Received-SPF: pass (google.com: domain of linux-nfs-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Sat, 27 Aug 2022 23:46:28 +0100
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     John Hubbard <jhubbard@nvidia.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Jens Axboe <axboe@kernel.dk>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Christoph Hellwig <hch@infradead.org>,
        "Darrick J . Wong" <djwong@kernel.org>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna@kernel.org>, Jan Kara <jack@suse.cz>,
        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>
Subject: Re: [PATCH 3/6] iov_iter: new iov_iter_pin_pages*() routines
Message-ID: <YwqexJOL9GcOKRg1@ZenIV>
References: <20220827083607.2345453-1-jhubbard@nvidia.com>
 <20220827083607.2345453-4-jhubbard@nvidia.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20220827083607.2345453-4-jhubbard@nvidia.com>
Sender: Al Viro <viro@ftp.linux.org.uk>
Precedence: bulk

On Sat, Aug 27, 2022 at 01:36:04AM -0700, John Hubbard wrote:
> Provide two new wrapper routines that are intended for user space pages
> only:
> 
>     iov_iter_pin_pages()
>     iov_iter_pin_pages_alloc()
> 
> Internally, these routines call pin_user_pages_fast(), instead of
> get_user_pages_fast().
> 
> As always, callers must use unpin_user_pages() or a suitable FOLL_PIN
> variant, to release the pages, if they actually were acquired via
> pin_user_pages_fast().
> 
> This is a prerequisite to converting bio/block layers over to use
> pin_user_pages_fast().

You do realize that O_DIRECT on ITER_BVEC is possible, right?