Re: Top 10 bugs/warnings for the week of March 23rd, 2008

[Ingo Molnar <mingo@elte.hu>]

* Theodore Tso <tytso@mit.edu> wrote:

> > > Looking at the filesystem UUID could help -- this is an ID that is 
> > > present as data on the disk, and that is even independent of the 
> > > bus type. See also /dev/disk/by-uuid.
> >   Yes, but as Oliver wrote if someone modified the filesystem in the mean
> > time, you won't notice it - UUID doesn't help here.
> 
> That part you could figure out in userspace, by looking at the last 
> mount and last modified time in the superblock.  But the problem is 
> it's too late.  If you had buffers which had been "in flight" at the 
> time when the USB stick was pulled, the kernel isn't going to be able 
> to send them to the new instantiation of the device for the freshly 
> installed USB stick.  And I don't think we want to put 
> filesystem-specific UUID and superblock parsing code in the generic 
> USB layer!

yeah, i agree it's all ugly - but it's really our making not the user's 
;-)

i think we could and should go to quite some length to properly support 
a rather benign-appearing usecase such as the user removing stuff from a 
modern computer (stuff that is not specifically bolted down that is). 
Violating a few artificial abstraction layers within the kernel is a lot 
better than losing user data, IMHO.

	Ingo