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SubjectRe: [dm-devel] [PATCH v5] fault-injection: introduce kvmalloc fallback options
On Thu, Apr 26, 2018 at 05:50:20PM -0400, Mikulas Patocka wrote:
> How is the user or developer supposed to learn about this option, if
> he gets no crash at all?

Look in /sys/kernel/debug/fail* ? That actually lets you
filter by module, process etc.

I think this patch conflates two things:

1. Make kvmalloc use the vmalloc path.
This seems a bit narrow.
What is special about kvmalloc? IMHO nothing - it's yet another user
of __GFP_NORETRY or __GFP_RETRY_MAYFAIL. As any such
user, it either recovers correctly or not.
So IMHO it's just a case of
making __GFP_NORETRY, __GFP_RETRY_MAYFAIL, or both
fail once in a while.
Seems like a better extension to me than focusing on vmalloc.
I think you will find more bugs this way.

2. Ability to control this from a separate config
option.

It's still not that clear to me why is this such a
hard requirement. If a distro wants to force specific
boot time options, why isn't CONFIG_CMDLINE sufficient?

But assuming it's important to control this kind of
fault injection to be controlled from
a dedicated menuconfig option, why not the rest of
faults?

IMHO if you split 1/2 up, and generalize, the path upstream
will be much smoother.

Hope this helps.

--
MST

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