[GFS2] Readpages support

This adds readpages support (and also corrects a small bug in
the readpage error path at the same time). Hopefully this will
improve performance by allowing GFS to submit larger lumps of
I/O at a time.

In order to simplify the setting of BH_Boundary, it currently gets
set when we hit the end of a indirect pointer block. There is
always a boundary at this point with the current allocation code.
It doesn't get all the boundaries right though, so there is still
room for improvement in this.

See comments in fs/gfs2/ops_address.c for further information about
readpages with GFS2.

Signed-off-by: Steven Whitehouse

fs/gfs2/ops_super.c

@@ -92,7 +92,6 @@ static void gfs2_put_super(struct super_block *sb)
 		if (error)
 			gfs2_io_error(sdp);
 	}
-
 	/*  At this point, we're through modifying the disk  */
 
 	/*  Release stuff  */
@@ -125,12 +124,10 @@ static void gfs2_put_super(struct super_block *sb)
 	gfs2_jindex_free(sdp);
 	/*  Take apart glock structures and buffer lists  */
 	gfs2_gl_hash_clear(sdp, WAIT);
-
 	/*  Unmount the locking protocol  */
 	gfs2_lm_unmount(sdp);
 
 	/*  At this point, we're through participating in the lockspace  */
-
 	gfs2_sys_fs_del(sdp);
 	vfree(sdp);
 	sb->s_fs_info = NULL;