linux-kernel - Re: [PATCH][next] printk: ringbuffer: support dataless records

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Message-ID: <20200721025450.GA5678@jagdpanzerIV.localdomain>
Date:   Tue, 21 Jul 2020 11:54:50 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marco Elver <elver@...gle.com>, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] printk: ringbuffer: support dataless records

On (20/07/20 16:07), John Ogness wrote:
>  
> +/* Determine if a logical position refers to a data-less block. */
> +#define LPOS_DATALESS(lpos)		((lpos) & 1UL)
> +

[..]

> @@ -1402,7 +1396,9 @@ static int prb_read(struct printk_ringbuffer *rb, u64 seq,
>  	/* Copy text data. If it fails, this is a data-less record. */
>  	if (!copy_data(&rb->text_data_ring, &desc.text_blk_lpos, desc.info.text_len,
>  		       r->text_buf, r->text_buf_size, line_count)) {
> -		return -ENOENT;
> +		/* Report an error if there should have been data. */
> +		if (desc.info.text_len != 0)
> +			return -ENOENT;
>  	}

If this is a dataless record then should copy_data() return error?

Otherwise, looks good to me
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>

	-ss