Re: [PATCH 2/4] FIXUP: iomap: aligning to larger than fs block size doesn't make sense

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

On Thu, Oct 23, 2025 at 03:55:43PM +0200, Christoph Hellwig wrote:
> All of the VFS and helpers assume that the file system block size must
> be larger or equal to the device block size.  So doing a max of both
> doesn't really make much sense.  Siplify the code in iomap_dio_bio_iter

                                   Simplify

> to do a simple if/else.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

With that fixed,
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/iomap/direct-io.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index ce9cbd2bace0..8d094d6f5f3e 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -336,17 +336,19 @@ static int iomap_dio_bio_iter(struct iomap_iter *iter, struct iomap_dio *dio)
>  	int nr_pages, ret = 0;
>  	u64 copied = 0;
>  	size_t orig_count;
> -	unsigned int alignment = bdev_logical_block_size(iomap->bdev);
> +	unsigned int alignment;
>  
>  	if ((pos | length) & (bdev_logical_block_size(iomap->bdev) - 1))
>  		return -EINVAL;
>  
>  	/*
> -	 * Align to the larger one of bdev and fs block size, to meet the
> -	 * alignment requirement of both layers.
> +	 * File systems that write out of place and always allocate new blocks
> +	 * need each bio to be block aligned as that's the unit of allocation.
>  	 */
>  	if (dio->flags & IOMAP_DIO_FSBLOCK_ALIGNED)
> -		alignment = max(alignment, fs_block_size);
> +		alignment = fs_block_size;
> +	else
> +		alignment = bdev_logical_block_size(iomap->bdev);
>  
>  	if (dio->flags & IOMAP_DIO_WRITE) {
>  		bio_opf |= REQ_OP_WRITE;
> -- 
> 2.47.3
> 
>