linux-kernel - Re: [PATCH v2 6/7] NFS: direct-io: convert to FOLL

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Date:   Mon, 5 Sep 2022 23:49:50 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Jens Axboe <axboe@...nel.dk>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Miklos Szeredi <miklos@...redi.hu>,
        Christoph Hellwig <hch@...radead.org>,
        "Darrick J . Wong" <djwong@...nel.org>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna@...nel.org>, Jan Kara <jack@...e.cz>,
        David Hildenbrand <david@...hat.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-xfs@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 6/7] NFS: direct-io: convert to FOLL_PIN pages

On Tue, Aug 30, 2022 at 09:18:42PM -0700, John Hubbard wrote:
static void nfs_direct_release_pages(struct iov_iter *iter, struct page **pages,
				     unsigned int npages)
>  {
> -	unsigned int i;
> -	for (i = 0; i < npages; i++)
> -		put_page(pages[i]);
> +	if (user_backed_iter(iter) || iov_iter_is_bvec(iter))
> +		dio_w_unpin_user_pages(pages, npages);
> +	else
> +		release_pages(pages, npages);

Instead of having this magic in all kinds of places, we need a helper
that takes the page array, npages and iter->type and does the right
thing.