linux-kernel - Re: [PATCH v7 8/8] mm: Renumber FOLL_GET and FOLL

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Date:   Fri, 20 Jan 2023 18:59:25 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     David Howells <dhowells@...hat.com>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>,
        Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        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 8/8] mm: Renumber FOLL_GET and FOLL_PIN down

On Fri, Jan 20, 2023 at 05:55:56PM +0000, David Howells wrote:
> Renumber FOLL_GET and FOLL_PIN down to bit 0 and 1 respectively so that
> they are coincidentally the same as BIO_PAGE_REFFED and BIO_PAGE_PINNED and
> also so that they can be stored in the bottom two bits of a page pointer
> (something I'm looking at for zerocopy socket fragments).
> 
> Signed-off-by: David Howells <dhowells@...hat.com>

Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>

Although I was hoping you'd renumber some of the others since we
currently have gaps at 0x200, 0x400, 0x1000, and 0x4000 as well
as the 0x40 you're using here.