linux-kernel - Re: [PATCH 4/4] UBI: Implement bitrot checking

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Date:	Sun, 12 Apr 2015 18:31:01 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Richard Weinberger <richard@....at>
Cc:	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	dedekind1@...il.com
Subject: Re: [PATCH 4/4] UBI: Implement bitrot checking

On Sun, 12 Apr 2015 18:14:40 +0200
Richard Weinberger <richard@....at> wrote:

> > IMHO the following code chunk, starting here:
> > 
> >> +			wl_wrk = prepare_erase_work(e, -1, -1, 1);
> >> +			if (IS_ERR(wl_wrk)) {
> >> +				err = PTR_ERR(wl_wrk);
> >> +				goto out;
> >> +			}
> >> +
> >> +			__schedule_ubi_work(ubi, wl_wrk);
> > 
> > and ending here ^, could be placed in an helper function
> > (re_erase_peb ?)
> 
> As long we have only one user of that pattern I'd keep it as is.
> We have in UBI already a gazillion helper functions.

Okay, then maybe you should comment what you're doing here: erase an
already erased PEB where bitflips have occured.

> 
> >> +			err = 0;
> >> +		}
> >> +		/*
> >> +		 * e is target of a move operation, all we can do is kicking
> >> +		 * wear leveling such that we can catch it later or wear
> >> +		 * leveling itself scrubbs the PEB.
> >> +		 */
> >> +		else if (ubi->move_to == e || ubi->move_from == e) {
> >> +			spin_unlock(&ubi->wl_lock);
> >> +
> >> +			err = ensure_wear_leveling(ubi, 1);
> >> +		}
> >> +		/*
> >> +		 * e is member of a fastmap pool. We are not allowed to
> >> +		 * remove it from that pool as the on-flash fastmap data
> >> +		 * structure refers to it. Let's schedule a new fastmap write
> >> +		 * such that the said PEB can get released.
> >> +		 */
> >> +		else {
> >> +			ubi_schedule_fm_work(ubi);
> >> +			spin_unlock(&ubi->wl_lock);
> >> +
> >> +			err = 0;
> >> +		}
> > 
> > I'm nitpicking again, but I like to have a single place where spinlocks
> > are locked and unlocked, so here is a rework suggestion for the code
> > inside the 'if (err == UBI_IO_BITFLIPS)' statement:
> 
> A single lock/unlock place is nice but in this case the whole logic fits
> into a single page on screen. "do_this" and "do_that" variables don't make
> the code more readable IMHO.
> But as with all nitpicks it is a matter of taste and we could waste multiple
> days on such things.

Isn't that the whole point of code reviews :-P ?


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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