Re: device-specific qid.version behaviour (was Re: [9fans] QTCTL?)

[Charles Forsyth <forsyth@terzarima.net>]

> really?  so you're writing to a cd and you forget about it.  you're
> between sessions when you swap cds.  /dev/sdXX should
> a)  allow you to continue writing, wrecking the second cd, or
> b)  give you an error.
> or, you've read a directory on a floppy.  somebody swaps the flop.
> you want
> a)  to get the old information
> b)  for dosfs to get wacked over the head so it rereads everything.
> 
> if you choose b), you need devsd to act like it does.

i don't understand why qid.vers is involved.
it's the read and writes that mustn't be misleading, so they
return a suitable diagnostic (the one that's used by devsd.c is reasonably clear-cut,
but devfloppy.c's could be better).  that condition lasts until the device
is reopened (or whatever is appropriate).  it works for exported devices.
i've probably just lost the plot, which i think is easy enough,
both for me anyway, and probably for anyone in this case.