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Subject: Re: umount
Date: Mon, 28 Nov 2005 12:51:54 -0500
Message-ID: <Pine.LNX.4.61.0511281229560.8176@chaos.analogic.com>
Thread-Topic: umount
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From: "linux-os \(Dick Johnson\)" <linux-os@analogic.com>
To: "Mark Knecht" <markknecht@gmail.com>
Cc: "Patrick McFarland" <diablod3@gmail.com>, <gcoady@gmail.com>,
       <Andries.Brouwer@cwi.nl>, <linux-kernel@vger.kernel.org>
Reply-To: "linux-os \(Dick Johnson\)" <linux-os@analogic.com>
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On Mon, 28 Nov 2005, Mark Knecht wrote:

> On 11/27/05, Jim Crilly <jim@why.dont.jablowme.net> wrote:
>> On 11/27/05 09:01:07PM -0500, Patrick McFarland wrote:
>>> On Sunday 27 November 2005 20:42, Mark Knecht wrote:
>>>> On 11/27/05, Grant Coady <grant_lkml@dodo.com.au> wrote:
>>>>> It leaves me with a little distrust of linux' handling of non-locked
>>>>> removable media (as opposed to lockable media like a zipdisk or cdrom).
>>>>>
>>>>> Grant.
>>>>
>>>> Under Windows, if a 1394 drive is unplugged without unmounting, it you
>>>> get a pop up dialog on screen telling you that data may be lost, etc.
>>>> while under any of the main environments I've tried under Linux
>>>> (Gnome, KDE, fluxbox) there are no such messages to the user. I have
>>>> not investigated log files very deeply, other than to say that dmesg
>>>> will show the drive going away but doesn't say it was a problem.
>>>>
>>>> I realize it's probably 100x more difficult to do this under Linux, at
>>>> least at the gui level, but I agree with your main point that my trust
>>>> factor is just a bit lower here.
>>>
>>> No, WIndows says that because it is unable to mount a partition as sync,
>>> unlike Linux. Linux Desktop Environments simply don't tell the user because
>>> no data is lost if they unplug the media.
>>
>> Both of those statements are not true.
>
> Jim,
>   I'm not clear if 'both statements' included any of mine or not? :-)
>
>   You discussed the event I was thinking of. I am writing to a 1394
> drive, bus powered or not, and while the write is occuring I unplug
> the cable. Clearly the data being written is not going to finish, and
> that's expected, but the 'reduced confidence' issue is that I'm not
> told directly of the event. Granted I'll eventually discover it in
> some indrect manner, like a GUI action failing or something timing
> out. However in Windows I do appreciate the clear message that this
> has happened.
>
> Thanks,
> Mark
>

Doesn't your GUI show a 'console' window? I don't use the GUI,
but the last time I checked, there was a 'console' window that
showed the error messages. This was standard with Sun.

If you can find the 'console' window in your distribution, activate
it. If it doesn't have one, contact your vendor or make one. There
needs to be some visible evidence that something is going wrong.

Although the messages may 'come from' the kernel, they are not
produced by the kernel. It is not the responsibility of the kernel
to display messages. The kernel writes those messages to a virtual
file, /proc/kmsg. It is, again, user-mode code that is supposed
to put those messages someplace useful. If the user-mode code
isn't doing that, contact your vendor. On this distribution,
syslogd reads /proc/kmsg and writes formatted data to /dev/console
and to various log-files so there already is a daemon that is
supposed to handle this.

A 'console' program, trivially reads /dev/console and writes
to STDOUT_FILENO. That will get all the messages onto your GUI
screen.


>> At least in XP removable media is
>> mounted sync by default, you have to go into the device manager and toggle
>> a radio button to "optimize for performance" before it'll do async writes.
>> I think the setting was the opposite in Win2K but I can't say for sure.
>>
>> And even with sync writes it's possible to unplug the drive before the
>> write completes and if the drive is powered by USB there's no way to know
>> just how much data made it to disk. Ideally the kernel would emit some
>> message so that HAL or something can catch it and popup a message or
>> something.
>>
>>
>> Jim.
>>
> -
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Cheers,
Dick Johnson
Penguin : Linux version 2.6.13.4 on an i686 machine (5589.55 BogoMips).
Warning : 98.36% of all statistics are fiction.
.

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