linux-kernel - Re: [PATCH v7 2/8] iov_iter: Add a function to extract a page list from an iterator

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Message-ID: <c3e0b810-9f17-edb7-de6b-7849273381d0@nvidia.com>
Date:   Mon, 23 Jan 2023 15:07:48 -0800
From:   John Hubbard <jhubbard@...dia.com>
To:     Jan Kara <jack@...e.cz>, David Howells <dhowells@...hat.com>
CC:     David Hildenbrand <david@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Jens Axboe <axboe@...nel.dk>, Jeff Layton <jlayton@...nel.org>,
        "Logan Gunthorpe" <logang@...tatee.com>,
        <linux-fsdevel@...r.kernel.org>, <linux-block@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, "Christoph Hellwig" <hch@....de>,
        <linux-mm@...ck.org>
Subject: Re: [PATCH v7 2/8] iov_iter: Add a function to extract a page list
 from an iterator

On 1/23/23 08:11, Jan Kara wrote:
>> For cifs RDMA, do I need to make it pass in FOLL_LONGTERM?  And does that need
>> a special cleanup?
> 
> FOLL_LONGTERM doesn't need a special cleanup AFAIK. It should be used
> whenever there isn't reasonably bound time after which the page is
> unpinned. So in case CIFS sets up RDMA and then it is up to userspace how
> long the RDMA is going to be running it should be using FOLL_LONGTERM. The

Yes, we have been pretty consistently deciding that RDMA generally
implies FOLL_LONGTERM. (And furthermore, FOLL_LONGTERM implies
FOLL_PIN--that one is actually enforced by the gup/pup APIs.)


thanks,
-- 
John Hubbard
NVIDIA