pNFS/filelayout: Specify the layout segment range in LAYOUTGET

Move from only requesting 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 if it wants, but partial layouts will no
longer cause an error.
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/filelayout/filelayout.c

@@ -871,8 +871,8 @@ filelayout_pg_init_read(struct nfs_pageio_descriptor *pgio,
 	if (!pgio->pg_lseg) {
 		pgio->pg_lseg = fl_pnfs_update_layout(pgio->pg_inode,
 						      nfs_req_openctx(req),
-						      0,
-						      NFS4_MAX_UINT64,
+						      req_offset(req),
+						      req->wb_bytes,
 						      IOMODE_READ,
 						      false,
 						      GFP_KERNEL);
@@ -895,8 +895,8 @@ filelayout_pg_init_write(struct nfs_pageio_descriptor *pgio,
 	if (!pgio->pg_lseg) {
 		pgio->pg_lseg = fl_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);