Re: removing external usb hdd without unmounting causes reboot?
: By the way, the problem apparently has been solved in : DragonFly BSD (i.e. DF BSD does not panic when a mounted : FS is physically removed). Maybe it is worth to have a We didn't do much here. Just started pulling devices, looking at the crash dumps, and fixing things. Basically it was just a collection of minor bugs... things like certain error paths in UFS (which only occur on an I/O error) had bugs, or caused corruption instead of properly handling the error, and various bits and pieces of the USB I/O path would get ripped out on the device pull while still referenced by other bits of the USB I/O path. You will also have to look at the way vfs flushing handles errors in order to allow a filesystem to be force-unmounted after the device has been pulled. Basically you have to make umount -f work and you have to make sure it properly dereferencing the underlying device and properly destroys the (now unwritable) dirty buffers. -Matt Matthew Dillon [EMAIL PROTECTED] ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Peter Jeremy wrote: Dennis Melentyev wrote: Is there any correct way to initiate funding to rewrite VM/VFS related parts (getting non-panicable removable devices)? Who should one contact for this? I would suggest that the first step is finding someone (or a few people) with the necessary skills who is/are willing to work on the problem. Offering funding may increase the potential pool but will not automatically solve the skills/knowledge issue. By the way, the problem apparently has been solved in DragonFly BSD (i.e. DF BSD does not panic when a mounted FS is physically removed). Maybe it is worth to have a look at what they did to fix it, and possibly port it over to FreeBSD. On the other hand, the internal data structures of the VM subsystem have diverged quite a lot from FreeBSD, so I don't know if it would really help. (No, I'm not volunteering; lack of time and interest.) Best regards Oliver -- Oliver Fromme, secnetix GmbH Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd Perl is worse than Python because people wanted it worse. -- Larry Wall ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Hi Oliver! 2007/7/30, Oliver Fromme [EMAIL PROTECTED]: Peter Jeremy wrote: Dennis Melentyev wrote: Is there any correct way to initiate funding to rewrite VM/VFS related parts (getting non-panicable removable devices)? Who should one contact for this? I would suggest that the first step is finding someone (or a few people) with the necessary skills who is/are willing to work on the problem. Offering funding may increase the potential pool but will not automatically solve the skills/knowledge issue. By the way, the problem apparently has been solved in DragonFly BSD (i.e. DF BSD does not panic when a mounted FS is physically removed). Maybe it is worth to have a look at what they did to fix it, and possibly port it over to FreeBSD. On the other hand, the internal data structures of the VM subsystem have diverged quite a lot from FreeBSD, so I don't know if it would really help. (No, I'm not volunteering; lack of time and interest.) That was I asking same question in DragonflyBSD list :) But yes, VFS and VM in FBSD and DFBSD are way too differ since 4.1 times. It is not an option, sadly. -- Dennis Melentyev ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Hello Peter, Thank you for your answer. 2007/7/28, Peter Jeremy [EMAIL PROTECTED]: On 2007-Jul-27 18:29:44 +0300, Dennis Melentyev [EMAIL PROTECTED] wrote: [skipped architectural description, and, thank for it] I'd rather consider this problem as security one. I think that is a very long stretch. Well, it is. :) Is there any correct way to initiate funding to rewrite VM/VFS related parts (getting non-panicable removable devices)? Who should one contact for this? I would suggest that the first step is finding someone (or a few people) with the necessary skills who is/are willing to work on the problem. Offering funding may increase the potential pool but will not automatically solve the skills/knowledge issue. Got your point. As for initiating funding, you have several options: 1) Do it yourself: Find someone(s) to do the work (either by approaching likely candidates or advertising on FreeBSD lists), get an indication of the necessary funding and then raise the funds yourself. 2) Approach the FreeBSD Foundation, with or without names. 3) Approach corporations that are FreeBSD-friendly. Yahoo! and Apple are the first ones that come to mind. I'd probably try 2nd and 3rd items - unfortunately I can't offer enough myself. Hope, it would be possible to find enough support from the community and/or corporations. Thanks for the clues! -- Dennis Melentyev ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Hello Peter and everybody, Sorry for continuing this thread, but let's not forgot the security aspect of this issue: If you run amd on some host configured to automount USB drives, it's easy to force DoS attack. Just insert the flash/HDD and remove it short after it's mounted. Sure, it's almost close to ability of just pulling off power cable or pressing reset, but still a problem. Even if nobody will put out the USB stick, just in case of a Flash with dead blocks on it or just badly formatted one it's too easy to get totally unexpected panics. I'd rather consider this problem as security one. Is there any correct way to initiate funding to rewrite VM/VFS related parts (getting non-panicable removable devices)? Who should one contact for this? PS. Happy sysadmin day! *drink* 2007/7/24, Peter Jeremy [EMAIL PROTECTED]: On 2007-Jul-23 16:15:56 +0200, Oliver Fromme [EMAIL PROTECTED] wrote: So, currently the best work-around is to use amd with a very short timeout. Or simply remember to umount your removable media manually. Or ports/emulators/mtools -- Peter Jeremy -- Dennis Melentyev ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On 2007-Jul-27 18:29:44 +0300, Dennis Melentyev [EMAIL PROTECTED] wrote: Sorry for continuing this thread, but let's not forgot the security aspect of this issue: If you run amd on some host configured to automount USB drives, it's easy to force DoS attack. Just insert the flash/HDD and remove it short after it's mounted. It's almost impossible to secure a machine against someone with physical access to that machine. As you point out, pushing the reset button or pulling the power cable works. USB stick, just in case of a Flash with dead blocks on it or just badly formatted one it's too easy to get totally unexpected panics. There are two distinct issues here: When you remove the hardware, the low-level datastructures get freed but the high level (FS) code still points into those (now freed) structures - ie you have use-after-free errors. As has been pointed out, resolving these issues is difficult because they affect many different areas within the kernel. If the filesystem is corrupt, then it is no longer internally consistent and assumptions/requirements in the FS code are no longer valid. It is possible that assert() checks are tripped or implicit assumptions in the code are violated, possibly leading to panics. Bad blocks could lead to similar behaviour. Fixing these problems is (in general) not hard because it's mostly just adding appropriate checks in the FS code and I believe that most of the cases where this can occur have already been corrected. I'd rather consider this problem as security one. I think that is a very long stretch. Is there any correct way to initiate funding to rewrite VM/VFS related parts (getting non-panicable removable devices)? Who should one contact for this? I would suggest that the first step is finding someone (or a few people) with the necessary skills who is/are willing to work on the problem. Offering funding may increase the potential pool but will not automatically solve the skills/knowledge issue. As for initiating funding, you have several options: 1) Do it yourself: Find someone(s) to do the work (either by approaching likely candidates or advertising on FreeBSD lists), get an indication of the necessary funding and then raise the funds yourself. 2) Approach the FreeBSD Foundation, with or without names. 3) Approach corporations that are FreeBSD-friendly. Yahoo! and Apple are the first ones that come to mind. -- Peter Jeremy pgpH7uZiEFGpr.pgp Description: PGP signature
Re: removing external usb hdd without unmounting causes reboot?
On 2007-Jul-23 16:15:56 +0200, Oliver Fromme [EMAIL PROTECTED] wrote: So, currently the best work-around is to use amd with a very short timeout. Or simply remember to umount your removable media manually. Or ports/emulators/mtools -- Peter Jeremy pgpDLc0Ghx67i.pgp Description: PGP signature
Re: removing external usb hdd without unmounting causes reboot?
Stefan Esser wrote: Oliver Fromme wrote: Momchil Ivanov wrote: I don`t know how things work, but shutting down the system when some mounted fs is no longer present seems like the wrong thing to me. As Josh wrote, it's expected. The problem is known to exist for a long time already (probably as long as FreeBSD itself exists), and if there was an easy solution, certainly someone would have fixed it. I have to check this, but AFAIK this problem exists only for devices/partitions that are mounted R/W. Do you happen to know this? (I can not risk to crash my box right now for a test ;-) I'm afraid the problem affects _all_ mounts, including read-only mounts. There once was an autofs implementation, but IIRC it has later been removed. It could not only automatically mount removable media, but it could also help with the problem of devices that are rarely written to, but still mounted R/W just in case for easy write-access. Long time ago I had the idea that a clean file system could be mounted R/O after a short delay. When all dirty buffers are flushed, the device could be forcefully disconnected without causing inconsistencies in the kernel. If there are no open file descriptors, the super-block could be written with the clean flag set, to signal that no fsck is needed when the partition is mounted next time. Internally, the device can be treated as R/O, with the only exeption that an attempted write is not rejected, but that it instead triggers the change back to R/W operation (this means setting the in-RAM copy of the super-block to dirty before the write is allowed to proceed as normal). That's a very interesting idea. Unfortunately it doesn't solve the problem, because read-only mounts have the same problem, unfortunately. So, currently the best work-around is to use amd with a very short timeout. Or simply remember to umount your removable media manually. Best regards Oliver -- Oliver Fromme, secnetix GmbH Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd 'Instead of asking why a piece of software is using 1970s technology, start asking why software is ignoring 30 years of accumulated wisdom.' ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Saturday 21 July 2007 20:50:21 Zoran Kolic wrote: This topic is extremely interesting. For me, unmounting usb device is not so hard to do. I remember -r flag to mount with just read option. So, if hand follows the brain impuls, put another impuls to unmount it first. Yup. But this is only valid for advenced users. -- - Best regards, Nikolay Pavlov. - signature.asc Description: This is a digitally signed message part.
Re: removing external usb hdd without unmounting causes reboot?
On Sat, 21 Jul 2007 17:19:51 +0200
Stefan Esser [EMAIL PROTECTED] wrote:
Norberto Meijome schrieb:
On Thu, 19 Jul 2007 17:38:14 +0200
[LoN]Kamikaze [EMAIL PROTECTED] wrote:
As I mentioned earlier I remember it working during the 5.3 era on Stable,
at
some point it worked. I even remember removing my CD-Rom drive from my
Thinkpad
without running atacontrol detach. The system just took it and the drive
just
continued working after I put it back in.
on 6.2-STABLE (of a few days ago), i have this happening a couple of times
with no adverse effect at all.
Burn DVD/Cd, when finished, hald detects the disk, mounts it, /dev/cd0 in
/media/whatever.
i can eject the disk just fine (which in itself is weird, i think) the
device is still there...
umount /dev/cd0
works fine and off it goes. other than that, no, i havent tried to access
the device in question
In that case the device has been mounted R/O before, and if
you don't remove it in the middle of a transaction, there
is nothing the kernel might want to do with the physical
device to unmount it (and even within a transfer, this ought
to be caught by the driver). For that reason I had suggested
to have a soft-R/O mode for removable devices, which together
with a very short flush delay might allow such a device to
be mounted R/O nearly all the time (tm) ;-) This is not
a perfect solution, but it is similar to the way USB sticks
are used with Windows/XP: Wait a second or two and remove it.
While not perfect this covers the case of MP3 players or
digicams that are mounted as USB storage devices, and many
other cases. To make this a perfect solution is much harder,
but even a simple implementation would be a big step forward.
Yes, I agree it would be a good interim solution.
thx!
_
{Beto|Norberto|Numard} Meijome
It is a lesson which all history teaches wise men, to put trust in ideas, and
not in circumstances.
Emerson
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Re: removing external usb hdd without unmounting causes reboot?
On Sat, 21 Jul 2007 20:44:13 -0600 (MDT)
M. Warner Losh [EMAIL PROTECTED] wrote:
In message: [EMAIL PROTECTED]
Norberto Meijome [EMAIL PROTECTED] writes:
: On Thu, 19 Jul 2007 09:02:50 -0600 (MDT)
: M. Warner Losh [EMAIL PROTECTED] wrote:
:
: In message: [EMAIL PROTECTED]
: Momchil Ivanov [EMAIL PROTECTED] writes:
: : What is then the reason for the kernel not being able to unmount a
: : filesystem whose provider is no longer present?
:
: The problem is that the device driver has wound down, deallocated
: memory, etc. Now the kernel comes along with stale references to the
: device and panic ensues. It is really just that simple. There's no
: replacement of the now-dead device with dead calls.
:
: And even if you fixed that, most of the file systems in the tree today
: do not tolerate errors on writes at all and that also leads to
: panics. This is why firewire freezes the I/Os rather than failing
: them (and why umount -f on a firewire drive hangs).
:
: Please point me to the correct RTFM, because I feel this worth it :)
src/sys/fs/..., src/sys/kern/... and src/sys/vm/... are your best bets.
: Is there a reason why the kernel cannot check 'upwards' if a device
: is being used, ie mounted ? and prevent the unloading of the device
: driver ?
Check, sure, it can check. But what does a simple check accomplish if
the filesystem panics if the underlying media returns an error? The
problem isn't as simple as just looking in one place or another, but
rather systemic in nature.
thanks Warner. What do you estimate is the cost (time, at least) to investigate
and fix this issue? SoC project? 4 mth project?
cheers,
B
_
{Beto|Norberto|Numard} Meijome
Anyone who isn't confused here doesn't really understand what's going on.
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Re: removing external usb hdd without unmounting causes reboot?
Norberto Meijome schrieb: On Thu, 19 Jul 2007 17:38:14 +0200 [LoN]Kamikaze [EMAIL PROTECTED] wrote: As I mentioned earlier I remember it working during the 5.3 era on Stable, at some point it worked. I even remember removing my CD-Rom drive from my Thinkpad without running atacontrol detach. The system just took it and the drive just continued working after I put it back in. on 6.2-STABLE (of a few days ago), i have this happening a couple of times with no adverse effect at all. Burn DVD/Cd, when finished, hald detects the disk, mounts it, /dev/cd0 in /media/whatever. i can eject the disk just fine (which in itself is weird, i think) the device is still there... umount /dev/cd0 works fine and off it goes. other than that, no, i havent tried to access the device in question In that case the device has been mounted R/O before, and if you don't remove it in the middle of a transaction, there is nothing the kernel might want to do with the physical device to unmount it (and even within a transfer, this ought to be caught by the driver). For that reason I had suggested to have a soft-R/O mode for removable devices, which together with a very short flush delay might allow such a device to be mounted R/O nearly all the time (tm) ;-) This is not a perfect solution, but it is similar to the way USB sticks are used with Windows/XP: Wait a second or two and remove it. While not perfect this covers the case of MP3 players or digicams that are mounted as USB storage devices, and many other cases. To make this a perfect solution is much harder, but even a simple implementation would be a big step forward. Regards, STefan ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
From: Norberto Meijome [EMAIL PROTECTED] i can eject the disk just fine (which in itself is weird, i think) the device is still there... umount /dev/cd0 works fine and off it goes. other than that, no, i havent tried to access the device in question I never saw that behaviour. It really should not eject. As you, I use scsi emulation, with no acd device at all. This topic is extremely interesting. For me, unmounting usb device is not so hard to do. I remember -r flag to mount with just read option. So, if hand follows the brain impuls, put another impuls to unmount it first. Zoran ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
In message: [EMAIL PROTECTED] Norberto Meijome [EMAIL PROTECTED] writes: : On Thu, 19 Jul 2007 09:02:50 -0600 (MDT) : M. Warner Losh [EMAIL PROTECTED] wrote: : : In message: [EMAIL PROTECTED] : Momchil Ivanov [EMAIL PROTECTED] writes: : : What is then the reason for the kernel not being able to unmount a : : filesystem whose provider is no longer present? : : The problem is that the device driver has wound down, deallocated : memory, etc. Now the kernel comes along with stale references to the : device and panic ensues. It is really just that simple. There's no : replacement of the now-dead device with dead calls. : : And even if you fixed that, most of the file systems in the tree today : do not tolerate errors on writes at all and that also leads to : panics. This is why firewire freezes the I/Os rather than failing : them (and why umount -f on a firewire drive hangs). : : Please point me to the correct RTFM, because I feel this worth it :) src/sys/fs/..., src/sys/kern/... and src/sys/vm/... are your best bets. : Is there a reason why the kernel cannot check 'upwards' if a device : is being used, ie mounted ? and prevent the unloading of the device : driver ? Check, sure, it can check. But what does a simple check accomplish if the filesystem panics if the underlying media returns an error? The problem isn't as simple as just looking in one place or another, but rather systemic in nature. Warner ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On 19/07/07, M. Warner Losh [EMAIL PROTECTED] wrote: [...] The best one can do without massive buffer cache work is what firewire does: it has one attachment to handle all umass devices. When the device goes away, it pauses all operations to that device. If the device comes back, it resumes the I/O . If the device never comes back, then the I/O never finishes. Is this safe? I don't know where locking occurs in this case, but if locking occurs on a very low level it's potentially dangerous. If a device is removed (either on purpose or by accident) the kernel can't determine the state of the filesystem anymore. So the user could plug the device into another machine, start some write operations on the device, and put it back into the FreeBSD machine. This wouldn't know anything about the changes done, and just flush its buffer, probably using blocks that have been filled previously. It's a pity that FreeBSD can't handle these situations. Since no one here on this list has enough money to get development on the road, maybe we could try collecting money? Everyone interested in seeing this issue fixed offers the amount of money he/she likes to spend... I guess for a Summer of Code project this issue would be to big to fix, wouldn't it? ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
RE: removing external usb hdd without unmounting causes reboot?
It won't fix it. The problem is dangling pointers to devices that no longer exist. And like all dangling references after 'free' you get bad thing happening. Believe me, if it were easy, it would have been fixed. If it was moderate to fix, it would have been fixed. It is a hard problem that people have put lots of hours into to try to resolve. To imply otherwise is really insulting to all those people (myself include) that have tried to fix this. There is a simple but ugly way to fix it, similar to what the FireWire layer does. The idea is for the USB layer to create a device that never goes away when it first sees the stick and pass that device that never goes away to the other layers. Even if the storage device is removed, the device still does not go away. The virtual device can generate errors if the physical device is missing. The virtual device can be cleaned up when the device is unmounted. This will ensure that the 'umount -f' process generates errors (which it will ignore) rather than crashes (which are somewhat harder to ignore). DS ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Hi, Am 20.07.2007 um 08:16 schrieb Christian Walther: [...] It's a pity that FreeBSD can't handle these situations. Since no one here on this list has enough money to get development on the road, maybe we could try collecting money? Everyone interested in seeing this issue fixed offers the amount of money he/she likes to spend... I guess for a Summer of Code project this issue would be to big to fix, wouldn't it? Especially if I think about software RAID it's really a show-stopper. I remember a stress-test of *vinum* (without the g) years ago when I pulled the plug on one of the disks of a RAID5-plex... Obviously there's no change at all concerning this problem. - -- Ciao/BSD - Matthias Matthias Schuendehuettemsch [at] snafu.de, Berlin (Germany) PGP-Key at pgp.mit.edu and wwwkeys.de.pgp.net ID: 0xDDFB0A5F -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.6 (Darwin) iD8DBQFGoTatf1BNcN37Cl8RAmTRAJ99PXwWaHxUq4I8P++hcMhpL5PSlwCgg5/R 9gy1Gj2+JYTRB5OvGOWFDF4= =XVsv -END PGP SIGNATURE- ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Thu, 19 Jul 2007 17:38:14 +0200
[LoN]Kamikaze [EMAIL PROTECTED] wrote:
As I mentioned earlier I remember it working during the 5.3 era on Stable, at
some point it worked. I even remember removing my CD-Rom drive from my
Thinkpad
without running atacontrol detach. The system just took it and the drive just
continued working after I put it back in.
on 6.2-STABLE (of a few days ago), i have this happening a couple of times with
no adverse effect at all.
Burn DVD/Cd, when finished, hald detects the disk, mounts it, /dev/cd0 in
/media/whatever.
i can eject the disk just fine (which in itself is weird, i think) the
device is still there...
umount /dev/cd0
works fine and off it goes. other than that, no, i havent tried to access the
device in question
_
{Beto|Norberto|Numard} Meijome
The people have always some champion whom they set over them and nurse into
greatness...
This and no other is the root from which a tyrant springs; when he first
appears he is a protector.
Plato
I speak for myself, not my employer. Contents may be hot. Slippery when wet.
Reading disclaimers makes you go blind. Writing them is worse. You have been
Warned.
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Re: removing external usb hdd without unmounting causes reboot?
On Thu, 19 Jul 2007 09:02:50 -0600 (MDT)
M. Warner Losh [EMAIL PROTECTED] wrote:
In message: [EMAIL PROTECTED]
Momchil Ivanov [EMAIL PROTECTED] writes:
: What is then the reason for the kernel not being able to unmount a
: filesystem whose provider is no longer present?
The problem is that the device driver has wound down, deallocated
memory, etc. Now the kernel comes along with stale references to the
device and panic ensues. It is really just that simple. There's no
replacement of the now-dead device with dead calls.
And even if you fixed that, most of the file systems in the tree today
do not tolerate errors on writes at all and that also leads to
panics. This is why firewire freezes the I/Os rather than failing
them (and why umount -f on a firewire drive hangs).
Please point me to the correct RTFM, because I feel this worth it :)
Is there a reason why the kernel cannot check 'upwards' if a device is being
used, ie mounted ? and prevent the unloading of the device driver ?
thanks for your time illuminating this ignoramus :)
_
{Beto|Norberto|Numard} Meijome
Egotism is the anesthetic that dulls the pain of stupidity.
Frank Leahy
I speak for myself, not my employer. Contents may be hot. Slippery when wet.
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Re: removing external usb hdd without unmounting causes reboot?
Hi,
How Mac OS X handle this? Method, tricks, code, etc...
Does Linux reboot when this happen?
One can argue the kernel is so different between OS X, Linux and FBSD,
but it is still better to compare WIN vs FBSD (or NTFS vs UFS).
Or may be I am wrong.
BTW,
I hardly ever put a USB Disk on our FBSD Servers,
but never had problem disconnect USB/Firewire Disk on my Powerbook.
Julius
On Thu 19 Jul 2007, at 11:02, Norberto Meijome wrote:
On Wed, 18 Jul 2007 17:41:04 +0200 (CEST)
Oliver Fromme [EMAIL PROTECTED] wrote:
If you have problems remembering,
This is very interesting thread indeed
I have found that mounting remote SMB shares will panic the kernel
too, but
only if i try to access it while 'gone' . If I remember correctly,
if i thread
carefully around it, i can manage to shutdown everything and it
will only panic
at the very last minute when the kernel tries to unmount.
And, from my point of view, the explanation 'well, don't remove
your mounted
devices without unmounting them first' is rubbish - the problem is not
necessarily users removing them, but ALL the reasons that could
cause an
unwanted and unplanned removal. Like a network outage in the case
of smbfs. or
someone killing the power on a USB device. I can't see why the
whole kernel
should die on you. Yes, i understand there are architectural
reasons for this -
then the architecture is not right anymore, i think.
another work-around
is to use the auto mounter daemon (amd(8)). It umounts
file systems automatically that are not in use.
Another nice feature of amd(8) is that you don't have
to mount the file system either -- Simply plug the USB
stick in, then access it, and amd(8) will automatically
mount it for you.
Now, something I dont understand - amd runs
at user level, and it mounts filesystems, and nothing dies when the
filesystems
go away (other than the obvious cases for the applications trying
to write to
the FS in question). Doesn't amd , at some point , have to tell the
kernel
'please mount this filesystem' here or there? Isn't the kernel
STILL involved
in all this? and why doesnt the kernel panic when the FS goes away?
The same goes for hald - it doesn't work flawlessly, but it does
the trick, and
i cant recall an instance when it crashed the kernel.
re. USB disks, could we not by default use amd to mount USB
devices? It seems
the obvious native replacement for hald + polkitd + dbus I use in
XFCE with
Thunar on my laptop...
TIA!
_
{Beto|Norberto|Numard} Meijome
Never attribute to malice what can adequately be explained by
incompetence.
I speak for myself, not my employer. Contents may be hot. Slippery
when wet.
Reading disclaimers makes you go blind. Writing them is worse. You
have been
Warned.
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Re: removing external usb hdd without unmounting causes reboot?
Oliver Fromme wrote: Momchil Ivanov wrote: On Wednesday 18 July 2007 15:52:42 [LoN]Kamikaze wrote: Josh Paetzel wrote: Yes, it's expected behavior. The workaround is to not unplug mounted devices. (There's nothing special about USB here, if you unplugged an IDE drive you'd get the same behavior) Wouldn't it make some sense not to panic if mounted devices that are in sync get removed? A few applications might get in trouble, but that's hardly a reason to bring a whole system down. I don`t know how things work, but shutting down the system when some mounted fs is no longer present seems like the wrong thing to me. As Josh wrote, it's expected. The problem is known to exist for a long time already (probably as long as FreeBSD itself exists), and if there was an easy solution, certainly someone would have fixed it. I remember on 5.3 I removed a mounted USB stick. The system did not panic, all I had to do was to plug the stick back in to be able to unmount it. So the behaviour has been more tolerant, in the past. ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Norberto Meijome wrote: On Wed, 18 Jul 2007 17:41:04 +0200 (CEST) Oliver Fromme [EMAIL PROTECTED] wrote: another work-around is to use the auto mounter daemon (amd(8)). It umounts file systems automatically that are not in use. Another nice feature of amd(8) is that you don't have to mount the file system either -- Simply plug the USB stick in, then access it, and amd(8) will automatically mount it for you. Now, something I dont understand - amd runs at user level, and it mounts filesystems, and nothing dies when the filesystems go away (other than the obvious cases for the applications trying to write to the FS in question). Doesn't amd , at some point , have to tell the kernel 'please mount this filesystem' here or there? Isn't the kernel STILL involved in all this? and why doesnt the kernel panic when the FS goes away? The trick is that amd unmounts the device after a couple of seconds, so when someone accidentally removes a usb drive, it doesn't really matter. Amd will simply fail to mount it on the next access. If you remove the device during or shortly after accessing it, it still will panic the system. ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Thursday 19 July 2007 09:17:48 [LoN]Kamikaze wrote: Norberto Meijome wrote: On Wed, 18 Jul 2007 17:41:04 +0200 (CEST) Oliver Fromme [EMAIL PROTECTED] wrote: another work-around is to use the auto mounter daemon (amd(8)). It umounts file systems automatically that are not in use. Another nice feature of amd(8) is that you don't have to mount the file system either -- Simply plug the USB stick in, then access it, and amd(8) will automatically mount it for you. Now, something I dont understand - amd runs at user level, and it mounts filesystems, and nothing dies when the filesystems go away (other than the obvious cases for the applications trying to write to the FS in question). Doesn't amd , at some point , have to tell the kernel 'please mount this filesystem' here or there? Isn't the kernel STILL involved in all this? and why doesnt the kernel panic when the FS goes away? The trick is that amd unmounts the device after a couple of seconds, so when someone accidentally removes a usb drive, it doesn't really matter. Amd will simply fail to mount it on the next access. If you remove the device during or shortly after accessing it, it still will panic the system. What is then the reason for the kernel not being able to unmount a filesystem whose provider is no longer present? What in the process of unmounting denies unmounting a filesystem whose provider is no longer available? Why can the kernel not just inform all programs that files have to be closed and are unaccessible any more, then consider the fs as unmounted and remove any bits of it left in the VM. Why can kernel not just ignore interruped/pending writes to that fs, drop the data, return an error to the program that initiated the write and just go on. -- PGP KeyID: 0x3118168B Keyserver: pgp.mit.edu Key fingerprint BB50 2983 0714 36DC D02E 158A E03D 56DA 3118 168B pgpK94L1KnIM6.pgp Description: PGP signature
Re: removing external usb hdd without unmounting causes reboot?
On Thu 19 Jul 2007, at 15:43, Momchil Ivanov wrote: On Thursday 19 July 2007 09:17:48 [LoN]Kamikaze wrote: Norberto Meijome wrote: On Wed, 18 Jul 2007 17:41:04 +0200 (CEST) Oliver Fromme [EMAIL PROTECTED] wrote: another work-around is to use the auto mounter daemon (amd(8)). It umounts file systems automatically that are not in use. Another nice feature of amd(8) is that you don't have to mount the file system either -- Simply plug the USB stick in, then access it, and amd(8) will automatically mount it for you. Now, something I dont understand - amd runs at user level, and it mounts filesystems, and nothing dies when the filesystems go away (other than the obvious cases for the applications trying to write to the FS in question). Doesn't amd , at some point , have to tell the kernel 'please mount this filesystem' here or there? Isn't the kernel STILL involved in all this? and why doesnt the kernel panic when the FS goes away? The trick is that amd unmounts the device after a couple of seconds, so when someone accidentally removes a usb drive, it doesn't really matter. Amd will simply fail to mount it on the next access. If you remove the device during or shortly after accessing it, it still will panic the system. What is then the reason for the kernel not being able to unmount a filesystem whose provider is no longer present? What in the process of unmounting denies unmounting a filesystem whose provider is no longer available? Why can the kernel not just inform all programs that files have to be closed and are unaccessible any more, then consider the fs as unmounted and remove any bits of it left in the VM. Why can kernel not just ignore interruped/ pending writes to that fs, drop the data, return an error to the program that initiated the write and just go on. -- PGP KeyID: 0x3118168B Keyserver: pgp.mit.edu Key fingerprint BB50 2983 0714 36DC D02E 158A E03D 56DA 3118 168B Hi, How Mac OS X handle this? Method, tricks, code, etc... Does Linux reboot when this happen? The kernel is different between OS X, Linux and FBSD. Why FBSD handle this by reboot? Does reboot clean up everything? BTW, I hardly ever put a USB Disk on our FBSD Servers, but never had problem disconnect USB/Firewire Disk on my Powerbook. Julius ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Hi All! 2007/7/19, Momchil Ivanov [EMAIL PROTECTED]: On Thursday 19 July 2007 09:17:48 [LoN]Kamikaze wrote: Norberto Meijome wrote: On Wed, 18 Jul 2007 17:41:04 +0200 (CEST) Oliver Fromme [EMAIL PROTECTED] wrote: another work-around is to use the auto mounter daemon (amd(8)). It umounts file systems automatically that are not in use. Another nice feature of amd(8) is that you don't have to mount the file system either -- Simply plug the USB stick in, then access it, and amd(8) will automatically mount it for you. Now, something I dont understand - amd runs at user level, and it mounts filesystems, and nothing dies when the filesystems go away (other than the obvious cases for the applications trying to write to the FS in question). Doesn't amd , at some point , have to tell the kernel 'please mount this filesystem' here or there? Isn't the kernel STILL involved in all this? and why doesnt the kernel panic when the FS goes away? The trick is that amd unmounts the device after a couple of seconds, so when someone accidentally removes a usb drive, it doesn't really matter. Amd will simply fail to mount it on the next access. If you remove the device during or shortly after accessing it, it still will panic the system. What is then the reason for the kernel not being able to unmount a filesystem whose provider is no longer present? What in the process of unmounting denies unmounting a filesystem whose provider is no longer available? Why can the kernel not just inform all programs that files have to be closed and are unaccessible any more, then consider the fs as unmounted and remove any bits of it left in the VM. Why can kernel not just ignore interruped/pending writes to that fs, drop the data, return an error to the program that initiated the write and just go on. For me, the most expected behaviour of API is the same as socket one: In case recv/send fails (socket peer gone, router in-the-middle is died, excavator came across the cables, etc) I just get a timeout (for the first time), then (once remote socket is considered closed) just return with -1 and appropriate errno set. Since every (not braindamaged) program expect possible disk failures, everyone checks for return/errno. It should be extremely safe to just supply notify userland with -1/errno to handle over the error case at application level. Since I do understand the complexity and impact of VM/[V]FS code, I'd rather vote for funding an external project on better VM/VFS separation and improvement. Later, this project codebase must be merged into the CURRENT, tested and go STABLE the usual way. The famous Floppy issue of FreeBSD MUST go away, it's just a shame and long standing base for unpleasant rumor/jokes. Could it be the good task for FreeBSD Foundation or what ever other investor? Sorry for adding just 0.02UAH instead of real $20-30-50 of personal money to the fund's account. If there is such a fund for this particular problem, I'll vote with money instead of bytes. I believe, there will be a lot more people willing to do the same to gain enough funding. -- Dennis Melentyev ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
on 18/07/2007 20:34 Mark Linimon said the following: On Wed, Jul 18, 2007 at 10:05:59AM -0700, Jeremy Chadwick wrote: Bottom line here is that the kernel panics when removing a USB device that has filesystems mounted. s/USB // I also have a hard time believing that the reason it hasn't been fixed is because there isn't an easy fix. I'm under the impression it hasn't been fixed because either no one cares enough to fix it (using the workaround as a scapegoat excuse), or because the majority of people do not use USB-based storage devices. The reason is not the USB stack; the reason (IIRC) is that the FreeBSD VM was written with the default assumption that Devices Never Go Away. A large rewrite, I'm told, will be needed to fix this, and the code is convoluted and tricky. No one finds the situation acceptable; introducing the scapegoat word isn't going to win you any support. The problem is not a weekend's worth of work to fix, nor does it have anything to do with avoidance by one particular maintainer, which you apparently had encountered before. Well, here's my two kopiykas. Apparently there is somebody who tried to fix this problem, but for some reason (most probably language barrier) his attempt is largely unnoticed so far. Here is a link to a posting to freebsd-fs: http://lists.freebsd.org/pipermail/freebsd-fs/2007-June/003370.html Here's a discussion about this patch (in Russian): http://www.opennet.ru/openforum/vsluhforumID9/6467.html I have not tried this patch myself. I am not qualified enough to comment on its quality and the author admitted that this is more of a workaround or hack rather than perfect solution. Also, the patch seems to be msdosfs-centered. But there are some success reports on the forum mentioned above. So I thought that this is a good opportunity to draw more attention to the patch in hope that more people will try it and look at it and something good will result from it. -- Andriy Gapon ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
on 19/07/2007 13:03 Daniel O'Connor said the following: Andriy Gapon wrote: Well, here's my two kopiykas. Apparently there is somebody who tried to fix this problem, but for some reason (most probably language barrier) his attempt is largely unnoticed so far. Here is a link to a posting to freebsd-fs: http://lists.freebsd.org/pipermail/freebsd-fs/2007-June/003370.html The language barrier won't help, especially since there is no English discussion about how the patch works. Well, barriers usually stop something :-) There are some comments in Russian, maybe someone will find time to translate, maybe even me... FreeBSD VFS comitters are rare, ones that understand Russian are probably almost non-existent :) There's always a chance. Also it would be nice if the patch was a unified diff rather than x-patch as that makes it much easier to review. Patches _are_ unified diffs. The fact that some not-so-smart software decided that text/x-patch is a non-text attachment is indeed inconvenient. -- Andriy Gapon ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Andriy Gapon wrote: Well, barriers usually stop something :-) Heh :) There are some comments in Russian, maybe someone will find time to translate, maybe even me... It could come in handy. FreeBSD VFS comitters are rare, ones that understand Russian are probably almost non-existent :) There's always a chance. Indeed. Also it would be nice if the patch was a unified diff rather than x-patch as that makes it much easier to review. Patches _are_ unified diffs. The fact that some not-so-smart software decided that text/x-patch is a non-text attachment is indeed inconvenient. Oops, I am in Windows land at the moment and it mangled them :( The .bin extension is somewhat confusing as well.. ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Andriy Gapon wrote: on 18/07/2007 20:34 Mark Linimon said the following: On Wed, Jul 18, 2007 at 10:05:59AM -0700, Jeremy Chadwick wrote: Bottom line here is that the kernel panics when removing a USB device that has filesystems mounted. s/USB // I also have a hard time believing that the reason it hasn't been fixed is because there isn't an easy fix. I'm under the impression it hasn't been fixed because either no one cares enough to fix it (using the workaround as a scapegoat excuse), or because the majority of people do not use USB-based storage devices. The reason is not the USB stack; the reason (IIRC) is that the FreeBSD VM was written with the default assumption that Devices Never Go Away. A large rewrite, I'm told, will be needed to fix this, and the code is convoluted and tricky. No one finds the situation acceptable; introducing the scapegoat word isn't going to win you any support. The problem is not a weekend's worth of work to fix, nor does it have anything to do with avoidance by one particular maintainer, which you apparently had encountered before. Well, here's my two kopiykas. Apparently there is somebody who tried to fix this problem, but for some reason (most probably language barrier) his attempt is largely unnoticed so far. Here is a link to a posting to freebsd-fs: http://lists.freebsd.org/pipermail/freebsd-fs/2007-June/003370.html The language barrier won't help, especially since there is no English discussion about how the patch works. FreeBSD VFS comitters are rare, ones that understand Russian are probably almost non-existent :) Also it would be nice if the patch was a unified diff rather than x-patch as that makes it much easier to review. ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Thu, 19 Jul 2007 19:49:22 +0930 Daniel O'Connor [EMAIL PROTECTED] wrote: Andriy Gapon wrote: Well, barriers usually stop something :-) Heh :) There are some comments in Russian, maybe someone will find time to translate, maybe even me... It could come in handy. FreeBSD VFS comitters are rare, ones that understand Russian are probably almost non-existent :) There's always a chance. Indeed. http://translate.google.com/translate?u=http%3A%2F%2Fwww.opennet.ru%2Fopenforum%2FvsluhforumID9%2F6467.htmllangpair=ru%7Cenhl=enie=UTF8 Useful? Seems comprehensible enough (maybe a wrong impression since I understand Russian text). Nikola Lečić ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On 2007-Jul-19 00:57:57 +0200, Momchil Ivanov [EMAIL PROTECTED] wrote: I think you are missing the point here and it is that the drive is already gone, so you do not have to care about it. I don't think anyone is missing this point. The most natural way for me seems to be that the OS should just return errors to the programs trying any I/O on that drive. May be when a drive is unplugged the OS has to mark it and the mounted file systems as not being there until all opened files on it are closed, return errors for all I/O except for closing opened files. And when all files are closed consider the fs as unmounted and remove the drive from the kernel. And everyone I am aware of agrees that this is what _should_ happen. Unfortunately, as has already been mentioned, the filesystem and VM code have a very incestuous relationship and actually _making_ FreeBSD behave this way is (from all accounts) very difficult. There is already an entry on the project ideas list to at least make this work for MSDOSFS (http://www.freebsd.org/projects/ideas/#p-msdosfs - also part of SOC2007). This is my idea of how things should be done. Ensuring that a file system is in a consistent state after drive disconnect is something completely different Note that UFS+softupdates already implements this. -- Peter Jeremy pgp3niumMyzcX.pgp Description: PGP signature
Re: removing external usb hdd without unmounting causes reboot?
On 2007-Jul-19 08:58:27 +0200, [LoN]Kamikaze [EMAIL PROTECTED] wrote: I remember on 5.3 I removed a mounted USB stick. The system did not panic, all I had to do was to plug the stick back in to be able to unmount it. So the behaviour has been more tolerant, in the past. Did you or the syncer thread try to write to the stick whilst it was absent? If not then the OS would have been unaware of its absence. -- Peter Jeremy pgpvTXMlOHCAu.pgp Description: PGP signature
Re: removing external usb hdd without unmounting causes reboot?
In message: [EMAIL PROTECTED] [LoN]Kamikaze [EMAIL PROTECTED] writes: : Josh Paetzel wrote: : On Wednesday 18 July 2007, Momchil Ivanov wrote: : Hi, : : I am running FreeBSD 6.2-STABLE #11: Sat Jul 14 16:27:12 CEST 2007 : and accidently unplugged the USB hub to which my external hdd : together with a mouse were connected and this caused my machine to : freeze for some seconds and then reboot. At that moment the hdd was : mounted and I was playing music out of it. : After that I tried to reproduce it :) so just plugged only the hdd : directly, mounted it and started playing music files from it. When : I unplugged the USB cable the same thing happened: short freeze, : and then reboot. Is this expected behaviour? And is there some way : to avoid the freeze and reboot? : : Thanks. : : Yes, it's expected behavior. The workaround is to not unplug mounted : devices. (There's nothing special about USB here, if you unplugged an : IDE drive you'd get the same behavior) : : : Wouldn't it make some sense not to panic if mounted devices that are in sync : get removed? A few applications might get in trouble, but that's hardly a : reason to bring a whole system down. This is this week's winner in the Zen Master of the Obvious award. Yes. It is a known problem that should be fixed. Warner ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
In message: [EMAIL PROTECTED] Baldur Gislason [EMAIL PROTECTED] writes: : I vaguely remember being able to yank out USB drives in 5.x and just make : usbd execute a forced umount without any problems. FAT32 drives mind you. : On 6.2 I haven't even been able to unplug a USB drive even if I unmount it : first, always results in a kernel panic. This has never worked. Not even on 5.x. Or 4.10. I've tested these both recently accidentally... Warner ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
In message: [EMAIL PROTECTED] Jeremy Chadwick [EMAIL PROTECTED] writes: : If someone wants to work on this and needs devices/toys (thumb drives, : external enclosures + hard disks), let me know, I will be more than : happy to buy them the hardware needed. Willing to fund the work on it too? This is a volunteer project, and you have to motivate people to work on this. Tirades in mailing lists has proven to be ineffective in the past. I've looked at the issue, and generically, if a device goes away, it is *HARD* to not panic. The same thing happens if you eject a CF card in a PC Card adapter in a PC Card slot. The best one can do without massive buffer cache work is what firewire does: it has one attachment to handle all umass devices. When the device goes away, it pauses all operations to that device. If the device comes back, it resumes the I/O . If the device never comes back, then the I/O never finishes. Warner ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
In message: [EMAIL PROTECTED] Momchil Ivanov [EMAIL PROTECTED] writes: : On Wednesday 18 July 2007 19:34:06 Mark Linimon wrote: : On Wed, Jul 18, 2007 at 10:05:59AM -0700, Jeremy Chadwick wrote: : Bottom line here is that the kernel panics when removing a USB device : that has filesystems mounted. : : s/USB // : : Just a dumb question: what does umount -f does? And doing something like : that when a fs goes away shouldn`t fix it? It won't fix it. The problem is dangling pointers to devices that no longer exist. And like all dangling references after 'free' you get bad thing happening. : If the problem is in general with a file system, regardless of the provider, : then what does one do when a mounted smbfs becomes unavailable due to remote : host down, no route to host or some other network related problems? Same : question for NFS mounted filesystems? In those cases, the device doesn't go away. Just the remote host. This is a big difference. Believe me, if it were easy, it would have been fixed. If it was moderate to fix, it would have been fixed. It is a hard problem that people have put lots of hours into to try to resolve. To imply otherwise is really insulting to all those people (myself include) that have tried to fix this. Warner ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
In message: [EMAIL PROTECTED] Jeremy Chadwick [EMAIL PROTECTED] writes: : This would alleviate concerns over data loss, would it not? No. The problem is more basic: the device *driver* is gone. All the code unwinding has happened. The physical device is also gone, which is what triggered the detach. Doing synchronous writes wouldn't help. The next time the file system was touched, it would dereference a device that no longer exists, giving random results, in this case a crash. Meaning no disrespect for enthusiastic users, I really wish that people with suggestions would actually try to fix it themselves before making such obviously wrong comments. I have the right to say this because I have tried to fix this, and have run into these issues. Like I've said before, if it were easy, one of the dozen or so people that have tried to fix it in the past 8 years would have succeeded. Warner ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Thu, Jul 19, 2007 at 08:48:21AM -0600, M. Warner Losh wrote: In message: [EMAIL PROTECTED] Jeremy Chadwick [EMAIL PROTECTED] writes: : If someone wants to work on this and needs devices/toys (thumb drives, : external enclosures + hard disks), let me know, I will be more than : happy to buy them the hardware needed. Willing to fund the work on it too? This is a volunteer project, and you have to motivate people to work on this. I'm one man with a single day job. I only make so much money a year, most of which goes to rent and co-location bills. Remaining amounts usually go to small hobby projects of mine, or donating money to folks like phk@ to work on features that I'll benefit from (serial console work comes to mind, ditto with BTX fixes). What I'm saying is that I can't afford (literally -- I don't have the cash) to pay someone US$40/hour for programming efforts (especially when I know it'd be a 8-12 week job), but I *can* afford to donate a few hundred bucks getting someone hardware who has the know-how to fix or test things much better than myself. Most of the time though I'm told I have the hardware I need -- it's a matter of finding the time! Ain't that the truth. :-) Besides working on ports (which I've been slacking on as of late), this is how I try to help/contribute to the FreeBSD community. The best one can do without massive buffer cache work is what firewire does: it has one attachment to handle all umass devices. When the device goes away, it pauses all operations to that device. If the device comes back, it resumes the I/O . If the device never comes back, then the I/O never finishes. This sounds good. -- | Jeremy Chadwickjdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB | ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
In message: [EMAIL PROTECTED] [LoN]Kamikaze [EMAIL PROTECTED] writes: : Oliver Fromme wrote: : Momchil Ivanov wrote: :On Wednesday 18 July 2007 15:52:42 [LoN]Kamikaze wrote: : Josh Paetzel wrote: : Yes, it's expected behavior. The workaround is to not unplug mounted : devices. (There's nothing special about USB here, if you unplugged an : IDE drive you'd get the same behavior) : : Wouldn't it make some sense not to panic if mounted devices that are in : sync get removed? A few applications might get in trouble, but that's : hardly a reason to bring a whole system down. : :I don`t know how things work, but shutting down the system when some :mounted fs is no longer present seems like the wrong thing to me. : : As Josh wrote, it's expected. The problem is known : to exist for a long time already (probably as long : as FreeBSD itself exists), and if there was an easy : solution, certainly someone would have fixed it. : : I remember on 5.3 I removed a mounted USB stick. The system did not panic, all : I had to do was to plug the stick back in to be able to unmount it. So the : behaviour has been more tolerant, in the past. I'm pretty sure that 5.3 panics when you do this. At least my 5.3 machine at work did last time I tried it, which was just last week. Warner ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
In message: [EMAIL PROTECTED] Norberto Meijome [EMAIL PROTECTED] writes: : re. USB disks, could we not by default use amd to mount USB devices? It seems : the obvious native replacement for hald + polkitd + dbus I use in XFCE with : Thunar on my laptop... Won't work. Once the device driver is already gone and devd/dbus gets the notification, it is already too late. umount -f will cause I/O to a device that no longer exists, causing the panic. Warner ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
In message: [EMAIL PROTECTED] Momchil Ivanov [EMAIL PROTECTED] writes: : What is then the reason for the kernel not being able to unmount a : filesystem whose provider is no longer present? The problem is that the device driver has wound down, deallocated memory, etc. Now the kernel comes along with stale references to the device and panic ensues. It is really just that simple. There's no replacement of the now-dead device with dead calls. And even if you fixed that, most of the file systems in the tree today do not tolerate errors on writes at all and that also leads to panics. This is why firewire freezes the I/Os rather than failing them (and why umount -f on a firewire drive hangs). Warner ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Nikola Lecic wrote: http://translate.google.com/translate?u=http%3A%2F%2Fwww.opennet.ru%2Fopenforum%2FvsluhforumID9%2F6467.htmllangpair=ru%7Cenhl=enie=UTF8 Useful? Seems comprehensible enough (maybe a wrong impression since I understand Russian text). I'm not a VFS guru, alas :) ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
M. Warner Losh wrote: In message: [EMAIL PROTECTED] Baldur Gislason [EMAIL PROTECTED] writes: : I vaguely remember being able to yank out USB drives in 5.x and just make : usbd execute a forced umount without any problems. FAT32 drives mind you. : On 6.2 I haven't even been able to unplug a USB drive even if I unmount it : first, always results in a kernel panic. This has never worked. Not even on 5.x. Or 4.10. I've tested these both recently accidentally... Warner As I mentioned earlier I remember it working during the 5.3 era on Stable, at some point it worked. I even remember removing my CD-Rom drive from my Thinkpad without running atacontrol detach. The system just took it and the drive just continued working after I put it back in. Anyway, is there a way to convince the kernel that removable devices are NFS mounts? I suppose there'd be an additional layer required that clusters file operations to consistent atomic operations similar to NFS. ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Thursday 19 July 2007, M. Warner Losh wrote: In message: [EMAIL PROTECTED] Jeremy Chadwick [EMAIL PROTECTED] writes: : If someone wants to work on this and needs devices/toys (thumb : drives, external enclosures + hard disks), let me know, I will be : more than happy to buy them the hardware needed. Willing to fund the work on it too? This is a volunteer project, and you have to motivate people to work on this. Tirades in mailing lists has proven to be ineffective in the past. I've looked at the issue, and generically, if a device goes away, it is *HARD* to not panic. The same thing happens if you eject a CF card in a PC Card adapter in a PC Card slot. The best one can do without massive buffer cache work is what firewire does: it has one attachment to handle all umass devices. When the device goes away, it pauses all operations to that device. If the device comes back, it resumes the I/O . If the device never comes back, then the I/O never finishes. Warner Just curious, but what, if any, is the performance hit with this strategy? I could care less about performance on a usb stick, but if we are talking about changes that are going to affect all filesystems regardless of storage device implimentation then I'm sort of interested. eg: I wouldn't be happy trading filesystem performance for avoiding a panic that is trivial to avoid in the first place. -- Thanks, Josh Paetzel pgpmLTsui8umW.pgp Description: PGP signature
Re: removing external usb hdd without unmounting causes reboot?
On Thu, 19 Jul 2007, M. Warner Losh wrote: In message: [EMAIL PROTECTED] [LoN]Kamikaze [EMAIL PROTECTED] writes: : Oliver Fromme wrote: : Momchil Ivanov wrote: :On Wednesday 18 July 2007 15:52:42 [LoN]Kamikaze wrote: : Josh Paetzel wrote: : Yes, it's expected behavior. The workaround is to not unplug mounted : devices. (There's nothing special about USB here, if you unplugged an : IDE drive you'd get the same behavior) : : Wouldn't it make some sense not to panic if mounted devices that are in : sync get removed? A few applications might get in trouble, but that's : hardly a reason to bring a whole system down. : :I don`t know how things work, but shutting down the system when some :mounted fs is no longer present seems like the wrong thing to me. : : As Josh wrote, it's expected. The problem is known : to exist for a long time already (probably as long : as FreeBSD itself exists), and if there was an easy : solution, certainly someone would have fixed it. : : I remember on 5.3 I removed a mounted USB stick. The system did not panic, all : I had to do was to plug the stick back in to be able to unmount it. So the : behaviour has been more tolerant, in the past. I'm pretty sure that 5.3 panics when you do this. At least my 5.3 machine at work did last time I tried it, which was just last week. 5.4 too. Now at 5.5-STABLE, on APM if it matters, I've had much fun several times having the laptop, when on battery, suspend/resume with a USB stick mounted on da0 (msdosfs or ufs) - without removing the device. With rc.suspend kldunload'ing usb and rc.resume kldload'ing it (as recommended for UHCI and, iirc, needed here) then on resume umass0 detaches reattaches, but assigns the stick to da1. mount still shows the da0sX mount. It doesn't panic unless / until something accesses da0. So at least I usually get a window to reboot, the only way out. Sure I've learned don't do that but it's painful when I forget .. Might this new USB stack offer any relief to this need to unload/reload usb on s/r, and if so keep hold of a mount (assuming the stick remains)? Cheers, Ian ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
In message: [EMAIL PROTECTED] Jeremy Chadwick [EMAIL PROTECTED] writes: : On Thu, Jul 19, 2007 at 08:48:21AM -0600, M. Warner Losh wrote: : In message: [EMAIL PROTECTED] : Jeremy Chadwick [EMAIL PROTECTED] writes: : : If someone wants to work on this and needs devices/toys (thumb drives, : : external enclosures + hard disks), let me know, I will be more than : : happy to buy them the hardware needed. : : Willing to fund the work on it too? This is a volunteer project, and : you have to motivate people to work on this. : : I'm one man with a single day job. I only make so much money a year, : most of which goes to rent and co-location bills. Remaining amounts : usually go to small hobby projects of mine, or donating money to folks : like phk@ to work on features that I'll benefit from (serial console : work comes to mind, ditto with BTX fixes). : : What I'm saying is that I can't afford (literally -- I don't have the : cash) to pay someone US$40/hour for programming efforts (especially when : I know it'd be a 8-12 week job), but I *can* afford to donate a few : hundred bucks getting someone hardware who has the know-how to fix or : test things much better than myself. Most of the time though I'm told : I have the hardware I need -- it's a matter of finding the time! A total fix would be a lot of effort. Some of it would be easy to incrementally adopt, while other parts would have ripples far and wide. : Besides working on ports (which I've been slacking on as of late), this : is how I try to help/contribute to the FreeBSD community. Yea. I understand that. : The best one can do without massive buffer cache work is what firewire : does: it has one attachment to handle all umass devices. When the : device goes away, it pauses all operations to that device. If the : device comes back, it resumes the I/O . If the device never comes : back, then the I/O never finishes. : : This sounds good. It likely is the easiest 'bang for buck' solution. Warner ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
removing external usb hdd without unmounting causes reboot?
Hi, I am running FreeBSD 6.2-STABLE #11: Sat Jul 14 16:27:12 CEST 2007 and accidently unplugged the USB hub to which my external hdd together with a mouse were connected and this caused my machine to freeze for some seconds and then reboot. At that moment the hdd was mounted and I was playing music out of it. After that I tried to reproduce it :) so just plugged only the hdd directly, mounted it and started playing music files from it. When I unplugged the USB cable the same thing happened: short freeze, and then reboot. Is this expected behaviour? And is there some way to avoid the freeze and reboot? Thanks. -- PGP KeyID: 0x3118168B Keyserver: pgp.mit.edu Key fingerprint BB50 2983 0714 36DC D02E 158A E03D 56DA 3118 168B ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Wed, Jul 18, 2007 at 11:42:26AM +0200, Momchil Ivanov wrote: accidently unplugged the USB hub to which my external hdd together with a mouse were connected and this caused my machine to freeze for some seconds and then reboot. Yes, this is a known problem, for which there is no workaround at the moment. mcl ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Wednesday 18 July 2007, Momchil Ivanov wrote: Hi, I am running FreeBSD 6.2-STABLE #11: Sat Jul 14 16:27:12 CEST 2007 and accidently unplugged the USB hub to which my external hdd together with a mouse were connected and this caused my machine to freeze for some seconds and then reboot. At that moment the hdd was mounted and I was playing music out of it. After that I tried to reproduce it :) so just plugged only the hdd directly, mounted it and started playing music files from it. When I unplugged the USB cable the same thing happened: short freeze, and then reboot. Is this expected behaviour? And is there some way to avoid the freeze and reboot? Thanks. Yes, it's expected behavior. The workaround is to not unplug mounted devices. (There's nothing special about USB here, if you unplugged an IDE drive you'd get the same behavior) -- Thanks, Josh Paetzel pgpUBWpa2fyAG.pgp Description: PGP signature
Re: removing external usb hdd without unmounting causes reboot?
Josh Paetzel wrote: On Wednesday 18 July 2007, Momchil Ivanov wrote: Hi, I am running FreeBSD 6.2-STABLE #11: Sat Jul 14 16:27:12 CEST 2007 and accidently unplugged the USB hub to which my external hdd together with a mouse were connected and this caused my machine to freeze for some seconds and then reboot. At that moment the hdd was mounted and I was playing music out of it. After that I tried to reproduce it :) so just plugged only the hdd directly, mounted it and started playing music files from it. When I unplugged the USB cable the same thing happened: short freeze, and then reboot. Is this expected behaviour? And is there some way to avoid the freeze and reboot? Thanks. Yes, it's expected behavior. The workaround is to not unplug mounted devices. (There's nothing special about USB here, if you unplugged an IDE drive you'd get the same behavior) Wouldn't it make some sense not to panic if mounted devices that are in sync get removed? A few applications might get in trouble, but that's hardly a reason to bring a whole system down. ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Wednesday 18 July 2007 15:52:42 [LoN]Kamikaze wrote: Josh Paetzel wrote: On Wednesday 18 July 2007, Momchil Ivanov wrote: Hi, I am running FreeBSD 6.2-STABLE #11: Sat Jul 14 16:27:12 CEST 2007 and accidently unplugged the USB hub to which my external hdd together with a mouse were connected and this caused my machine to freeze for some seconds and then reboot. At that moment the hdd was mounted and I was playing music out of it. After that I tried to reproduce it :) so just plugged only the hdd directly, mounted it and started playing music files from it. When I unplugged the USB cable the same thing happened: short freeze, and then reboot. Is this expected behaviour? And is there some way to avoid the freeze and reboot? Thanks. Yes, it's expected behavior. The workaround is to not unplug mounted devices. (There's nothing special about USB here, if you unplugged an IDE drive you'd get the same behavior) Wouldn't it make some sense not to panic if mounted devices that are in sync get removed? A few applications might get in trouble, but that's hardly a reason to bring a whole system down. I don`t know how things work, but shutting down the system when some mounted fs is no longer present seems like the wrong thing to me. It`s surely safe :) just bring everything down in order to ensure not messing things ups. But nowadays there are a lot of USB devices and umounting every time is something that one is surely going to forget once and ooops everyting goes down. If the same thing happens when a network fs is mounted (say NFS or SMBFS) and then becomes unavailable due to network outages (wireless connections break easily compared to cable connections, and nowadays the former become popular), then I think it should be fixed. Windows doesn`t reboot if you unplug the usb or network cable, which I think is the right way of handling these kind of situations. Idea: do something like umount -f when a fs becomes unavailabe, just tell every program that files are unaccessible? I don`t have the programming skills and knowledge of how freebsd works, that`s why I can only help with feedback and ideas :) Shutting down the system without user`s desire seems like a problem to me, regardless of the reason. And problems are there to be solved. -- PGP KeyID: 0x3118168B Keyserver: pgp.mit.edu Key fingerprint BB50 2983 0714 36DC D02E 158A E03D 56DA 3118 168B pgpIlHaW3FprO.pgp Description: PGP signature
Re: removing external usb hdd without unmounting causes reboot?
I vaguely remember being able to yank out USB drives in 5.x and just make usbd execute a forced umount without any problems. FAT32 drives mind you. On 6.2 I haven't even been able to unplug a USB drive even if I unmount it first, always results in a kernel panic. Baldur On Wed, Jul 18, 2007 at 08:39:46AM -0500, Josh Paetzel wrote: On Wednesday 18 July 2007, Momchil Ivanov wrote: Hi, I am running FreeBSD 6.2-STABLE #11: Sat Jul 14 16:27:12 CEST 2007 and accidently unplugged the USB hub to which my external hdd together with a mouse were connected and this caused my machine to freeze for some seconds and then reboot. At that moment the hdd was mounted and I was playing music out of it. After that I tried to reproduce it :) so just plugged only the hdd directly, mounted it and started playing music files from it. When I unplugged the USB cable the same thing happened: short freeze, and then reboot. Is this expected behaviour? And is there some way to avoid the freeze and reboot? Thanks. Yes, it's expected behavior. The workaround is to not unplug mounted devices. (There's nothing special about USB here, if you unplugged an IDE drive you'd get the same behavior) -- Thanks, Josh Paetzel ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Momchil Ivanov wrote: On Wednesday 18 July 2007 15:52:42 [LoN]Kamikaze wrote: Josh Paetzel wrote: Yes, it's expected behavior. The workaround is to not unplug mounted devices. (There's nothing special about USB here, if you unplugged an IDE drive you'd get the same behavior) Wouldn't it make some sense not to panic if mounted devices that are in sync get removed? A few applications might get in trouble, but that's hardly a reason to bring a whole system down. I don`t know how things work, but shutting down the system when some mounted fs is no longer present seems like the wrong thing to me. As Josh wrote, it's expected. The problem is known to exist for a long time already (probably as long as FreeBSD itself exists), and if there was an easy solution, certainly someone would have fixed it. Just remember to always umount first, and you're safe. In the early 90s I panicked a FreeBSD machine by removing a floppy disk that was mounted. I did that mistake only once -- afterwards I always remembered. If you have problems remembering, another work-around is to use the auto mounter daemon (amd(8)). It umounts file systems automatically that are not in use. Another nice feature of amd(8) is that you don't have to mount the file system either -- Simply plug the USB stick in, then access it, and amd(8) will automatically mount it for you. Best regards Oliver -- Oliver Fromme, secnetix GmbH Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd I learned Java 3 years before Python. It was my language of choice. It took me two weekends with Python before I was more productive with it than with Java. -- Anthony Roberts ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Wed, Jul 18, 2007 at 05:03:03PM +0200, Momchil Ivanov wrote: Windows doesn`t reboot if you unplug the usb or network cable, which I think is the right way of handling these kind of situations. Windows also (as of XP; I don't think it was this way in 2000) by default disables read/write caching on all USB-plugged storage devices. This was done because people were unplugging USB storage devices without shutting them down (going to the systray and selecting the device then choosing Stop to ensure all caches were flushed and data on the device had been written). The performance hit is pretty major, but the attitude is safety first. You can, of course, toggle the caching feature per device/drive, but you'll need to Stop the device before removing it from the USB bus. -- | Jeremy Chadwickjdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB | ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Wednesday 18 July 2007 17:41:04 Oliver Fromme wrote: As Josh wrote, it's expected. The problem is known to exist for a long time already (probably as long as FreeBSD itself exists), and if there was an easy solution, certainly someone would have fixed it. Just remember to always umount first, and you're safe. In the early 90s I panicked a FreeBSD machine by removing a floppy disk that was mounted. I did that mistake only once -- afterwards I always remembered. If you have problems remembering, another work-around is to use the auto mounter daemon (amd(8)). It umounts file systems automatically that are not in use. Another nice feature of amd(8) is that you don't have to mount the file system either -- Simply plug the USB stick in, then access it, and amd(8) will automatically mount it for you. Best regards Oliver I started the thread just because it hit me today. I wanted to disconnect my mouse and forgot that the hdd is connected to the same hub, I realized that after having unplugged the usb hub and saw the system freeze. I know that this has been an issue for a long time. With cdroms it`s easy, the tray won`t open until you umount the cd fs, floppies. nowadays they have been replaced by usb sticks, but they have no trays as cdroms do :) moreover people use other usb storages too and unplugging those is just as simple as unpluging the cable. I think this is a critical problem and needs to be addressed, avoiding it doesn`t solve it. As technology advances I think FreeBSD has to advance too. You said you paniced a system in the early 90s, which is more than 10 years from now. In the past floppy disks were maybe the only problem, but nowadays as storage is cheap more and more people use USB storage devices, and these are easy to unplug. It`s even worse if you have a laptop, since it`s easier to connect everything to a hub (mouse, hdds, other usb stuff) and connect/disconnect it. In the days before common storage devices (hard drives) where fixed inside the computer`s case, so unpluging a hard drive when the computer was running was considered as insane, so panicing is ok. Nowadays things have changed. USB (maybe Firewire too, have no experience with that) offers a simple way to connect/disconnect devices to your computer (here I have to note: not just one!), having a laptop and 1,2,3 or even more external storage devices is something usual. That`s why I think this particular problem needs to be addressed. Thanks for the tip about amd(8) I will give it a try. -- PGP KeyID: 0x3118168B Keyserver: pgp.mit.edu Key fingerprint BB50 2983 0714 36DC D02E 158A E03D 56DA 3118 168B pgpPIKc8k2BdR.pgp Description: PGP signature
Re: removing external usb hdd without unmounting causes reboot?
This really struck me as a problem when I had a short power outage and my external USB hard drive wasn't plugged into the UPS. Laptop didn't reboot from the power outage but it rebooted anyway because it lost a hard drive (which was mounted but I wasn't doing any work on) Baldur On Wed, Jul 18, 2007 at 06:30:44PM +0200, Momchil Ivanov wrote: On Wednesday 18 July 2007 17:41:04 Oliver Fromme wrote: As Josh wrote, it's expected. The problem is known to exist for a long time already (probably as long as FreeBSD itself exists), and if there was an easy solution, certainly someone would have fixed it. Just remember to always umount first, and you're safe. In the early 90s I panicked a FreeBSD machine by removing a floppy disk that was mounted. I did that mistake only once -- afterwards I always remembered. If you have problems remembering, another work-around is to use the auto mounter daemon (amd(8)). It umounts file systems automatically that are not in use. Another nice feature of amd(8) is that you don't have to mount the file system either -- Simply plug the USB stick in, then access it, and amd(8) will automatically mount it for you. Best regards Oliver I started the thread just because it hit me today. I wanted to disconnect my mouse and forgot that the hdd is connected to the same hub, I realized that after having unplugged the usb hub and saw the system freeze. I know that this has been an issue for a long time. With cdroms it`s easy, the tray won`t open until you umount the cd fs, floppies. nowadays they have been replaced by usb sticks, but they have no trays as cdroms do :) moreover people use other usb storages too and unplugging those is just as simple as unpluging the cable. I think this is a critical problem and needs to be addressed, avoiding it doesn`t solve it. As technology advances I think FreeBSD has to advance too. You said you paniced a system in the early 90s, which is more than 10 years from now. In the past floppy disks were maybe the only problem, but nowadays as storage is cheap more and more people use USB storage devices, and these are easy to unplug. It`s even worse if you have a laptop, since it`s easier to connect everything to a hub (mouse, hdds, other usb stuff) and connect/disconnect it. In the days before common storage devices (hard drives) where fixed inside the computer`s case, so unpluging a hard drive when the computer was running was considered as insane, so panicing is ok. Nowadays things have changed. USB (maybe Firewire too, have no experience with that) offers a simple way to connect/disconnect devices to your computer (here I have to note: not just one!), having a laptop and 1,2,3 or even more external storage devices is something usual. That`s why I think this particular problem needs to be addressed. Thanks for the tip about amd(8) I will give it a try. -- PGP KeyID: 0x3118168B Keyserver: pgp.mit.edu Key fingerprint BB50 2983 0714 36DC D02E 158A E03D 56DA 3118 168B ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Wed, Jul 18, 2007 at 06:30:44PM +0200, Momchil Ivanov wrote: On Wednesday 18 July 2007 17:41:04 Oliver Fromme wrote: As Josh wrote, it's expected. The problem is known to exist for a long time already (probably as long as FreeBSD itself exists), and if there was an easy solution, certainly someone would have fixed it. I think this is a critical problem and needs to be addressed, avoiding it doesn`t solve it. I agree. I also have a hard time believing that the reason it hasn't been fixed is because there isn't an easy fix. I'm under the impression it hasn't been fixed because either no one cares enough to fix it (using the workaround as a scapegoat excuse), or because the majority of people do not use USB-based storage devices. All of this brings me back a few years when I went on a quest to write a application that interfaced with a Logitech USB webcam for FreeBSD (for a streaming fishtank camera). I found that USB alternative indexes were broken (the code was there, but did not work), which the camera relied upon. When I reported the issue to the FreeBSD USB stack maintainer at the time (who will remain nameless since he enjoyed arguing rather than fixing or working with me), I was told 2 things: I just ported this from NetBSD, don't blame me, Alt. indexes aren't commonly used so I don't really care. So, based on my experience as documented above, I would say the reasons I listed are dead on. Bottom line here is that the kernel panics when removing a USB device that has filesystems mounted. This shouldn't happen. Spitting out errors on the console is one thing, but a panic is another. Sometimes things cannot be avoided (re: unmount and you'll be fine), such as cats pulling on USB hub AC power cables and other such things. If someone wants to work on this and needs devices/toys (thumb drives, external enclosures + hard disks), let me know, I will be more than happy to buy them the hardware needed. -- | Jeremy Chadwickjdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB | ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Wed, Jul 18, 2007 at 10:05:59AM -0700, Jeremy Chadwick wrote: Bottom line here is that the kernel panics when removing a USB device that has filesystems mounted. s/USB // I also have a hard time believing that the reason it hasn't been fixed is because there isn't an easy fix. I'm under the impression it hasn't been fixed because either no one cares enough to fix it (using the workaround as a scapegoat excuse), or because the majority of people do not use USB-based storage devices. The reason is not the USB stack; the reason (IIRC) is that the FreeBSD VM was written with the default assumption that Devices Never Go Away. A large rewrite, I'm told, will be needed to fix this, and the code is convoluted and tricky. No one finds the situation acceptable; introducing the scapegoat word isn't going to win you any support. The problem is not a weekend's worth of work to fix, nor does it have anything to do with avoidance by one particular maintainer, which you apparently had encountered before. mcl ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Nobody's said what the problem is. I'm not a filesystem code monkey, but IIRC, the problem is that the filesystem plays fast and loose with pointers and is too closely related to the VM. One solution is (as mentioned) a userland filesystem that doesn't panic. automount approximates this if you set the disconnect interval short ( 5 seconds). The other way to look at this, though, is the general goal of not panicing when it can be avoided. As a research OS, it's my feeling that BSD derived unixes have followed the if in doubt, panic regime. I don't think this is appropriate to a modern desktop or server OS. To my mind, an OS should only panic if there are indications of hardware corruption in a subsystem that can't be turned off. Ie: memory bad: panic; controller bad, turn off controller. In this particular case, we have unmount -f. If there are no dirty buffers, the USB system triggering the equivalent of unomunt -f should succeed. If we only mount usb devices async, this should be sufficient for most cases. If there are dirty buffers, what do we loose by just forgetting about them? The filesystem on the device is already as corrupt as its going to be... ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Wednesday 18 July 2007 19:34:06 Mark Linimon wrote: On Wed, Jul 18, 2007 at 10:05:59AM -0700, Jeremy Chadwick wrote: Bottom line here is that the kernel panics when removing a USB device that has filesystems mounted. s/USB // Just a dumb question: what does umount -f does? And doing something like that when a fs goes away shouldn`t fix it? If the problem is in general with a file system, regardless of the provider, then what does one do when a mounted smbfs becomes unavailable due to remote host down, no route to host or some other network related problems? Same question for NFS mounted filesystems? -- PGP KeyID: 0x3118168B Keyserver: pgp.mit.edu Key fingerprint BB50 2983 0714 36DC D02E 158A E03D 56DA 3118 168B pgpfXbuzcbviO.pgp Description: PGP signature
Re: removing external usb hdd without unmounting causes reboot?
Momchil Ivanov wrote: On Wednesday 18 July 2007 19:34:06 Mark Linimon wrote: On Wed, Jul 18, 2007 at 10:05:59AM -0700, Jeremy Chadwick wrote: Bottom line here is that the kernel panics when removing a USB device that has filesystems mounted. s/USB // Just a dumb question: what does umount -f does? And doing something like that when a fs goes away shouldn`t fix it? If the problem is in general with a file system, regardless of the provider, then what does one do when a mounted smbfs becomes unavailable due to remote host down, no route to host or some other network related problems? Same question for NFS mounted filesystems? !DSPAM:1,469e538b20763944420674! Wow, quite a thread going on over this issue. I'll throw my 2cents into the ring also :) From a desktop perspective, it makes total sense to not have the system crash just because a USB disk was unplugged while mounted. When a new end user does this for the first time and the system crashes, usually the first thing they assume is that it's a bug. Then somebody like me comes around and tells them to unmount it first. Then usually the next thing they say is something along the lines of That's so early 90's, why can't you guys get your act together? I can understand requiring unmounting for devices such as CD's or internal IDE / SCSI hard drives. With a CD at least you can physically lock the drive bay to prevent the user from ejecting until unmounted first. However, with a USB the ballgame changes, the whole concept is to be hot-swappable, plugin and unplug at will. If a normal desktop user copies a file to a USB disk and the file transfer dialog is done, then they should be able to unplug it, without a total system crash. That being said, I think it would be a good idea to at least have the kernel / HAL or some process maybe warn the user that they should unmount the USB disk first, to prevent data loss at minimum. But I think this can be improved, so you don't have to deal with an entire system panic :P When that happens you gotta reboot, fsck, and run the risk of something really being corrupted on the drive :( -- Kris Moore PC-BSD Software http://www.pcbsd.com ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Wednesday 18 July 2007, Mark Linimon wrote: On Wed, Jul 18, 2007 at 10:05:59AM -0700, Jeremy Chadwick wrote: Bottom line here is that the kernel panics when removing a USB device that has filesystems mounted. s/USB // I also have a hard time believing that the reason it hasn't been fixed is because there isn't an easy fix. I'm under the impression it hasn't been fixed because either no one cares enough to fix it (using the workaround as a scapegoat excuse), or because the majority of people do not use USB-based storage devices. The reason is not the USB stack; the reason (IIRC) is that the FreeBSD VM was written with the default assumption that Devices Never Go Away. A large rewrite, I'm told, will be needed to fix this, and the code is convoluted and tricky. No one finds the situation acceptable; introducing the scapegoat word isn't going to win you any support. The problem is not a weekend's worth of work to fix, nor does it have anything to do with avoidance by one particular maintainer, which you apparently had encountered before. mcl Panicing really is the right thing to do with the current architecture. Not panicing when a mounted filesystem disappears runs the risk of corrupting other mounted filesystems. Mark is entirely correct, FreeBSD faces an architecture problem here in that the vm and filesystems we have today were not designed in an era when they could just disappear from a running system. The BSD way isn't to apply a quick and dirty little hack to fix the 'problem', it's to design the system properly. And this is assuming a quick and dirty hack even exists. The other problem you're running in to with UFS anyways is that there is no chance to 'unmount' the filesystem when you disconnect the drive. By the time anything has a chance to realize it's gone it's too late. Whether the disk is in the middle of a write, still has buffers to be written out, or is perfectly clean and needs to just be marked as such by the time the OS realizes any of that needs to be done the drive is no longer physically connected to the computer. What might need to happen is a redesign of the vm subsystem so that it can safely deal with mounted filesystems going away, and designing a filesystem that doesn't need to be unmounted specifically for removeable devices. Doesn't sound trivial to me. Or You can just not remove devices with mounted filesystems from your computer. -- Thanks, Josh Paetzel pgpBhbiMYM6HX.pgp Description: PGP signature
Re: removing external usb hdd without unmounting causes reboot?
Oliver Fromme wrote: Momchil Ivanov wrote: On Wednesday 18 July 2007 15:52:42 [LoN]Kamikaze wrote: Josh Paetzel wrote: Yes, it's expected behavior. The workaround is to not unplug mounted devices. (There's nothing special about USB here, if you unplugged an IDE drive you'd get the same behavior) Wouldn't it make some sense not to panic if mounted devices that are in sync get removed? A few applications might get in trouble, but that's hardly a reason to bring a whole system down. I don`t know how things work, but shutting down the system when some mounted fs is no longer present seems like the wrong thing to me. As Josh wrote, it's expected. The problem is known to exist for a long time already (probably as long as FreeBSD itself exists), and if there was an easy solution, certainly someone would have fixed it. I have to check this, but AFAIK this problem exists only for devices/partitions that are mounted R/W. Do you happen to know this? (I can not risk to crash my box right now for a test ;-) There once was an autofs implementation, but IIRC it has later been removed. It could not only automatically mount removable media, but it could also help with the problem of devices that are rarely written to, but still mounted R/W just in case for easy write-access. Long time ago I had the idea that a clean file system could be mounted R/O after a short delay. When all dirty buffers are flushed, the device could be forcefully disconnected without causing inconsistencies in the kernel. If there are no open file descriptors, the super-block could be written with the clean flag set, to signal that no fsck is needed when the partition is mounted next time. Internally, the device can be treated as R/O, with the only exeption that an attempted write is not rejected, but that it instead triggers the change back to R/W operation (this means setting the in-RAM copy of the super-block to dirty before the write is allowed to proceed as normal). Removable devices and dealing with a device that is gone and re-appears (either the same device or one that takes its place) needs special consideration, e.g. by checking a disk label and flushing cached blocks that were associated with the device that now is definitely gone. I had this idea back when floppy disks were common, but with USB memory sticks and devices the same situation exists ... The mode change to R/O could be triggered by a timer after the necessary condition exists (e.g. half a second after the last write to the device with no dirty buffers left). The system already knows whether there are dirty buffers for a partition, it is not hard to detect this case. The other parameter of interest is whether there are any open files on that partition (which decides whether the super-block can be marked as clean). This functionality could be implemented within an autofs as a special case (mount only R/O and upgrade only when needed and for as long as necessary), but I think it should be not too hard to add as a small in-kernel modification ... Regards, STefan ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Wed, Jul 18, 2007 at 11:54:19AM -0700, Kris Moore wrote: That being said, I think it would be a good idea to at least have the kernel / HAL or some process maybe warn the user that they should unmount the USB disk first, to prevent data loss at minimum. But I think this can be improved, so you don't have to deal with an entire system panic :P When that happens you gotta reboot, fsck, and run the risk of something really being corrupted on the drive :( So there's two issues here: 1) Kernel panics when a device (regardless of type (USB, SATA, etc.)) is removed from the system with filesystems mounted, 2) Concern over data loss when device is removed. As I mentioned earlier in the thread, Windows addresses #2 by marking all filesystems on USB storage devices (thumb drives, HDDs, etc.) as synchronous (e.g. mount -o sync). The impact is slow I/O, but it's safe. It seems like we'd be able to implement such a transparent feature into the subsystem where filesystems mounted from USB devices would use synchronous I/O (mount -o sync). I don't know how this would be coded, since there would have to be some way to figure out a physical device type (USB mass storage devices show up as /dev/daXXX). Providing an override option for those who know what they're doing, (umount /mnt then physically remove device) would be nice too. This would alleviate concerns over data loss, would it not? -- | Jeremy Chadwickjdc at parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP: 4BD6C0CB | ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Zaphod Beeblebrox wrote: One solution is (as mentioned) a userland filesystem that doesn't panic. automount approximates this if you set the disconnect interval short ( 5 seconds). Unfortunately the approximation is far from perfect because it takes noticable time to mount a msdosfs on large drives (I think the FAT is being read?). The other way to look at this, though, is the general goal of not panicing when it can be avoided. As a research OS, it's my feeling that BSD derived unixes have followed the if in doubt, panic regime. I don't think this is appropriate to a modern desktop or server OS. Agreed very much, though some of the older hackers here seem to like the old approach. signature.asc Description: OpenPGP digital signature
Re: removing external usb hdd without unmounting causes reboot?
Jeremy Chadwick wrote: On Wed, Jul 18, 2007 at 11:54:19AM -0700, Kris Moore wrote: That being said, I think it would be a good idea to at least have the kernel / HAL or some process maybe warn the user that they should unmount the USB disk first, to prevent data loss at minimum. But I think this can be improved, so you don't have to deal with an entire system panic :P When that happens you gotta reboot, fsck, and run the risk of something really being corrupted on the drive :( So there's two issues here: 1) Kernel panics when a device (regardless of type (USB, SATA, etc.)) is removed from the system with filesystems mounted, 2) Concern over data loss when device is removed. As I mentioned earlier in the thread, Windows addresses #2 by marking all filesystems on USB storage devices (thumb drives, HDDs, etc.) as synchronous (e.g. mount -o sync). The impact is slow I/O, but it's safe. It seems like we'd be able to implement such a transparent feature into the subsystem where filesystems mounted from USB devices would use synchronous I/O (mount -o sync). I don't know how this would be coded, since there would have to be some way to figure out a physical device type (USB mass storage devices show up as /dev/daXXX). Providing an override option for those who know what they're doing, (umount /mnt then physically remove device) would be nice too. This would alleviate concerns over data loss, would it not? This sounds like an excellent idea to me. If something along these lines were implemented, it would be very helpful for us on the desktop end of things. -- Kris Moore PC-BSD Software http://www.pcbsd.com ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
Josh Paetzel wrote: designing a filesystem that doesn't need to be unmounted specifically for removeable devices. Or just do what Windows does on its hard-drive-mounted NTFS and MSDOS file systems and mark it clean after several seconds of inactivity. This also helps solve other problems like power failures, laptop battery drainage (in its common form and when the battery dies while the system is suspened). signature.asc Description: OpenPGP digital signature
Re: removing external usb hdd without unmounting causes reboot?
Mark Linimon wrote: The reason is not the USB stack; the reason (IIRC) is that the FreeBSD VM was written with the default assumption that Devices Never Go Away. A large rewrite, I'm told, will be needed to fix this, and the code is convoluted and tricky. I also feel that the institutial knowledge about the VM+VFS+UFS conglomerate seems to be going away. There were many attempts to port file systems to FreeBSD that have stopped dead once they've reached read-only phase, and recent problems with UFS looked really ugly (I don't even know if they are solved - I'm scared of filling up UFS drives right now :) ). My first production ZFS panicked the other day so ZFS is not yet the answer. (And yes, I know I'm complaining without suggesting solutions). signature.asc Description: OpenPGP digital signature
Re: removing external usb hdd without unmounting causes reboot?
On 18 Jul, Momchil Ivanov wrote: If the problem is in general with a file system, regardless of the provider, then what does one do when a mounted smbfs becomes unavailable due to remote host down, no route to host or some other network related problems? Same question for NFS mounted filesystems? In the case of NFS, nothing happens if the filesystem is idle. If the filesystem is active, any pending operations are retried indefinitely by periodically resending the I/O requests if the file system is hard mounted. If the filesystem is soft mounted, then the I/O requests are eventually timed out with the appropriate error status returned to the process on the client. An important difference between NFS and UFS is that a loss of network connectivity (or a clean server reboot) can't cause any filesystem inconsistencies in the NFS case because complex filesystem operations that require multiple disk operations are treated as atomic operations between the client and server. For example, creating a new directory requires a number of physical disk writes in the UFS case, and unplugging the disk in the middle would result in an inconsistent filesystem state. In the NFS case, creating a new directory only requires only one NFS operation over the wire, and the client is allowed to keep retrying the operation until it receives a status response from the server. Retries might be necessary if either the request or the response packet was dropped by the network, the server crashed, etc. ___ freebsd-stable@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to [EMAIL PROTECTED]
Re: removing external usb hdd without unmounting causes reboot?
On Wednesday 18 July 2007 21:03:10 Josh Paetzel wrote: On Wednesday 18 July 2007, Mark Linimon wrote: On Wed, Jul 18, 2007 at 10:05:59AM -0700, Jeremy Chadwick wrote: Bottom line here is that the kernel panics when removing a USB device that has filesystems mounted. s/USB // I also have a hard time believing that the reason it hasn't been fixed is because there isn't an easy fix. I'm under the impression it hasn't been fixed because either no one cares enough to fix it (using the workaround as a scapegoat excuse), or because the majority of people do not use USB-based storage devices. The reason is not the USB stack; the reason (IIRC) is that the FreeBSD VM was written with the default assumption that Devices Never Go Away. A large rewrite, I'm told, will be needed to fix this, and the code is convoluted and tricky. No one finds the situation acceptable; introducing the scapegoat word isn't going to win you any support. The problem is not a weekend's worth of work to fix, nor does it have anything to do with avoidance by one particular maintainer, which you apparently had encountered before. mcl Panicing really is the right thing to do with the current architecture. Not panicing when a mounted filesystem disappears runs the risk of corrupting other mounted filesystems. Mark is entirely correct, FreeBSD faces an architecture problem here in that the vm and filesystems we have today were not designed in an era when they could just disappear from a running system. The BSD way isn't to apply a quick and dirty little hack to fix the 'problem', it's to design the system properly. And this is assuming a quick and dirty hack even exists. The other problem you're running in to with UFS anyways is that there is no chance to 'unmount' the filesystem when you disconnect the drive. By the time anything has a chance to realize it's gone it's too late. Whether the disk is in the middle of a write, still has buffers to be written out, or is perfectly clean and needs to just be marked as such by the time the OS realizes any of that needs to be done the drive is no longer physically connected to the computer. I think you are missing the point here and it is that the drive is already gone, so you do not have to care about it. The state of the drive`s filesystem is of no interest since you cannot to anything to change it any more. The point is that the drive is gone. If you were in the middle of a write, you just return an error (like your disk is going physically bad/ some broken cable issue... for instance) and forget about the data you wanted to write, the drive is not there any more. Maybe I am naive and uneducated enough (don`t know how freebsd does things, nor am I a programmer) but I will give my 2 stotinki here. The most natural way for me seems to be that the OS should just return errors to the programs trying any I/O on that drive. May be when a drive is unplugged the OS has to mark it and the mounted file systems as not being there until all opened files on it are closed, return errors for all I/O except for closing opened files. And when all files are closed consider the fs as unmounted and remove the drive from the kernel. This is my idea of how things should be done. Ensuring that a file system is in a consistent state after drive disconnect is something completely different (wanted to discuss just disconnecting devices, not filesystems that can be disconnected without unmount, not ensuring fully operational file system even it a case of disconnected drive). One can try to implement something here (as mentioned in some of the replies), but not necessary. If the user has unpluged the device without unmounting it first he might be left with a broken file system on that drive, we cannot do anything, so we should not care about it, it`s his mistake and his fs fucked up. The point is that unpluging should not lead to system crash, which is in my opinion critical system error. I as user I should be able to unplug any external device without crashing the OS. Doing this and thus leaving me with a broken filesystem or some other device issues should be considered my error. Thus I should learn the hard way to unmount first. Designing a filesystem or some hacks to ensure consistent state after disconnect should not be in the scope of this thread and problem, I think. What might need to happen is a redesign of the vm subsystem so that it can safely deal with mounted filesystems going away, and designing a filesystem that doesn't need to be unmounted specifically for removeable devices. Doesn't sound trivial to me. Or You can just not remove devices with mounted filesystems from your computer. -- PGP KeyID: 0x3118168B Keyserver: pgp.mit.edu Key fingerprint BB50 2983 0714 36DC D02E 158A E03D 56DA 3118 168B ___ freebsd-stable@freebsd.org mailing
Re: removing external usb hdd without unmounting causes reboot?
On Wed, 18 Jul 2007 17:41:04 +0200 (CEST)
Oliver Fromme [EMAIL PROTECTED] wrote:
If you have problems remembering,
This is very interesting thread indeed
I have found that mounting remote SMB shares will panic the kernel too, but
only if i try to access it while 'gone' . If I remember correctly, if i thread
carefully around it, i can manage to shutdown everything and it will only panic
at the very last minute when the kernel tries to unmount.
And, from my point of view, the explanation 'well, don't remove your mounted
devices without unmounting them first' is rubbish - the problem is not
necessarily users removing them, but ALL the reasons that could cause an
unwanted and unplanned removal. Like a network outage in the case of smbfs. or
someone killing the power on a USB device. I can't see why the whole kernel
should die on you. Yes, i understand there are architectural reasons for this -
then the architecture is not right anymore, i think.
another work-around
is to use the auto mounter daemon (amd(8)). It umounts
file systems automatically that are not in use.
Another nice feature of amd(8) is that you don't have
to mount the file system either -- Simply plug the USB
stick in, then access it, and amd(8) will automatically
mount it for you.
Now, something I dont understand - amd runs
at user level, and it mounts filesystems, and nothing dies when the filesystems
go away (other than the obvious cases for the applications trying to write to
the FS in question). Doesn't amd , at some point , have to tell the kernel
'please mount this filesystem' here or there? Isn't the kernel STILL involved
in all this? and why doesnt the kernel panic when the FS goes away?
The same goes for hald - it doesn't work flawlessly, but it does the trick, and
i cant recall an instance when it crashed the kernel.
re. USB disks, could we not by default use amd to mount USB devices? It seems
the obvious native replacement for hald + polkitd + dbus I use in XFCE with
Thunar on my laptop...
TIA!
_
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I speak for myself, not my employer. Contents may be hot. Slippery when wet.
Reading disclaimers makes you go blind. Writing them is worse. You have been
Warned.
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