New warning in nvme_setup_discard

[Oleksandr Natalenko]

Hello.

On pátek 16. července 2021 4:16:18 CEST Ming Lei wrote:
> >  850     if (WARN_ON_ONCE(n != segments)) {
> 
> What is 'n' and 'segments'?

So, I used this change to check that:

```
diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 66973bb56305..0a64f2f77daf 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -847,7 +847,8 @@ static blk_status_t nvme_setup_discard(struct nvme_ns *ns, 
struct request *req,
 		n++;
 	}
 
-	if (WARN_ON_ONCE(n != segments)) {
+	if (unlikely(n != segments)) {
+		pr_warn("nvme_setup_discard: n != segments (%u != %u)\n", n, 
segments);
 		if (virt_to_page(range) == ns->ctrl->discard_page)
 			clear_bit_unlock(0, &ns->ctrl->discard_page_busy);
 		else

```

and the result is:

```
nvme_setup_discard: n != segments (3 != 2)
nvme_setup_discard: n != segments (12 != 11)
```

(those are from different boots)

Thanks.

-- 
Oleksandr Natalenko (post-factum)