linux-kernel - Re: Bug in BLKBSZSET/GET ioctl ?

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Message-ID: <4EFBEC7C.4060902@cn.fujitsu.com>
Date:	Thu, 29 Dec 2011 12:28:44 +0800
From:	Wanlong Gao <gaowanlong@...fujitsu.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
CC:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Bug in BLKBSZSET/GET ioctl ?

On 12/29/2011 12:20 PM, Wu Fengguang wrote:

> On Thu, Dec 29, 2011 at 11:51:45AM +0800, Wanlong Gao wrote:
>> Hi all:
>>
>> This is first reported to *libguestfs*: https://bugzilla.redhat.com/show_bug.cgi?id=624335
>>
>> Then, I looked into upstream util-linux and it seems nothing wrong. I'm not convinced that it's a kernel bug.
>>
>> produce:
>>
>> ---
>> # ./util-linux/disk-utils/blockdev --getbsz /dev/sda6
>> 4096
>> # ./util-linux/disk-utils/blockdev --setbsz 2048 /dev/sda6
>> # ./util-linux/disk-utils/blockdev --getbsz /dev/sda6
>> 4096
>> # ./util-linux/disk-utils/blockdev --setbsz 512 /dev/sda6
>> # ./util-linux/disk-utils/blockdev --getbsz /dev/sda6
>> 4096
> 
> I think each blockdev invocation is working on a *new* bdev object.


But the address of *new* bdev is the same?
I did printk, and they all returned the same address.

> You'll get consistent results if somehow keep it referenced, for


But isn't it a bug? It seems that the setbsz has no effect?

Thanks,
-Wanlong

> example, run a background copy task:
> 
> # cp /dev/sda6 /dev/null &
> 
> # ./util-linux/disk-utils/blockdev --getbsz /dev/sda6
> # ./util-linux/disk-utils/blockdev --setbsz 512 /dev/sda6
> # ./util-linux/disk-utils/blockdev --getbsz /dev/sda6
> 
> Thanks,
> Fengguang
> 


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