linux-kernel - Re: [PATCH] sd: close hole in > 2T device rejection when !CONFIG

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Date:   Tue, 4 Apr 2017 23:54:55 +0000
From:   Bart Van Assche <Bart.VanAssche@...disk.com>
To:     "martin.petersen@...cle.com" <martin.petersen@...cle.com>
CC:     "jejb@...ux.vnet.ibm.com" <jejb@...ux.vnet.ibm.com>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "steve@...idescorp.com" <steve@...idescorp.com>,
        "steve.magnani@...idescorp.com" <steve.magnani@...idescorp.com>
Subject: Re: [PATCH] sd: close hole in > 2T device rejection when
 !CONFIG_LBDAF

On Tue, 2017-04-04 at 19:35 -0400, Martin K. Petersen wrote:
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index fb9b4d29af0b..6084c415c070 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -2102,6 +2102,16 @@ static void read_capacity_error(struct scsi_disk *sdkp, struct scsi_device *sdp,
>  
>  #define READ_CAPACITY_RETRIES_ON_RESET	10
>  
> +static bool sd_addressable_capacity(u64 lba, unsigned int sector_size)
> +{
> +	u64 last_sector = lba + 1ULL << ilog2(sector_size) - 9;
> +
> +	if (sizeof(sector_t) == 4 && last_sector > 0xffffffffULL)
> +		return false;
> +
> +	return true;
> +}

Hello Martin,

How about replacing 0xffffffffULL with U32_MAX, adding parentheses in the
last_sector computation to make clear that + and - have precedence over <<
and adding a comment above sd_addressable_capacity() that explains its
purpose and also that the shift operation must not be replaced with a call
to logical_to_sectors()? Otherwise this patch looks fine to me.

Thanks,

Bart.