What I tried to say before with my test is just that for the test case, the O_DIRECT flag results in the fallback behavior which seems to be described in section 5.9 of http://www.faqs.org/docs/Linux-HOWTO/NFS- HOWTO.html#MOUNTOPTIONS (which is that the use of O_SYNC, when the export is sync should result in all requests being done with the NFS_FILE_SYNC flag set in the request and reply). This removes the need of the COMMIT call as the reply to a WRITE with NFS_FILE_SYNC only returns when the data is written to disk on the server.
What we see on both Lucid and Natty is that, regardless of the O_SYNC file flag used on open, it keeps using the newer style WRITE with UNSTABLE set plus COMMIT. I extended the testcase to write 100 blocks and checked the tcpdump for that. Both clients produce a commit for every write request sent even without fsync calls. So from a data integrity point of view there is no difference between the old mode and the new mode. So in the end this is a matter of documentation and to a degree performance. Should a client be able to influence the method used for the transfer? Also the way chosen for now requires more network traffic. Doing a write and commit for all the writes just seems a waste of network bandwidth (as the same could be done with just a write with the file sync flag set). -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/709392 Title: NFS client does not submit "nfs_file_sync" write requests when the file open call includes O_SYNC. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
