Re: [PATCH 12/12] iomap: build the writeback code without CONFIG_BLOCK

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

On Fri, Jun 27, 2025 at 09:02:45AM +0200, Christoph Hellwig wrote:
> Allow fuse to use the iomap writeback code even when CONFIG_BLOCK is
> not enabled.  Do this with an ifdef instead of a separate file to keep
> the iomap_folio_state local to buffered-io.c.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Seems reasonable to me...
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/iomap/Makefile      |   6 +--
>  fs/iomap/buffered-io.c | 113 ++++++++++++++++++++++-------------------
>  2 files changed, 64 insertions(+), 55 deletions(-)
> 
> diff --git a/fs/iomap/Makefile b/fs/iomap/Makefile
> index 69e8ebb41302..f7e1c8534c46 100644
> --- a/fs/iomap/Makefile
> +++ b/fs/iomap/Makefile
> @@ -9,9 +9,9 @@ ccflags-y += -I $(src)		# needed for trace events
>  obj-$(CONFIG_FS_IOMAP)		+= iomap.o
>  
>  iomap-y				+= trace.o \
> -				   iter.o
> -iomap-$(CONFIG_BLOCK)		+= buffered-io.o \
> -				   direct-io.o \
> +				   iter.o \
> +				   buffered-io.o
> +iomap-$(CONFIG_BLOCK)		+= direct-io.o \
>  				   ioend.o \
>  				   fiemap.o \
>  				   seek.o
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 1a9ade77aeeb..6ceeb0e2fc13 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -284,6 +284,46 @@ static void iomap_adjust_read_range(struct inode *inode, struct folio *folio,
>  	*lenp = plen;
>  }
>  
> +static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
> +		loff_t pos)
> +{
> +	const struct iomap *srcmap = iomap_iter_srcmap(iter);
> +
> +	return srcmap->type != IOMAP_MAPPED ||
> +		(srcmap->flags & IOMAP_F_NEW) ||
> +		pos >= i_size_read(iter->inode);
> +}
> +
> +/**
> + * iomap_read_inline_data - copy inline data into the page cache
> + * @iter: iteration structure
> + * @folio: folio to copy to
> + *
> + * Copy the inline data in @iter into @folio and zero out the rest of the folio.
> + * Only a single IOMAP_INLINE extent is allowed at the end of each file.
> + * Returns zero for success to complete the read, or the usual negative errno.
> + */
> +static int iomap_read_inline_data(const struct iomap_iter *iter,
> +		struct folio *folio)
> +{
> +	const struct iomap *iomap = iomap_iter_srcmap(iter);
> +	size_t size = i_size_read(iter->inode) - iomap->offset;
> +	size_t offset = offset_in_folio(folio, iomap->offset);
> +
> +	if (folio_test_uptodate(folio))
> +		return 0;
> +
> +	if (WARN_ON_ONCE(size > iomap->length))
> +		return -EIO;
> +	if (offset > 0)
> +		ifs_alloc(iter->inode, folio, iter->flags);
> +
> +	folio_fill_tail(folio, offset, iomap->inline_data, size);
> +	iomap_set_range_uptodate(folio, offset, folio_size(folio) - offset);
> +	return 0;
> +}
> +
> +#ifdef CONFIG_BLOCK
>  static void iomap_finish_folio_read(struct folio *folio, size_t off,
>  		size_t len, int error)
>  {
> @@ -323,45 +363,6 @@ struct iomap_readpage_ctx {
>  	struct readahead_control *rac;
>  };
>  
> -/**
> - * iomap_read_inline_data - copy inline data into the page cache
> - * @iter: iteration structure
> - * @folio: folio to copy to
> - *
> - * Copy the inline data in @iter into @folio and zero out the rest of the folio.
> - * Only a single IOMAP_INLINE extent is allowed at the end of each file.
> - * Returns zero for success to complete the read, or the usual negative errno.
> - */
> -static int iomap_read_inline_data(const struct iomap_iter *iter,
> -		struct folio *folio)
> -{
> -	const struct iomap *iomap = iomap_iter_srcmap(iter);
> -	size_t size = i_size_read(iter->inode) - iomap->offset;
> -	size_t offset = offset_in_folio(folio, iomap->offset);
> -
> -	if (folio_test_uptodate(folio))
> -		return 0;
> -
> -	if (WARN_ON_ONCE(size > iomap->length))
> -		return -EIO;
> -	if (offset > 0)
> -		ifs_alloc(iter->inode, folio, iter->flags);
> -
> -	folio_fill_tail(folio, offset, iomap->inline_data, size);
> -	iomap_set_range_uptodate(folio, offset, folio_size(folio) - offset);
> -	return 0;
> -}
> -
> -static inline bool iomap_block_needs_zeroing(const struct iomap_iter *iter,
> -		loff_t pos)
> -{
> -	const struct iomap *srcmap = iomap_iter_srcmap(iter);
> -
> -	return srcmap->type != IOMAP_MAPPED ||
> -		(srcmap->flags & IOMAP_F_NEW) ||
> -		pos >= i_size_read(iter->inode);
> -}
> -
>  static int iomap_readpage_iter(struct iomap_iter *iter,
>  		struct iomap_readpage_ctx *ctx)
>  {
> @@ -554,6 +555,27 @@ void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops)
>  }
>  EXPORT_SYMBOL_GPL(iomap_readahead);
>  
> +static int iomap_read_folio_range(const struct iomap_iter *iter,
> +		struct folio *folio, loff_t pos, size_t len)
> +{
> +	const struct iomap *srcmap = iomap_iter_srcmap(iter);
> +	struct bio_vec bvec;
> +	struct bio bio;
> +
> +	bio_init(&bio, srcmap->bdev, &bvec, 1, REQ_OP_READ);
> +	bio.bi_iter.bi_sector = iomap_sector(srcmap, pos);
> +	bio_add_folio_nofail(&bio, folio, len, offset_in_folio(folio, pos));
> +	return submit_bio_wait(&bio);
> +}
> +#else
> +static int iomap_read_folio_range(const struct iomap_iter *iter,
> +		struct folio *folio, loff_t pos, size_t len)
> +{
> +	WARN_ON_ONCE(1);
> +	return -EIO;
> +}
> +#endif /* CONFIG_BLOCK */
> +
>  /*
>   * iomap_is_partially_uptodate checks whether blocks within a folio are
>   * uptodate or not.
> @@ -667,19 +689,6 @@ iomap_write_failed(struct inode *inode, loff_t pos, unsigned len)
>  					 pos + len - 1);
>  }
>  
> -static int iomap_read_folio_range(const struct iomap_iter *iter,
> -		struct folio *folio, loff_t pos, size_t len)
> -{
> -	const struct iomap *srcmap = iomap_iter_srcmap(iter);
> -	struct bio_vec bvec;
> -	struct bio bio;
> -
> -	bio_init(&bio, srcmap->bdev, &bvec, 1, REQ_OP_READ);
> -	bio.bi_iter.bi_sector = iomap_sector(srcmap, pos);
> -	bio_add_folio_nofail(&bio, folio, len, offset_in_folio(folio, pos));
> -	return submit_bio_wait(&bio);
> -}
> -
>  static int __iomap_write_begin(const struct iomap_iter *iter,
>  		const struct iomap_write_ops *write_ops, size_t len,
>  		struct folio *folio)
> -- 
> 2.47.2
> 
>