Re: [PATCH 05/17] iomap: respect maximum I/O size in iomap_dio_bio_iter_one

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

On Mon, Aug 31, 2026 at 09:39:53AM +0300, Christoph Hellwig wrote:
> Respect the maximum I/O size set for PI-enabled I/O in
> iomap_dio_bio_iter_one, otherwise bio_integrity_alloc_buf could
> under-allocate the integrity buffer when the initial kmalloc fails.
> 
> Currently this should not be triggered as file systems that limit the
> size for PI always use bounce buffering, but this will change soon.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

This makes sense, as the !DIO_BOUNCE path will soon get used for the
"don't bounce, just try it and see if it fails" code path.

Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/iomap/direct-io.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index bc726d47b7dc..91f5b67718a5 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -336,6 +336,7 @@ static ssize_t iomap_dio_bio_iter_one(struct iomap_iter *iter,
>  		struct iomap_dio *dio, loff_t pos, unsigned int alignment,
>  		blk_opf_t op)
>  {
> +	unsigned int maxsize = iomap_max_bio_size(&iter->iomap);
>  	unsigned int nr_vecs;
>  	struct bio *bio;
>  	ssize_t ret;
> @@ -353,14 +354,12 @@ static ssize_t iomap_dio_bio_iter_one(struct iomap_iter *iter,
>  	bio->bi_private = dio;
>  	bio->bi_end_io = iomap_dio_bio_end_io;
>  
> -
>  	if (dio->flags & IOMAP_DIO_BOUNCE)
> -		ret = bio_iov_iter_bounce(bio, dio->submit.iter,
> -				iomap_max_bio_size(&iter->iomap), alignment);
> +		ret = bio_iov_iter_bounce(bio, dio->submit.iter, maxsize,
> +				alignment);
>  	else
> -		ret = bio_iov_iter_get_pages(bio, dio->submit.iter,
> -				BIO_MAX_SIZE, bdev_dma_alignment(bio->bi_bdev),
> -				alignment - 1);
> +		ret = bio_iov_iter_get_pages(bio, dio->submit.iter, maxsize,
> +				bdev_dma_alignment(bio->bi_bdev), alignment - 1);
>  	if (unlikely(ret))
>  		goto out_put_bio;
>  	ret = bio->bi_iter.bi_size;
> -- 
> 2.53.0
> 
>