linux-kernel - Re: [PATCH v7 7/8] blktrace: ensure our debugfs dir exists

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Message-ID: <379e1fc9-a070-7730-71cd-aee7f582d403@acm.org>
Date:   Sat, 20 Jun 2020 10:33:29 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Luis Chamberlain <mcgrof@...nel.org>, axboe@...nel.dk,
        viro@...iv.linux.org.uk, gregkh@...uxfoundation.org,
        rostedt@...dmis.org, mingo@...hat.com, jack@...e.cz,
        ming.lei@...hat.com, nstange@...e.de, akpm@...ux-foundation.org
Cc:     mhocko@...e.com, yukuai3@...wei.com, martin.petersen@...cle.com,
        jejb@...ux.ibm.com, linux-block@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 7/8] blktrace: ensure our debugfs dir exists

On 2020-06-19 13:47, Luis Chamberlain wrote:
> diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
> index e6e2d25fdbd6..098780ec018f 100644
> --- a/kernel/trace/blktrace.c
> +++ b/kernel/trace/blktrace.c
> @@ -538,6 +538,18 @@ static int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
>  #endif
>  		bt->dir = dir = debugfs_create_dir(buts->name, blk_debugfs_root);
>  
> +	/*
> +	 * As blktrace relies on debugfs for its interface the debugfs directory
> +	 * is required, contrary to the usual mantra of not checking for debugfs
> +	 * files or directories.
> +	 */
> +	if (IS_ERR_OR_NULL(dir)) {
> +		pr_warn("debugfs_dir not present for %s so skipping\n",
> +			buts->name);

Maybe mention in the message what is being skipped (block tracing)?

> +		ret = -ENOENT;
> +		goto err;
> +	}
> +
>  	bt->dev = dev;
>  	atomic_set(&bt->dropped, 0);
>  	INIT_LIST_HEAD(&bt->running_list);

Anyway:

Reviewed-by: Bart Van Assche <bvanassche@....org>