[PATCH] nvme: Fix nvme_setup_command metadata trace event for cdw10

[John Garry <john.garry@huawei.com>]

For x86_64 allmodconfig I get this warning:

In function ‘fortify_memcpy_chk’,
    inlined from ‘perf_trace_nvme_setup_cmd’ at drivers/nvme/host/./trace.h:47:1:
./include/linux/fortify-string.h:352:4: error: call to ‘__read_overflow2_field’ declared with attribute warning: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Werror]
    __read_overflow2_field(q_size_field, size);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In function ‘fortify_memcpy_chk’,
    inlined from ‘trace_event_raw_event_nvme_setup_cmd’ at drivers/nvme/host/./trace.h:47:1:
./include/linux/fortify-string.h:352:4: error: call to ‘__read_overflow2_field’ declared with attribute warning: detected read beyond size of field (2nd parameter); maybe use struct_group()? [-Werror]
    __read_overflow2_field(q_size_field, size);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

cdw10 metadata is 24 bytes, and we try to copy size of cdw10 metadata from
nvme_command.common.cdw10 into that cdw10 metadata, but
nvme_command.common.cdw10 is only 4 bytes in size.

Fix by making the trace metadata size as 4 bytes.

I find that this warning started first appearing from commit f68f2ff91512
("fortify: Detect struct member overflows in memcpy() at compile-time").

Signed-off-by: John Garry <john.garry@huawei.com>

diff --git a/drivers/nvme/host/trace.h b/drivers/nvme/host/trace.h
index b5f85259461a..d6d35f935006 100644
--- a/drivers/nvme/host/trace.h
+++ b/drivers/nvme/host/trace.h
@@ -57,7 +57,7 @@ TRACE_EVENT(nvme_setup_cmd,
 		__field(u16, cid)
 		__field(u32, nsid)
 		__field(bool, metadata)
-		__array(u8, cdw10, 24)
+		__array(u8, cdw10, 4)
 	    ),
 	    TP_fast_assign(
 		__entry->ctrl_id = nvme_req(req)->ctrl->instance;
-- 
2.35.3