Re: [PATCH v1 14/16] fuse: use iomap for read_folio

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

On Fri, Aug 29, 2025 at 04:56:25PM -0700, Joanne Koong wrote:
> Read folio data into the page cache using iomap. This gives us granular
> uptodate tracking for large folios, which optimizes how much data needs
> to be read in. If some portions of the folio are already uptodate (eg
> through a prior write), we only need to read in the non-uptodate
> portions.
> 
> Signed-off-by: Joanne Koong <joannelkoong@gmail.com>

Looks fine to me,
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/fuse/file.c | 72 ++++++++++++++++++++++++++++++++++----------------
>  1 file changed, 49 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 5525a4520b0f..bdfb13cdee4b 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -828,22 +828,62 @@ static int fuse_do_readfolio(struct file *file, struct folio *folio,
>  	return 0;
>  }
>  
> +static int fuse_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> +			    unsigned int flags, struct iomap *iomap,
> +			    struct iomap *srcmap)
> +{
> +	iomap->type = IOMAP_MAPPED;
> +	iomap->length = length;
> +	iomap->offset = offset;
> +	return 0;
> +}
> +
> +static const struct iomap_ops fuse_iomap_ops = {
> +	.iomap_begin	= fuse_iomap_begin,
> +};
> +
> +struct fuse_fill_read_data {
> +	struct file *file;
> +};
> +
> +static int fuse_iomap_read_folio_range_async(const struct iomap_iter *iter,
> +					     struct folio *folio, loff_t pos,
> +					     size_t len)
> +{
> +	struct fuse_fill_read_data *data = iter->private;
> +	struct file *file = data->file;
> +	size_t off = offset_in_folio(folio, pos);
> +	int ret;
> +
> +	/*
> +	 *  for non-readahead read requests, do reads synchronously since
> +	 *  it's not guaranteed that the server can handle out-of-order reads
> +	 */
> +	iomap_start_folio_read(folio, len);
> +	ret = fuse_do_readfolio(file, folio, off, len);
> +	iomap_finish_folio_read(folio, off, len, ret);
> +	return ret;
> +}
> +
> +static const struct iomap_read_ops fuse_iomap_read_ops = {
> +	.read_folio_range = fuse_iomap_read_folio_range_async,
> +};
> +
>  static int fuse_read_folio(struct file *file, struct folio *folio)
>  {
>  	struct inode *inode = folio->mapping->host;
> +	struct fuse_fill_read_data data = {
> +		.file = file,
> +	};
>  	int err;
>  
> -	err = -EIO;
> -	if (fuse_is_bad(inode))
> -		goto out;
> -
> -	err = fuse_do_readfolio(file, folio, 0, folio_size(folio));
> -	if (!err)
> -		folio_mark_uptodate(folio);
> +	if (fuse_is_bad(inode)) {
> +		folio_unlock(folio);
> +		return -EIO;
> +	}
>  
> +	err = iomap_read_folio(folio, &fuse_iomap_ops, &fuse_iomap_read_ops, &data);
>  	fuse_invalidate_atime(inode);
> - out:
> -	folio_unlock(folio);
>  	return err;
>  }
>  
> @@ -1394,20 +1434,6 @@ static const struct iomap_write_ops fuse_iomap_write_ops = {
>  	.read_folio_range = fuse_iomap_read_folio_range,
>  };
>  
> -static int fuse_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> -			    unsigned int flags, struct iomap *iomap,
> -			    struct iomap *srcmap)
> -{
> -	iomap->type = IOMAP_MAPPED;
> -	iomap->length = length;
> -	iomap->offset = offset;
> -	return 0;
> -}
> -
> -static const struct iomap_ops fuse_iomap_ops = {
> -	.iomap_begin	= fuse_iomap_begin,
> -};
> -
>  static ssize_t fuse_cache_write_iter(struct kiocb *iocb, struct iov_iter *from)
>  {
>  	struct file *file = iocb->ki_filp;
> -- 
> 2.47.3
> 
>