pNFS: Ensure we check layout segment validity in the pg_init() callback

If we have a layout segment cached in pgio->pg_lseg, we should check it
for validity before reusing it in a new RPC request. Otherwise, if we
recoalesce, we can end up looping forever.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/flexfilelayout/flexfilelayout.c

@@ -846,6 +846,7 @@ ff_layout_pg_init_read(struct nfs_pageio_descriptor *pgio,
 	int ds_idx;
 
 retry:
+	pnfs_generic_pg_check_layout(pgio);
 	/* Use full layout for now */
 	if (!pgio->pg_lseg)
 		ff_layout_pg_get_read(pgio, req, false);
@@ -894,6 +895,7 @@ ff_layout_pg_init_write(struct nfs_pageio_descriptor *pgio,
 	int status;
 
 retry:
+	pnfs_generic_pg_check_layout(pgio);
 	if (!pgio->pg_lseg) {
 		pgio->pg_lseg = pnfs_update_layout(pgio->pg_inode,
 						   req->wb_context,