linux-kernel - Re: [patch 2/2] bootmem: Node-setup agnostic free

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Message-ID: <86802c440804150028t33fabd7fn40d3d47d0482bfc1@mail.gmail.com>
Date:	Tue, 15 Apr 2008 00:28:34 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Andrew Morton" <akpm@...ux-foundation.org>
Cc:	"Andi Kleen" <andi@...stfloor.org>,
	"Johannes Weiner" <hannes@...urebad.de>,
	linux-kernel@...r.kernel.org, "Ingo Molnar" <mingo@...e.hu>,
	"Yasunori Goto" <y-goto@...fujitsu.com>,
	"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
	"Christoph Lameter" <clameter@....com>
Subject: Re: [patch 2/2] bootmem: Node-setup agnostic free_bootmem()

On Tue, Apr 15, 2008 at 12:15 AM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
>
> On Tue, 15 Apr 2008 00:04:03 -0700 "Yinghai Lu" <yhlu.kernel@...il.com> wrote:
>
>  > On Mon, Apr 14, 2008 at 11:23 PM, Andrew Morton
>  > <akpm@...ux-foundation.org> wrote:
>  > >
>  > > On Sun, 13 Apr 2008 18:56:57 +0200 Andi Kleen <andi@...stfloor.org> wrote:
>  > >
>  > >  > Johannes Weiner <hannes@...urebad.de> writes:
>  > >  >
>  > >  > > Make free_bootmem() look up the node holding the specified address
>  > >  > > range which lets it work transparently on single-node and multi-node
>  > >  > > configurations.
>  > >  >
>  > >  > Acked-by: Andi Kleen <andi@...stfloor.org>
>  > >  >
>  > >  > This is far better than the original change it replaces and which
>  > >  > I also objected to in review.
>  > >  >
>  > >
>  > >  So...  do we think these two patches are sufficiently safe and important for
>  > >  2.6.25?
>  >
>  > the patch is wrong
>  >
>
>  The last I saw was this:
>
>
>  On Sun, 13 Apr 2008 12:57:22 +0200 Johannes Weiner <hannes@...urebad.de> wrote:
>
>  > Hi,
>  >
>  > "Yinghai Lu" <yhlu.kernel@...il.com> writes:
>  >
>  > > On Sat, Apr 12, 2008 at 3:33 PM, Johannes Weiner <hannes@...urebad.de> wrote:
>  > > ...
>
> > >
>  > > could have chance that bootmem with reserved_early that is crossing
>  > > the nodes.
>  >
>  > Upstream reserve_bootmem_core() would BUG() on a caller trying to cross
>  > nodes, so I don't see where this chance could come from.
>
>  Is that what you're referring to?
>
>  Was Johannes observation incorrect?  If so, why?

my patch with free_bootmem will make sure free_bootmem_core only free
bootmem in the bdata scope.
so free_bootmem can handle the cross_node bootmem that is done by
reserve_early ( done in another patch, is dropped by you because took
Jonannes).

in setup_arch for x86_64 there is one free_bootmem that is used when
ramdisk is falled out of ram map. that could be crossed by bootloader
and kexec, and kernel or second kernel is memmap=NN@SS to execlue some
memory.

anyway that is extrem case, but my patch could handle that.

I wonder if any regression caused by my previous patch? maybe on other platform?

YH
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