linux-kernel - Re: [PATCH 3/6] UBI: Fastmap: Notify user in case of an ubi_update

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Message-ID: <5485A596.3020304@nod.at>
Date:	Mon, 08 Dec 2014 14:20:22 +0100
From:	Richard Weinberger <richard@....at>
To:	Tanya Brokhman <tlinder@...eaurora.org>, dedekind1@...il.com
CC:	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] UBI: Fastmap: Notify user in case of an ubi_update_fastmap()
 failure

Am 08.12.2014 um 14:00 schrieb Tanya Brokhman:
>>>>> Why do you fail the whole function (ubi_wl_get_peb) if fastmap update failed? Its possible that the fm_pools were refilled correctly, and the actual fastmap_write failed, so
>>>>> there
>>>>> is nothing preventing the user to get peb allocated and continue working. You invalidate the fastmap, so if powercut occurs a full scan will be performed. So its possible to
>>>>> allocate from fm_pools (although fastmap is not valid on disc) and try writing fastmap again when the pools filled up.
>>>>> I'm for the ubi_msg but against "return -ENOSPC;"
>>>>
>>>> Maybe the case you've described is powercut safe, but there can be other unsafe cases.
>>>> Let's stay on the safe side and be paranoid, it does not hurt.
>>>> If fastmap has proven stable we can start with tricky optimizations.
>>>
>>> I'm sorry that I'm being petty here but the commit msg states that you "notify the user in case of update fastamap failure". It says nothing about you failing ubi_wl_get_peb as
>>> well. And this is a major change. At least divide this into 2 patches (so I can disagree to the function failing and agree to the msg to user :) )
>>
>> With user I meant users of that function.
> 
> I still don't like it.
> Leaving this one for Artem... sorry

BTW: With my latest patch applied "[PATCH] UBI: Fastmap: Fix possible fastmap inconsistency" your assumption that we
can have the pools refilled in case if an ubi_update_fastmap() error is no longer correct.
Before my patch ubi_update_fastmap() the pools have been refilled much too early, this is an bug and got fixed.

Thanks,
//richard
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