linux-kernel - Re: [PATCH 18/34] mm: Update vma_iter_store() to use MAS_WARN

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Message-ID: <20230427010707.GG1496740@google.com>
Date:   Thu, 27 Apr 2023 10:07:07 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        maple-tree@...ts.infradead.org, Petr Mladek <pmladek@...e.com>
Subject: Re: [PATCH 18/34] mm: Update vma_iter_store() to use MAS_WARN_ON()

Cc-ing Petr

On (23/04/25 10:09), Liam R. Howlett wrote:
> +	if (MAS_WARN_ON(&vmi->mas, vmi->mas.node != MAS_START &&
> +			vmi->mas.index > vma->vm_start)) {
> +		printk("%lx > %lx\n", vmi->mas.index, vma->vm_start);
> +		printk("store of vma %lx-%lx", vma->vm_start, vma->vm_end);
> +		printk("into slot    %lx-%lx", vmi->mas.index, vmi->mas.last);
>  	}

[..]

> +	if (MAS_WARN_ON(&vmi->mas, vmi->mas.node != MAS_START &&
> +			vmi->mas.last <  vma->vm_start)) {
> +		printk("%lx < %lx\n", vmi->mas.last, vma->vm_start);
> +		printk("store of vma %lx-%lx", vma->vm_start, vma->vm_end);
> +		printk("into slot    %lx-%lx", vmi->mas.index, vmi->mas.last);
>  	}

Any reason for "store of vma" and "into slot" to be two separate
printk()-s? It's not guaranteed that these will be printed as a
continuous line. A single printk should work fine:

	pr_foo("store of vma %lx-%lx into slot    %lx-%lx", ...);

The line probably needs to be terminated with \n unless you expect
more pr_cont() printks after this, which doesn't look like a case.
Additionally, do you want to pass a specific loglevel? E.g. pr_debug()?