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    SubjectRe: [PATCH 0/6] detect online disk resize
    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



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