linux-kernel - Re: [PATCH] printk: kmsg_dump: revert msg_print

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Date:   Thu, 14 Jan 2021 16:49:50 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: kmsg_dump: revert msg_print_text() workaround

On Thu 2021-01-14 10:11:11, John Ogness wrote:
> The old msg_print_text() function only filled up to size-1 bytes of
> the buffer. A workaround for this quirky behavior was implemented
> with commit c9dccacfccc7 ("printk: Do not lose last line in kmsg
> buffer dump").
> 
> However, with commit 896fbe20b4e2 ("printk: use the lockless
> ringbuffer"), msg_print_text() was replaced by,
> which will fill the full buffer. Therefore, the workaround is now
> incorrectly assuming less data can fit into the buffer. Revert the
> workaround.

We should make record_print_text() behave the same as msg_print_text()
behaved. There might be more users affected by this change and even
in userspace :-(

Let's discuss it in the other thread
https://lore.kernel.org/lkml/87im8038v7.fsf@jogness.linutronix.de/

Best Regards,
Petr