blk-mq: blk_mq_tag_to_rq should handle flush request

flush request is special, which borrows the tag from the parent
request. Hence blk_mq_tag_to_rq needs special handling to return
the flush request from the tag.

Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

2 files changed, 12 insertions, 4 deletions

diff --git a/block/blk-flush.c b/block/blk-flush.c
index ef608b35d9be..ff87c664b7df 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -223,8 +223,10 @@ static void flush_end_io(struct request *flush_rq, int error)
         struct request *rq, *n;
         unsigned long flags = 0;
 
-        if (q->mq_ops)
+        if (q->mq_ops) {
                 spin_lock_irqsave(&q->mq_flush_lock, flags);
+                q->flush_rq->cmd_flags = 0;
+        }
 
         running = &q->flush_queue[q->flush_running_idx];
         BUG_ON(q->flush_pending_idx == q->flush_running_idx);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6160128085fc..21f952ab3581 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -541,9 +541,15 @@ void blk_mq_kick_requeue_list(struct request_queue *q)
 }
 EXPORT_SYMBOL(blk_mq_kick_requeue_list);
 
-struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags, unsigned int tag)
+struct request *blk_mq_tag_to_rq(struct blk_mq_hw_ctx *hctx, unsigned int tag)
 {
-        return tags->rqs[tag];
+        struct request_queue *q = hctx->queue;
+
+        if ((q->flush_rq->cmd_flags & REQ_FLUSH_SEQ) &&
+            q->flush_rq->tag == tag)
+                return q->flush_rq;
+
+        return hctx->tags->rqs[tag];
 }
 EXPORT_SYMBOL(blk_mq_tag_to_rq);
 
@@ -572,7 +578,7 @@ static void blk_mq_timeout_check(void *__data, unsigned long *free_tags)
                 if (tag >= hctx->tags->nr_tags)
                         break;
 
-                rq = blk_mq_tag_to_rq(hctx->tags, tag++);
+                rq = blk_mq_tag_to_rq(hctx, tag++);
                 if (rq->q != hctx->queue)
                         continue;
                 if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags))