Re: [PATCH 2/3] mm, bootmem: panic in bootmem alloc functions even if slab is available

Hello, Sasha.

2012/12/28 Sasha Levin [off-list ref]:

On 12/27/2012 06:04 PM, David Rientjes wrote:

quoted

On Thu, 27 Dec 2012, Sasha Levin wrote:

quoted

That's exactly what happens with the patch. Note that in the current upstream
version there are several slab checks scattered all over.

In this case for example, I'm removing it from __alloc_bootmem_node(), but the
first code line of__alloc_bootmem_node_nopanic() is:

        if (WARN_ON_ONCE(slab_is_available()))
                return kzalloc(size, GFP_NOWAIT);

You're only talking about mm/bootmem.c and not mm/nobootmem.c, and notice
that __alloc_bootmem_node() does not call __alloc_bootmem_node_nopanic(),
it calls ___alloc_bootmem_node_nopanic().

Holy cow, this is an underscore hell.


Thanks,
Sasha

I have a different idea.
How about removing fallback allocation in bootmem.c completely?
I don't know why it is there exactly.
But, warning for 'slab_is_available()' is there for a long time.
So, most people who misuse fallback allocation change their code adequately.
I think that removing fallback at this time is valid. Isn't it?

Fallback allocation may cause possible bug.
If someone free a memory from fallback allocation,
it can't be handled properly.

So, IMHO, at this time, we should remove fallback allocation in
bootmem.c entirely.
Please let me know what I misunderstand.

Thanks.

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