linux-kernel - Re: [PATCH v21 3/6] block: Replace BIO_NO_PAGE_REF with BIO_PAGE

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Message-ID: <20230523080740.jpqdcwyzws3drwyr@quack3>
Date:   Tue, 23 May 2023 10:07:40 +0200
From:   Jan Kara <jack@...e.cz>
To:     David Howells <dhowells@...hat.com>
Cc:     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 v21 3/6] block: Replace BIO_NO_PAGE_REF with
 BIO_PAGE_REFFED with inverted logic

On Mon 22-05-23 21:57:41, 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().
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> Signed-off-by: David Howells <dhowells@...hat.com>
> Reviewed-by: John Hubbard <jhubbard@...dia.com>
> cc: Al Viro <viro@...iv.linux.org.uk>
> cc: Jens Axboe <axboe@...nel.dk>
> cc: Jan Kara <jack@...e.cz>
> cc: Matthew Wilcox <willy@...radead.org>
> cc: Logan Gunthorpe <logang@...tatee.com>
> cc: linux-block@...r.kernel.org

Looks good to me. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
> 
> Notes:
>     ver #8)
>      - Split out from another patch [hch].
>      - Don't default to BIO_PAGE_REFFED [hch].
>     
>     ver #5)
>      - Split from patch that uses iov_iter_extract_pages().
> 
>  block/bio.c               | 2 +-
>  block/blk-map.c           | 1 +
>  fs/direct-io.c            | 2 ++
>  fs/iomap/direct-io.c      | 1 -
>  include/linux/bio.h       | 2 +-
>  include/linux/blk_types.h | 2 +-
>  6 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 043944fd46eb..8516adeaea26 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1191,7 +1191,6 @@ void bio_iov_bvec_set(struct bio *bio, struct iov_iter *iter)
>  	bio->bi_io_vec = (struct bio_vec *)iter->bvec;
>  	bio->bi_iter.bi_bvec_done = iter->iov_offset;
>  	bio->bi_iter.bi_size = size;
> -	bio_set_flag(bio, BIO_NO_PAGE_REF);
>  	bio_set_flag(bio, BIO_CLONED);
>  }
>  
> @@ -1336,6 +1335,7 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
>  		return 0;
>  	}
>  
> +	bio_set_flag(bio, BIO_PAGE_REFFED);
>  	do {
>  		ret = __bio_iov_iter_get_pages(bio, iter);
>  	} while (!ret && iov_iter_count(iter) && !bio_full(bio, 0));
> diff --git a/block/blk-map.c b/block/blk-map.c
> index 04c55f1c492e..33d9f6e89ba6 100644
> --- a/block/blk-map.c
> +++ b/block/blk-map.c
> @@ -282,6 +282,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
>  	if (blk_queue_pci_p2pdma(rq->q))
>  		extraction_flags |= ITER_ALLOW_P2PDMA;
>  
> +	bio_set_flag(bio, BIO_PAGE_REFFED);
>  	while (iov_iter_count(iter)) {
>  		struct page **pages, *stack_pages[UIO_FASTIOV];
>  		ssize_t bytes;
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 0b380bb8a81e..ad20f3428bab 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -402,6 +402,8 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio,
>  		bio->bi_end_io = dio_bio_end_aio;
>  	else
>  		bio->bi_end_io = dio_bio_end_io;
> +	/* for now require references for all pages */
> +	bio_set_flag(bio, BIO_PAGE_REFFED);
>  	sdio->bio = bio;
>  	sdio->logical_offset_in_bio = sdio->cur_page_fs_offset;
>  }
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 66a9f10e3207..08873f0627dd 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -203,7 +203,6 @@ static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio,
>  	bio->bi_private = dio;
>  	bio->bi_end_io = iomap_dio_bio_end_io;
>  
> -	bio_set_flag(bio, BIO_NO_PAGE_REF);
>  	__bio_add_page(bio, page, len, 0);
>  	iomap_dio_submit_bio(iter, dio, bio, pos);
>  }
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 7f53be035cf0..0922729acd26 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -488,7 +488,7 @@ void zero_fill_bio(struct bio *bio);
>  
>  static inline void bio_release_pages(struct bio *bio, bool mark_dirty)
>  {
> -	if (!bio_flagged(bio, BIO_NO_PAGE_REF))
> +	if (bio_flagged(bio, BIO_PAGE_REFFED))
>  		__bio_release_pages(bio, mark_dirty);
>  }
>  
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 740afe80f297..dfd2c2cb909d 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -323,7 +323,7 @@ struct bio {
>   * bio flags
>   */
>  enum {
> -	BIO_NO_PAGE_REF,	/* don't put release vec pages */
> +	BIO_PAGE_REFFED,	/* put pages in bio_release_pages() */
>  	BIO_CLONED,		/* doesn't own data */
>  	BIO_BOUNCED,		/* bio is a bounce bio */
>  	BIO_QUIET,		/* Make BIO Quiet */
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR