netdev - Re: [PATCH v2 0/4] bugfix: Introduce sendpages_ok() to check sendpage

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Date: Tue, 4 Jun 2024 07:42:24 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Christoph Hellwig <hch@....de>
Cc: Ofir Gal <ofir.gal@...umez.com>, davem@...emloft.net,
 linux-block@...r.kernel.org, linux-nvme@...ts.infradead.org,
 netdev@...r.kernel.org, ceph-devel@...r.kernel.org, dhowells@...hat.com,
 edumazet@...gle.com, pabeni@...hat.com, kbusch@...nel.org, axboe@...nel.dk,
 sagi@...mberg.me, philipp.reisner@...bit.com, lars.ellenberg@...bit.com,
 christoph.boehmwalder@...bit.com, idryomov@...il.com, xiubli@...hat.com
Subject: Re: [PATCH v2 0/4] bugfix: Introduce sendpages_ok() to check
 sendpage_ok() on contiguous pages

On Tue, 4 Jun 2024 06:30:41 +0200 Christoph Hellwig wrote:
> On Sat, Jun 01, 2024 at 03:36:10PM -0700, Jakub Kicinski wrote:
> > On Fri, 31 May 2024 09:32:14 +0200 Christoph Hellwig wrote:  
> > > I still find it hightly annoying that we can't have a helper that
> > > simply does the right thing for callers, but I guess this is the
> > > best thing we can get without a change of mind from the networking
> > > maintainers..  
> > 
> > Change mind about what? Did I miss a discussion?  
> 
> Having a net helper to just send some memory in the most efficient
> way and leave it up to the networking code to decide if it wants
> to use sendpage or sendmsg internally as needed instead of burdening
> the caller.

I'd guess the thinking was that if we push back the callers would
switch the relevant allocations to be page-backed. But we can add
a comment above the helper that says "you'd be better off using
page frags and calling sendmsg(MSG_SPLICE_PAGES) directly".