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SubjectRe: [PATCH v8 07/10] block: Switch to pinning pages.
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On 23.01.23 18:30, 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@redhat.com>
> cc: Al Viro <viro@zeniv.linux.org.uk>
> cc: Jens Axboe <axboe@kernel.dk>
> cc: Jan Kara <jack@suse.cz>
> cc: Christoph Hellwig <hch@lst.de>
> cc: Matthew Wilcox <willy@infradead.org>
> cc: Logan Gunthorpe <logang@deltatee.com>
> cc: linux-block@vger.kernel.org
> ---
>
> Notes:
> 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 | 7 ++++---
> block/blk.h | 28 ++++++++++++++++++++++++++++
> include/linux/bio.h | 3 ++-
> include/linux/blk_types.h | 1 +
> 4 files changed, 35 insertions(+), 4 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 40c2b01906da..6f98bcfc0c92 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1170,13 +1170,14 @@ bool bio_add_folio(struct bio *bio, struct folio *folio, size_t len,
>
> void __bio_release_pages(struct bio *bio, bool mark_dirty)
> {
> + unsigned int gup_flags = bio_to_gup_flags(bio);
> struct bvec_iter_all iter_all;
> struct bio_vec *bvec;
>
> 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);
> + page_put_unpin(bvec->bv_page, gup_flags);
> }
> }
> EXPORT_SYMBOL_GPL(__bio_release_pages);
> @@ -1496,8 +1497,8 @@ 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 run one page_put_unpin() against 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 4c3b3325219a..294044d696e0 100644
> --- a/block/blk.h
> +++ b/block/blk.h
> @@ -425,6 +425,34 @@ 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);
>
> +/*
> + * Set the cleanup mode for a bio from an iterator and the extraction flags.
> + */
> +static inline void bio_set_cleanup_mode(struct bio *bio, struct iov_iter *iter)
> +{
> + unsigned int cleanup_mode = iov_iter_extract_mode(iter);
> +
> + if (cleanup_mode & FOLL_GET)
> + bio_set_flag(bio, BIO_PAGE_REFFED);
> + if (cleanup_mode & FOLL_PIN)
> + bio_set_flag(bio, BIO_PAGE_PINNED);

Can FOLL_GET ever happen?

IOW, can't this even be

if (user_backed_iter(iter))
bio_set_flag(bio, BIO_PAGE_PINNED);

--
Thanks,

David / dhildenb

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