blk-mq: pair blk_mq_start_request / blk_mq_requeue_request
Make sure we have a proper pairing between starting and requeueing
requests. Move the dma drain and REQ_END setup into blk_mq_start_request,
and make sure blk_mq_requeue_request properly undoes them, giving us
a pair of function to prepare and unprepare a request without leaving
side effects.
Together this ensures we always clean up properly after
BLK_MQ_RQ_QUEUE_BUSY returns from ->queue_rq.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 0480710..1fa9dd1 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -377,7 +377,7 @@
}
EXPORT_SYMBOL(blk_mq_complete_request);
-static void blk_mq_start_request(struct request *rq)
+static void blk_mq_start_request(struct request *rq, bool last)
{
struct request_queue *q = rq->q;
@@ -390,6 +390,25 @@
*/
rq->deadline = jiffies + q->rq_timeout;
set_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
+
+ if (q->dma_drain_size && blk_rq_bytes(rq)) {
+ /*
+ * Make sure space for the drain appears. We know we can do
+ * this because max_hw_segments has been adjusted to be one
+ * fewer than the device can handle.
+ */
+ rq->nr_phys_segments++;
+ }
+
+ /*
+ * Flag the last request in the series so that drivers know when IO
+ * should be kicked off, if they don't do it on a per-request basis.
+ *
+ * Note: the flag isn't the only condition drivers should do kick off.
+ * If drive is busy, the last request might not have the bit set.
+ */
+ if (last)
+ rq->cmd_flags |= REQ_END;
}
static void blk_mq_requeue_request(struct request *rq)
@@ -398,6 +417,11 @@
trace_block_rq_requeue(q, rq);
clear_bit(REQ_ATOM_STARTED, &rq->atomic_flags);
+
+ rq->cmd_flags &= ~REQ_END;
+
+ if (q->dma_drain_size && blk_rq_bytes(rq))
+ rq->nr_phys_segments--;
}
struct blk_mq_timeout_data {
@@ -565,29 +589,8 @@
rq = list_first_entry(&rq_list, struct request, queuelist);
list_del_init(&rq->queuelist);
- blk_mq_start_request(rq);
- if (q->dma_drain_size && blk_rq_bytes(rq)) {
- /*
- * make sure space for the drain appears we
- * know we can do this because max_hw_segments
- * has been adjusted to be one fewer than the
- * device can handle
- */
- rq->nr_phys_segments++;
- }
-
- /*
- * Last request in the series. Flag it as such, this
- * enables drivers to know when IO should be kicked off,
- * if they don't do it on a per-request basis.
- *
- * Note: the flag isn't the only condition drivers
- * should do kick off. If drive is busy, the last
- * request might not have the bit set.
- */
- if (list_empty(&rq_list))
- rq->cmd_flags |= REQ_END;
+ blk_mq_start_request(rq, list_empty(&rq_list));
ret = q->mq_ops->queue_rq(hctx, rq);
switch (ret) {
