[PATCH v2] nvme: keep ctrl->namespaces ordered

[Christoph Hellwig]

Various places in the nvme code that rely on ctrl->namespace to be
ordered.  Ensure that the namespae is inserted into the list at the
right position from the start instead of sorting it after the fact.

Also use the chance to check for duplicates.  These should not happen,
but with consumer hardware we can't ever be careful enough.

Fixes: 540c801c65eb ("NVMe: Implement namespace list scanning")
Reported-by: Anton Eidelman <anton.eidelman at gmail.com>
Signed-off-by: Christoph Hellwig <hch at lst.de>
---

Changes since v1:
 - check for duplicate NSIDs

 drivers/nvme/host/core.c | 47 +++++++++++++++++++++++++---------------
 1 file changed, 29 insertions(+), 18 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 97f8211cf92c1..b3b0b17cc2317 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -13,7 +13,6 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/backing-dev.h>
-#include <linux/list_sort.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/pr.h>
@@ -3716,15 +3715,6 @@ static int nvme_init_ns_head(struct nvme_ns *ns, unsigned nsid,
 	return ret;
 }
 
-static int ns_cmp(void *priv, const struct list_head *a,
-		const struct list_head *b)
-{
-	struct nvme_ns *nsa = container_of(a, struct nvme_ns, list);
-	struct nvme_ns *nsb = container_of(b, struct nvme_ns, list);
-
-	return nsa->head->ns_id - nsb->head->ns_id;
-}
-
 struct nvme_ns *nvme_find_get_ns(struct nvme_ctrl *ctrl, unsigned nsid)
 {
 	struct nvme_ns *ns, *ret = NULL;
@@ -3745,6 +3735,33 @@ struct nvme_ns *nvme_find_get_ns(struct nvme_ctrl *ctrl, unsigned nsid)
 }
 EXPORT_SYMBOL_NS_GPL(nvme_find_get_ns, NVME_TARGET_PASSTHRU);
 
+/*
+ * Add the namespace to the controller list while keeping the list ordered.
+ */
+static bool nvme_ns_add_to_ctrl_list(struct nvme_ns *ns)
+{
+	struct nvme_ns *tmp;
+
+	down_write(&ns->ctrl->namespaces_rwsem);
+	list_for_each_entry_reverse(tmp, &ns->ctrl->namespaces, list) {
+		if (tmp->head->ns_id == ns->head->ns_id)
+			goto out_duplicate;
+		if (tmp->head->ns_id < ns->head->ns_id) {
+			list_add(&tmp->list, &ns->ctrl->namespaces);
+			goto out_unlock;
+		}
+	}
+
+	list_add_tail(&ns->list, &ns->ctrl->namespaces);
+out_unlock:
+	up_write(&ns->ctrl->namespaces_rwsem);
+	return true;
+out_duplicate:
+	up_write(&ns->ctrl->namespaces_rwsem);
+	dev_warn(ns->ctrl->device, "duplicate nsid %u\n", ns->head->ns_id);
+	return false;
+}
+
 static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
 		struct nvme_ns_ids *ids)
 {
@@ -3794,10 +3811,8 @@ static void nvme_alloc_ns(struct nvme_ctrl *ctrl, unsigned nsid,
 	if (nvme_update_ns_info(ns, id))
 		goto out_unlink_ns;
 
-	down_write(&ctrl->namespaces_rwsem);
-	list_add_tail(&ns->list, &ctrl->namespaces);
-	up_write(&ctrl->namespaces_rwsem);
-
+	if (!nvme_ns_add_to_ctrl_list(ns))
+		goto out_unlink_ns;
 	nvme_get_ctrl(ctrl);
 
 	if (device_add_disk(ctrl->device, ns->disk, nvme_ns_id_attr_groups))
@@ -4082,10 +4097,6 @@ static void nvme_scan_work(struct work_struct *work)
 	if (nvme_scan_ns_list(ctrl) != 0)
 		nvme_scan_ns_sequential(ctrl);
 	mutex_unlock(&ctrl->scan_lock);
-
-	down_write(&ctrl->namespaces_rwsem);
-	list_sort(NULL, &ctrl->namespaces, ns_cmp);
-	up_write(&ctrl->namespaces_rwsem);
 }
 
 /*
-- 
2.30.2