linux-kernel - Re: [RFC] block: check partition alignment

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Message-ID: <64f82273-adc6-ce79-5d1f-ae4b54efd240@wdc.com>
Date:   Thu, 15 Dec 2016 09:55:36 +0900
From:   Damien Le Moal <damien.lemoal@....com>
To:     Stefan Haberland <sth@...ux.vnet.ibm.com>, axboe@...nel.dk,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     hoeppner@...ux.vnet.ibm.com, sebott@...ux.vnet.ibm.com
Subject: Re: [RFC] block: check partition alignment


> sd.c ensures that the logical block size (sector size in sd.c) is a
> power of 2 between 512 and 4096. So you can use:
> 
> if (p.start & (bdev_physical_block_size(bdev) - 1))

Sorry, that was a little too short as a complete proof:
sd.c ensures that the logical block size (sector size in sd.c) is a
power of 2 between 512 and 4096, and the physical block size is a power
of 2 number of logical blocks. So the physical block size is also always
a power of 2.

> 
> Or use div_u64_rem to avoid an error on 32 bits builds.
> 
> Best regards.
> 

-- 
Damien Le Moal, Ph.D.
Sr. Manager, System Software Research Group,
Western Digital Corporation
Damien.LeMoal@....com
(+81) 0466-98-3593 (ext. 513593)
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Kanagawa, 252-0888 Japan
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