linux-kernel - Re: [PATCH v21 4/6] block: Add BIO_PAGE_PINNED and associated infrastructure

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Date:   Tue, 23 May 2023 10:08:44 +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 4/6] block: Add BIO_PAGE_PINNED and associated
 infrastructure

On Mon 22-05-23 21:57:42, David Howells wrote:
> Add BIO_PAGE_PINNED to indicate that the pages in a bio are pinned
> (FOLL_PIN) and that the pin will need removing.
> 
> Signed-off-by: David Howells <dhowells@...hat.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> 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 #10)
>      - Drop bio_set_cleanup_mode(), open coding it instead.
>     
>     ver #9)
>      - Only consider pinning in bio_set_cleanup_mode().  Ref'ing pages in
>        struct bio is going away.
>      - page_put_unpin() is removed; call unpin_user_page() and put_page()
>        directly.
>      - Use bio_release_page() in __bio_release_pages().
>      - BIO_PAGE_PINNED and BIO_PAGE_REFFED can't both be set, so use if-else
>        when testing both of them.
>     
>     ver #8)
>      - Move the infrastructure to clean up pinned pages to this patch [hch].
>      - Put BIO_PAGE_PINNED before BIO_PAGE_REFFED as the latter should
>        probably be removed at some point.  FOLL_PIN can then be renumbered
>        first.
> 
>  block/bio.c               |  6 +++---
>  block/blk.h               | 12 ++++++++++++
>  include/linux/bio.h       |  3 ++-
>  include/linux/blk_types.h |  1 +
>  4 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/block/bio.c b/block/bio.c
> index 8516adeaea26..17bd01ecde36 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1169,7 +1169,7 @@ void __bio_release_pages(struct bio *bio, bool mark_dirty)
>  	bio_for_each_segment_all(bvec, bio, iter_all) {
>  		if (mark_dirty && !PageCompound(bvec->bv_page))
>  			set_page_dirty_lock(bvec->bv_page);
> -		put_page(bvec->bv_page);
> +		bio_release_page(bio, bvec->bv_page);
>  	}
>  }
>  EXPORT_SYMBOL_GPL(__bio_release_pages);
> @@ -1489,8 +1489,8 @@ void bio_set_pages_dirty(struct bio *bio)
>   * the BIO and re-dirty the pages in process context.
>   *
>   * It is expected that bio_check_pages_dirty() will wholly own the BIO from
> - * here on.  It will run one put_page() against each page and will run one
> - * bio_put() against the BIO.
> + * here on.  It will unpin each page and will run one bio_put() against the
> + * BIO.
>   */
>  
>  static void bio_dirty_fn(struct work_struct *work);
> diff --git a/block/blk.h b/block/blk.h
> index 45547bcf1119..e1ded2ccb3ca 100644
> --- a/block/blk.h
> +++ b/block/blk.h
> @@ -420,6 +420,18 @@ int bio_add_hw_page(struct request_queue *q, struct bio *bio,
>  		struct page *page, unsigned int len, unsigned int offset,
>  		unsigned int max_sectors, bool *same_page);
>  
> +/*
> + * Clean up a page appropriately, where the page may be pinned, may have a
> + * ref taken on it or neither.
> + */
> +static inline void bio_release_page(struct bio *bio, struct page *page)
> +{
> +	if (bio_flagged(bio, BIO_PAGE_PINNED))
> +		unpin_user_page(page);
> +	else if (bio_flagged(bio, BIO_PAGE_REFFED))
> +		put_page(page);
> +}
> +
>  struct request_queue *blk_alloc_queue(int node_id);
>  
>  int disk_scan_partitions(struct gendisk *disk, fmode_t mode);
> diff --git a/include/linux/bio.h b/include/linux/bio.h
> index 0922729acd26..8588bcfbc6ef 100644
> --- a/include/linux/bio.h
> +++ b/include/linux/bio.h
> @@ -488,7 +488,8 @@ void zero_fill_bio(struct bio *bio);
>  
>  static inline void bio_release_pages(struct bio *bio, bool mark_dirty)
>  {
> -	if (bio_flagged(bio, BIO_PAGE_REFFED))
> +	if (bio_flagged(bio, BIO_PAGE_REFFED) ||
> +	    bio_flagged(bio, BIO_PAGE_PINNED))
>  		__bio_release_pages(bio, mark_dirty);
>  }
>  
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index dfd2c2cb909d..8ef209e3aa96 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -323,6 +323,7 @@ struct bio {
>   * bio flags
>   */
>  enum {
> +	BIO_PAGE_PINNED,	/* Unpin pages in bio_release_pages() */
>  	BIO_PAGE_REFFED,	/* put pages in bio_release_pages() */
>  	BIO_CLONED,		/* doesn't own data */
>  	BIO_BOUNCED,		/* bio is a bounce bio */
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR