On 02/03/2026 12:36, Nilay Shroff wrote:
On 2/25/26 9:02 PM, John Garry wrote:
Add code for path selection.
NVMe ANA is abstracted into enum mpath_access_state. The motivation
here is
so that SCSI ALUA can be used. Callbacks .is_disabled, .is_optimized,
.get_access_state are added to get the path access state.
Path selection modes round-robin, NUMA, and queue-depth are added, same
as NVMe supports.
NVMe has almost like-for-like equivalents here:
- __mpath_find_path() -> __nvme_find_path()
- mpath_find_path() -> nvme_find_path()
and similar for all introduced callee functions.
Functions mpath_set_iopolicy() and mpath_get_iopolicy() are added for
setting default iopolicy.
A separate mpath_iopolicy structure is introduced. There is no iopolicy
member included in the mpath_head structure as it may not suit NVMe,
where
iopolicy is per-subsystem and not per namespace.
Signed-off-by: John Garry <[email protected]>
---
include/linux/multipath.h | 36 ++++++
lib/multipath.c | 251 ++++++++++++++++++++++++++++++++++++++
2 files changed, 287 insertions(+)
diff --git a/include/linux/multipath.h b/include/linux/multipath.h
index be9dd9fb83345..c964a1aba9c42 100644
--- a/include/linux/multipath.h
+++ b/include/linux/multipath.h
@@ -7,6 +7,22 @@
extern const struct block_device_operations mpath_ops;
+enum mpath_iopolicy_e {
+ MPATH_IOPOLICY_NUMA,
+ MPATH_IOPOLICY_RR,
+ MPATH_IOPOLICY_QD,
+};
+
+struct mpath_iopolicy {
+ enum mpath_iopolicy_e iopolicy;
+};
+
+enum mpath_access_state {
+ MPATH_STATE_OPTIMIZED,
+ MPATH_STATE_ACTIVE,
+ MPATH_STATE_INVALID = 0xFF
+};
Hmm so here we don't have MPATH_STATE_NONOPTIMIZED.
We are morphing NVME_ANA_NONOPTIMIZED as MPATH_STATE_ACTIVE.
Yes, well it is treated the same (as NVME_ANA_NONOPTIMIZED) for path
selection.
Is it because SCSI doesn't have (NONOPTIMIZED) state?
It does have an active (and optimal) state, but I think that keeping
NVMe terminology may be better for now.
+
struct mpath_disk {
struct gendisk *disk;
struct kref ref;
@@ -18,10 +34,16 @@ struct mpath_disk {
struct mpath_device {
struct list_head siblings;
+ atomic_t nr_active;
struct gendisk *disk;
+ int numa_node;
};
I haven't seen any API which help set nr_active or numa_node.
I missed setting numa_node for NVMe. About nr_active, that is set/read
by the NVMe code, like nvme_mpath_start_request(). I did try to abstract
that function into a common helper, but it just becomes a mess.
Do we need to have those under struct mpath_head_template ?
I think that the drivers can handle these directly.
Thanks
