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SubjectRe: [PATCH] nvme: Fix nvme_setup_command metadata trace event for cdw10
On Wed, Jul 06, 2022 at 06:18:25PM +0200, Christoph Hellwig wrote:
> On Wed, Jul 06, 2022 at 10:13:22AM -0600, Keith Busch wrote:
> > Did you test what the trace looks like afte this? We're losing valuable trace
> > data here. The field is supposed to get CDW's 10 - 15, so that's 24 bytes. I
> > don't know why it cares that the address of the field being read is only 4
> > bytes; we want everything that comes after it too.
>
> Because accesses should not spawn boundaries of members in structs unless
> copying the entire struct. If we want to trace the various fields we
> need to individually assign them.
>
> Anyway, I'm dropping this patch from nvme-5.19 for now to let the
> discussion conclude.

How about this instead?

---
diff --git a/drivers/nvme/host/trace.h b/drivers/nvme/host/trace.h
index b5f85259461a..3c5e7fa03707 100644
--- a/drivers/nvme/host/trace.h
+++ b/drivers/nvme/host/trace.h
@@ -69,7 +69,7 @@ TRACE_EVENT(nvme_setup_cmd,
__entry->metadata = !!blk_integrity_rq(req);
__entry->fctype = cmd->fabrics.fctype;
__assign_disk_name(__entry->disk, req->q->disk);
- memcpy(__entry->cdw10, &cmd->common.cdw10,
+ memcpy(__entry->cdw10, &cmd->common.bytes,
sizeof(__entry->cdw10));
),
TP_printk("nvme%d: %sqid=%d, cmdid=%u, nsid=%u, flags=0x%x, meta=0x%x, cmd=(%s %s)",
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index e3934003f239..1be226871763 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -906,12 +906,17 @@ struct nvme_common_command {
__le32 cdw2[2];
__le64 metadata;
union nvme_data_ptr dptr;
- __le32 cdw10;
- __le32 cdw11;
- __le32 cdw12;
- __le32 cdw13;
- __le32 cdw14;
- __le32 cdw15;
+ union {
+ struct {
+ __le32 cdw10;
+ __le32 cdw11;
+ __le32 cdw12;
+ __le32 cdw13;
+ __le32 cdw14;
+ __le32 cdw15;
+ };
+ __u8 bytes[24];
+ };
};

struct nvme_rw_command {
--
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