Re: [fuse-devel] FUSE ignores all errors on release

[Joshua J. B. <de...@co...>]

This is discussed a bit in the FAQ.  See=20
http://fuse.sourceforge.net/wiki/index.php/FAQ#API , particularly "Wouldn't=
=20
it be simpler if there were a single close() method?" .

The short answer is, it's not possible because the Linux kernel isn't=20
designed that way.  It's not possible for FUSE to know which close() call=20
from userspace triggered a given release().

On Thursday 10 August 2006 15:56, Gerard J. Cerchio wrote:
> I am implementing a media independent archive file system in FUSE.
>
> According to the documentation in fuse.h, flush is not guaranteed to be
> called at any time in the write cycle and there is no way to
> discriminate a final flush from any intermediate one.
>
> I therefore must perform all my post write data integrity checks in the
> release call and return an error if the data is not verified on the
> media. In fact, I actually transfer all my data to the target media
> during the release.
>
> Whether or not the application checks the status of the close call is a
> controllable risk in the environments that the file system is going to
> be used.
>
> The problem is there is no processing of the release call's error return
> in the FUSE library system. In fact, the library call for do_release is
> declared a void.
>
> My question is "Does FUSE have a deep problem handling error returns
> from release or is this a trivial modification to the FUSE project?"
>
> It seemed to me that the solution required trivial changes in fuse.c:
>
>     In the method do_release, change to return the error code
>     In the method fuse_release pass the return code to reply_error.
>
> I have implemented the changes and now see error codes being passed to
> the debug trace.  Alas,  I do not see the error return being passed to
> the fclose in my little test program that does check error returns on
> release.
>
> Any one care to comment?  Is this going to require changes to the kernel
> module?
>
> Gerard Cerchio
>
>
>
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=2D-=20
Joshua J. Berry

"I haven't lost my mind -- it's backed up on tape somewhere."
    -- /usr/games/fortune