Re: Questions : disk partition re-reading

From: Rogier Wolff (R.E.Wolff_at_BitWizard.nl)
Date: 04/20/04

  • Next message: Marcelo Tosatti: "Re: 2.4.26 doesn't compile? ("error: `__cmpxchg' previously defined here")" 
    Date:	Tue, 20 Apr 2004 16:36:35 +0200
To: Andries Brouwer <aebr@win.tue.nl>

    On Tue, Apr 20, 2004 at 09:46:50AM +0200, Andries Brouwer wrote:
    > You must distinguish the on-disk partition table and the kernel
    > partition table. You can change the on-disk partition table just by
    > writing to it, but that does not change the kernel's ideas.
    > You can change the kernel partition table using the right ioctls
    > but that does not change the bits on disk.
    >
    > Usually one does
    > blockdev --rereadpt /dev/something
    > after changing media, or after writing to the partition table,
    > but that will fail if the disk is busy.

    Which reminds me: Too bad the kernel says "Busy" without really
    thinking aboutit.

    Assume that I have a
            <hda1> swap 1G (*)
            <hda2> root 19G (active)
            <free space>

    disk, and want to add an extra partition. Maybe I have a 20G image
    which I want to copy onto 20, 40, 60, 80, 120 and 200Gb disks. I can
    then add the third partition as a /data or a /tmp partition. However
    as the active root is on that disk I have to reboot. But in fact I
    don't intend to change the active partition.

    So, there should be objections if I want the new partitioning scheme
    to be:

            <hda1> swap 1.5G
            <hda2> root 19G (active)
            <free space>

    then there is a problem and I can understand "Busy". But if the new
    scheme is:

            <hda1> swap 1G
            <hda2> root 19G (active)
            <hda3> data 20G <unformatted>

    then I don't understand the reason for refusing the rereadpt request.

    Anybody want to code this up?

            Roger.

    (*) usually active as well, but easily deactivated. So lets pretend
    it's inactive for this discussion. 

    -- 
** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2600998 **
*-- BitWizard writes Linux device drivers for any device you may have! --*
**** "Linux is like a wigwam -  no windows, no gates, apache inside!" ****
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  • Next message: Marcelo Tosatti: "Re: 2.4.26 doesn't compile? ("error: `__cmpxchg' previously defined here")"

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