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From: Matthew Wilcox <willy@infradead.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	linux-block@vger.kernel.org
Subject: Re: [PATCH v15 02/17] block: Add bio_for_each_folio_all()
Date: Fri, 23 Jul 2021 03:40:27 +0100	[thread overview]
Message-ID: <YPosG9HKRBt9+GUy@casper.infradead.org> (raw)
In-Reply-To: <YPZxp6ZbRGYYBnYK@infradead.org>

On Tue, Jul 20, 2021 at 08:48:07AM +0200, Christoph Hellwig wrote:
> On Mon, Jul 19, 2021 at 07:39:46PM +0100, Matthew Wilcox (Oracle) wrote:
> >  #define bio_for_each_bvec_all(bvl, bio, i)		\
> >  	for (i = 0, bvl = bio_first_bvec_all(bio);	\
> > -	     i < (bio)->bi_vcnt; i++, bvl++)		\
> > +	     i < (bio)->bi_vcnt; i++, bvl++)
> 
> Pleae split out this unrelated fixup.
> 
> > +static inline
> > +void bio_first_folio(struct folio_iter *fi, struct bio *bio, int i)
> 
> Please fix the strange formatting.

static inline void bio_first_folio(struct folio_iter *fi, struct bio *bio,
		int i)

> > +{
> > +	struct bio_vec *bvec = bio_first_bvec_all(bio) + i;
> > +
> > +	fi->folio = page_folio(bvec->bv_page);
> > +	fi->offset = bvec->bv_offset +
> > +			PAGE_SIZE * (bvec->bv_page - &fi->folio->page);
> 
> Can we have a little helper for the offset in folio calculation, like:
> 
> static inline size_t offset_of_page_in_folio(struct page *page)
> {
> 	return (bvec->bv_page - &page_folio(page)->page) * PAGE;
> }
> 
> as that makes the callers a lot easier to read.

I've spent most of today thinking about this one.  I actually don't
want to make this easy to read.  This is code that, in an ideal world,
would not exist.  A bio_vec should not contain a struct page; it should
probably be:

struct bio_vec {
	phys_addr_t bv_start;
	unsigned int bv_len;
};

and then the helper to get from a bio_vec to a folio_iter looks like:

	fi->folio = pfn_folio(bvec->bv_start >> PAGE_SHIFT);
	fi->offset = offset_in_folio(fi->folio, bvec->bv_start);

If instead we decide to keep bvecs the way they are, we can at
least turn the bv_page into bv_folio, and then we won't need this
code either.

  reply	other threads:[~2021-07-23  2:40 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-19 18:39 [PATCH v15 00/17] Folio support in block + iomap layers Matthew Wilcox (Oracle)
2021-07-19 18:39 ` [PATCH v15 01/17] block: Add bio_add_folio() Matthew Wilcox (Oracle)
2021-07-20  1:28   ` Darrick J. Wong
2021-07-20  6:42   ` Christoph Hellwig
2021-07-20 11:16     ` Matthew Wilcox
2021-07-22 16:27     ` Matthew Wilcox
2021-07-30  8:25   ` Ming Lei
2021-07-30 11:30     ` Matthew Wilcox
2021-07-19 18:39 ` [PATCH v15 02/17] block: Add bio_for_each_folio_all() Matthew Wilcox (Oracle)
2021-07-20  1:29   ` Darrick J. Wong
2021-07-20  1:59     ` Matthew Wilcox
2021-07-20  6:48   ` Christoph Hellwig
2021-07-23  2:40     ` Matthew Wilcox [this message]
2021-07-20 12:05   ` kernel test robot
2021-07-20 12:05   ` kernel test robot
2021-07-20 12:26   ` kernel test robot
2021-07-19 18:39 ` [PATCH v15 03/17] iomap: Convert to_iomap_page to take a folio Matthew Wilcox (Oracle)
2021-07-20  6:49   ` Christoph Hellwig
2021-07-19 18:39 ` [PATCH v15 04/17] iomap: Convert iomap_page_create " Matthew Wilcox (Oracle)
2021-07-20  6:50   ` Christoph Hellwig
2021-07-19 18:39 ` [PATCH v15 05/17] iomap: Convert iomap_page_release " Matthew Wilcox (Oracle)
2021-07-20  6:52   ` Christoph Hellwig
2021-07-20 11:29     ` Matthew Wilcox
2021-07-20 11:40       ` Christoph Hellwig
2021-07-19 18:39 ` [PATCH v15 06/17] iomap: Convert iomap_releasepage to use " Matthew Wilcox (Oracle)
2021-07-20  6:54   ` Christoph Hellwig
2021-07-20 23:56   ` Darrick J. Wong
2021-07-19 18:39 ` [PATCH v15 07/17] iomap: Convert iomap_invalidatepage " Matthew Wilcox (Oracle)
2021-07-20  6:55   ` Christoph Hellwig
2021-07-20 23:57   ` Darrick J. Wong
2021-07-19 18:39 ` [PATCH v15 08/17] iomap: Pass the iomap_page into iomap_set_range_uptodate Matthew Wilcox (Oracle)
2021-07-20  6:57   ` Christoph Hellwig
2021-07-20 11:36     ` Matthew Wilcox
2021-07-19 18:39 ` [PATCH v15 09/17] iomap: Use folio offsets instead of page offsets Matthew Wilcox (Oracle)
2021-07-20  6:59   ` Christoph Hellwig
2021-07-20 11:42     ` Matthew Wilcox
2021-07-19 18:39 ` [PATCH v15 10/17] iomap: Convert bio completions to use folios Matthew Wilcox (Oracle)
2021-07-20  7:08   ` Christoph Hellwig
2021-07-19 18:39 ` [PATCH v15 11/17] iomap: Convert readahead and readpage to use a folio Matthew Wilcox (Oracle)
2021-07-20  7:09   ` Christoph Hellwig
2021-07-19 18:39 ` [PATCH v15 12/17] iomap: Convert iomap_page_mkwrite " Matthew Wilcox (Oracle)
2021-07-20  7:13   ` Christoph Hellwig
2021-07-19 18:39 ` [PATCH v15 13/17] iomap: Convert iomap_write_begin and iomap_write_end to folios Matthew Wilcox (Oracle)
2021-07-20  7:15   ` Christoph Hellwig
2021-07-20 23:59   ` Darrick J. Wong
2021-07-19 18:39 ` [PATCH v15 14/17] iomap: Convert iomap_read_inline_data to take a folio Matthew Wilcox (Oracle)
2021-07-20  7:16   ` Christoph Hellwig
2021-07-19 18:39 ` [PATCH v15 15/17] iomap: Convert iomap_write_end_inline " Matthew Wilcox (Oracle)
2021-07-20  7:17   ` Christoph Hellwig
2021-07-19 18:40 ` [PATCH v15 16/17] iomap: Convert iomap_add_to_ioend " Matthew Wilcox (Oracle)
2021-07-20  7:20   ` Christoph Hellwig
2021-07-20 11:45     ` Matthew Wilcox
2021-07-21  0:12   ` Darrick J. Wong
2021-07-21  4:27     ` Christoph Hellwig
2021-07-21  4:31       ` Matthew Wilcox
2021-07-21 15:28         ` Darrick J. Wong
2021-07-19 18:40 ` [PATCH v15 17/17] iomap: Convert iomap_migrate_page to use folios Matthew Wilcox (Oracle)
2021-07-20  7:21   ` Christoph Hellwig
2021-07-20 13:30   ` kernel test robot
2021-07-21  0:02   ` Darrick J. Wong
2021-07-20  8:44 ` [PATCH v15 00/17] Folio support in block + iomap layers Christoph Hellwig
2021-07-20 11:08   ` Matthew Wilcox

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