linux-kernel - Re: [PATCH] block: Do not call sector

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Message-ID: <52781FD7.9050507@kernel.dk>
Date:	Mon, 04 Nov 2013 15:29:43 -0700
From:	Jens Axboe <axboe@...nel.dk>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: Do not call sector_div() with a 64-bit divisor

On 11/04/2013 06:00 AM, Geert Uytterhoeven wrote:
> do_div() (called by sector_div() if CONFIG_LBDAF=y) is meant for divisions
> of 64-bit number by 32-bit numbers.  Passing 64-bit divisor types caused
> issues in the past on 32-bit platforms, cfr. commit
> ea077b1b96e073eac5c3c5590529e964767fc5f7 ("m68k: Truncate base in
> do_div()").
> 
> As queue_limits.max_discard_sectors and .discard_granularity are unsigned
> int, max_discard_sectors and granularity should be unsigned int.
> As bdev_discard_alignment() returns int, alignment should be int.
> Now 2 calls to sector_div() can be replaced by 32-bit arithmetic:
>   - The 64-bit modulo operation can become a 32-bit modulo operation,
>   - The 64-bit division and multiplication can be replaced by a 32-bit
>     modulo operation and a subtraction.

Thanks Geert, applied.

-- 
Jens Axboe

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