On Sun, 2010-11-21 at 05:46 -0500, Christoph Hellwig wrote: > On Fri, Nov 19, 2010 at 04:26:35PM -0500, Trond Myklebust wrote: > > If the application requests O_DIRECT/O_SYNC or calls fsync(), we are > > required by POSIX to ensure the data is safe on disk. The presence of an > > NFS delegation does not change that requirement. > > That's not quite correct. O_DIRECT for one is not actually specific in > Posix at all, and the documented Linux semantics only say that the > pagecache should not be used (even if it sometimes is with various > filesystems). There is not guarantee that data actually is on disk or > reachable, for that you need to add the O_SYNC/O_DYSNC flag in addition > or use fsync/fdatasync. True. We treat the O_DIRECT case as being the same as O_DIRECT|O_SYNC because we don't currently have a way to locate and track outstanding O_DIRECT rpc calls, and so fsync() has no effect. We do, however support aio/dio, and so people who want better writev() syscall latency can use that... Cheers Trond -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
