Re: New copyfile system call - discuss before LSF?

Pavel Machek
2013-03-31T08:25:53Z

Hi!
On Sat 2013-03-30 22:38:35, AEDilger Gmail wrote:
> On 2013-03-30, at 14:45, Pavel Machek <pavel@ucw.cz> wrote:
> > On Sat 2013-03-30 13:08:39, Andreas Dilger wrote:
> >> 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.
> >
> > Hmm. open_deleted_file() will still need to get a directory... so it
> > will still need a path. Perhaps open("/foo/bar/mnt", O_DELETED) would
> > be acceptable interface?
>
> Yes, that would be reasonable, and/or possibly openat(fd, NULL, AT_FDCWD|AT_UNLINKED)?

openat() is better interface for this, I'd say.

BTW... I don't think this has to be done at the same time as splice()
[or how it ends up being called] changes...

Pavel
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