[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
diff --git a/fs/gfs2/unlinked.c b/fs/gfs2/unlinked.c
index 24b91c2..0d2314a 100644
--- a/fs/gfs2/unlinked.c
+++ b/fs/gfs2/unlinked.c
@@ -35,11 +35,12 @@
 	int new = 0;
 	struct buffer_head *bh;
 	int error;
+	int boundary;
 
 	block = slot / sdp->sd_ut_per_block;
 	offset = slot % sdp->sd_ut_per_block;
 
-	error = gfs2_block_map(ip, block, &new, &dblock, NULL);
+	error = gfs2_block_map(ip->i_vnode, block, &new, &dblock, &boundary);
 	if (error)
 		return error;
 	error = gfs2_meta_read(ip->i_gl, dblock, DIO_START | DIO_WAIT, &bh);
@@ -354,7 +355,7 @@
 
 		if (!extlen) {
 			int new = 0;
-			error = gfs2_block_map(ip, x, &new, &dblock, &extlen);
+			error = gfs2_extent_map(ip->i_vnode, x, &new, &dblock, &extlen);
 			if (error)
 				goto fail;
 		}