pNFS: Fix LAYOUTGET handling of NFS4ERR_BAD_STATEID and NFS4ERR_EXPIRED

We want to recover the open stateid if there is no layout stateid
and/or the stateid argument matches an open stateid.
Otherwise throw out the existing layout and recover from scratch, as
the layout stateid is bad.

Fixes: 183d9e7b ("pnfs: rework LAYOUTGET retry handling")
Cc: stable@vger.kernel.org # 4.7
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>

fs/nfs/nfs4proc.c

@@ -7886,6 +7886,7 @@ nfs4_layoutget_handle_exception(struct rpc_task *task,
 	struct pnfs_layout_hdr *lo;
 	int nfs4err = task->tk_status;
 	int err, status = 0;
+	LIST_HEAD(head);
 
 	dprintk("--> %s tk_status => %d\n", __func__, -task->tk_status);
 
@@ -7930,21 +7931,18 @@ nfs4_layoutget_handle_exception(struct rpc_task *task,
 	case -NFS4ERR_BAD_STATEID:
 		exception->timeout = 0;
 		spin_lock(&inode->i_lock);
-		if (nfs4_stateid_match(&lgp->args.stateid,
+		lo = NFS_I(inode)->layout;
+		/* If the open stateid was bad, then recover it. */
+		if (!lo || test_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags) ||
+		    nfs4_stateid_match_other(&lgp->args.stateid,
 					&lgp->args.ctx->state->stateid)) {
 			spin_unlock(&inode->i_lock);
-			/* If the open stateid was bad, then recover it. */
 			exception->state = lgp->args.ctx->state;
 			break;
 		}
-		lo = NFS_I(inode)->layout;
-		if (lo && !test_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags) &&
-		    nfs4_stateid_match_other(&lgp->args.stateid, &lo->plh_stateid)) {
-			LIST_HEAD(head);
 
 		/*
 		 * Mark the bad layout state as invalid, then retry
-			 * with the current stateid.
 		 */
 		set_bit(NFS_LAYOUT_INVALID_STID, &lo->plh_flags);
 		pnfs_mark_matching_lsegs_invalid(lo, &head, NULL, 0);
@@ -7952,8 +7950,6 @@ nfs4_layoutget_handle_exception(struct rpc_task *task,
 		pnfs_free_lseg_list(&head);
 		status = -EAGAIN;
 		goto out;
-		} else
-			spin_unlock(&inode->i_lock);
 	}
 
 	err = nfs4_handle_exception(server, nfs4err, exception);