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Date:   Sun, 22 May 2022 13:07:55 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     Christoph Hellwig <hch@lst.de>,
        Matthew Wilcox <willy@infradead.org>,
        linux-fsdevel@vger.kernel.org
Subject: Re: [RFC] what to do with IOCB_DSYNC?
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On Sun, May 22, 2022 at 07:02:01AM -0600, Jens Axboe wrote:
> +static void iter_uaddr_advance(struct iov_iter *i, size_t size)
> +{
> +}

How could that possibly work?  At the very least you want to do
what xarray does - you *must* decrement ->count and shift ->iov_offset.
Matter of fact, I'd simply go with a bit of reorder and had it go
for if (iter_is_uaddr(i) || iter_is_xarray(i)) in there...