Messages in this thread | | | Subject | Re: New copyfile system call - discuss before LSF? | From | Andreas Dilger <> | Date | Sat, 30 Mar 2013 13:08:39 -0700 |
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On 2013-03-30, at 12:49 PM, Pavel Machek wrote: > Hmm, really? AFAICT it would be simple to provide an > open_deleted_file("directory") syscall. You'd open_deleted_file(), > copy source file into it, then fsync(), then link it into filesystem. > > That should have atomicity properties reflected.
Actually, the open_deleted_file() syscall is quite useful for many different things all by itself. Lots of applications need to create temporary files that are unlinked at application failure (without a race if app crashes after creating the file, but before unlinking). It also avoids exposing temporary files into the namespace if other applications are accessing the directory.
We've added a library routine that does this for Lustre in a hackish way (magical filename created in target directory) for being able to migrate files between data servers, HSM, defragmentation, rsync, etc.
Cheers, Andreas
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