On Fri, 08 Apr 2011 13:39:16 -0400 Steve Rago <sar@xxxxxxxxxxxx> wrote: > > I wonder if we should sync the file when someone sets O_SYNC this way. > > If we don't then there is a period during which we have an fd which has > > O_SYNC set, but it has pending unwritten data. An O_SYNC fd should > > never be in such a state! > > Why not? Because it's inconsistent. An O_SYNC fd never has outstanding writeout. Except for in this one new and special time window between a setfl() and the next write(). It's not a big deal, but it's somewhat ugly and merits thinking about. > If I write something in non-synchronous mode, then change the file descriptor to synchronous mode, I should > not make any assumptions about what was written prior to this point. If I care that much, I'll call fsync. Well. You can call fsync() after every write() too. > All that > matters is that the operating system honors the contract as specified by the system call API. There's a lot more to it than that. Things like quality-of-implementation and principle-of-least-surprise. We used to have a particular relationship between an O_SYNC fd and the state of the inode which it represents. With this patch, that relationship no longer holds. As I say: not a big deal IMO, but it should be aired and thought about. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
