Re: [PATCH 12/16] ntfs3: remove copy and pasted iomap code

["Darrick J. Wong" <djwong@kernel.org>]

On Mon, Feb 23, 2026 at 05:20:12AM -0800, Christoph Hellwig wrote:
> ntfs3 copied the iomap code without attribution or talking to the
> maintainers, to hook into the bio completion for (unexplained) zeroing.

Well they /did/ attribute it...

> Fix this by just overriding the bio completion handler in the submit
> handler.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/ntfs3/inode.c | 51 +++---------------------------------------------
>  1 file changed, 3 insertions(+), 48 deletions(-)
> 
> diff --git a/fs/ntfs3/inode.c b/fs/ntfs3/inode.c
> index 7ab4e18f8013..60af9f8e0366 100644
> --- a/fs/ntfs3/inode.c
> +++ b/fs/ntfs3/inode.c
> @@ -605,63 +605,18 @@ static void ntfs_iomap_read_end_io(struct bio *bio)
>  	bio_put(bio);
>  }
>  
> -/*
> - * Copied from iomap/bio.c.

...extremely poorly, by not recording their reasons for copy-pasting the
code.

> - */
> -static int ntfs_iomap_bio_read_folio_range(const struct iomap_iter *iter,
> -					   struct iomap_read_folio_ctx *ctx,
> -					   size_t plen)
> -{
> -	struct folio *folio = ctx->cur_folio;
> -	const struct iomap *iomap = &iter->iomap;
> -	loff_t pos = iter->pos;
> -	size_t poff = offset_in_folio(folio, pos);
> -	loff_t length = iomap_length(iter);
> -	sector_t sector;
> -	struct bio *bio = ctx->read_ctx;
> -
> -	sector = iomap_sector(iomap, pos);
> -	if (!bio || bio_end_sector(bio) != sector ||
> -	    !bio_add_folio(bio, folio, plen, poff)) {
> -		gfp_t gfp = mapping_gfp_constraint(folio->mapping, GFP_KERNEL);
> -		gfp_t orig_gfp = gfp;
> -		unsigned int nr_vecs = DIV_ROUND_UP(length, PAGE_SIZE);
> -
> -		if (bio)
> -			submit_bio(bio);
> -
> -		if (ctx->rac) /* same as readahead_gfp_mask */
> -			gfp |= __GFP_NORETRY | __GFP_NOWARN;
> -		bio = bio_alloc(iomap->bdev, bio_max_segs(nr_vecs), REQ_OP_READ,
> -				gfp);
> -		/*
> -		 * If the bio_alloc fails, try it again for a single page to
> -		 * avoid having to deal with partial page reads.  This emulates
> -		 * what do_mpage_read_folio does.
> -		 */
> -		if (!bio)
> -			bio = bio_alloc(iomap->bdev, 1, REQ_OP_READ, orig_gfp);
> -		if (ctx->rac)
> -			bio->bi_opf |= REQ_RAHEAD;
> -		bio->bi_iter.bi_sector = sector;
> -		bio->bi_end_io = ntfs_iomap_read_end_io;
> -		bio_add_folio_nofail(bio, folio, plen, poff);
> -		ctx->read_ctx = bio;
> -	}
> -	return 0;
> -}

Yeah, identical to iomap_bio_read_folio_range except for setting
bi_end_io.

Don't copy-paste stuff.
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> -
>  static void ntfs_iomap_bio_submit_read(const struct iomap_iter *iter,
>  		struct iomap_read_folio_ctx *ctx)
>  {
>  	struct bio *bio = ctx->read_ctx;
>  
> +	bio->bi_end_io = ntfs_iomap_read_end_io;
>  	submit_bio(bio);
>  }
>  
>  static const struct iomap_read_ops ntfs_iomap_bio_read_ops = {
> -	.read_folio_range = ntfs_iomap_bio_read_folio_range,
> -	.submit_read = ntfs_iomap_bio_submit_read,
> +	.read_folio_range	= iomap_bio_read_folio_range,
> +	.submit_read		= ntfs_iomap_bio_submit_read,
>  };
>  
>  static int ntfs_read_folio(struct file *file, struct folio *folio)
> -- 
> 2.47.3
> 
>