ocfs2: Support xfs style space reservation ioctls

We re-use the RESVSP/UNRESVSP ioctls from xfs which allow the user to
allocate and deallocate regions to a file without zeroing data or changing
i_size.

Though renamed, the structure passed in from user is identical to struct
xfs_flock64. The three fields that are actually used right now are l_whence,
l_start and l_len.

This should get ocfs2 immediate compatibility with userspace software using
the pre-existing xfs ioctls.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
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;