Re: [rfc] fsync_range?

[Jamie Lokier <jamie@shareable.org>]

Nick Piggin wrote:
> On Wed, Jan 21, 2009 at 03:15:00AM +0000, Jamie Lokier wrote:
> > Nick Piggin wrote:
> > An additional couple of flags to sync_file_range() would sort out the
> > API:
> > 
> >    SYNC_FILE_RANGE_METADATA
> > 
> >       Commit the file metadata such as modification time and
> >       attributes.  Think fsync() versus fdatasync().
> 
> Note that the problems with sync_file_range is not that it lacks a
> metadata flag like fsync vs fdatasync. It is that it does not even
> sync the metadata required to retrieve the data (which of course
> fdatasync must do, otherwise it would be useless).

Oh, I agree about that.

(Different meaning of metadata, btw.  That's the term used in O_SYNC
vs. O_DSYNC documentation for other unixes that I've read, that's why
I used it in that flag, for consistency with other unixes.)

> This is just another reason why I prefer to just try to evolve the
> traditional fsync interface slowly.

But sync_file_range() has a bug, which you've pointed out - the
missing _data-retrieval_ metadata isn't synced.  In other words, it's
completely useless.

If that bug isn't going to be fixed, delete sync_file_range()
altogether.  There's no point keeping it if it's broken.  And if it's
fixed, it'll do what your fsync_range() does, so why have both?

-- Jamie