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SubjectRe: [RFC] atomic open(..., O_CREAT | ...)
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ty den 09.08.2005 Klokka 08:47 (-0700) skreiv Bryan Henderson:
> >Intents are meant as optimisations, not replacements for existing
> >operations. I'm therefore not really comfortable about having them
> >return errors at all.
>
> That's true of normal intents, but not what are called intents here. A
> normal intent merely expresses an intent, and it can be totally ignored
> without harm to correctness. But these "intents" were designed to be
> responded to by actually performing the foreshadowed operation now -
> irreversibly.
>
> Linux needs an atomic lookup/open/create in order to participate in a
> shared filesystem and provide a POSIX interface (where shared filesystem
> means a filesystem that is simultaneously accessed by something besides
> the Linux system in question). Some operating systems do this simply with
> a VFS lookup/open/create function. Linux does it with this intents
> interface.
>
> It's hard to merge the concepts in code or in one's mind, which is why
> we're here now. A filesystem driver that needs to do atomic
> lookup/open/create has to bend over backwards to split the operation
> across the three filesystem driver calls that Linux wants to make.
>
> I've always preferred just to have a new inode operation for
> lookup/open/create (mirroring the POSIX open operation, used for all opens
> if available), but if enough arguments to lookup can do it, that's
> practically as good. But that means returning final status from lookup,
> and not under any circumstance proceeding to create or open when the
> filesystem driver has said the entire operation is complete.

Have you looked at how we're dealing with this in NFSv4?

Cheers,
Trond

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