Messages in this thread | | | Date | Sun, 12 Apr 2015 21:53:12 +0200 | From | Richard Weinberger <> | Subject | Re: [PATCH 4/4] UBI: Implement bitrot checking |
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Am 12.04.2015 um 21:20 schrieb Boris Brezillon: > Unless I'm missing something, it should be pretty easy to implement: > adding the following lines at the end of bitrot_check_worker() should do > the trick > > if (e->pnum + 1 < ubi->peb_count) { > wl_wrk->e = ubi->lookuptbl[e->pnum + 1]; > __schedule_ubi_work(ubi, wl_wrk); > } else { > atomic_dec(&ubi->bit_rot_work); > } >
It will suffer from the same race issue as my current approach. While e is scheduled another worker could free it in case of an fatal error.
>> I'd like to avoid works which schedule again other works. >> In the current way it is clear where the work is scheduled and how much. > > Yes, but the memory consumption induced by this approach can be pretty > big on modern NAND chips (on 32 bit platforms, ubi_work is 32 octets > large, and on modern NANDs you often have 4096 blocks, so a UBI device > of 4000 block is pretty common => 4000 * 32 = 125 KiB).
While I agree that consuming memory is not very nice I don't think that 125KiB is a big deal.
> For standard wear leveling requests, using a ubi_work per request is > sensible since you can't know in advance which block will be queued for > wear-leveling operation next time. > In your case, you're scanning all blocks in ascending order, which > makes it a good candidate for this 'one work for all bitrot checks' > approach.
The good news is that I have an idea to solve both problems the race and the memory issue. It should be pretty easy to implement. Patches will materialize in a few days.
Thanks, //richard
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