Re: adding proper O_SYNC/O_DSYNC, was Re: O_DIRECT and barriers

From: Christoph Hellwig
Date: Fri Aug 28 2009 - 19:46:46 EST


On Sat, Aug 29, 2009 at 12:06:23AM +0100, Jamie Lokier wrote:
> Christoph Hellwig wrote:
> > - given that our current O_SYNC really is and always has been actuall
> > Posix O_DSYNC
>
> Are you sure about this?
>
> >From http://www-01.ibm.com/support/docview.wss?uid=isg1IZ01704 :
>
> Error description
>
> LINUX O_DIRECT/O_SYNC TAKES TOO MANY IOS

That is for GPFS, and out of tree filesystem with binary components.
It could be that they took linux O_SYNC for real O_SYNC. Any filesystem
using the generic helpers in Linux has gotten the O_DSYNC semantics at
least as long as I have worked on Linux filesystems, which is getting
close to 10 years now. I'll do some code archaelogy before we'll move
with this to be sure.

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