From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Thu, 13 Sep 2018 09:43:51 -0700 From: Matthew Wilcox To: David Howells Cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 00/10] iov_iter: Add new iters and use with AFS Message-ID: <20180913164351.GC11574@bombadil.infradead.org> References: <20180913161054.GB11574@bombadil.infradead.org> <153685389564.14766.11306559824641824935.stgit@warthog.procyon.org.uk> <17352.1536855503@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <17352.1536855503@warthog.procyon.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: On Thu, Sep 13, 2018 at 05:18:23PM +0100, David Howells wrote: > Matthew Wilcox wrote: > > > > (5) Add an ITER_DISCARD iterator type. This provides an iterator that > > > simply discards anything written to it. It cannot be used as a data > > > source. > > > > May I suggest an ITER_ZERO iterator type instead? It acts like /dev/zero; > > writes are discarded (as you have here) and reads return zeroes. > > I've wanted such a thing in the past, but got distracted away from > > that project. > > I thought about that, but the zero-filling is not as easy to implement as the > discard side - plus I don't have any use case to test it with. > > Do you have a use case in mind? At the time I did it, it was useful in dax, but I don't know if it is any more. It might serve to replace iov_iter_zero().