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Date:   Tue, 6 Sep 2022 00:16:11 -0700
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Subject: Re: [PATCH v2 6/7] NFS: direct-io: convert to FOLL_PIN pages
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To:     Christoph Hellwig <hch@infradead.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Jens Axboe <axboe@kernel.dk>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Miklos Szeredi <miklos@szeredi.hu>,
        "Darrick J . Wong" <djwong@kernel.org>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna@kernel.org>, Jan Kara <jack@suse.cz>,
        David Hildenbrand <david@redhat.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-xfs@vger.kernel.org, linux-nfs@vger.kernel.org,
        linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
References: <20220831041843.973026-1-jhubbard@nvidia.com>
 <20220831041843.973026-7-jhubbard@nvidia.com>
 <YxbtjijmfGaKIbIV@infradead.org>
From:   John Hubbard <jhubbard@nvidia.com>
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On 9/5/22 23:49, Christoph Hellwig wrote:
> 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.

Yes, Miklos asked for much the same thing, too. :)

thanks,

-- 
John Hubbard
NVIDIA