pnfs: don't check sequence on new stateids in layoutget

When layoutget returns an entirely new layout stateid it should not
check the generation counter as the new stateid will start with a new
counter entirely unrelated to old one.

The current behavior causes constant layoutget failures against a block
server which allocates a new stateid after an recall that removed all
outstanding layouts.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/pnfs.c

@@ -682,17 +682,6 @@ static bool pnfs_seqid_is_newer(u32 s1, u32 s2)
 	return (s32)(s1 - s2) > 0;
 }
 
-static void
-pnfs_verify_layout_stateid(struct pnfs_layout_hdr *lo,
-		const nfs4_stateid *new,
-		struct list_head *free_me_list)
-{
-	if (nfs4_stateid_match_other(&lo->plh_stateid, new))
-		return;
-	/* Layout is new! Kill existing layout segments */
-	pnfs_mark_matching_lsegs_invalid(lo, free_me_list, NULL);
-}
-
 /* update lo->plh_stateid with new if is more recent */
 void
 pnfs_set_layout_stateid(struct pnfs_layout_hdr *lo, const nfs4_stateid *new,
@@ -1367,16 +1356,29 @@ pnfs_layout_process(struct nfs4_layoutget *lgp)
 		goto out_forget_reply;
 	}
 
-	if (pnfs_layoutgets_blocked(lo, 1) ||
-	    pnfs_layout_stateid_blocked(lo, &res->stateid)) {
+	if (pnfs_layoutgets_blocked(lo, 1)) {
 		dprintk("%s forget reply due to state\n", __func__);
 		goto out_forget_reply;
 	}
 
-	/* Check that the new stateid matches the old stateid */
-	pnfs_verify_layout_stateid(lo, &res->stateid, &free_me);
-	/* Done processing layoutget. Set the layout stateid */
+	if (nfs4_stateid_match_other(&lo->plh_stateid, &res->stateid)) {
+		/* existing state ID, make sure the sequence number matches. */
+		if (pnfs_layout_stateid_blocked(lo, &res->stateid)) {
+			dprintk("%s forget reply due to sequence\n", __func__);
+			goto out_forget_reply;
+		}
 		pnfs_set_layout_stateid(lo, &res->stateid, false);
+	} else {
+		/*
+		 * We got an entirely new state ID.  Mark all segments for the
+		 * inode invalid, and don't bother validating the stateid
+		 * sequence number.
+		 */
+		pnfs_mark_matching_lsegs_invalid(lo, &free_me, NULL);
+
+		nfs4_stateid_copy(&lo->plh_stateid, &res->stateid);
+		lo->plh_barrier = be32_to_cpu(res->stateid.seqid);
+	}
 
 	pnfs_get_lseg(lseg);
 	pnfs_layout_insert_lseg(lo, lseg);