On Fri, 21 Mar 2014 05:56:04 +0900 Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > Jeff Layton wrote: > > That's expected behavior. The kernel believes that the file is frozen in > > length so it returns short read() calls until the size is updated. > > The "size is updated" means "stat() detects the growth of file size", > doesn't it? Then, the former is expected behavior. > > > > > cache=loose is very much not recommended for use when you have multiple > > hosts accessing files on the server (or access by processes on the > > server itself). It only gives you "loose" cache coherency. The whole > > point of it is to allow the client to cache data even when the protocol > > says that it shouldn't. > > But why is the latter ( "read() returns non-0 when stat() detects the growth > of file size but the data actually read is '\0'" ) is expected behavior? > It sounds like a bug that the client caches '\0' (data nobody has ever wrote) > instead of '.' (data somebody wrote when the file size grew). > Yeah, that sounds wrong. What should happen is that the cache is invalidated when the size changes. It's possible there is a race in that code however. The locking around it is pretty sloppy... > > > > cache=strict is what is recommended and that's the default these days. > > Yes, I suggested a customer using CIFS on RHEL6 to use cache=none or > cache=strict , for that customer's system does not work as expected due to > the latter behavior when using "tail -f" for checking for appended log. Yeah, cache=strict should work much better for that sort of use-case. -- Jeff Layton <jlayton@xxxxxxxxxx> -- 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
