int ocfs2_update_inode_atime(struct inode *inode,
 			     struct buffer_head *bh);
 
+int ocfs2_change_file_space(struct file *file, unsigned int cmd,
+			    struct ocfs2_space_resv *sr);
+
 #endif /* OCFS2_FILE_H */
diff --git a/fs/ocfs2/ioctl.c b/fs/ocfs2/ioctl.c
index f3ad21a..bd68c3f 100644
--- a/fs/ocfs2/ioctl.c
+++ b/fs/ocfs2/ioctl.c
@@ -14,6 +14,7 @@
 #include "ocfs2.h"
 #include "alloc.h"
 #include "dlmglue.h"
+#include "file.h"
 #include "inode.h"
 #include "journal.h"
 
@@ -115,6 +116,7 @@
 {
 	unsigned int flags;
 	int status;
+	struct ocfs2_space_resv sr;
 
 	switch (cmd) {
 	case OCFS2_IOC_GETFLAGS:
@@ -130,6 +132,14 @@
 
 		return ocfs2_set_inode_attr(inode, flags,
 			OCFS2_FL_MODIFIABLE);
+	case OCFS2_IOC_RESVSP:
+	case OCFS2_IOC_RESVSP64:
+	case OCFS2_IOC_UNRESVSP:
+	case OCFS2_IOC_UNRESVSP64:
+		if (copy_from_user(&sr, (int __user *) arg, sizeof(sr)))
+			return -EFAULT;
+
+		return ocfs2_change_file_space(filp, cmd, &sr);
 	default:
 		return -ENOTTY;
 	}
@@ -148,6 +158,11 @@
 	case OCFS2_IOC32_SETFLAGS:
 		cmd = OCFS2_IOC_SETFLAGS;
 		break;
+	case OCFS2_IOC_RESVSP:
+	case OCFS2_IOC_RESVSP64:
+	case OCFS2_IOC_UNRESVSP:
+	case OCFS2_IOC_UNRESVSP64:
+		break;
 	default:
 		return -ENOIOCTLCMD;
 	}
diff --git a/fs/ocfs2/ocfs2_fs.h b/fs/ocfs2/ocfs2_fs.h
index c20a74b..82f8a75 100644
--- a/fs/ocfs2/ocfs2_fs.h
+++ b/fs/ocfs2/ocfs2_fs.h
@@ -175,6 +175,32 @@
 #define OCFS2_IOC32_SETFLAGS	_IOW('f', 2, int)
 
 /*
+ * Space reservation / allocation / free ioctls and argument structure
+ * are designed to be compatible with XFS.
+ *
+ * ALLOCSP* and FREESP* are not and will never be supported, but are
+ * included here for completeness.
+ */
+struct ocfs2_space_resv {
+	__s16		l_type;
+	__s16		l_whence;
+	__s64		l_start;
+	__s64		l_len;		/* len == 0 means until end of file */
+	__s32		l_sysid;
+	__u32		l_pid;
+	__s32		l_pad[4];	/* reserve area			    */
+};
+
+#define OCFS2_IOC_ALLOCSP		_IOW ('X', 10, struct ocfs2_space_resv)
+#define OCFS2_IOC_FREESP		_IOW ('X', 11, struct ocfs2_space_resv)
+#define OCFS2_IOC_RESVSP		_IOW ('X', 40, struct ocfs2_space_resv)
+#define OCFS2_IOC_UNRESVSP	_IOW ('X', 41, struct ocfs2_space_resv)
+#define OCFS2_IOC_ALLOCSP64	_IOW ('X', 36, struct ocfs2_space_resv)
+#define OCFS2_IOC_FREESP64	_IOW ('X', 37, struct ocfs2_space_resv)
+#define OCFS2_IOC_RESVSP64	_IOW ('X', 42, struct ocfs2_space_resv)
+#define OCFS2_IOC_UNRESVSP64	_IOW ('X', 43, struct ocfs2_space_resv)
+
+/*
  * Journal Flags (ocfs2_dinode.id1.journal1.i_flags)
  */
 #define OCFS2_JOURNAL_DIRTY_FL	(0x00000001)	/* Journal needs recovery */
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index f07718a..3a5a1ed 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -115,8 +115,6 @@
 static struct inode *ocfs2_alloc_inode(struct super_block *sb);
 static void ocfs2_destroy_inode(struct inode *inode);
 
-static unsigned long long ocfs2_max_file_offset(unsigned int blockshift);
-
 static const struct super_operations ocfs2_sops = {
 	.statfs		= ocfs2_statfs,
 	.alloc_inode	= ocfs2_alloc_inode,
@@ -321,7 +319,7 @@
 /* From xfs_super.c:xfs_max_file_offset
  * Copyright (c) 2000-2004 Silicon Graphics, Inc.
  */
-static unsigned long long ocfs2_max_file_offset(unsigned int blockshift)
+unsigned long long ocfs2_max_file_offset(unsigned int blockshift)
 {
 	unsigned int pagefactor = 1;
 	unsigned int bitshift = BITS_PER_LONG - 1;
diff --git a/fs/ocfs2/super.h b/fs/ocfs2/super.h
index 783f527..3b9cb3d 100644
--- a/fs/ocfs2/super.h
+++ b/fs/ocfs2/super.h
@@ -45,4 +45,6 @@
 
 #define ocfs2_abort(sb, fmt, args...) __ocfs2_abort(sb, __PRETTY_FUNCTION__, fmt, ##args)
 
+unsigned long long ocfs2_max_file_offset(unsigned int blockshift);
+
 #endif /* OCFS2_SUPER_H */