Re: [PATCH] md/md-linear: Enable atomic writes

[Yu Kuai]

在 2025/09/04 0:10, John Garry 写道:
> All the infrastructure has already been plumbed to support this for
> stacked devices, so just enable the request_queue limits features flag.
>
> A note about chunk sectors for linear arrays:
> While it is possible to set a chunk sectors param for building a linear
> array, this is for specifying the granularity at which data sectors from
> the device are used. It is not the same as a stripe size, like for RAID0.
>
> As such, it is not appropriate to set chunk_sectors request queue limit to
> the same value, as chunk_sectors request limit is a boundary for which
> requests cannot straddle.
>
> However, request_queue limit max_hw_sectors is set to chunk sectors, which
> almost has the same effect as setting chunk_sectors limit.
>
> Signed-off-by: John Garry <john.g.garry@xxxxxxxxxx>
>
> diff --git a/drivers/md/md-linear.c b/drivers/md/md-linear.c
> index 5d9b081153757..30ac29b990c9b 100644
> --- a/drivers/md/md-linear.c
> +++ b/drivers/md/md-linear.c
> @@ -74,6 +74,7 @@ static int linear_set_limits(struct mddev *mddev)
>   	lim.max_hw_sectors = mddev->chunk_sectors;
>   	lim.max_write_zeroes_sectors = mddev->chunk_sectors;
>   	lim.io_min = mddev->chunk_sectors << 9;
> +	lim.features |= BLK_FEAT_ATOMIC_WRITES;
>   	err = mddev_stack_rdev_limits(mddev, &lim, MDDEV_STACK_INTEGRITY);
>   	if (err)
>   		return err;

LGRM
Reviewed-by: Yu Kuai <yukuai3@xxxxxxxxxx>