linux-kernel - Re: [PATCH] [3/16] POISON: Handle poisoned pages in page free

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Date:	Wed, 8 Apr 2009 16:39:17 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org
Subject: Re: [PATCH] [3/16] POISON: Handle poisoned pages in page free

On Wed, Apr 8, 2009 at 3:51 PM, Andi Kleen <andi@...stfloor.org> wrote:
>> >
>> >        /*
>> > +        * Page may have been marked bad before process is freeing it.
>> > +        * Make sure it is not put back into the free page lists.
>> > +        */
>> > +       if (PagePoison(page)) {
>> > +               /* check more flags here... */
>>
>> How about adding WARNING with some information(ex, pfn, flags..).
>
> The memory_failure() code is already quite chatty. Don't think more
> noise is needed currently.

Sure.

> Or are you worrying about the case where a page gets corrupted
> by software and suddenly has Poison bits set? (e.g. 0xff everywhere).
> That would deserve a printk, but I'm not sure how to reliably test for
> that. After all a lot of flag combinations are valid.

I misunderstood your code.
That's because you add the code in bad_page.

As you commented, your intention was to prevent bad page from returning buddy.
Is right ?
If it is right, how about adding prevention code to free_pages_check ?
Now, bad_page is for showing the information that why it is bad page
I don't like emergency exit in bad_page.

> -Andi
>
> --
> ak@...ux.intel.com -- Speaking for myself only.
>



-- 
Kinds regards,
Minchan Kim
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