netdev - Re: [RFC PATCH] iov_iter: Add an iterator-of-iterators

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Message-ID: <438D8115-68AE-47C6-B942-485814B77416@hammerspace.com>
Date:   Wed, 22 Mar 2023 18:47:09 +0000
From:   Trond Myklebust <trondmy@...merspace.com>
To:     David Howells <dhowells@...hat.com>
CC:     Matthew Wilcox <willy@...radead.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        Jens Axboe <axboe@...nel.dk>,
        Jeffrey Layton <jlayton@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Anna Schumaker <anna@...nel.org>,
        Charles Edward Lever <chuck.lever@...cle.com>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>
Subject: Re: [RFC PATCH] iov_iter: Add an iterator-of-iterators



> On Mar 22, 2023, at 14:15, David Howells <dhowells@...hat.com> wrote:
> 
> Trond Myklebust <trondmy@...merspace.com> wrote:
> 
>> Add an enum iter_type for ITER_ITER ? :-)
> 
> Well, you asked for it...  It's actually fairly straightforward once
> ITER_PIPE is removed.
> 
> ---
> iov_iter: Add an iterator-of-iterators
> 
> Provide an I/O iterator that takes an array of iterators and iterates over
> them in turn.  Then make the sunrpc service code (and thus nfsd) use it.
> 
> In this particular instance, the svc_tcp_sendmsg() sets up an array of
> three iterators: once for the marker+header, one for the body and one
> optional one for the tail, then sets msg_iter to be an
> iterator-of-iterators across them.

Cool! This is something that can be used on the receive side as well, so very useful. I can imagine it might also open up a few more use cases for ITER_XARRAY.

Thanks!
  Trond

_________________________________
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@...merspace.com