UBIFS: TNC / GC race fixes

- update GC sequence number if any nodes may have been moved
even if GC did not finish the LEB
- don't ignore error return when reading

Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

fs/ubifs/gc.c

@@ -334,15 +334,15 @@ int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
 
 		err = move_nodes(c, sleb);
 		if (err)
-			goto out;
+			goto out_inc_seq;
 
 		err = gc_sync_wbufs(c);
 		if (err)
-			goto out;
+			goto out_inc_seq;
 
 		err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0, 0, 0);
 		if (err)
-			goto out;
+			goto out_inc_seq;
 
 		/* Allow for races with TNC */
 		c->gced_lnum = lnum;
@@ -369,6 +369,14 @@ int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
 out:
 	ubifs_scan_destroy(sleb);
 	return err;
+
+out_inc_seq:
+	/* We may have moved at least some nodes so allow for races with TNC */
+	c->gced_lnum = lnum;
+	smp_wmb();
+	c->gc_seq += 1;
+	smp_wmb();
+	goto out;
 }
 
 /**

fs/ubifs/tnc.c

@@ -1476,7 +1476,7 @@ again:
 	}
 
 	err = fallible_read_node(c, key, &zbr, node);
-	if (maybe_leb_gced(c, zbr.lnum, gc_seq1)) {
+	if (err <= 0 || maybe_leb_gced(c, zbr.lnum, gc_seq1)) {
 		/*
 		 * The node may have been GC'ed out from under us so try again
 		 * while keeping the TNC mutex locked.