linux-kernel - Re: [PATCH v20 29/32] block: Replace BIO_NO_PAGE_REF with BIO_PAGE

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Message-ID: <ZGhFCCBdlSWWcG1G@infradead.org>
Date:   Fri, 19 May 2023 20:56:56 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Kent Overstreet <kent.overstreet@...ux.dev>
Cc:     David Howells <dhowells@...hat.com>, Jens Axboe <axboe@...nel.dk>,
        Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Hillf Danton <hdanton@...a.com>,
        Christian Brauner <brauner@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Christoph Hellwig <hch@....de>,
        John Hubbard <jhubbard@...dia.com>
Subject: Re: [PATCH v20 29/32] block: Replace BIO_NO_PAGE_REF with
 BIO_PAGE_REFFED with inverted logic

On Fri, May 19, 2023 at 09:26:07PM -0400, Kent Overstreet wrote:
> On Fri, May 19, 2023 at 08:40:44AM +0100, David Howells wrote:
> > From: Christoph Hellwig <hch@....de>
> > 
> > Replace BIO_NO_PAGE_REF with a BIO_PAGE_REFFED flag that has the inverted
> > meaning is only set when a page reference has been acquired that needs to
> > be released by bio_release_pages().
> 
> What was the motivation for this patch?

So that is only is set when we need to release a page, instead telling
code to not release it when it otherwise would, where otherwise would
is implicit and undocumented and changes in this series.