* [PATCH] blk-mq: fix passthrough plugging
@ 2022-05-12 14:00 Ming Lei
2022-05-12 14:45 ` Jens Axboe
0 siblings, 1 reply; 2+ messages in thread
From: Ming Lei @ 2022-05-12 14:00 UTC (permalink / raw)
To: Jens Axboe; +Cc: linux-block, Ming Lei, Christoph Hellwig
First we can't add request into plug list in blk_mq_request_bypass_insert
which may be called when flushing plug list, so nested plug is caused.
Second if polled passthrough request is inserted via blk_execute_rq(),
it can't be added to plug list too since io polling needs the request
to be issued to driver.
Fixes the two by moving plugging into blk_execute_rq_no_wait().
Cc: Christoph Hellwig <hch@lst.de>
Fixes: 1c2d2fff6dc0 ("block: wire-up support for passthrough plugging")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
block/blk-mq.c | 114 +++++++++++++++++++++++++++----------------------
1 file changed, 63 insertions(+), 51 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 2cf011b57cf9..ed1869a305c4 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1169,6 +1169,62 @@ static void blk_end_sync_rq(struct request *rq, blk_status_t error)
complete(waiting);
}
+/*
+ * Allow 2x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple
+ * queues. This is important for md arrays to benefit from merging
+ * requests.
+ */
+static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)
+{
+ if (plug->multiple_queues)
+ return BLK_MAX_REQUEST_COUNT * 2;
+ return BLK_MAX_REQUEST_COUNT;
+}
+
+static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
+{
+ struct request *last = rq_list_peek(&plug->mq_list);
+
+ if (!plug->rq_count) {
+ trace_block_plug(rq->q);
+ } else if (plug->rq_count >= blk_plug_max_rq_count(plug) ||
+ (!blk_queue_nomerges(rq->q) &&
+ blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
+ blk_mq_flush_plug_list(plug, false);
+ trace_block_plug(rq->q);
+ }
+
+ if (!plug->multiple_queues && last && last->q != rq->q)
+ plug->multiple_queues = true;
+ if (!plug->has_elevator && (rq->rq_flags & RQF_ELV))
+ plug->has_elevator = true;
+ rq->rq_next = NULL;
+ rq_list_add(&plug->mq_list, rq);
+ plug->rq_count++;
+}
+
+static void __blk_execute_rq_nowait(struct request *rq, bool at_head,
+ rq_end_io_fn *done, bool use_plug)
+{
+ WARN_ON(irqs_disabled());
+ WARN_ON(!blk_rq_is_passthrough(rq));
+
+ rq->end_io = done;
+
+ blk_account_io_start(rq);
+
+ if (use_plug && current->plug) {
+ blk_add_rq_to_plug(current->plug, rq);
+ return;
+ }
+ /*
+ * don't check dying flag for MQ because the request won't
+ * be reused after dying flag is set
+ */
+ blk_mq_sched_insert_request(rq, at_head, true, false);
+}
+
+
/**
* blk_execute_rq_nowait - insert a request to I/O scheduler for execution
* @rq: request to insert
@@ -1184,18 +1240,8 @@ static void blk_end_sync_rq(struct request *rq, blk_status_t error)
*/
void blk_execute_rq_nowait(struct request *rq, bool at_head, rq_end_io_fn *done)
{
- WARN_ON(irqs_disabled());
- WARN_ON(!blk_rq_is_passthrough(rq));
-
- rq->end_io = done;
+ __blk_execute_rq_nowait(rq, at_head, done, true);
- blk_account_io_start(rq);
-
- /*
- * don't check dying flag for MQ because the request won't
- * be reused after dying flag is set
- */
- blk_mq_sched_insert_request(rq, at_head, true, false);
}
EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
@@ -1233,8 +1279,13 @@ blk_status_t blk_execute_rq(struct request *rq, bool at_head)
DECLARE_COMPLETION_ONSTACK(wait);
unsigned long hang_check;
+ /*
+ * iopoll requires request to be submitted to driver, so can't
+ * use plug
+ */
rq->end_io_data = &wait;
- blk_execute_rq_nowait(rq, at_head, blk_end_sync_rq);
+ __blk_execute_rq_nowait(rq, at_head, blk_end_sync_rq,
+ !blk_rq_is_poll(rq));
/* Prevent hang_check timer from firing at us during very long I/O */
hang_check = sysctl_hung_task_timeout_secs;
@@ -2340,40 +2391,6 @@ void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
blk_mq_hctx_mark_pending(hctx, ctx);
}
-/*
- * Allow 2x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple
- * queues. This is important for md arrays to benefit from merging
- * requests.
- */
-static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)
-{
- if (plug->multiple_queues)
- return BLK_MAX_REQUEST_COUNT * 2;
- return BLK_MAX_REQUEST_COUNT;
-}
-
-static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
-{
- struct request *last = rq_list_peek(&plug->mq_list);
-
- if (!plug->rq_count) {
- trace_block_plug(rq->q);
- } else if (plug->rq_count >= blk_plug_max_rq_count(plug) ||
- (!blk_queue_nomerges(rq->q) &&
- blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {
- blk_mq_flush_plug_list(plug, false);
- trace_block_plug(rq->q);
- }
-
- if (!plug->multiple_queues && last && last->q != rq->q)
- plug->multiple_queues = true;
- if (!plug->has_elevator && (rq->rq_flags & RQF_ELV))
- plug->has_elevator = true;
- rq->rq_next = NULL;
- rq_list_add(&plug->mq_list, rq);
- plug->rq_count++;
-}
-
/**
* blk_mq_request_bypass_insert - Insert a request at dispatch list.
* @rq: Pointer to request to be inserted.
@@ -2387,12 +2404,7 @@ void blk_mq_request_bypass_insert(struct request *rq, bool at_head,
bool run_queue)
{
struct blk_mq_hw_ctx *hctx = rq->mq_hctx;
- struct blk_plug *plug = current->plug;
- if (plug) {
- blk_add_rq_to_plug(plug, rq);
- return;
- }
spin_lock(&hctx->lock);
if (at_head)
list_add(&rq->queuelist, &hctx->dispatch);
--
2.31.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] blk-mq: fix passthrough plugging
2022-05-12 14:00 [PATCH] blk-mq: fix passthrough plugging Ming Lei
@ 2022-05-12 14:45 ` Jens Axboe
0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2022-05-12 14:45 UTC (permalink / raw)
To: ming.lei; +Cc: Christoph Hellwig, linux-block
On Thu, 12 May 2022 22:00:10 +0800, Ming Lei wrote:
> First we can't add request into plug list in blk_mq_request_bypass_insert
> which may be called when flushing plug list, so nested plug is caused.
>
> Second if polled passthrough request is inserted via blk_execute_rq(),
> it can't be added to plug list too since io polling needs the request
> to be issued to driver.
>
> [...]
Applied, thanks!
[1/1] blk-mq: fix passthrough plugging
commit: a327c341dc65e38af7a2398e7313e6f2c4a813db
Best regards,
--
Jens Axboe
^ permalink raw reply [flat|nested] 2+ messages in thread
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2022-05-12 14:00 [PATCH] blk-mq: fix passthrough plugging Ming Lei
2022-05-12 14:45 ` Jens Axboe
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