fs: export empty_aops

With the ->sync_page() hook gone, we have a few users that
add their own static address_space_operations without any
functions defined.

fs/inode.c already has an empty_aops that it uses for init
purposes. Lets export that and use it in the places where
an otherwise empty aops was defined.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

4 files changed, 12 insertions, 5 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 5f4e11aaeb5c..33c963d08ab4 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -125,6 +125,14 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_wb_list_lock);
 static DECLARE_RWSEM(iprune_sem);
 
 /*
+ * Empty aops. Can be used for the cases where the user does not
+ * define any of the address_space operations.
+ */
+const struct address_space_operations empty_aops = {
+};
+EXPORT_SYMBOL(empty_aops);
+
+/*
  * Statistics gathering..
  */
 struct inodes_stat_t inodes_stat;
@@ -176,7 +184,6 @@ int proc_nr_inodes(ctl_table *table, int write,
  */
 int inode_init_always(struct super_block *sb, struct inode *inode)
 {
-        static const struct address_space_operations empty_aops;
         static const struct inode_operations empty_iops;
         static const struct file_operations empty_fops;
         struct address_space *const mapping = &inode->i_data;
diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index 9d2dc6b4348e..1168059c7efd 100644
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -495,8 +495,6 @@ unsigned nilfs_page_count_clean_buffers(struct page *page,
 void nilfs_mapping_init(struct address_space *mapping,
                         struct backing_dev_info *bdi)
 {
-        static const struct address_space_operations empty_aops;
-
         mapping->host = NULL;
         mapping->flags = 0;
         mapping_set_gfp_mask(mapping, GFP_NOFS);
diff --git a/fs/ubifs/xattr.c b/fs/ubifs/xattr.c
index c74400f88fe0..3299f469e712 100644
--- a/fs/ubifs/xattr.c
+++ b/fs/ubifs/xattr.c
@@ -56,6 +56,7 @@
  */
 
 #include "ubifs.h"
+#include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/xattr.h>
 #include <linux/posix_acl_xattr.h>
@@ -80,7 +81,6 @@ enum {
 };
 
 static const struct inode_operations none_inode_operations;
-static const struct address_space_operations none_address_operations;
 static const struct file_operations none_file_operations;
 
 /**
@@ -130,7 +130,7 @@ static int create_xattr(struct ubifs_info *c, struct inode *host,
         }
 
         /* Re-define all operations to be "nothing" */
-        inode->i_mapping->a_ops = &none_address_operations;
+        inode->i_mapping->a_ops = &empty_aops;
         inode->i_op = &none_inode_operations;
         inode->i_fop = &none_file_operations;
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 52f283c1edb2..1b95af37e3b3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -613,6 +613,8 @@ struct address_space_operations {
         int (*error_remove_page)(struct address_space *, struct page *);
 };
 
+extern const struct address_space_operations empty_aops;
+
 /*
  * pagecache_write_begin/pagecache_write_end must be used by general code
  * to write into the pagecache.