Re: [patch 2.6.8.1] BSD accounting: update chars transferred value

[Christoph Hellwig <hch@infradead.org>]

On Wed, Sep 08, 2004 at 11:06:57AM +0200, Guillaume Thouvenin wrote:
> Hello,
> 
>   The goal of this patch is to improve BSD accounting by using what 
> is done in the CSA into BSD accounting. The final goal is to have a
> uniform accounting structure. 
> 
>   This patch updates information given by BSD accounting concerning
> bytes read and written. A field is already present in the BSD accounting
> structure but it is never updated. We don't add information about blocks
> read and written because, as it was discussed in previous email, the 
> information is inaccurate. Most writes which are flushed delayed would 
> get accounted to pdflushd. Thus, one solution to get this kind of 
> information is to add counters when the write back is performed. The 
> problem is that we don't know how to get information about the IID at 
> the page level (ie from struct page). So we remove this information for 
> the moment and it will be provided in another patch.
> 
> Changelog:
>   
>   - Adds two counters in the task_struct (rchar, wchar)
>   - Init fields during the creation of the process (during the fork)
>   - File I/O operations are done through sys_read(), sys_write(), 
>     sys_readv(), sys_writev() and sys_sendfile(). Thus we increment 
>     counters into those functions except with sys_sendfile(). For the
>     latter, the incrementation is done in the do_sendfile() because this
>     routine be directly called from the return of sys_sendfile().

I think it should be done in vfs_readv/vfs_write.  Else we'll miss the
updates from inekrnel consumers like nfsd.