panic after removing usb flash drive

Eric Anderson anderson at
Wed Aug 31 13:13:23 GMT 2005

Daniel O'Connor wrote:
> On Wednesday 31 August 2005 22:19, Eric Anderson wrote:
>>>Although last time I saw this discussed I came away with the impression
>>>that it wasn't possible for the kernel to do this..? (without substantial
>>>work anyway)
>>Why not just use the automounter to mount/umount this for you?  This
>>probably won't get around umounting while in use, but you might be able
>>to tell amd to use a umount -f on it.
> I would have thought you'd still get a panic anyway..?
> The VM will try and flush the dirty pages when you umount and consequently 
> panic.

My thinking was that amd would auto-unmount the filesystem when it isn't 
being used, and if the timeout is set low (I think the default is 5 
minutes), then once done using the flash, it would have time to umount 
before it was unplugged.  Now that I think about it though, if he is 
using it (and open files), it won't even attempt to unmount it anyhow.

This is where I think it would be great to have a sort of 'flashfs' - 
something like a UFS2 filesystem, but read only until a write happens, 
and all writes would be synchronous, and after the write occurs, the fs 
goes back to a 'read only' state.  Maybe this could be done with 
gjournal or even unionfs - mount the usb flash read only, do all writes 
to a memory backed disk, and then flush the writes out to the usb flash 
periodically.  Not perfect, but maybe this will stir some ideas up.


Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.

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