Re: [PATCH v7 4/8] block: Rename BIO_NO_PAGE_REF to BIO_PAGE_REFFED and invert the meaning

[Christoph Hellwig]

On Fri, Jan 20, 2023 at 05:55:52PM +0000, David Howells wrote:
> Rename BIO_NO_PAGE_REF to BIO_PAGE_REFFED and invert the meaning.  In a
> following patch I intend to add a BIO_PAGE_PINNED flag to indicate that the
> page needs unpinning and this way both flags have the same logic.
> 
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>

As pointed out last time, we really should not set the flag by default.
When a bio is allocated there are no pages to be released, that only
happens when we add dio-like pages to the bio.  Instead of explaining
why I mean again, I've put together a version of this series that
implements this and my other suggestions here:

http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/dio-pin-pages

This also tests fine with xfs and btrfs and nvme passthrough I/O.