linux-kernel - Re: [PATCH v6 09/34] bio: Rename BIO_NO_PAGE_REF to BIO_PAGE

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Date:   Wed, 18 Jan 2023 14:00:54 +0000
From:   David Howells <dhowells@...hat.com>
To:     Christoph Hellwig <hch@....de>
Cc:     dhowells@...hat.com, Al Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <willy@...radead.org>,
        Logan Gunthorpe <logang@...tatee.com>,
        linux-block@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
        Jeff Layton <jlayton@...nel.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 09/34] bio: Rename BIO_NO_PAGE_REF to BIO_PAGE_REFFED and invert the meaning

Actually, should I make it so that the bottom two bits of bi_flags are a
four-state variable and make it such that bio_release_page() gives a warning
if the state is 0 - ie. unset?

The states would then be, say:

	0	WARN(), do no cleanup
	1	FOLL_GET
	2	FOLL_PUT
	3	do no cleanup

This should help debug any places, such as iomap_dio_zero() that I just found,
that add pages with refs without calling iov_iter_extract_pages().

David