Nameless Temporary Files

Linux 3.11 rc2 

Here's an interesting snippet from Linus's announcement post regarding Linux 3.11 rc2:

 (a) the O_TMPFILE flag that is new to 3.11 has been going through a
few ABI/API cleanups (and a few fixes to the implementation too), but
I think we're done now. So if you're interested in the concept of
unnamed temporary files, go ahead and test it out. The lack of name
not only gets rid of races/complications with filename generation, it
can make the whole thing more efficient since you don't have the
directory operations that can cause serializing IO etc.

Interesting idea!  Temporary files that aren't burdened with having to have filenames.

It will be some time before sysadmins see this feature in production, but in this case I think it's best to get the word out early, especially since this new feature could cause "mystery drive space exhaustion".

Right now, the only discrepancy between "df" and "du" numbers is due to deleted files with still-opened file descriptors.  With this new feature, it appears that nameless temporary files will join the ranks of hard-to-spot possible root causes of space exhaustion.

It's not clear how these new files will be identifiable / distinquished, for example, in the output of "lsof".  

As I learn more about this new feature, I'll be sure to write about it.