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Date: Thu, 11 Jan 2018 10:06:36 +0100
From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: David Woodhouse <dwmw2@infradead.org>, Brian Norris
 <computersforpeace@gmail.com>, Boris Brezillon
 <boris.brezillon@free-electrons.com>, Marek Vasut <marek.vasut@gmail.com>,
 Richard Weinberger <richard@nod.at>, Cyrille Pitchen
 <cyrille.pitchen@wedev4u.fr>, linux-mtd@lists.infradead.org
Cc: Peter Pan <peterpansjtu@gmail.com>, Kyungmin Park
 <kyungmin.park@samsung.com>, Ladislav Michl <ladis@linux-mips.org>, Robert
 Jarzmik <robert.jarzmik@free.fr>, Frieder Schrempf
 <frieder.schrempf@exceet.de>
Subject: Re: [PATCH v5 1/3] mtd: mtdpart: Make ECC stat handling consistent
Message-ID: <20180111100636.3abe1459@bbrezillon>
In-Reply-To: <20180109085035.12438-1-boris.brezillon@free-electrons.com>
References: <20180109085035.12438-1-boris.brezillon@free-electrons.com>
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On Tue,  9 Jan 2018 09:50:33 +0100
Boris Brezillon <boris.brezillon@free-electrons.com> wrote:

> part_read() and part_read_oob() where counting ECC failures and
> bitflips differently. Adjust part_read_oob() to mimic what is done in
> part_read(). This is in needed to use ->_read_oob() as a fallback when
> when ->_read() is not implemented.
> 
> Note that bitflips and ECC failure accounting on MTD partitions is
> broken by design, because nothing prevents concurrent accesses to the
> underlying master MTD device between the moment we save the stats in a
> local variable and the moment master->_read[_oob]() returns. It's not
> something that can easily be fixed, so leave it like that for now.

Applied the series (also fixed the typo reported by Robert).

> 
> Suggested-by: Brian Norris <computersforpeace@gmail.com>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> Tested-by: Ladislav Michl <ladis@linux-mips.org>
> ---
> Changes in v5:
> - save master's ECC stats before calling ->_read_oob()
> 
> Changes in v4:
> - new patch
> ---
>  drivers/mtd/mtdpart.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
> index be088bccd593..79bf1f61c7a0 100644
> --- a/drivers/mtd/mtdpart.c
> +++ b/drivers/mtd/mtdpart.c
> @@ -105,6 +105,7 @@ static int part_read_oob(struct mtd_info *mtd, loff_t from,
>  		struct mtd_oob_ops *ops)
>  {
>  	struct mtd_part *part = mtd_to_part(mtd);
> +	struct mtd_ecc_stats stats;
>  	int res;
>  
>  	if (from >= mtd->size)
> @@ -126,13 +127,14 @@ static int part_read_oob(struct mtd_info *mtd, loff_t from,
>  			return -EINVAL;
>  	}
>  
> +	stats = part->parent->ecc_stats;
>  	res = part->parent->_read_oob(part->parent, from + part->offset, ops);
> -	if (unlikely(res)) {
> -		if (mtd_is_bitflip(res))
> -			mtd->ecc_stats.corrected++;
> -		if (mtd_is_eccerr(res))
> -			mtd->ecc_stats.failed++;
> -	}
> +	if (unlikely(mtd_is_eccerr(res)))
> +		mtd->ecc_stats.failed +=
> +			part->parent->ecc_stats.failed - stats.failed;
> +	else
> +		mtd->ecc_stats.corrected +=
> +			part->parent->ecc_stats.corrected - stats.corrected;
>  	return res;
>  }
>