Re: [PATCH v2 1/4] nvme: factor namespace-head queue-limit update

[John Garry <john.g.garry@oracle.com>]

On 06/08/2026 03:46, Yao Sang wrote:
> Move the namespace head queue-limit update out of nvme_update_ns_info().
> The new helper keeps the current queue_limits_stack_bdev() based behavior
> intact, including zoned resource handling, write-stream assignment,
> integrity setup, capacity and readonly updates, path revalidation, and
> namespace-head zone revalidation.
> 
> Keep queue-limit commit failures on the existing short-circuit path so
> capacity and namespace-head state are only updated after a successful
> limits update.
> 
> The helper gives namespace-head queue-limit updates a single NVMe-local
> entry point while keeping the namespace information refresh sequencing
> unchanged.

Like the cover letter, this message is too verbose. So much so that I 
lose track of what is important to note - that being the motivation for 
the change.

The motivation seems to be to just factor out the NS head update into a 
separate function as it deserves its own function and the code will be 
neater, but not because it will in future have multiple callsites.

> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Yao Sang <sangyao@kylinos.cn>
> ---
>   drivers/nvme/host/core.c | 104 +++++++++++++++++++++------------------
>   1 file changed, 56 insertions(+), 48 deletions(-)
> 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index cb93ada4376a..e3d27c0440db 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2528,6 +2528,60 @@ static void nvme_stack_zone_resources(struct queue_limits *t,
>   		min_not_zero(t->max_active_zones, b->max_active_zones);
>   }
>   
> +static int nvme_update_ns_head_limits(struct nvme_ns *ns,
> +		struct nvme_ns_info *info, bool unsupported)
> +{
> +	struct queue_limits *ns_lim = &ns->disk->queue->limits;
> +	struct request_queue *head_q = ns->head->disk->queue;
> +	struct queue_limits lim;
> +	unsigned int memflags;
> +	int ret;
> +
> +	lim = queue_limits_start_update(head_q);
> +	memflags = blk_mq_freeze_queue(head_q);
> +	/*
> +	 * queue_limits mixes values that are the hardware limitations
> +	 * for bio splitting with what is the device configuration.
> +	 *
> +	 * For NVMe the device configuration can change after e.g. a
> +	 * Format command, and we really want to pick up the new format
> +	 * value here. But we must still stack the queue limits to the
> +	 * least common denominator for multipathing to split the bios
> +	 * properly.
> +	 *
> +	 * To work around this, we explicitly set the device
> +	 * configuration to those that we just queried, but only stack
> +	 * the splitting limits in to make sure we still obey possibly
> +	 * lower limitations of other controllers.
> +	 */
> +	lim.logical_block_size = ns_lim->logical_block_size;
> +	lim.physical_block_size = ns_lim->physical_block_size;
> +	lim.io_min = ns_lim->io_min;
> +	lim.io_opt = ns_lim->io_opt;
> +	queue_limits_stack_bdev(&lim, ns->disk->part0, 0,
> +				ns->head->disk->disk_name);
> +	if (lim.features & BLK_FEAT_ZONED)
> +		nvme_stack_zone_resources(&lim, ns_lim);
> +	if (unsupported)
> +		ns->head->disk->flags |= GENHD_FL_HIDDEN;
> +	else
> +		nvme_init_integrity(ns->head, &lim, info);
> +	lim.max_write_streams = ns_lim->max_write_streams;
> +	lim.write_stream_granularity = ns_lim->write_stream_granularity;
> +	ret = queue_limits_commit_update(head_q, &lim);
> +	if (ret)
> +		goto unfreeze_head_queue;
> +
> +	set_capacity_and_notify(ns->head->disk, get_capacity(ns->disk));
> +	set_disk_ro(ns->head->disk, nvme_ns_is_readonly(ns, info));
> +	nvme_mpath_revalidate_paths(ns->head);
> +	ret = nvme_mpath_revalidate_zones(ns->head);
> +
> +unfreeze_head_queue:
> +	blk_mq_unfreeze_queue(head_q, memflags);
> +	return ret;
> +}
> +
>   static int nvme_update_ns_info(struct nvme_ns *ns, struct nvme_ns_info *info)
>   {
>   	bool unsupported = false;
> @@ -2566,54 +2620,8 @@ static int nvme_update_ns_info(struct nvme_ns *ns, struct nvme_ns_info *info)
>   		ret = 0;
>   	}
>   
> -	if (!ret && nvme_ns_head_multipath(ns->head)) {
> -		struct queue_limits *ns_lim = &ns->disk->queue->limits;
> -		struct queue_limits lim;
> -		unsigned int memflags;
> -
> -		lim = queue_limits_start_update(ns->head->disk->queue);
> -		memflags = blk_mq_freeze_queue(ns->head->disk->queue);
> -		/*
> -		 * queue_limits mixes values that are the hardware limitations
> -		 * for bio splitting with what is the device configuration.
> -		 *
> -		 * For NVMe the device configuration can change after e.g. a
> -		 * Format command, and we really want to pick up the new format
> -		 * value here.  But we must still stack the queue limits to the
> -		 * least common denominator for multipathing to split the bios
> -		 * properly.
> -		 *
> -		 * To work around this, we explicitly set the device
> -		 * configuration to those that we just queried, but only stack
> -		 * the splitting limits in to make sure we still obey possibly
> -		 * lower limitations of other controllers.
> -		 */
> -		lim.logical_block_size = ns_lim->logical_block_size;
> -		lim.physical_block_size = ns_lim->physical_block_size;
> -		lim.io_min = ns_lim->io_min;
> -		lim.io_opt = ns_lim->io_opt;
> -		queue_limits_stack_bdev(&lim, ns->disk->part0, 0,
> -					ns->head->disk->disk_name);
> -		if (lim.features & BLK_FEAT_ZONED)
> -			nvme_stack_zone_resources(&lim, ns_lim);
> -		if (unsupported)
> -			ns->head->disk->flags |= GENHD_FL_HIDDEN;
> -		else
> -			nvme_init_integrity(ns->head, &lim, info);
> -		lim.max_write_streams = ns_lim->max_write_streams;
> -		lim.write_stream_granularity = ns_lim->write_stream_granularity;
> -		ret = queue_limits_commit_update(ns->head->disk->queue, &lim);
> -		if (ret)
> -			goto unfreeze_head_queue;
> -
> -		set_capacity_and_notify(ns->head->disk, get_capacity(ns->disk));
> -		set_disk_ro(ns->head->disk, nvme_ns_is_readonly(ns, info));
> -		nvme_mpath_revalidate_paths(ns->head);
> -		ret = nvme_mpath_revalidate_zones(ns->head);
> -
> -unfreeze_head_queue:
> -		blk_mq_unfreeze_queue(ns->head->disk->queue, memflags);
> -	}
> +	if (!ret && nvme_ns_head_multipath(ns->head))
> +		ret = nvme_update_ns_head_limits(ns, info, unsupported);
>   
>   	return ret;
>   }