Re: RPC retransmission of write requests containing bogus data

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On Mon, 2008-10-20 at 15:25 +0100, Ian Campbell wrote:
> On Fri, 2008-10-17 at 09:22 -0400, Trond Myklebust wrote:
> > On Fri, 2008-10-17 at 14:01 +0100, Ian Campbell wrote:
> > > On Fri, 2008-10-17 at 08:48 -0400, Trond Myklebust wrote:
> > > > I don't see how this could be an RPC bug. The networking layer is
> > > > supposed to either copy the data sent to the socket, or take a reference
> > > > to any pages that are pushed via the ->sendpage() abi.
> > > > 
> > > > IOW: the pages are supposed to be still referenced by the networking
> > > > layer even if the NFS layer and page cache have dropped their
> > > > references.
> > > 
> > > The pages are still referenced by the networking layer. The problem is
> > > that the userspace app has been told that the write has completed so it
> > > is free to write new data to those pages.
> > > 
> > > Ian.
> > 
> > OK, I see your point.
> > 
> > Does this happen at all with NFSv4? I ask because the NFSv4 client will
> > always ensure that the TCP connection gets broken before a
> > retransmission. I wouldn't therefore expect any races between a reply to
> > the previous transmission and the new one...
> 
> It does seem to happen with NFSv4 too (see attached).

Actually, that was NFSv4 on 2.6.18, I guess I should test with something
newer since it looks like the TCP connection reset stuff is newer (it's
43d78ef2ba5bec26d0315859e8324bfc0be23766 right?)


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