blk-mq: fix blk_mq_all_tag_iter

blk_mq_all_tag_iter() is added to iterate all requests, so we should
fetch the request from ->static_rqs][] instead of ->rqs[] which is for
holding in-flight request only.

Fix it by adding flag of BT_TAG_ITER_STATIC_RQS.

Fixes: bf0beec0 ("blk-mq: drain I/O when all CPUs in a hctx are offline")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: John Garry <john.garry@huawei.com>
Cc: Dongli Zhang <dongli.zhang@oracle.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Daniel Wagner <dwagner@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq-tag.c

@@ -296,6 +296,7 @@ struct bt_tags_iter_data {
 
 #define BT_TAG_ITER_RESERVED		(1 << 0)
 #define BT_TAG_ITER_STARTED		(1 << 1)
+#define BT_TAG_ITER_STATIC_RQS		(1 << 2)
 
 static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 {
@@ -309,9 +310,12 @@ static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
 
 	/*
 	 * We can hit rq == NULL here, because the tagging functions
-	 * test and set the bit before assining ->rqs[].
+	 * test and set the bit before assigning ->rqs[].
 	 */
-	rq = tags->rqs[bitnr];
+	if (iter_data->flags & BT_TAG_ITER_STATIC_RQS)
+		rq = tags->static_rqs[bitnr];
+	else
+		rq = tags->rqs[bitnr];
 	if (!rq)
 		return true;
 	if ((iter_data->flags & BT_TAG_ITER_STARTED) &&
@@ -366,11 +370,13 @@ static void __blk_mq_all_tag_iter(struct blk_mq_tags *tags,
  *		indicates whether or not @rq is a reserved request. Return
  *		true to continue iterating tags, false to stop.
  * @priv:	Will be passed as second argument to @fn.
+ *
+ * Caller has to pass the tag map from which requests are allocated.
  */
 void blk_mq_all_tag_iter(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
 		void *priv)
 {
-	return __blk_mq_all_tag_iter(tags, fn, priv, 0);
+	return __blk_mq_all_tag_iter(tags, fn, priv, BT_TAG_ITER_STATIC_RQS);
 }
 
 /**