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

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Date:	Tue, 20 Oct 2015 10:22:56 -0300
From:	Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
To:	Brian Norris <computersforpeace@...il.com>
Cc:	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Richard Weinberger <richard@....at>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mtd: Add simple read disturb test

On 12 October 2015 at 21:11, Brian Norris <computersforpeace@...il.com> wrote:
> 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).
>

... and the converse also applies. The 'nandtest' tool is not that
NAND-specific,
and I've used it as a quick test on other types of flash devices.

> 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?
>
> If we make the move, we'd need to make sure to update the documentation
> (mtd-www.git).
>

+1 for improving mtd-utils and dropping in-kernel tests.

-- 
Ezequiel García, VanguardiaSur
www.vanguardiasur.com.ar
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