skip LAYOUTRETURN if layout is invalid

Currently, when IO to DS fails, client returns the layout and
retries against the MDS. However, then on umounting (inode eviction)
it returns the layout again.

This is because pnfs_return_layout() was changed in
commit d78471d3 ("pnfs/blocklayout: set PNFS_LAYOUTRETURN_ON_ERROR")
to always set NFS_LAYOUT_RETURN_REQUESTED so even if we returned
the layout, it will be returned again. Instead, let's also check
if we have already marked the layout invalid.
Signed-off-by: NOlga Kornievskaia <kolga@netapp.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/pnfs.c

@@ -1211,7 +1211,7 @@ _pnfs_return_layout(struct inode *ino)
 	LIST_HEAD(tmp_list);
 	nfs4_stateid stateid;
 	int status = 0;
-	bool send;
+	bool send, valid_layout;
 
 	dprintk("NFS: %s for inode %lu\n", __func__, ino->i_ino);
 
@@ -1232,6 +1232,7 @@ _pnfs_return_layout(struct inode *ino)
 			goto out_put_layout_hdr;
 		spin_lock(&ino->i_lock);
 	}
+	valid_layout = pnfs_layout_is_valid(lo);
 	pnfs_clear_layoutcommit(ino, &tmp_list);
 	pnfs_mark_matching_lsegs_invalid(lo, &tmp_list, NULL, 0);
 
@@ -1245,7 +1246,8 @@ _pnfs_return_layout(struct inode *ino)
 	}
 
 	/* Don't send a LAYOUTRETURN if list was initially empty */
-	if (!test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags)) {
+	if (!test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags) ||
+			!valid_layout) {
 		spin_unlock(&ino->i_lock);
 		dprintk("NFS: %s no layout segments to return\n", __func__);
 		goto out_put_layout_hdr;