blk-mq: fix iteration of busy bitmap

Commit 889fa31f00b2 was a bit too eager in reducing the loop count,
so we ended up missing queues in some configurations. Ensure that
our division rounds up, so that's not the case.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Fixes: 889fa31f00b2 ("blk-mq: reduce unnecessary software queue looping")
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq.c

@@ -41,7 +41,7 @@ static bool blk_mq_hctx_has_pending(struct blk_mq_hw_ctx *hctx)
 {
 	unsigned int i;
 
-	for (i = 0; i < hctx->ctx_map.map_size; i++)
+	for (i = 0; i < hctx->ctx_map.size; i++)
 		if (hctx->ctx_map.map[i].word)
 			return true;
 
@@ -730,7 +730,7 @@ static void flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list)
 	struct blk_mq_ctx *ctx;
 	int i;
 
-	for (i = 0; i < hctx->ctx_map.map_size; i++) {
+	for (i = 0; i < hctx->ctx_map.size; i++) {
 		struct blk_align_bitmap *bm = &hctx->ctx_map.map[i];
 		unsigned int off, bit;
 
@@ -1818,7 +1818,7 @@ static void blk_mq_map_swqueue(struct request_queue *q)
 		 * This is more accurate and more efficient than looping
 		 * over all possibly mapped software queues.
 		 */
-		map->map_size = hctx->nr_ctx / map->bits_per_word;
+		map->size = DIV_ROUND_UP(hctx->nr_ctx, map->bits_per_word);
 
 		/*
 		 * Initialize batch roundrobin counts

include/linux/blk-mq.h

@@ -13,7 +13,7 @@ struct blk_mq_cpu_notifier {
 };
 
 struct blk_mq_ctxmap {
-	unsigned int map_size;
+	unsigned int size;
 	unsigned int bits_per_word;
 	struct blk_align_bitmap *map;
 };