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Date: Thu, 4 Sep 2008 09:26:51 +0200
From: Jens Axboe <jens.axboe@oracle.com>
To: Andrew Patterson <andrew.patterson@hp.com>
Cc: linux-scsi@vger.kernel.org, James.Bottomley@HansenPartnership.com,
       linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk,
       andmike@linux.vnet.ibm.com, mike.miller@hp.com, genanr@emsphone.com,
       jmoyer@redhat.com
Subject: Re: [PATCH 0/6] detect online disk resize
Message-ID: <20080904072651.GX20055@kernel.dk>
References: <20080829231254.25065.66052.stgit@bluto.andrew>
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On Fri, Aug 29 2008, Andrew Patterson wrote:
> This is version 2 of a patch series I submitted back in May 2008. This
> version now checks for device size changes in the rescan_partitions()
> routine.  Which in turn is called when a device is opened and in the
> BLKRRPART ioctl.
> 
> I am resubmitting this patch series as I got little response the
> previous time.  Al Viro has told me offline that he would look at it this
> time.
> 
> This patch series handles online disk resizes that are currently not
> completely recognized by the kernel using the existing revalidate_disk
> routines.  An online resize can occur when growing or shrinking a
> Fibre Channel LUN or perhaps by adding a disk to an existing RAID
> volume.
> 
> The kernel currently recognizes a device size change when the
> lower-level revalidate_disk routines are called; however, the block
> layer does not use the new size while it has any current openers on
> the device. So, for example, if LVM has an volume open on the device,
> you will generally not see the size change until after a reboot. We
> fix this problem by creating a wrapper to be used with lower-level
> revalidate_disk routines.  This wrapper first calls the lower-level
> driver's revalidate_disk routine. It then compares the gendisk
> capacity to the block devices inode size. If there is a difference, we
> adjust the block device's size. If the size has changed, we then flush
> the disk for safety. The size is also checked in rescan_partitions
> which is called when the device is opened or when the BLKRRPART ioctl
> is called.
> 
> There are several ways to "kick off" a device size change:
> 
> 1. For SCSI devices do:
> 
>   # echo 1 > /sys/class/scsi_device/<device>/device/rescan
> 
>   or
> 
>   # blockdev --rereadpt <device file>
> 
> 2. Other devices (not device mapper)
> 
>   # blockdev --rereadpt <device file>
> 
> I have tested this patch on SCSI and SmartArray (cciss)
> devices. Device mapper still does not recognize device size changes
> until the device is restarted.
> 
> Jeff Moyer and Andy Ryan have done some light testing on the previous
> version of this series.
> 
> This patch set has been tested with scsi-misc-2.6. It also applies to
> linux-next with some minor, obvious changes.

This version looks sane to me. Care to resend against for-2.6.28 of the
block repo?

-- 
Jens Axboe