Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Wed, 9 Dec 2020 12:05:31 +0000
From:   Christoph Hellwig <hch@infradead.org>
To:     Pavel Begunkov <asml.silence@gmail.com>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Jens Axboe <axboe@kernel.dk>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org,
        linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
        Matthew Wilcox <willy@infradead.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Ming Lei <ming.lei@redhat.com>
Subject: Re: [PATCH 2/2] block: no-copy bvec for direct IO
Message-ID: <20201209120531.GA9598@infradead.org>
References: <cover.1607477897.git.asml.silence@gmail.com>
 <51905c4fcb222e14a1d5cb676364c1b4f177f582.1607477897.git.asml.silence@gmail.com>
 <20201209084005.GC21968@infradead.org>
 <63057f61-85e5-4720-3532-1a1ba05ab41a@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <63057f61-85e5-4720-3532-1a1ba05ab41a@gmail.com>
Precedence: bulk

On Wed, Dec 09, 2020 at 12:01:27PM +0000, Pavel Begunkov wrote:
> On 09/12/2020 08:40, Christoph Hellwig wrote:
> >> +	/*
> >> +	 * In practice groups of pages tend to be accessed/reclaimed/refaulted
> >> +	 * together. To not go over bvec for those who didn't set BIO_WORKINGSET
> >> +	 * approximate it by looking at the first page and inducing it to the
> >> +	 * whole bio
> >> +	 */
> >> +	if (unlikely(PageWorkingset(iter->bvec->bv_page)))
> >> +		bio_set_flag(bio, BIO_WORKINGSET);
> > 
> > IIRC the feedback was that we do not need to deal with BIO_WORKINGSET
> > at all for direct I/O.
> 
> I was waiting for the conversation to unfold, i.e. for Johannes to
> answer. BTW, would the same (skipping BIO_WORKINGSET) stand true for
> iomap?

iomap direct I/O: yes.