[GFS2] Clean up internal read function

As requested by Christoph, this patch cleans up GFS2's internal
read function so that it no longer uses the do_generic_mapping_read
function. This function is obsolete and GFS2 is the last user of it.

As a side effect the internal read code gets smaller and easier
to read and gfs2_readpage is split into two. One function has the locking
and the other function has the rest of the logic.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
diff --git a/fs/gfs2/ops_inode.h b/fs/gfs2/ops_inode.h
index 34f0caa..edb519c 100644
--- a/fs/gfs2/ops_inode.h
+++ b/fs/gfs2/ops_inode.h
@@ -16,5 +16,9 @@
 extern const struct inode_operations gfs2_dir_iops;
 extern const struct inode_operations gfs2_symlink_iops;
 extern const struct inode_operations gfs2_dev_iops;
+extern const struct file_operations gfs2_file_fops;
+extern const struct file_operations gfs2_dir_fops;
+
+extern void gfs2_set_inode_flags(struct inode *inode);
 
 #endif /* __OPS_INODE_DOT_H__ */