Re: Where Is Dirty Data Flushed During NFSv4 Delegation Recall?

["Zhou Jifeng" <zhoujifeng@kylinsec.com.cn>]

> > On Thu, 2025-09-11 at 10:30 +0800, Zhou Jifeng wrote:
> > Hello everyone, I have a question that has been bothering me for a
> > long
> >  time. I would like to ask a familiar friend to help explain it. In
> > the NFSv4
> >  protocol, it is clearly defined that during the delegation RECALL
> > processing, the client needs to write the modified cache to the
> > server
> > side. However, throughout the process, I have not found the code for
> > flushing dirty data in the kernel NFS client. I have repeatedly
> > reviewed
> > the code logic of nfs4_callback_recall and nfs4_state_manager, but
> > still
> > cannot understand where the dirty data is flushed.
> >
> > My question is: When the client is handling the RECALL operation,
> > where
> > does the process of flushing the dirty data take place?
> >
> 
> The question of when to flush dirty data isn't determined by the NFSv4
> RECALL operation spec. It is decided by the client caching model and by
> POSIX.
> Please read the "nfs(5)" manpage and the section on close-to-open cache
> consistency.
> 
-> -
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trondmy@kernel.org, trond.myklebust@hammerspace.com

Hi Trond,

The nfs(5) manual page and the close-to-open consistency you mentioned
have been of great help to my understanding. Thank you very much.

Best regards
Zhou Jifeng