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Re: undeletion at filesystem level or in extra filesystem?


From: Thomas Bushnell, BSG
Subject: Re: undeletion at filesystem level or in extra filesystem?
Date: 04 Oct 2002 11:42:51 -0700
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2

nisse@lysator.liu.se (Niels Möller) writes:
> 
> My main concern is that the file update pattern open, write, close,
> should be atomic when seen by other processes. I.e if some other
> process opens the file for reading in the middle of the update, it
> should see the previous version, independently of what the updating
> process is doing.

I would like this too, but it's contrary to Posix, which *guarantees*
that other process *will* see the file in intermediate states, unless
you use one single write call.  (And even then, they must be able to
see the file in its truncated state if they check between the open and
the write.)

I agree this sucks, but we're stuck with it.

We could certainly add a new O_ATOMIC flag or something like that,
which would have the better semantics.





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