On Mon, Jul 25, 2016 at 11:04:32PM -0400, Noah Misch wrote: > On Sat, Jul 23, 2016 at 04:50:57PM -0400, Jeff Layton wrote: > > On Sat, 2016-07-23 at 16:12 -0400, Noah Misch wrote: > > > With the Linux kernel as both NFS client and server, I'm seeing a race > > > condition where open() can return EACCES for a just-created file. Is this > > > expected behavior? POSIX implicitly allows it, but I failed to locate any > > > discussion of it. I have attached a test program; here, it witnesses the race > > > for roughly a dozen of the 4096 files it creates (different files each time). > > > This is due to a limitation of NFSv3 and NFSv4.0. When you do an > > exclusive create, the atime and mtime get set to a particular set of > > values (the verifier), and the client is expected to override those > > values with a follow-on SETATTR call once it gets those values back. > > This is to prevent problems during certain server reboot scenarios. > > > > The NFS server also sets the mode to 0000 during this time (since the > > client can't even set the mode during the operation). > > Interesting; that fully explains it. Thanks. > > > NFSv4.1 is less subject to this problem. You may want to try using that > > and see if it's any better. > > I will look into that. Mounting with vers=4.1 eliminated the unwanted behavior. Thanks for the tip. -- 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
