Subject: Re: nfs vs pagedaemon
To: None <>
From: YAMAMOTO Takashi <>
List: tech-kern
Date: 04/10/2003 10:15:03

> yea, this makes sense.  the more general description of the problem
> is that nfs_strategy() should only use the commit mechanism when it's
> being called from VOP_PUTPAGES() on an NFS vnode, but there are other
> ways that nfs_strategy() can be called.  NFS swap files is one way we
> can go wrong, but there are others, such as using an NFS file for
> a vnd backing file.  one way to fix this more completely would be to
> have the NFS VOP_PUTPAGES() path add an extra flag to its buffers
> that nfs_strategy() can look at to decide if it should use stable writes.
> I had written this up a while back but didn't commit it for some reason.
> the diff is attached if you want to pursue it.

the patch seems to disable commit mechanism even in the case of
synchronous B_PAGEIO. it's a overkill, isn't it?

> to allow unstable writes for NFS swap files, it may be possible to
> transfer ownership of the pages being paged out from the original
> anon or aobj to the NFS vnode before sending the data to the server.
> I haven't thought it through though, so this may not work out very well.

do you mean having nfs_bio take ownership of pages and
free corresponding nfs's own overwritten page?
it sounds too complicated...