linux-kernel - Re: [PATCH] mm: BUG when __kmap_atomic

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Date:	Wed, 30 Jul 2014 03:37:21 -0700
From:	Davidlohr Bueso <davidlohr@...com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Chintan Pandya <cpandya@...eaurora.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] mm: BUG when __kmap_atomic_idx crosses boundary


On Wed, 2014-07-30 at 02:06 -0700, Andrew Morton wrote:
> On Wed, 30 Jul 2014 14:22:35 +0530 Chintan Pandya <cpandya@...eaurora.org> wrote:
> 
> > __kmap_atomic_idx >= KM_TYPE_NR or < ZERO is a bug.
> > Report it even if CONFIG_DEBUG_HIGHMEM is not enabled.
> > That saves much debugging efforts.
> 
> Please take considerably more care when preparing patch changelogs.
> 
> kmap_atomic() is a very commonly called function so we'll need much
> more detail than this to justify adding overhead to it.
> 
> I don't think CONFIG_DEBUG_HIGHMEM really needs to exist.  We could do
> s/CONFIG_DEBUG_HIGHMEM/CONFIG_DEBUG_VM/g and perhaps your secret bug
> whatever it was would have been found more easily.

Agreed, it would be nice to fold DEBUG_HIGHMEM into DEBUG_VM. However
you'd still need some kind of intermediate option as DEBUG_VM must still
exist if !HIGHMEM.

Thanks,
Davidlohr


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