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From: Steven Rostedt <rostedt@goodmis.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>,
	linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org
Subject: Re: [PATCH 2/2] tracing/blktrace: Fix to allow setting same value
Date: Thu, 16 Aug 2018 10:38:02 -0400
Message-ID: <20180816103802.08678002@gandalf.local.home> (raw)
In-Reply-To: <153441307534.6024.2684721209411781531.stgit@devbox>

On Thu, 16 Aug 2018 18:51:15 +0900
Masami Hiramatsu <mhiramat@kernel.org> wrote:

> Current trace-enable attribute in sysfs returns an error
> if user writes the same setting value as current one,
> e.g.
> 
>   # cat /sys/block/sda/trace/enable
>   0
>   # echo 0 > /sys/block/sda/trace/enable
>   bash: echo: write error: Invalid argument
>   # echo 1 > /sys/block/sda/trace/enable
>   # echo 1 > /sys/block/sda/trace/enable
>   bash: echo: write error: Device or resource busy
> 
> But this is not a preferred behavior, it should ignore
> if new setting is same as current one. This fixes the
> problem as below.
> 
>   # cat /sys/block/sda/trace/enable
>   0
>   # echo 0 > /sys/block/sda/trace/enable
>   # echo 1 > /sys/block/sda/trace/enable
>   # echo 1 > /sys/block/sda/trace/enable
> 
> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> Cc: Jens Axboe <axboe@kernel.dk>
> Cc: linux-block@vger.kernel.org
> ---
>  kernel/trace/blktrace.c |   11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index 987d9a9ae283..e67db1e8a000 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -1602,11 +1602,11 @@ static int blk_trace_remove_queue(struct request_queue *q)
>  	struct blk_trace *bt;
>  
>  	bt = xchg(&q->blk_trace, NULL);
> -	if (bt == NULL)
> -		return -EINVAL;
> +	if (bt != NULL) {
> +		put_probe_ref();
> +		blk_trace_free(bt);
> +	}
>  
> -	put_probe_ref();
> -	blk_trace_free(bt);
>  	return 0;
>  }
>  
> @@ -1619,6 +1619,9 @@ static int blk_trace_setup_queue(struct request_queue *q,
>  	struct blk_trace *bt = NULL;
>  	int ret = -ENOMEM;
>  
> +	if (q->blk_trace)
> +		return 0;
> +
>  	bt = kzalloc(sizeof(*bt), GFP_KERNEL);
>  	if (!bt)
>  		return -ENOMEM;

Hmm, why not just do this? Does this fix it too?

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 987d9a9ae283..10b2b9c5fd25 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -1841,6 +1841,8 @@ static ssize_t sysfs_blk_trace_attr_store(struct device *dev,
 	mutex_lock(&q->blk_trace_mutex);
 
 	if (attr == &dev_attr_enable) {
+		if (!!value == !!q->blk_trace)
+			goto out_unlock_bdev;
 		if (value)
 			ret = blk_trace_setup_queue(q, bdev);
 		else

-- Steve

  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <153441301698.6024.1680500212551396320.stgit@devbox>
2018-08-16  9:51 ` Masami Hiramatsu
2018-08-16 14:38   ` Steven Rostedt [this message]
2018-08-16 16:38     ` Masami Hiramatsu
2018-08-16 16:49       ` Steven Rostedt
2018-08-16 17:07         ` Masami Hiramatsu

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