[GFS2] Add gfs2_internal_read()

Add the new external read function. Its temporarily in jdata.c
even though the protoype is in ops_file.h - this will change
shortly. The current implementation will change to a page cache
one when that happens.

In order to effect the above changes, the various internal inodes
now have Linux inodes attached to them. We keep the references to
the Linux inodes, rather than the gfs2_inodes in the super block.

In order to get everything to work correctly I've had to reorder
the init sequence on mount (which I should probably have done
earlier when .gfs2_admin was made visible).

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

fs/gfs2/ops_file.h

@@ -10,6 +10,10 @@
 #ifndef __OPS_FILE_DOT_H__
 #define __OPS_FILE_DOT_H__
 
+extern int gfs2_internal_read(struct gfs2_inode *ip,
+			      struct file_ra_state *ra_state,
+			      char *buf, loff_t *pos, unsigned size);
+
 extern struct file_operations gfs2_file_fops;
 extern struct file_operations gfs2_dir_fops;