linux-kernel - Re: [PATCH v3 2/2] iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter

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Date:   Fri, 18 Aug 2023 13:26:59 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     'David Howells' <dhowells@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@...t.de>,
        Christian Brauner <christian@...uner.io>,
        Jeff Layton <jlayton@...nel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] iov_iter: Don't deal with iter->copy_mc in
 memcpy_from_iter_mc()

On Fri, Aug 18, 2023 at 12:16:23PM +0000, David Laight wrote:
> > > +	ITER_IOVEC = 1,
> > > +	ITER_UBUF = 2,
> > > +	ITER_KVEC = 4,
> > > +	ITER_BVEC = 8,
> > > +	ITER_XARRAY = 16,
> > > +	ITER_DISCARD = 32,
> 
> IIRC Linus had type:6 - that doesn't leave any headroom
> for additional types (even though they shouldn't proliferate).

I have proposed an ITER_KBUF in the past (it is to KVEC as UBUF is
to IOVEC).  I didn't care enough to keep pushing it, but it's clearly
a common idiom.