ext4: Remove i_ext_generation from ext4_inode_info structure

The i_ext_generation was incremented, but never used.  Remove it to
slim down the ext4_inode_info structure.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4_extents.h

@@ -194,11 +194,6 @@ static inline unsigned short ext_depth(struct inode *inode)
 	return le16_to_cpu(ext_inode_hdr(inode)->eh_depth);
 }
 
-static inline void ext4_ext_tree_changed(struct inode *inode)
-{
-	EXT4_I(inode)->i_ext_generation++;
-}
-
 static inline void
 ext4_ext_invalidate_cache(struct inode *inode)
 {

fs/ext4/ext4_i.h

@@ -117,7 +117,6 @@ struct ext4_inode_info {
 	struct inode vfs_inode;
 	struct jbd2_inode jinode;
 
-	unsigned long i_ext_generation;
 	struct ext4_ext_cache i_cached_extent;
 	/*
 	 * File creation time. Its function is same as that of

fs/ext4/extents.c

@@ -1621,7 +1621,6 @@ int ext4_ext_insert_extent(handle_t *handle, struct inode *inode,
 		ext4_ext_drop_refs(npath);
 		kfree(npath);
 	}
-	ext4_ext_tree_changed(inode);
 	ext4_ext_invalidate_cache(inode);
 	return err;
 }
@@ -2232,7 +2231,6 @@ static int ext4_ext_remove_space(struct inode *inode, ext4_lblk_t start)
 		}
 	}
 out:
-	ext4_ext_tree_changed(inode);
 	ext4_ext_drop_refs(path);
 	kfree(path);
 	ext4_journal_stop(handle);