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Date: Mon, 8 Jan 2018 22:25:24 +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: Robert Jarzmik <robert.jarzmik@free.fr>, Kyungmin Park
 <kyungmin.park@samsung.com>, Peter Pan <peterpansjtu@gmail.com>, Frieder
 Schrempf <frieder.schrempf@exceet.de>, Ladislav Michl
 <ladis@linux-mips.org>, Miquel RAYNAL <miquel.raynal@free-electrons.com>
Subject: Re: [PATCH v4 1/3] mtd: mtdpart: Make ECC stat handling consistent
Message-ID: <20180108222524.6bf00481@bbrezillon>
In-Reply-To: <20180108211542.11891-2-boris.brezillon@free-electrons.com>
References: <20180108211542.11891-1-boris.brezillon@free-electrons.com>
 <20180108211542.11891-2-boris.brezillon@free-electrons.com>
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On Mon,  8 Jan 2018 22:15:40 +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.
> 
> Suggested-by: Brian Norris <computersforpeace@gmail.com>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> ---
> Changes in v4:
> - new patch
> ---
>  drivers/mtd/mtdpart.c | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
> index be088bccd593..283e8526713b 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)
> @@ -127,12 +128,12 @@ static int part_read_oob(struct mtd_info *mtd, loff_t from,
>  	}
>  

Missing

	stats = part->parent->ecc_stats;

here.

I'll send a new version. Sorry for the inconvenience.

>  	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;
>  }
>