Messages in this thread | | | Subject | Re: [RFC][PATCH] UBI: Make MTD_UBI_FASTMAP non-experimental | From | Marek Vasut <> | Date | Thu, 30 Mar 2017 12:01:41 +0200 |
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On 03/29/2017 10:04 PM, Richard Weinberger wrote: > Jesper, > > Am 29.03.2017 um 17:38 schrieb Jesper Nilsson: >> MTD_UBI_FASTMAP has been set as experimental since it >> was merged back in 2012. >> >> There hasn't been much change in the format, >> so we can consider the feature stable and start >> being careful about breaking the format. >> (This is somewhat of a pre-requisite for anyone actually >> using the feature in the real world and depending on it) >> >> Drop the experimental note and the warning text about >> the on-flash format not being finalized. > > I fully agree, we can drop this note. But we have to add another > one. > While Fastmap is a nice feature to speed-up the attach time it > comes with a cost. It makes UBI less robust. I saw issues > on NAND chips which misbehaved slightly where UBI was able to > recover when using a full scan but not when Fastmap was used. > The UBI full scan code is paranoid and can sort out problems > very early, with Fastmap enabled you lose this valuable property. > > So, users should enable Fastmap only when they absolutely need > a very fast attach time and be very sure that the NAND works as > expected.
So we should document this with a big fat warning and set fastmap to default=n ?
-- Best regards, Marek Vasut
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