nvme: export zoned namespaces without Zone Append support read-only

Allow ZNS NVMe SSDs to present a read-only namespace when append is not
supported, instead of rejecting the namespace directly.

This allows (i) the namespace to be used in read-only mode, which is not
a problem as the append command only affects the write path, and (ii) to
use standard management tools such as nvme-cli to choose a different
format or firmware slot that is compatible with the Linux zoned block
device.
Signed-off-by: Javier González <javier.gonz@samsung.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/core.c

@@ -2125,7 +2125,8 @@ static void nvme_update_disk_info(struct gendisk *disk,
 	nvme_config_discard(disk, ns);
 	nvme_config_write_zeroes(disk, ns);
 
-	if (id->nsattr & NVME_NS_ATTR_RO)
+	if ((id->nsattr & NVME_NS_ATTR_RO) ||
+	    test_bit(NVME_NS_FORCE_RO, &ns->flags))
 		set_disk_ro(disk, true);
 }
 

drivers/nvme/host/nvme.h

@@ -452,6 +452,7 @@ struct nvme_ns {
 #define NVME_NS_REMOVING	0
 #define NVME_NS_DEAD     	1
 #define NVME_NS_ANA_PENDING	2
+#define NVME_NS_FORCE_RO	3
 
 	struct nvme_fault_inject fault_inject;
 

drivers/nvme/host/zns.c

@@ -55,12 +55,17 @@ int nvme_update_zone_info(struct nvme_ns *ns, unsigned lbaf)
 	int status;
 
 	/* Driver requires zone append support */
-	if (!(le32_to_cpu(log->iocs[nvme_cmd_zone_append]) &
+	if ((le32_to_cpu(log->iocs[nvme_cmd_zone_append]) &
 			NVME_CMD_EFFECTS_CSUPP)) {
+		if (test_and_clear_bit(NVME_NS_FORCE_RO, &ns->flags))
 			dev_warn(ns->ctrl->device,
-			"append not supported for zoned namespace:%d\n",
+				 "Zone Append supported for zoned namespace:%d. Remove read-only mode\n",
+				 ns->head->ns_id);
+	} else {
+		set_bit(NVME_NS_FORCE_RO, &ns->flags);
+		dev_warn(ns->ctrl->device,
+			 "Zone Append not supported for zoned namespace:%d. Forcing to read-only mode\n",
 			 ns->head->ns_id);
-		return -EINVAL;
 	}
 
 	/* Lazily query controller append limit for the first zoned namespace */