Re: Of removable devices

From: david parsons (orc@pell.portland.or.us)
Date: Sat Feb 19 2000 - 06:18:46 EST


In article <linux.kernel.m3itzmbbtb.fsf@toy.mandrakesoft.com>,
Francis GALIEGUE <francis@mandrakesoft.com> wrote:
>David Balazic <david.balazic@uni-mb.si> writes:
>
>> >
>> > And who gets the notice if no one is there? or no one is logged in?
>>
>[skipped sarcasm]
>>
>> The one that ejected the medium , obviously.
>> echo "Put that back in , son !" > /dev/console
>>
>> satisfied ?
>>
>
>No. The sole role of the kernel in case of broken hardware
>(hence, floppies) is to ensure data integrity, not to tell the user
>"please insert floppy #adead007". Easing removable media manipulation
>would sure be a great plus (for users), but not to the expense of
>unneeded and unnecessary tell-user-what-to-do stuff.

    Only if it's done incorrectly. If there's glue to put a notifier
    in, then all the kernel has to do when it attempts to write out data
    to a device that's not there anymore is tickle the notifier, then
    defer the writes 'til the next time sync rolls around. No notifier
    == data is written to the afterlife with the traditional vomiting of
    error messages to syslog, the console, or whereever.

>And even if user space notification and report were implemented and
>functional, a user in a hurry is a user in a hurry and would be far
>away from the culprit machine

    That would be a badly implemented userland. I couldn't imagine
    mounting anything async with a notifier, for then the machine that's
    not running update won't notice that the floppy's gone for several
    weeks.

    A sick notifier could be a simple shellscript, called by mount:

        #! /bin/sh

        DEV=$1
        MAJOR=$2
        MINOR=$3
        mknod /dev/$DEV.tickle $MAJOR $MINOR

        trap 0 1 2 3 9 15 "rm -f /dev/$DEV.tickle"

        while read tickle; do
            dialog --msgbox --wait 5 "Please put $DEV back"
            sync $DEV
        done < /dev/$DEV.notify
        exit 0

    with fstab being something like

        /dev/ide0/drive0 /zip removable,notifier,user,noauto 0 0

                  ____
    david parsons \bi/ A more sophisticated tickler is left as an exercise
                   \/ for the reader.

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