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nvme-multipath: Add visibility for round-robin io-policy

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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: Hannes Reinecke <hare@suse.de>
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
This commit is contained in:
Nilay Shroff
2025-01-12 18:11:44 +05:30
committed by Keith Busch
parent 316dabe608
commit 4dbd2b2ebe
4 changed files with 130 additions and 4 deletions
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14
drivers/nvme/host/sysfs.c
View File

@@ -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,
};