Re: [PATCH 09/10] block: add FALLOC_FL_WRITE_ZEROES support

[Christoph Hellwig]

On Wed, Jun 04, 2025 at 10:08:49AM +0800, Zhang Yi wrote:
> @@ -856,6 +856,13 @@ static long blkdev_fallocate(struct file *file, int mode, loff_t start,
>  	/* Fail if we don't recognize the flags. */
>  	if (mode & ~BLKDEV_FALLOC_FL_SUPPORTED)
>  		return -EOPNOTSUPP;
> +	/*
> +	 * Don't allow writing zeroes if the device does not enable the
> +	 * unmap write zeroes operation.
> +	 */
> +	if (!bdev_write_zeroes_unmap(bdev) &&
> +	    (mode & FALLOC_FL_WRITE_ZEROES))

Cosmetic nitpick, but I'd turn the check around to check the mode first
as that's easier to read.  The whole check also fits onto a single line:

	if ((mode & FALLOC_FL_WRITE_ZEROES) && !bdev_write_zeroes_unmap(bdev))

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@xxxxxx>