Messages in this thread | | | Subject | Re: adding proper O_SYNC/O_DSYNC, was Re: O_DIRECT and barriers | From | Trond Myklebust <> | Date | Fri, 28 Aug 2009 17:43:05 -0400 |
| |
On Fri, 2009-08-28 at 17:29 -0400, Christoph Hellwig wrote: > On Fri, Aug 28, 2009 at 05:16:14PM -0400, Trond Myklebust wrote: > > On Fri, 2009-08-28 at 17:08 -0400, Christoph Hellwig wrote: > > > #define O_SYNC (O_FULLSYNC|O_DSYNC) > > > > > > - during the normal merge window I will add a real implementation for > > > for O_FULLSYNC and O_RSYNC > > > > > > P.S. better naming suggestions for O_FULLSYNC welcome > > > > Basically you are just ensuring that the metadata changes are being > > synced together with the data changes, so how about O_ISYNC (inode > > sync)? > > Yeah. Thinking about this a bit more we should define this flag > much more clearly. In the obvious implementation it would not actually > do anything if it's set on it's own. We would only check it if O_DSYNC > is already set to decided if we want to set the datasync argument to > ->fsync to 0 or 1 for the generic filesystems (and similar things for > filesystems not using the generic helper). > > If we deem that this is too unsafe we could make sure O_DSYNC always > gets set on this fag in ->open, but if we make sure O_SYNC is defined > like the one above in the kernel headers and glibc we should be fine. > > Although in that case a name that doesn't suggest that it actually does > something useful would be better.
If you are going to automatically set O_DSYNC in open(), then fcntl(F_SETFL) might get a bit nasty.
Imagine using it after the open in order to clear the O_ISYNC flag; you'll still be left with the O_DSYNC (which you never set in the first place). That would be confusing...
Cheers Trond
| |