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Date: Mon, 20 Oct 2014 17:33:21 +0100 (BST)
From: Steve B <steve@baconbits.demon.co.uk>
To: Artem Bityutskiy <dedekind1@gmail.com>
Subject: Re: UBI/UBFS: ubi_eba_read_leb() reporting unmapped LEB
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Thanks again, plenty for me to thing about!

On Mon, 20 Oct 2014, Artem Bityutskiy wrote:

> On Mon, 2014-10-20 at 16:25 +0100, Steve B wrote:
>> Thank you very much for your suggestions Artem, gives me plenty to look
>> into :)
>
> May be this will be also a useful piece of data.
>
> Back several years ago, we saw ext4 not recovering after power cuts on
> eMMC.
>
> We knew ext4 is extremely complex, so we decided to go and test if eMMC
> does the right job. Namely, if I submit data, they sync, does eMMC make
> sure the data are on the media?
>
> Adrian (the other UBIFS author) implemented the eMMC power cut test. And
> he found that you may write to block A, they sync, then write to block
> B, and have power cut, and after reboot block A is corrupted. So
> interrupted write to block B affected a different block A.
>
> We reported to the eMMC vendor, and the vendor acknowledged the problem
> and we got newer eMMC, which was devoid of the issue. And our ext4
> issues went away, it became a lot better.
>
> This is why I say may be stressing UBI could be a good idea. It may be
> waste of time too, though, if the problem is in UBIFS, or if the test
> won't reveal a problem in UBI because the test is not good enough. But
> it may also hit the nail quickly.
>
> Artem.
>
>
>