linux-kernel - Re: [PATCH v2] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

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Message-ID: <20150727233219.GA1720@dhcp-17-102.nay.redhat.com>
Date:	Tue, 28 Jul 2015 07:32:19 +0800
From:	Baoquan He <bhe@...hat.com>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Dave Young <dyoung@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Vivek Goyal <vgoyal@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] Do not reserve crashkernel high memory if crashkernel
 low memory reserving failed

On 07/27/15 at 11:31am, Yinghai Lu wrote:
> >>  #else
> >>  static void __init reserve_crashkernel(void)
> 
> No, you can not move the calling position for reserve_crashkernel_low().
> 
> old sequence:
> 
> memblock_find_in_range  for high
> memblock_reserve for high
> memblock_find_in_range  for low
> memblock_reserve for low
> 
> now you change to:
> memblock_find_in_range  for high
> memblock_find_in_range  for low
> memblock_reserve for low
> memblock_reserve for high
> 
> during memblock_reserve, we would double the memblock reserve array.
> So there is possibility that new membock reserve array is overlapped with
> range for  crashdump high.
> 
> so you should keep the old sequence, and if reserve_crashkernel_low fail,
> just call memblock_free to free high range that is reserved before.

Right, memblock_double_array need avoid the required region. Will
repost.

> 
> Thanks
> 
> Yinghai
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