[PATCH 19/30] block: remove non mq parts from the flush code

Jens Axboe
2018-10-31T17:59:11Z

block/blk-flush.c | 154 +++++++++-------------------------------------
block/blk.h | 4 +-
2 files changed, 31 insertions(+), 127 deletions(-)

diff --git a/block/blk-flush.c b/block/blk-flush.c
index 8b44b86779da..9baa9a119447 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -134,16 +134,8 @@ static void blk_flush_restore_request(struct request *rq)

static bool blk_flush_queue_rq(struct request *rq, bool add_front)
{
- if (rq->q->mq_ops) {
- blk_mq_add_to_requeue_list(rq, add_front, true);
- return false;
- } else {
- if (add_front)
- list_add(&rq->queuelist, &rq->q->queue_head);
- else
- list_add_tail(&rq->queuelist, &rq->q->queue_head);
- return true;
- }
+ blk_mq_add_to_requeue_list(rq, add_front, true);
+ return false;
}

/**
@@ -204,10 +196,7 @@ static bool blk_flush_complete_seq(struct request *rq,
BUG_ON(!list_empty(&rq->queuelist));
list_del_init(&rq->flush.list);
blk_flush_restore_request(rq);
- if (q->mq_ops)
- blk_mq_end_request(rq, error);
- else
- __blk_end_request_all(rq, error);
+ blk_mq_end_request(rq, error);
break;

default:
@@ -226,20 +215,17 @@ static void flush_end_io(struct request *flush_rq, blk_status_t error)
struct request *rq, *n;
unsigned long flags = 0;
struct blk_flush_queue *fq = blk_get_flush_queue(q, flush_rq->mq_ctx);
+ struct blk_mq_hw_ctx *hctx;

- if (q->mq_ops) {
- struct blk_mq_hw_ctx *hctx;
-
- /* release the tag's ownership to the req cloned from */
- spin_lock_irqsave(&fq->mq_flush_lock, flags);
- hctx = blk_mq_map_queue(q, flush_rq->mq_ctx->cpu);
- if (!q->elevator) {
- blk_mq_tag_set_rq(hctx, flush_rq->tag, fq->orig_rq);
- flush_rq->tag = -1;
- } else {
- blk_mq_put_driver_tag_hctx(hctx, flush_rq);
- flush_rq->internal_tag = -1;
- }
+ /* release the tag's ownership to the req cloned from */
+ spin_lock_irqsave(&fq->mq_flush_lock, flags);
+ hctx = blk_mq_map_queue(q, flush_rq->mq_ctx->cpu);
+ if (!q->elevator) {
+ blk_mq_tag_set_rq(hctx, flush_rq->tag, fq->orig_rq);
+ flush_rq->tag = -1;
+ } else {
+ blk_mq_put_driver_tag_hctx(hctx, flush_rq);
+ flush_rq->internal_tag = -1;
}

running = &fq->flush_queue[fq->flush_running_idx];
@@ -248,9 +234,6 @@ static void flush_end_io(struct request *flush_rq, blk_status_t error)
/* account completion of the flush request */
fq->flush_running_idx ^= 1;

- if (!q->mq_ops)
- elv_completed_request(q, flush_rq);
-
/* and push the waiting requests to the next stage */
list_for_each_entry_safe(rq, n, running, flush.list) {
unsigned int seq = blk_flush_cur_seq(rq);
@@ -259,24 +242,8 @@ static void flush_end_io(struct request *flush_rq, blk_status_t error)
queued |= blk_flush_complete_seq(rq, fq, seq, error);
}

- /*
- * Kick the queue to avoid stall for two cases:
- * 1. Moving a request silently to empty queue_head may stall the
- * queue.
- * 2. When flush request is running in non-queueable queue, the
- * queue is hold. Restart the queue after flush request is finished
- * to avoid stall.
- * This function is called from request completion path and calling
- * directly into request_fn may confuse the driver. Always use
- * kblockd.
- */
- if (queued || fq->flush_queue_delayed) {
- WARN_ON(q->mq_ops);
- blk_run_queue_async(q);
- }
fq->flush_queue_delayed = 0;
- if (q->mq_ops)
- spin_unlock_irqrestore(&fq->mq_flush_lock, flags);
+ spin_unlock_irqrestore(&fq->mq_flush_lock, flags);
}

/**
@@ -301,6 +268,7 @@ static bool blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq,
struct request *first_rq =
list_first_entry(pending, struct request, flush.list);
struct request *flush_rq = fq->flush_rq;
+ struct blk_mq_hw_ctx *hctx;

/* C1 described at the top of this file */
if (fq->flush_pending_idx != fq->flush_running_idx || list_empty(pending))
@@ -334,19 +302,15 @@ static bool blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq,
* In case of IO scheduler, flush rq need to borrow scheduler tag
* just for cheating put/get driver tag.
*/
- if (q->mq_ops) {
- struct blk_mq_hw_ctx *hctx;
-
- flush_rq->mq_ctx = first_rq->mq_ctx;
-
- if (!q->elevator) {
- fq->orig_rq = first_rq;
- flush_rq->tag = first_rq->tag;
- hctx = blk_mq_map_queue(q, first_rq->mq_ctx->cpu);
- blk_mq_tag_set_rq(hctx, first_rq->tag, flush_rq);
- } else {
- flush_rq->internal_tag = first_rq->internal_tag;
- }
+ flush_rq->mq_ctx = first_rq->mq_ctx;
+
+ if (!q->elevator) {
+ fq->orig_rq = first_rq;
+ flush_rq->tag = first_rq->tag;
+ hctx = blk_mq_map_queue(q, first_rq->mq_ctx->cpu);
+ blk_mq_tag_set_rq(hctx, first_rq->tag, flush_rq);
+ } else {
+ flush_rq->internal_tag = first_rq->internal_tag;
}

flush_rq->cmd_flags = REQ_OP_FLUSH | REQ_PREFLUSH;
@@ -358,49 +322,6 @@ static bool blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq,
return blk_flush_queue_rq(flush_rq, false);
}

-static void flush_data_end_io(struct request *rq, blk_status_t error)
-{
- struct request_queue *q = rq->q;
- struct blk_flush_queue *fq = blk_get_flush_queue(q, NULL);
-
- lockdep_assert_held(q->queue_lock);
-
- /*
- * Updating q->in_flight[] here for making this tag usable
- * early. Because in blk_queue_start_tag(),
- * q->in_flight[BLK_RW_ASYNC] is used to limit async I/O and
- * reserve tags for sync I/O.
- *
- * More importantly this way can avoid the following I/O
- * deadlock:
- *
- * - suppose there are 40 fua requests comming to flush queue
- * and queue depth is 31
- * - 30 rqs are scheduled then blk_queue_start_tag() can't alloc
- * tag for async I/O any more
- * - all the 30 rqs are completed before FLUSH_PENDING_TIMEOUT
- * and flush_data_end_io() is called
- * - the other rqs still can't go ahead if not updating
- * q->in_flight[BLK_RW_ASYNC] here, meantime these rqs
- * are held in flush data queue and make no progress of
- * handling post flush rq
- * - only after the post flush rq is handled, all these rqs
- * can be completed
- */
-
- elv_completed_request(q, rq);
-
- /* for avoiding double accounting */
- rq->rq_flags &= ~RQF_STARTED;
-
- /*
- * After populating an empty queue, kick it to avoid stall. Read
- * the comment in flush_end_io().
- */
- if (blk_flush_complete_seq(rq, fq, REQ_FSEQ_DATA, error))
- blk_run_queue_async(q);
-}
-
static void mq_flush_data_end_io(struct request *rq, blk_status_t error)
{
struct request_queue *q = rq->q;
@@ -443,9 +364,6 @@ void blk_insert_flush(struct request *rq)
unsigned int policy = blk_flush_policy(fflags, rq);
struct blk_flush_queue *fq = blk_get_flush_queue(q, rq->mq_ctx);

- if (!q->mq_ops)
- lockdep_assert_held(q->queue_lock);
-
/*
* @policy now records what operations need to be done. Adjust
* REQ_PREFLUSH and FUA for the driver.
@@ -468,10 +386,7 @@ void blk_insert_flush(struct request *rq)
* complete the request.
*/
if (!policy) {
- if (q->mq_ops)
- blk_mq_end_request(rq, 0);
- else
- __blk_end_request(rq, 0, 0);
+ blk_mq_end_request(rq, 0);
return;
}

@@ -484,10 +399,7 @@ void blk_insert_flush(struct request *rq)
*/
if ((policy & REQ_FSEQ_DATA) &&
!(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {
- if (q->mq_ops)
- blk_mq_request_bypass_insert(rq, false);
- else
- list_add_tail(&rq->queuelist, &q->queue_head);
+ blk_mq_request_bypass_insert(rq, false);
return;
}

@@ -499,17 +411,12 @@ void blk_insert_flush(struct request *rq)
INIT_LIST_HEAD(&rq->flush.list);
rq->rq_flags |= RQF_FLUSH_SEQ;
rq->flush.saved_end_io = rq->end_io; /* Usually NULL */
- if (q->mq_ops) {
- rq->end_io = mq_flush_data_end_io;

- spin_lock_irq(&fq->mq_flush_lock);
- blk_flush_complete_seq(rq, fq, REQ_FSEQ_ACTIONS & ~policy, 0);
- spin_unlock_irq(&fq->mq_flush_lock);
- return;
- }
- rq->end_io = flush_data_end_io;
+ rq->end_io = mq_flush_data_end_io;

+ spin_lock_irq(&fq->mq_flush_lock);
blk_flush_complete_seq(rq, fq, REQ_FSEQ_ACTIONS & ~policy, 0);
+ spin_unlock_irq(&fq->mq_flush_lock);
}

/**
@@ -575,8 +482,7 @@ struct blk_flush_queue *blk_alloc_flush_queue(struct request_queue *q,
if (!fq)
goto fail;

- if (q->mq_ops)
- spin_lock_init(&fq->mq_flush_lock);
+ spin_lock_init(&fq->mq_flush_lock);

rq_sz = round_up(rq_sz + cmd_size, cache_line_size());
fq->flush_rq = kzalloc_node(rq_sz, flags, node);
diff --git a/block/blk.h b/block/blk.h
index a1841b8ff129..57a302bf5a70 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -114,9 +114,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
static inline struct blk_flush_queue *blk_get_flush_queue(
struct request_queue *q, struct blk_mq_ctx *ctx)
{
- if (q->mq_ops)
- return blk_mq_map_queue(q, ctx->cpu)->fq;
- return q->fq;
+ return blk_mq_map_queue(q, ctx->cpu)->fq;
}

static inline void __blk_get_queue(struct request_queue *q)
--
2.17.1