Re: [PATCH] mm: BUG when __kmap_atomic_idx crosses boundary

From: Chintan Pandya
Date: Thu Jul 31 2014 - 01:36:37 EST

On 07/30/2014 02:36 PM, Andrew Morton wrote:
On Wed, 30 Jul 2014 14:22:35 +0530 Chintan Pandya<cpandya@xxxxxxxxxxxxxx> 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.
Okay. I will prepare new commit message.

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.
Um, we didn't get bug directly hitting here.

__kmap_atomic_idx should not be equal to KM_TYPE_NR anyway. So, at least I will share that patch. For changing DEBUG_HIGHMEM to DEBUG_VM, I will work on it.

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