Re: [PATCH 3/4] nvme: fix max_discard_sectors calculation

[Damien Le Moal <dlemoal@kernel.org>]

On 7/7/23 18:46, Christoph Hellwig wrote:
> ctrl->max_discard_sectors stores a value that is potentially based of
> the DMRSL field in Identify Controller, which is in units of LBAs and
> thus dependent on the Format of a namespace.
> 
> Fix this by moving the calculation of max_discard_sectors entirely
> into nvme_config_discard and replacing the ctrl->max_discard_sectors
> value with a local variable so that the calculation is always

I do not see a local variable replacement... May be you meant direct calls to
blk_queue_max_discard_sectors() ?

Other than that, looks OK to me.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>

> namespace-specific.
> 
> Fixes: 1a86924e4f46 ("nvme: fix interpretation of DMRSL")
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  drivers/nvme/host/core.c | 22 ++++++++++------------
>  drivers/nvme/host/nvme.h |  1 -
>  2 files changed, 10 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index 2d6c1f4ad7f5c8..05372bec3b7aff 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -1721,20 +1721,21 @@ static void nvme_config_discard(struct gendisk *disk, struct nvme_ns *ns)
>  	struct request_queue *queue = disk->queue;
>  	u32 size = queue_logical_block_size(queue);
>  
> -	if (ctrl->dmrsl && ctrl->dmrsl <= nvme_sect_to_lba(ns, UINT_MAX))
> -		ctrl->max_discard_sectors = nvme_lba_to_sect(ns, ctrl->dmrsl);
> +	BUILD_BUG_ON(PAGE_SIZE / sizeof(struct nvme_dsm_range) <
> +			NVME_DSM_MAX_RANGES);
>  
> -	if (ctrl->max_discard_sectors == 0) {
> +	if (ctrl->dmrsl && ctrl->dmrsl <= nvme_sect_to_lba(ns, UINT_MAX)) {
> +		blk_queue_max_discard_sectors(queue,
> +				nvme_lba_to_sect(ns, ctrl->dmrsl));
> +	} else if (ctrl->oncs & NVME_CTRL_ONCS_DSM) {
> +		blk_queue_max_discard_sectors(queue, UINT_MAX);
> +	} else {
>  		blk_queue_max_discard_sectors(queue, 0);
>  		return;
>  	}
>  
> -	BUILD_BUG_ON(PAGE_SIZE / sizeof(struct nvme_dsm_range) <
> -			NVME_DSM_MAX_RANGES);
> -
>  	queue->limits.discard_granularity = size;
>  
> -	blk_queue_max_discard_sectors(queue, ctrl->max_discard_sectors);
>  	blk_queue_max_discard_segments(queue, ctrl->max_discard_segments);
>  
>  	if (ctrl->quirks & NVME_QUIRK_DEALLOCATE_ZEROES)
> @@ -2870,13 +2871,10 @@ static int nvme_init_non_mdts_limits(struct nvme_ctrl *ctrl)
>  	struct nvme_id_ctrl_nvm *id;
>  	int ret;
>  
> -	if (ctrl->oncs & NVME_CTRL_ONCS_DSM) {
> -		ctrl->max_discard_sectors = UINT_MAX;
> +	if (ctrl->oncs & NVME_CTRL_ONCS_DSM)
>  		ctrl->max_discard_segments = NVME_DSM_MAX_RANGES;
> -	} else {
> -		ctrl->max_discard_sectors = 0;
> +	else
>  		ctrl->max_discard_segments = 0;
> -	}
>  
>  	/*
>  	 * Even though NVMe spec explicitly states that MDTS is not applicable
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index f35647c470afad..d59ed2ba1c37ca 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -296,7 +296,6 @@ struct nvme_ctrl {
>  	u32 max_hw_sectors;
>  	u32 max_segments;
>  	u32 max_integrity_segments;
> -	u32 max_discard_sectors;
>  	u32 max_discard_segments;
>  	u32 max_zeroes_sectors;
>  #ifdef CONFIG_BLK_DEV_ZONED

-- 
Damien Le Moal
Western Digital Research