idr: fix a subtle bug in idr_get_next()

javilonas · May 29, 2015 · 303e2e5 · 303e2e5
1 parent bee6482
commit 303e2e5
Showing 1 changed file with 8 additions and 1 deletion.
diff --git a/lib/idr.c b/lib/idr.c
@@ -738,7 +738,14 @@ int idr_for_each(struct idr *idp,
 				break;
 		}
 
-		id += 1 << n;
+		/*
+		 * Proceed to the next layer at the current level.  Unlike
+		 * idr_for_each(), @id isn't guaranteed to be aligned to
+		 * layer boundary at this point and adding 1 << n may
+		 * incorrectly skip IDs.  Make sure we jump to the
+		 * beginning of the next layer using round_up().
+		 */
+		id = round_up(id + 1, 1 << n);
 		while (n < fls(id)) {
 			n += IDR_BITS;
 			p = *--paa;