nvmet: add set feature tracing support

A nvme connect command produces following trace from the target side.

Before:
kworker/0:1H-56 [000] .... 9012.155139: nvmet_req_init: nvmet1: qid=0, cmdid=16, nsid=0, flags=0x40, meta=0x0, cmd=(nvme_admin_set_features, cdw10=07 00 00 00 07 00 07 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00)
kworker/0:1H-56 [000] .... 9012.872272: nvmet_req_init: nvmet1: qid=0, cmdid=13, nsid=0, flags=0x40, meta=0x0, cmd=(nvme_admin_set_features, cdw10=0b 00 00 00 00 09 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00)

cmdline:/sys/kernel/debug/tracing# cat trace | grep feature
kworker/0:1H-56 [000] .... 203.493914: nvmet_req_init: nvmet1: qid=0, cmdid=29, nsid=0, flags=0x40, meta=0x0, cmd=(nvme_admin_set_features, fid=0x7, sv=0x0, cdw11=0x70007)
kworker/0:1H-56 [000] .... 204.197079: nvmet_req_init: nvmet1: qid=0, cmdid=29, nsid=0, flags=0x40, meta=0x0, cmd=(nvme_admin_set_features, fid=0xb, sv=0x0, cdw11=0x900)

Using ',' to separate different field like others in
nvmet_trace_admin_get_features.

Signed-off-by: Hou Pu <[e-mail]>
Signed-off-by: Christoph Hellwig <[e-mail]>

drivers/nvme/target/trace.c

···
 	u8 sel = cdw10[1] & 0x7;
 	u32 cdw11 = get_unaligned_le32(cdw10 + 4);
 
-	trace_seq_printf(p, "fid=0x%x sel=0x%x cdw11=0x%x", fid, sel, cdw11);
+	trace_seq_printf(p, "fid=0x%x, sel=0x%x, cdw11=0x%x", fid, sel, cdw11);
 	trace_seq_putc(p, 0);
 
 	return ret;
···
 
 	trace_seq_printf(p, "slba=0x%llx, mndw=0x%x, rl=0x%x, atype=%u",
 			slba, mndw, rl, atype);
+	trace_seq_putc(p, 0);
+
+	return ret;
+}
+
+static const char *nvmet_trace_admin_set_features(struct trace_seq *p,
+						 u8 *cdw10)
+{
+	const char *ret = trace_seq_buffer_ptr(p);
+	u8 fid = cdw10[0];
+	u8 sv = cdw10[3] & 0x8;
+	u32 cdw11 = get_unaligned_le32(cdw10 + 4);
+
+	trace_seq_printf(p, "fid=0x%x, sv=0x%x, cdw11=0x%x", fid, sv, cdw11);
 	trace_seq_putc(p, 0);
 
 	return ret;
···
 	switch (opcode) {
 	case nvme_admin_identify:
 		return nvmet_trace_admin_identify(p, cdw10);
+	case nvme_admin_set_features:
+		return nvmet_trace_admin_set_features(p, cdw10);
 	case nvme_admin_get_features:
 		return nvmet_trace_admin_get_features(p, cdw10);
 	case nvme_admin_get_lba_status: