Re: [PATCH v3 03/15] iomap: store read/readahead bio generically

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

On Tue, Sep 16, 2025 at 04:44:13PM -0700, Joanne Koong wrote:
> Store the iomap_readpage_ctx bio generically as a "void *read_ctx".
> This makes the read/readahead interface more generic, which allows it to
> be used by filesystems that may not be block-based and may not have
> CONFIG_BLOCK set.
> 
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>

Wheee type changes :)
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/iomap/buffered-io.c | 29 ++++++++++++++---------------
>  1 file changed, 14 insertions(+), 15 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index ee96558b6d99..2a1709e0757b 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -353,13 +353,13 @@ static void iomap_read_end_io(struct bio *bio)
>  struct iomap_readpage_ctx {
>  	struct folio		*cur_folio;
>  	bool			cur_folio_in_bio;
> -	struct bio		*bio;
> +	void			*read_ctx;
>  	struct readahead_control *rac;
>  };
>  
>  static void iomap_bio_submit_read(struct iomap_readpage_ctx *ctx)
>  {
> -	struct bio *bio = ctx->bio;
> +	struct bio *bio = ctx->read_ctx;
>  
>  	if (bio)
>  		submit_bio(bio);
> @@ -374,6 +374,7 @@ static void iomap_bio_read_folio_range(const struct iomap_iter *iter,
>  	size_t poff = offset_in_folio(folio, pos);
>  	loff_t length = iomap_length(iter);
>  	sector_t sector;
> +	struct bio *bio = ctx->read_ctx;
>  
>  	ctx->cur_folio_in_bio = true;
>  	if (ifs) {
> @@ -383,9 +384,8 @@ static void iomap_bio_read_folio_range(const struct iomap_iter *iter,
>  	}
>  
>  	sector = iomap_sector(iomap, pos);
> -	if (!ctx->bio ||
> -	    bio_end_sector(ctx->bio) != sector ||
> -	    !bio_add_folio(ctx->bio, folio, plen, poff)) {
> +	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);
> @@ -394,22 +394,21 @@ static void iomap_bio_read_folio_range(const struct iomap_iter *iter,
>  
>  		if (ctx->rac) /* same as readahead_gfp_mask */
>  			gfp |= __GFP_NORETRY | __GFP_NOWARN;
> -		ctx->bio = bio_alloc(iomap->bdev, bio_max_segs(nr_vecs),
> -				     REQ_OP_READ, gfp);
> +		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 (!ctx->bio) {
> -			ctx->bio = bio_alloc(iomap->bdev, 1, REQ_OP_READ,
> -					     orig_gfp);
> -		}
> +		if (!bio)
> +			bio = bio_alloc(iomap->bdev, 1, REQ_OP_READ, orig_gfp);
>  		if (ctx->rac)
> -			ctx->bio->bi_opf |= REQ_RAHEAD;
> -		ctx->bio->bi_iter.bi_sector = sector;
> -		ctx->bio->bi_end_io = iomap_read_end_io;
> -		bio_add_folio_nofail(ctx->bio, folio, plen, poff);
> +			bio->bi_opf |= REQ_RAHEAD;
> +		bio->bi_iter.bi_sector = sector;
> +		bio->bi_end_io = iomap_read_end_io;
> +		bio_add_folio_nofail(bio, folio, plen, poff);
> +		ctx->read_ctx = bio;
>  	}
>  }
>  
> -- 
> 2.47.3
> 
>