linux-kernel - Re: [PATCH/RFC 3/3] s390: query dynamic DEBUG

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Message-ID: <20160126181903.GB4671@osiris>
Date:	Tue, 26 Jan 2016 19:19:03 +0100
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Christian Borntraeger <borntraeger@...ibm.com>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	linux-mm@...ck.org, linux-arch@...r.kernel.org,
	linux-s390@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH/RFC 3/3] s390: query dynamic DEBUG_PAGEALLOC setting

On Tue, Jan 26, 2016 at 10:18:25AM +0100, Christian Borntraeger wrote:
> We can use debug_pagealloc_enabled() to check if we can map
> the identity mapping with 1MB/2GB pages as well as to print
> the current setting in dump_stack.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
> ---
>  arch/s390/kernel/dumpstack.c |  4 +++-
>  arch/s390/mm/vmem.c          | 10 ++++------
>  2 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/s390/kernel/dumpstack.c b/arch/s390/kernel/dumpstack.c
> index dc8e204..a1c0530 100644
> --- a/arch/s390/kernel/dumpstack.c
> +++ b/arch/s390/kernel/dumpstack.c
> @@ -11,6 +11,7 @@
>  #include <linux/export.h>
>  #include <linux/kdebug.h>
>  #include <linux/ptrace.h>
> +#include <linux/mm.h>
>  #include <linux/module.h>
>  #include <linux/sched.h>
>  #include <asm/processor.h>
> @@ -186,7 +187,8 @@ void die(struct pt_regs *regs, const char *str)
>  	printk("SMP ");
>  #endif
>  #ifdef CONFIG_DEBUG_PAGEALLOC
> -	printk("DEBUG_PAGEALLOC");
> +	printk("DEBUG_PAGEALLOC(%s)",
> +		debug_pagealloc_enabled() ? "enabled" : "disabled");
>  #endif

I'd prefer if you change this to

	if (debug_pagealloc_enabled())
		printk("DEBUG_PAGEALLOC");

That way we can get rid of yet another ifdef. Having
"DEBUG_PAGEALLOC(disabled)" doesn't seem to be very helpful.