linux-kernel - Re: [PATCH] mtd: Add simple read disturb test

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Date:	Mon, 19 Oct 2015 23:11:15 +0200
From:	Richard Weinberger <richard@....at>
To:	Brian Norris <computersforpeace@...il.com>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:	linux-mtd@...ts.infradead.org, dwmw2@...radead.org,
	linux-kernel@...r.kernel.org, Daniel Walter <sahne@...ma-star.at>
Subject: Re: [PATCH] mtd: Add simple read disturb test

Am 13.10.2015 um 02:11 schrieb Brian Norris:
> Resurrecting this old thread, since it was mentioned at ELCE.
> 
> On Sun, Apr 12, 2015 at 09:31:20PM +0200, Boris Brezillon wrote:
>> On Thu, 02 Apr 2015 18:18:34 +0200
>> Richard Weinberger <richard@....at> wrote:
>>> Am 02.04.2015 um 18:04 schrieb Brian Norris:
>>>> On Thu, Apr 02, 2015 at 04:13:46PM +0200, Richard Weinberger wrote:
>>>>> This simple MTD tests allows the user to see when read disturb happens.
>>>>> By reading blocks over and over it reports flipped bits.
>>>>> Currently it reports only flipped bits of the worst page of a block.
>>>>> If within block X page P1 has 3 bit flips and P6 4, it will report 4.
>>>>> By default every 50th block is read.
>>>>
>>>> Didn't read through this much yet, but why do we need another in-kernel
>>>> test that coul (AFAICT) be easily replicated in userspace? The same goes
>>>> for several of the other tests, I think, actually. But at least with
>>>> those, we have a history of keeping them around, so it's not too much
>>>> burden [1].
>>>
>>> I've added the test to drivers/mtd/tests/ because it fits into.
>>> As simple as that.
>>>
>>>> Brian
>>>>
>>>> [1] Although there are some latent issues in these tests that are still
>>>> getting get worked out (e.g., bad handling of 64-bit casting; too large
>>>> of stacks; uninterruptibility). The latter two would not even exist if
>>>> we were in user space.
>>>
>>> uninterruptibility got solved by my "[PATCH] mtd: Make MTD tests cancelable" patch.
>>>
>>> But if we want to kill drivers/mtd/tests/ I'll happily help out.
>>
>> I'd vote for that solution too.
>> I've looked at in-kernel mtd tests, and I'm pretty sure they can all be
>> done in userland.
>> This would prevent any kernel crash caused by buggy test modules.  
>>
>>> Where shall we move these tests into? mtd-utils?
>>
>> I guess so, but I'll let Brian answer that one.
>> How about dispatching them in mtd-utils' tests/ directory (some of them
>> are NAND related tests, so creating a tests/nand would make sense,
>> and others are more generic).
> 
> mtd-utils makes sense to me. If we're going to do this, let's make it a
> policy to not add more to drivers/mtd/tests/ then. For instance, this
> one [1]. Also, would we drop the in-kernel tests completely?

I agree.
Ripping out in-kernel tests and moving them to mtd-utils seems legit to me.
While we're here, re-factoring existing tests in mtd-utils would also be nice.
I'm also thinking of making UBI tests more user friendly such that distros
can package them into their mtd-utils package.

> If we make the move, we'd need to make sure to update the documentation
> (mtd-www.git).
> 
> Brian
> 
> [1] http://lists.infradead.org/pipermail/linux-mtd/2015-September/062237.html
>     http://lists.infradead.org/pipermail/linux-mtd/2015-September/062236.html

Thanks,
//richard
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