linux-kernel - Re: [PATCH 03/13] mm: meminit: Only set page reserved in the memblock region

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Message-ID: <20150526102219.GB13750@suse.de>
Date:	Tue, 26 May 2015 11:22:19 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Tony Luck <tony.luck@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Nathan Zimmer <nzimmer@....com>,
	Dave Hansen <dave.hansen@...el.com>,
	Waiman Long <waiman.long@...com>,
	Scott Norton <scott.norton@...com>,
	Daniel J Blueman <daniel@...ascale.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/13] mm: meminit: Only set page reserved in the
 memblock region

On Fri, May 22, 2015 at 01:31:55PM -0700, Tony Luck wrote:
> On Tue, Apr 28, 2015 at 7:37 AM, Mel Gorman <mgorman@...e.de> wrote:
> > Currently each page struct is set as reserved upon initialization.
> > This patch leaves the reserved bit clear and only sets the reserved bit
> > when it is known the memory was allocated by the bootmem allocator. This
> > makes it easier to distinguish between uninitialised struct pages and
> > reserved struct pages in later patches.
> 
> On ia64 my linux-next builds now report a bunch of messages like this:
> 
> put_kernel_page: page at 0xe000000005588000 not in reserved memory
> put_kernel_page: page at 0xe000000005588000 not in reserved memory
> put_kernel_page: page at 0xe000000005580000 not in reserved memory
> put_kernel_page: page at 0xe000000005580000 not in reserved memory
> put_kernel_page: page at 0xe000000005580000 not in reserved memory
> put_kernel_page: page at 0xe000000005580000 not in reserved memory
> 
> the two different pages match up with two objects from the loaded kernel
> that get mapped by arch/ia64/mm/init.c:setup_gate()
> 
> a000000101588000 D __start_gate_section
> a000000101580000 D empty_zero_page
> 
> Should I look for a place to set the reserved bit on page structures for these
> addresses?

That would be preferred.

> Or just remove the test and message in put_kernel_page()
> [I added a debug "else" clause here - every caller passes in a page that is
> not reserved]
> 
>         if (!PageReserved(page))
>                 printk(KERN_ERR "put_kernel_page: page at 0x%p not in
> reserved memory\n",
>                        page_address(page));
> 

But as it's a debugging check that is ia-64 specific I think either
should be fine.

-- 
Mel Gorman
SUSE Labs
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