linux-kernel - Re: [PATCH] libnvdimm: fix badblock range handling of ARS range

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Message-ID: <20170710213116.GB27581@omniknight.lm.intel.com>
Date:   Mon, 10 Jul 2017 15:31:18 -0600
From:   Vishal Verma <vishal.l.verma@...el.com>
To:     Toshi Kani <toshi.kani@....com>
Cc:     dan.j.williams@...el.com, linux-nvdimm@...ts.01.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] libnvdimm: fix badblock range handling of ARS range

On 07/07, Toshi Kani wrote:
> __add_badblock_range() does not account sector alignment when
> it sets 'num_sectors'.  Therefore, an ARS error record range
> spanning across two sectors is set to a single sector length,
> which leaves the 2nd sector unprotected.
> 
> Change __add_badblock_range() to set 'num_sectors' properly.
> 
> Fixes: 0caeef63e6d2f866d85bb507bf63e0ce8ec91cef
> Signed-off-by: Toshi Kani <toshi.kani@....com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Vishal Verma <vishal.l.verma@...el.com>
> Cc: <stable@...r.kernel.org>
> ---
>  drivers/nvdimm/core.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)

Good find! I don't know why I assumed a poison entry spanning past the
end of a sector wouldn't span past multiple sectors :)

Reviewed-by: Vishal Verma <vishal.l.verma@...el.com>

> 
> diff --git a/drivers/nvdimm/core.c b/drivers/nvdimm/core.c
> index 2dee908..932c3994 100644
> --- a/drivers/nvdimm/core.c
> +++ b/drivers/nvdimm/core.c
> @@ -421,14 +421,15 @@ static void set_badblock(struct badblocks *bb, sector_t s, int num)
>  static void __add_badblock_range(struct badblocks *bb, u64 ns_offset, u64 len)
>  {
>  	const unsigned int sector_size = 512;
> -	sector_t start_sector;
> +	sector_t start_sector, end_sector;
>  	u64 num_sectors;
>  	u32 rem;
>  
>  	start_sector = div_u64(ns_offset, sector_size);
> -	num_sectors = div_u64_rem(len, sector_size, &rem);
> +	end_sector = div_u64_rem(ns_offset + len, sector_size, &rem);
>  	if (rem)
> -		num_sectors++;
> +		end_sector++;
> +	num_sectors = end_sector - start_sector;
>  
>  	if (unlikely(num_sectors > (u64)INT_MAX)) {
>  		u64 remaining = num_sectors;