[GFS2] Make our address_space_operations const

As per Christoph's patch:
http://www.kernel.org/git/?p=linux/kernel/git/steve/gfs2-2.6.git;a=commitdiff;h=f5e54d6e53a20cef45af7499e86164f0e0d16bb2

We mark struct address_space_operations const in GFS2.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/meta_io.c

@@ -159,7 +159,7 @@ static int gfs2_aspace_releasepage(struct page *page, gfp_t gfp_mask)
 	return try_to_free_buffers(page);
 }
 
-static struct address_space_operations aspace_aops = {
+static const struct address_space_operations aspace_aops = {
 	.writepage = gfs2_aspace_writepage,
 	.releasepage = gfs2_aspace_releasepage,
 };

fs/gfs2/ops_address.c

@@ -655,7 +655,7 @@ static ssize_t gfs2_direct_IO(int rw, struct kiocb *iocb,
 				    DIO_OWN_LOCKING);
 }
 
-struct address_space_operations gfs2_file_aops = {
+const struct address_space_operations gfs2_file_aops = {
 	.writepage = gfs2_writepage,
 	.readpage = gfs2_readpage,
 	.readpages = gfs2_readpages,

fs/gfs2/ops_address.h

@@ -10,7 +10,7 @@
 #ifndef __OPS_ADDRESS_DOT_H__
 #define __OPS_ADDRESS_DOT_H__
 
-extern struct address_space_operations gfs2_file_aops;
+extern const struct address_space_operations gfs2_file_aops;
 extern int gfs2_get_block(struct inode *inode, sector_t lblock,
 			  struct buffer_head *bh_result, int create);