blk-mq: rework flush sequencing logic
Witch to using a preallocated flush_rq for blk-mq similar to what's done
with the old request path. This allows us to set up the request properly
with a tag from the actually allowed range and ->rq_disk as needed by
some drivers. To make life easier we also switch to dynamic allocation
of ->flush_rq for the old path.
This effectively reverts most of
"blk-mq: fix for flush deadlock"
and
"blk-mq: Don't reserve a tag for flush request"
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/block/blk-flush.c b/block/blk-flush.c
index 9143e85..66e2b69 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -130,20 +130,26 @@
blk_clear_rq_complete(rq);
}
-static void mq_flush_data_run(struct work_struct *work)
+static void mq_flush_run(struct work_struct *work)
{
struct request *rq;
- rq = container_of(work, struct request, mq_flush_data);
+ rq = container_of(work, struct request, mq_flush_work);
memset(&rq->csd, 0, sizeof(rq->csd));
blk_mq_run_request(rq, true, false);
}
-static void blk_mq_flush_data_insert(struct request *rq)
+static bool blk_flush_queue_rq(struct request *rq)
{
- INIT_WORK(&rq->mq_flush_data, mq_flush_data_run);
- kblockd_schedule_work(rq->q, &rq->mq_flush_data);
+ if (rq->q->mq_ops) {
+ INIT_WORK(&rq->mq_flush_work, mq_flush_run);
+ kblockd_schedule_work(rq->q, &rq->mq_flush_work);
+ return false;
+ } else {
+ list_add_tail(&rq->queuelist, &rq->q->queue_head);
+ return true;
+ }
}
/**
@@ -187,12 +193,7 @@
case REQ_FSEQ_DATA:
list_move_tail(&rq->flush.list, &q->flush_data_in_flight);
- if (q->mq_ops)
- blk_mq_flush_data_insert(rq);
- else {
- list_add(&rq->queuelist, &q->queue_head);
- queued = true;
- }
+ queued = blk_flush_queue_rq(rq);
break;
case REQ_FSEQ_DONE:
@@ -216,9 +217,6 @@
}
kicked = blk_kick_flush(q);
- /* blk_mq_run_flush will run queue */
- if (q->mq_ops)
- return queued;
return kicked | queued;
}
@@ -230,10 +228,9 @@
struct request *rq, *n;
unsigned long flags = 0;
- if (q->mq_ops) {
- blk_mq_free_request(flush_rq);
+ if (q->mq_ops)
spin_lock_irqsave(&q->mq_flush_lock, flags);
- }
+
running = &q->flush_queue[q->flush_running_idx];
BUG_ON(q->flush_pending_idx == q->flush_running_idx);
@@ -263,48 +260,14 @@
* kblockd.
*/
if (queued || q->flush_queue_delayed) {
- if (!q->mq_ops)
- blk_run_queue_async(q);
- else
- /*
- * This can be optimized to only run queues with requests
- * queued if necessary.
- */
- blk_mq_run_queues(q, true);
+ WARN_ON(q->mq_ops);
+ blk_run_queue_async(q);
}
q->flush_queue_delayed = 0;
if (q->mq_ops)
spin_unlock_irqrestore(&q->mq_flush_lock, flags);
}
-static void mq_flush_work(struct work_struct *work)
-{
- struct request_queue *q;
- struct request *rq;
-
- q = container_of(work, struct request_queue, mq_flush_work);
-
- rq = blk_mq_alloc_request(q, WRITE_FLUSH|REQ_FLUSH_SEQ,
- __GFP_WAIT|GFP_ATOMIC, false);
- rq->cmd_type = REQ_TYPE_FS;
- rq->end_io = flush_end_io;
-
- blk_mq_run_request(rq, true, false);
-}
-
-/*
- * We can't directly use q->flush_rq, because it doesn't have tag and is not in
- * hctx->rqs[]. so we must allocate a new request, since we can't sleep here,
- * so offload the work to workqueue.
- *
- * Note: we assume a flush request finished in any hardware queue will flush
- * the whole disk cache.
- */
-static void mq_run_flush(struct request_queue *q)
-{
- kblockd_schedule_work(q, &q->mq_flush_work);
-}
-
/**
* blk_kick_flush - consider issuing flush request
* @q: request_queue being kicked
@@ -339,19 +302,31 @@
* different from running_idx, which means flush is in flight.
*/
q->flush_pending_idx ^= 1;
+
if (q->mq_ops) {
- mq_run_flush(q);
- return true;
+ struct blk_mq_ctx *ctx = first_rq->mq_ctx;
+ struct blk_mq_hw_ctx *hctx = q->mq_ops->map_queue(q, ctx->cpu);
+
+ blk_mq_rq_init(hctx, q->flush_rq);
+ q->flush_rq->mq_ctx = ctx;
+
+ /*
+ * Reuse the tag value from the fist waiting request,
+ * with blk-mq the tag is generated during request
+ * allocation and drivers can rely on it being inside
+ * the range they asked for.
+ */
+ q->flush_rq->tag = first_rq->tag;
+ } else {
+ blk_rq_init(q, q->flush_rq);
}
- blk_rq_init(q, &q->flush_rq);
- q->flush_rq.cmd_type = REQ_TYPE_FS;
- q->flush_rq.cmd_flags = WRITE_FLUSH | REQ_FLUSH_SEQ;
- q->flush_rq.rq_disk = first_rq->rq_disk;
- q->flush_rq.end_io = flush_end_io;
+ q->flush_rq->cmd_type = REQ_TYPE_FS;
+ q->flush_rq->cmd_flags = WRITE_FLUSH | REQ_FLUSH_SEQ;
+ q->flush_rq->rq_disk = first_rq->rq_disk;
+ q->flush_rq->end_io = flush_end_io;
- list_add_tail(&q->flush_rq.queuelist, &q->queue_head);
- return true;
+ return blk_flush_queue_rq(q->flush_rq);
}
static void flush_data_end_io(struct request *rq, int error)
@@ -407,11 +382,8 @@
/*
* @policy now records what operations need to be done. Adjust
* REQ_FLUSH and FUA for the driver.
- * We keep REQ_FLUSH for mq to track flush requests. For !FUA,
- * we never dispatch the request directly.
*/
- if (rq->cmd_flags & REQ_FUA)
- rq->cmd_flags &= ~REQ_FLUSH;
+ rq->cmd_flags &= ~REQ_FLUSH;
if (!(fflags & REQ_FUA))
rq->cmd_flags &= ~REQ_FUA;
@@ -560,5 +532,4 @@
void blk_mq_init_flush(struct request_queue *q)
{
spin_lock_init(&q->mq_flush_lock);
- INIT_WORK(&q->mq_flush_work, mq_flush_work);
}