Re: [RFC] shmgetfd idea

[Christoph Hellwig <hch@infradead.org>]

On Thu, Jan 30, 2014 at 05:02:40PM +0100, Kay Sievers wrote:
> Ashmem and kdbus can name the deleted files, which is useful for
> debugging and tools to show the associated name for the file
> descriptor. They also show up in /proc/$PID/maps/ and possibly in
> /proc/$PID/fd/.
> 
> O_TMPFILE always creates files with just the name "/". Unless that is
> changed we wouldn't want switch over to O_TMPFILE, because we would
> lose that nice feature.
> 
> Is there are way to "fix" O_TMPFILE to accept the name of the file to
> be created, instead of insisting to take only the leading directory as
> the argument?

As far as the VFS is concerned this should be fairly easily doable,
we'd just have to switch O_TMPFILE to the same lookup parent first
algorithm used for O_CREAT.  The filesystems shouldn't really care
at all as the name will never be stored on disk.

In fact such a full-path O_TMPFILE would be much nicer than the
current one as it has more similar arguments to the normal O_CREAT open
that I would document it as the default one, even if the old semantics
would have to still be supported for backwards compatibility.

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