Re: [RFC/PATCH 1/5] mtd: ubi: Read disturb infrastructure

From: Tanya Brokhman <tlinder@codeaurora.org>
To: Richard Weinberger <richard@nod.at>, dedeking1@gmail.com
Cc: Artem Bityutskiy <dedekind1@gmail.com>,
	linux-arm-msm@vger.kernel.org,
	open list <linux-kernel@vger.kernel.org>,
	linux-mtd@lists.infradead.org,
	Brian Norris <computersforpeace@gmail.com>,
	David Woodhouse <dwmw2@infradead.org>
Subject: Re: [RFC/PATCH 1/5] mtd: ubi: Read disturb infrastructure
Date: Sun, 28 Sep 2014 13:46:22 +0300	[thread overview]
Message-ID: <5427E6FE.3090906@codeaurora.org> (raw)
In-Reply-To: <5427CCD8.2090605@nod.at>

On 9/28/2014 11:54 AM, Richard Weinberger wrote:
> Am 28.09.2014 10:48, schrieb Tanya Brokhman:
>>>> @@ -424,6 +440,8 @@ struct ubi_fm_sb {
>>>>        __be32 used_blocks;
>>>>        __be32 block_loc[UBI_FM_MAX_BLOCKS];
>>>>        __be32 block_ec[UBI_FM_MAX_BLOCKS];
>>>> +    __be32 block_rc[UBI_FM_MAX_BLOCKS];
>>>> +    __be64 block_let[UBI_FM_MAX_BLOCKS];
>>>
>>> Doesn't this break the fastmap on-disk layout?
>>
>> What do you mean "break"? I verified fastmap feature is working. the whole read-disturb depends on it so I tested this thoroughly.
>
> Did you write a fastmap with your changes applied and then an attach using a fastmap implementation *without*
> you changes?
> I bet it will not work because the disk layout is now different.

you're right, it wont work. I did a set of attach/detach tests to verify 
fastmap, but of course with my changes.

> Linux is not the only user of fastmap. We need to be very careful here.

Could you please elaborate here? I'm not sure I understand the use case 
you're referring to.

>
> Thanks,
> //richard
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
>

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, 
hosted by The Linux Foundation