Commit 4dbd2b2e authored by Nilay Shroff's avatar Nilay Shroff Committed by Keith Busch
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nvme-multipath: Add visibility for round-robin io-policy 



This patch helps add nvme native multipath visibility for round-robin
io-policy. It creates a "multipath" sysfs directory under head gendisk
device node directory and then from "multipath" directory it adds a link
to each namespace path device the head node refers.

For instance, if we have a shared namespace accessible from two different
controllers/paths then we create a soft link to each path device from head
disk node as shown below:

$ ls -l /sys/block/nvme1n1/multipath/
nvme1c1n1 -> ../../../../../pci052e:78/052e:78:00.0/nvme/nvme1/nvme1c1n1
nvme1c3n1 -> ../../../../../pci058e:78/058e:78:00.0/nvme/nvme3/nvme1c3n1

In the above example, nvme1n1 is head gendisk node created for a shared
namespace and the namespace is accessible from nvme1c1n1 and nvme1c3n1
paths.

For round-robin I/O policy, we could easily infer from the above output
that I/O workload targeted to nvme1n1 would toggle across paths nvme1c1n1
and nvme1c3n1.

Reviewed-by: default avatarHannes Reinecke <hare@suse.de>
Signed-off-by: default avatarNilay Shroff <nilay@linux.ibm.com>
Signed-off-by: default avatarKeith Busch <kbusch@kernel.org>
parent 316dabe6

drivers/nvme/host/core.c

+3 −0
Original line number Diff line number Diff line
@@ -4020,6 +4020,9 @@ static void nvme_ns_remove(struct nvme_ns *ns) 


	if (!nvme_ns_head_multipath(ns->head))

		nvme_cdev_del(&ns->cdev, &ns->cdev_device);



	nvme_mpath_remove_sysfs_link(ns);



	del_gendisk(ns->disk);



	mutex_lock(&ns->ctrl->namespaces_lock);

drivers/nvme/host/multipath.c

+99 −0
Original line number Diff line number Diff line
@@ -686,6 +686,8 @@ static void nvme_mpath_set_live(struct nvme_ns *ns) 
		kblockd_schedule_work(&head->partition_scan_work);

	}



	nvme_mpath_add_sysfs_link(ns->head);



	mutex_lock(&head->lock);

	if (nvme_path_is_optimized(ns)) {

		int node, srcu_idx;
@@ -768,6 +770,25 @@ static void nvme_update_ns_ana_state(struct nvme_ana_group_desc *desc, 
	if (nvme_state_is_live(ns->ana_state) &&

	    nvme_ctrl_state(ns->ctrl) == NVME_CTRL_LIVE)

		nvme_mpath_set_live(ns);

	else {

		/*

		 * Add sysfs link from multipath head gendisk node to path

		 * device gendisk node.

		 * If path's ana state is live (i.e. state is either optimized

		 * or non-optimized) while we alloc the ns then sysfs link would

		 * be created from nvme_mpath_set_live(). In that case we would

		 * not fallthrough this code path. However for the path's ana

		 * state other than live, we call nvme_mpath_set_live() only

		 * after ana state transitioned to the live state. But we still

		 * want to create the sysfs link from head node to a path device

		 * irrespctive of the path's ana state.

		 * If we reach through here then it means that path's ana state

		 * is not live but still create the sysfs link to this path from

		 * head node if head node of the path has already come alive.

		 */

		if (test_bit(NVME_NSHEAD_DISK_LIVE, &ns->head->flags))

			nvme_mpath_add_sysfs_link(ns->head);

	}

}



static int nvme_update_ana_state(struct nvme_ctrl *ctrl,
@@ -967,6 +988,84 @@ static int nvme_lookup_ana_group_desc(struct nvme_ctrl *ctrl, 
	return -ENXIO; /* just break out of the loop */

}



void nvme_mpath_add_sysfs_link(struct nvme_ns_head *head)

{

	struct device *target;

	int rc, srcu_idx;

	struct nvme_ns *ns;

	struct kobject *kobj;



	/*

	 * Ensure head disk node is already added otherwise we may get invalid

	 * kobj for head disk node

	 */

	if (!test_bit(GD_ADDED, &head->disk->state))

		return;



	kobj = &disk_to_dev(head->disk)->kobj;



	/*

	 * loop through each ns chained through the head->list and create the

	 * sysfs link from head node to the ns path node

	 */

	srcu_idx = srcu_read_lock(&head->srcu);



	list_for_each_entry_rcu(ns, &head->list, siblings) {

		/*

		 * Avoid creating link if it already exists for the given path.

		 * When path ana state transitions from optimized to non-

		 * optimized or vice-versa, the nvme_mpath_set_live() is

		 * invoked which in truns call this function. Now if the sysfs

		 * link already exists for the given path and we attempt to re-

		 * create the link then sysfs code would warn about it loudly.

		 * So we evaluate NVME_NS_SYSFS_ATTR_LINK flag here to ensure

		 * that we're not creating duplicate link.

		 * The test_and_set_bit() is used because it is protecting

		 * against multiple nvme paths being simultaneously added.

		 */

		if (test_and_set_bit(NVME_NS_SYSFS_ATTR_LINK, &ns->flags))

			continue;



		/*

		 * Ensure that ns path disk node is already added otherwise we

		 * may get invalid kobj name for target

		 */

		if (!test_bit(GD_ADDED, &ns->disk->state))

			continue;



		target = disk_to_dev(ns->disk);

		/*

		 * Create sysfs link from head gendisk kobject @kobj to the

		 * ns path gendisk kobject @target->kobj.

		 */

		rc = sysfs_add_link_to_group(kobj, nvme_ns_mpath_attr_group.name,

				&target->kobj, dev_name(target));

		if (unlikely(rc)) {

			dev_err(disk_to_dev(ns->head->disk),

					"failed to create link to %s\n",

					dev_name(target));

			clear_bit(NVME_NS_SYSFS_ATTR_LINK, &ns->flags);

		}

	}



	srcu_read_unlock(&head->srcu, srcu_idx);

}



void nvme_mpath_remove_sysfs_link(struct nvme_ns *ns)

{

	struct device *target;

	struct kobject *kobj;



	if (!test_bit(NVME_NS_SYSFS_ATTR_LINK, &ns->flags))

		return;



	target = disk_to_dev(ns->disk);

	kobj = &disk_to_dev(ns->head->disk)->kobj;

	sysfs_remove_link_from_group(kobj, nvme_ns_mpath_attr_group.name,

			dev_name(target));

	clear_bit(NVME_NS_SYSFS_ATTR_LINK, &ns->flags);

}



void nvme_mpath_add_disk(struct nvme_ns *ns, __le32 anagrpid)

{

	if (nvme_ctrl_use_ana(ns->ctrl)) {

drivers/nvme/host/nvme.h

+14 −4
Original line number Diff line number Diff line
@@ -538,6 +538,7 @@ struct nvme_ns { 
#define NVME_NS_ANA_PENDING		2

#define NVME_NS_FORCE_RO		3

#define NVME_NS_READY			4

#define NVME_NS_SYSFS_ATTR_LINK	5



	struct cdev		cdev;

	struct device		cdev_device;
@@ -933,6 +934,7 @@ int nvme_getgeo(struct block_device *bdev, struct hd_geometry *geo); 
int nvme_dev_uring_cmd(struct io_uring_cmd *ioucmd, unsigned int issue_flags);



extern const struct attribute_group *nvme_ns_attr_groups[];

extern const struct attribute_group nvme_ns_mpath_attr_group;

extern const struct pr_ops nvme_pr_ops;

extern const struct block_device_operations nvme_ns_head_ops;

extern const struct attribute_group nvme_dev_attrs_group;
@@ -955,6 +957,8 @@ void nvme_mpath_default_iopolicy(struct nvme_subsystem *subsys); 
void nvme_failover_req(struct request *req);

void nvme_kick_requeue_lists(struct nvme_ctrl *ctrl);

int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl,struct nvme_ns_head *head);

void nvme_mpath_add_sysfs_link(struct nvme_ns_head *ns);

void nvme_mpath_remove_sysfs_link(struct nvme_ns *ns);

void nvme_mpath_add_disk(struct nvme_ns *ns, __le32 anagrpid);

void nvme_mpath_remove_disk(struct nvme_ns_head *head);

int nvme_mpath_init_identify(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id);
@@ -1009,6 +1013,12 @@ static inline void nvme_mpath_add_disk(struct nvme_ns *ns, __le32 anagrpid) 
static inline void nvme_mpath_remove_disk(struct nvme_ns_head *head)

{

}

static inline void nvme_mpath_add_sysfs_link(struct nvme_ns *ns)

{

}

static inline void nvme_mpath_remove_sysfs_link(struct nvme_ns *ns)

{

}

static inline bool nvme_mpath_clear_current_path(struct nvme_ns *ns)

{

	return false;

drivers/nvme/host/sysfs.c

+14 −0
Original line number Diff line number Diff line
@@ -299,8 +299,22 @@ static const struct attribute_group nvme_ns_attr_group = { 
	.is_visible	= nvme_ns_attrs_are_visible,

};



#ifdef CONFIG_NVME_MULTIPATH

static struct attribute *nvme_ns_mpath_attrs[] = {

	NULL,

};



const struct attribute_group nvme_ns_mpath_attr_group = {

	.name           = "multipath",

	.attrs		= nvme_ns_mpath_attrs,

};

#endif



const struct attribute_group *nvme_ns_attr_groups[] = {

	&nvme_ns_attr_group,

#ifdef CONFIG_NVME_MULTIPATH

	&nvme_ns_mpath_attr_group,

#endif

	NULL,

};