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From: Wu Fengguang <fengguang.wu@intel.com>
To: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Bug in BLKBSZSET/GET ioctl ?
Date: Thu, 29 Dec 2011 12:20:10 +0800	[thread overview]
Message-ID: <20111229042010.GA22132@localhost> (raw)
In-Reply-To: <4EFBE3D1.5030608@cn.fujitsu.com>

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

  parent reply	other threads:[~2011-12-29  4:20 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-12-29  3:51 Bug in BLKBSZSET/GET ioctl ? Wanlong Gao
2011-12-29  3:56 ` Wanlong Gao
2011-12-29  8:19   ` Richard W.M. Jones
2011-12-29  4:20 ` Wu Fengguang [this message]
2011-12-29  4:28   ` Wanlong Gao
2011-12-29  4:40     ` Wu Fengguang
2011-12-29  6:09       ` Wanlong Gao

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