On 23 Jul 2015 at 8:56, Paul Harris wrote:

> With this server comes the new "dedup" feature, that can automatically
> deduplify files.  This happens on a schedule, eg 2am saturday.  So suddenly
> we are getting messages of failures of software from all over the place,
> due to fs::is_regular_file()
>
> Deduped files have the REPARSE and SPARSE flag set.
> On the command line, you can run
> FSUTIL REPARSEPOINT QUERY
>
> and the "Reparse Tag Value" is 0x80000013
>
> Which is a relatively new flag known as IO_REPARSE_TAG_DEDUP
> https://msdn.microsoft.com/en-us/library/windows/desktop/aa365740%28v=vs.85%29.aspx
>
> These files act as normal files, you can fopen and fread them, so I assume
> they should be treated almost like symlink by boost... perhaps not quite a
> symlink because I assume the "lstat" link properties are identical to the
> file's stat properties.
>
>
> Typically, I iterate over directories and only process files if
> fs::is_regular_file(filename) is true.
>
> I wrote some code to check what the properties were on these files, and its
> not any of the possible enums detected by file_status::type().
>
> ideas?

Proposed Boost.AFIO doesn't support IO_REPARSE_TAG_DEDUP because I
have no access to any system to test the support upon.

However, if AFIO were to support IO_REPARSE_TAG_DEDUP, it would treat
it identically to a symlink/junction point.

I'd suggest Boost.Filesystem do the same, and treat pseudo-symlinks
as symlinks. That probably means adding full symlink support for
Filesystem on Windows. Here are some links to example implementation
code:

Reading a symlink target:
https://github.com/BoostGSoC13/boost.afio/blob/master/include/boost/af
io/v2/detail/impl/afio_iocp.ipp#L511

Writing a symlink:
https://github.com/BoostGSoC13/boost.afio/blob/master/include/boost/af
io/v2/detail/impl/afio_iocp.ipp#L848

Obviously best not allow rewriting a pseudo-symlink like
IO_REPARSE_TAG_DEDUP, make it read only.

Niall

--
ned Productions Limited Consulting
http://www.nedproductions.biz/
http://ie.linkedin.com/in/nialldouglas/



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