[NFS] question about file identifier in NFS trace data

[Trond Myklebust]

On Tue, 2006-08-29 at 11:12 +0800, Xue Peng Li wrote:
> Hi,
>     I am now working on NFS trace hooks of LKET. I want to know what file 
> is being operated for both client side and server 
> side NFS functions. On client side, two kinds of data can be used to 
> identify files, i.e. i_ino field of the inode object
> which can identify the filesystem inode on disk, and the other is NFS file 
> handler which is used to identify files between 
> client and server.On server side ,only NFS file handler received from 
> client can be used to identify file(It's very 
> complicated to convert it to inode object at nfsd_* probe point).
>  
>     I am not sure which one should be traced. If file handler is traced 
> ,there is another problem , the total length of
> file handler is 128 bytes,and for NFSV3 the length is variable. I am not 
> sure how many bytes should be traced, if 128 bytes
> are traced ,it's will so long for performance penalty, usually we only 
> trace serval bytes for one data.
> 
>    Could anyone give me some suggestions? Thanks in advance

See what we use for dprintk(): use dentries whenever possible, else use
the combination sb->s_id + fileid.

Cheers,
  Trond