linux-kernel - Re: [v6 PATCH] block: introduce block_rq

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Message-ID: <ff0d4285-471b-7a33-15a5-3ce89443b41a@nvidia.com>
Date:   Fri, 4 Feb 2022 08:35:02 +0000
From:   Chaitanya Kulkarni <chaitanyak@...dia.com>
To:     Yang Shi <shy828301@...il.com>
CC:     "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "axboe@...nel.dk" <axboe@...nel.dk>,
        "hch@...radead.org" <hch@...radead.org>
Subject: Re: [v6 PATCH] block: introduce block_rq_error tracepoint

Yang,

> Question 1 :- What prevents us from using the same format for
> both blk_rq_complete() and blk_rq_error() ?
> 
> Question 2 :- assuming that blk_rq_complete() and blk_rq_error()
> are using same format why can't we :-
> 
> declare DECLARE_EVENT_CLASS(blk_rq_completion....)
> and use that class for blk_rq_complete() and blk_rq_error() ?
> 
> since if I remember correctly we need to define a event class
> instead of duplicating a tracepoint with similar reporting.

What I meant is following compile tested patch (although it will
need to split into a prep patch in order to post it) :-

diff --git a/include/trace/events/block.h b/include/trace/events/block.h
index 27170e40e8c9..7f4dfbdf12a6 100644
--- a/include/trace/events/block.h
+++ b/include/trace/events/block.h
@@ -100,19 +100,7 @@ TRACE_EVENT(block_rq_requeue,
                   __entry->nr_sector, 0)
  );

-/**
- * block_rq_complete - block IO operation completed by device driver
- * @rq: block operations request
- * @error: status code
- * @nr_bytes: number of completed bytes
- *
- * The block_rq_complete tracepoint event indicates that some portion
- * of operation request has been completed by the device driver.  If
- * the @rq->bio is %NULL, then there is absolutely no additional work to
- * do for the request. If @rq->bio is non-NULL then there is
- * additional work required to complete the request.
- */
-TRACE_EVENT(block_rq_complete,
+DECLARE_EVENT_CLASS(block_rq_completion,

         TP_PROTO(struct request *rq, blk_status_t error, unsigned int 
nr_bytes),

@@ -144,6 +132,41 @@ TRACE_EVENT(block_rq_complete,
                   __entry->nr_sector, __entry->error)
  );

+/**
+ * block_rq_complete - block IO operation completed by device driver
+ * @rq: block operations request
+ * @error: status code
+ * @nr_bytes: number of completed bytes
+ *
+ * The block_rq_complete tracepoint event indicates that some portion
+ * of operation request has been completed by the device driver.  If
+ * the @rq->bio is %NULL, then there is absolutely no additional work to
+ * do for the request. If @rq->bio is non-NULL then there is
+ * additional work required to complete the request.
+ */
+DEFINE_EVENT(block_rq_completion, block_rq_complete,
+
+       TP_PROTO(struct request *rq, blk_status_t error, unsigned int 
nr_bytes),
+
+       TP_ARGS(rq, error, nr_bytes)
+);
+
+/**
+ * block_rq_error - block IO operation error reported by device driver
+ * @rq: block operations request
+ * @error: status code
+ * @nr_bytes: number of completed bytes
+ *
+ * The block_rq_error tracepoint event indicates that some portion
+ * of operation request has failed as reported by the device driver.
+ */
+DEFINE_EVENT(block_rq_completion, block_rq_error,
+
+       TP_PROTO(struct request *rq, blk_status_t error, unsigned int 
nr_bytes),
+
+       TP_ARGS(rq, error, nr_bytes)
+);
+
  DECLARE_EVENT_CLASS(block_rq,

         TP_PROTO(struct request *rq),
> 
> -ck
> 
>