Re: 2.4.0-test10-pre3:Oops in mm/filemap.c:filemap_write_pa

[Linus Torvalds]

On 20 Oct 2000, Trond Myklebust wrote:
> 
>      > invalidate_inode_pages nfs_zap_caches nfs_lock fcntl_setlk
>      > do_fcntl sys_fcntl
> 
>      > So I guess that NFS locking is really bad if the region is
>      > mmapped!
> 
> Yep, but that's a symptom, not a cause. We want to be able to run
> invalidate_inode_pages() safely at any moment, since the need can be
> triggered externally (because the server and client page caches
> disagree).

Well, the thing is, that if somebody has a page mapped, there's nothing we
can do if the server and client disagrees. 

We just cannot invalidate the page - people would actually lose data, and
would lose major local consistency guarantees that UNIX filesystems are
supposed to get. 

So it's a matter of one sort of consistency against another - and I think
the local consistency requirements are the stricter ones, considering that
we don't even _know_ whether the server has really changed those pages or
not..

                Linus

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