pNFS/flexfiles: Specify the layout segment range in LAYOUTGET

Move from requesting only full file layout segments, to requesting
layout segments that match our I/O size. This means the server is
still free to return a full file layout, but we will no longer
error out if it does not.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/flexfilelayout/flexfilelayout.c

@@ -798,8 +798,8 @@ ff_layout_pg_get_read(struct nfs_pageio_descriptor *pgio,
 	pnfs_put_lseg(pgio->pg_lseg);
 	pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
 					   nfs_req_openctx(req),
-					   0,
-					   NFS4_MAX_UINT64,
+					   req_offset(req),
+					   req->wb_bytes,
 					   IOMODE_READ,
 					   strict_iomode,
 					   GFP_KERNEL);
@@ -891,8 +891,8 @@ ff_layout_pg_init_write(struct nfs_pageio_descriptor *pgio,
 	if (!pgio->pg_lseg) {
 		pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
 						   nfs_req_openctx(req),
-						   0,
-						   NFS4_MAX_UINT64,
+						   req_offset(req),
+						   req->wb_bytes,
 						   IOMODE_RW,
 						   false,
 						   GFP_NOFS);