linux-kernel - Re: [Patch v4] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

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Message-ID: <20150923000255.GA2569@dhcp-17-102.nay.redhat.com>
Date:	Wed, 23 Sep 2015 08:02:55 +0800
From:	Baoquan He <bhe@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	yinghai@...nel.org, dyoung@...hat.com, jroedel@...e.de,
	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, bp@...e.de,
	linux-kernel@...r.kernel.org
Subject: Re: [Patch v4] Do not reserve crashkernel high memory if crashkernel
 low memory reserving failed

On 09/22/15 at 12:54pm, Andrew Morton wrote:
> > --- a/arch/x86/kernel/setup.c
> > +++ b/arch/x86/kernel/setup.c
> > @@ -493,7 +493,7 @@ static void __init memblock_x86_reserve_range_setup_data(void)
> >  # define CRASH_KERNEL_ADDR_HIGH_MAX	MAXMEM
> >  #endif
> >  
> > -static void __init reserve_crashkernel_low(void)
> > +static int __init reserve_crashkernel_low(void)
> >  {
> >  #ifdef CONFIG_X86_64
> >  	const unsigned long long alignment = 16<<20;	/* 16M */
> > @@ -522,17 +522,15 @@ static void __init reserve_crashkernel_low(void)
> >  	} else {
> >  		/* passed with crashkernel=0,low ? */
> >  		if (!low_size)
> > -			return;
> > +			return 0;
> 
> What's happening here?  It's returning "success" when
> parse_crashkernel_low() fails?

It's the case user specify "crashkernel=0,low" to disable
crashkernel low memory allocation explicitly. So here we parse the
cmdline and get it's in this case, reture 0 directly.

> 
> >  	}
> >  
> >  	low_base = memblock_find_in_range(low_size, (1ULL<<32),
> >  					low_size, alignment);
> >  
> >  	if (!low_base) {
> > -		if (!auto_set)
> > -			pr_info("crashkernel low reservation failed - No suitable area found.\n");
> > -
> > -		return;
> > +		pr_info("crashkernel low reservation failed - No suitable area found.\n");
> 
> That's not a terribly useful message.  If kdump is now unavailable and
> the operator needs to take some remedial action then we should inform
> them of this.
> 
> Also, such a message should have higher severity than KERN_INFO?

Yes, how about KERN_ERR? It's an unexpected result from kdump side
though it doesn't harm the normal kernel.


> 
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