Re: NFS: msync required for data writes to server?

[Andrew Morton <akpm@osdl.org>]

Linda Dunaphant <linda.dunaphant@ccur.com> wrote:
>
> The behavior that you describe is what I expected to see. However, with
>  my test program that mmap's the NFS file on the client, writes the data,
>  and then munmap's the file, this wasn't the case with the 2.6.9 based
>  kernel I was using. The file data was NEVER being written to the server.

There's something very wrong with that.

>  This afternoon I downloaded and built several later kernels. I found
>  that with 2.6.11, the problem still occurred. With 2.6.12-rc1, the
>  problem did not occur. I could see the proper data on the server. 
> 
>  Looking at the differences in fs/nfs between these trees I found a
>  change to nfs_file_release() in fs/nfs/file.c. When I applied this
>  change to my 2.6.9 tree, the data was written out to the server.
> 
>  @@ -105,6 +108,9 @@
>   static int
>   nfs_file_release(struct inode *inode, struct file *filp)
>   {
>  +       /* Ensure that dirty pages are flushed out with the right creds
>  */
>  +       if (filp->f_mode & FMODE_WRITE)
>  +               filemap_fdatawrite(filp->f_mapping);
>          return NFS_PROTO(inode)->file_release(inode, filp);
>   }

Well yes, that'll sync the file on close, but it doesn't explain the
original problem.