From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: Bug in BLKBSZSET/GET ioctl ? Date: Thu, 29 Dec 2011 12:20:10 +0800 Message-ID: <20111229042010.GA22132@localhost> References: <4EFBE3D1.5030608@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Wanlong Gao Return-path: Content-Disposition: inline In-Reply-To: <4EFBE3D1.5030608@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org 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