[PATCH v3] nvme: refresh multipath head zoned limits from path limits

[Yao Sang]

queue_limits_stack_bdev() updates the multipath head limits from the
path queue, but it does not propagate max_open_zones or
max_active_zones. As a result, a zoned multipath namespace head can
keep stale 0/0 values even after a ready path reports finite zoned
resource limits.

When refreshing the head limits in nvme_update_ns_info(), update the
zoned limits directly after stacking the path queue limits. Clamp
max_open_zones and max_active_zones against the current path limits
with min_not_zero(), and clear both fields when the resulting queue is
not zoned.

This avoids advertising "no limit" on the multipath head while keeping
the zoned-limit handling local to the nvme multipath update path.

Signed-off-by: Yao Sang <sangyao at kylinos.cn>
---
Changes in v3:
- Keep the fix local to the NVMe multipath update path, as suggested
  in review
- Drop the helper and update the zoned limits directly in
  nvme_update_ns_info().
- Keep explicit clearing of both zoned-limit fields when the resulting
  queue is not zoned.

Testing:
- blktests: nvme/005, nvme/057, nvme/058
- blktests: zbd/011, zbd/012, zbd/013, block/004
- blktests on /dev/nvme0n1: zbd/001, zbd/002, zbd/003, zbd/004,
  zbd/005, zbd/006

Link to v1:
https://lore.kernel.org/r/20260520091237.392802-1-sangyao@kylinos.cn

Link to v2:
https://lore.kernel.org/all/20260522075806.3168366-1-sangyao@kylinos.cn

 drivers/nvme/host/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index c3032d6ad6b1..18383a70e2c5 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2549,6 +2549,15 @@ static int nvme_update_ns_info(struct nvme_ns *ns, struct nvme_ns_info *info)
 		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) {
+			lim.max_open_zones = min_not_zero(lim.max_open_zones,
+							  ns_lim->max_open_zones);
+			lim.max_active_zones = min_not_zero(lim.max_active_zones,
+							    ns_lim->max_active_zones);
+		} else {
+			lim.max_open_zones = 0;
+			lim.max_active_zones = 0;
+		}
 		if (unsupported)
 			ns->head->disk->flags |= GENHD_FL_HIDDEN;
 		else
-- 
2.25.1