xfs: report "max_resp" used for min log size computation

Move the tracepoint that computes the size of the transaction used to
compute the minimum log size into xfs_log_get_max_trans_res so that we
only have to compute this stuff once.

Leave xfs_log_get_max_trans_res as a non-static function so that xfs_db
can call it to report the results of the userspace computation of the
same value to diagnose mkfs/kernel misinteractions.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_log_rlimit.c

@@ -76,6 +76,7 @@ xfs_log_get_max_trans_res(
 		*max_resp = resv.tr_attrsetm;	/* struct copy */
 		max_resp->tr_logres = attr_space;
 	}
+	trace_xfs_log_get_max_trans_res(mp, max_resp);
 }
 
 /*

fs/xfs/xfs_trace.h

@@ -3534,6 +3534,25 @@ DEFINE_EVENT(xfs_trans_resv_class, name, \
 DEFINE_TRANS_RESV_EVENT(xfs_trans_resv_calc);
 DEFINE_TRANS_RESV_EVENT(xfs_trans_resv_calc_minlogsize);
 
+TRACE_EVENT(xfs_log_get_max_trans_res,
+	TP_PROTO(struct xfs_mount *mp, const struct xfs_trans_res *res),
+	TP_ARGS(mp, res),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(uint, logres)
+		__field(int, logcount)
+	),
+	TP_fast_assign(
+		__entry->dev = mp->m_super->s_dev;
+		__entry->logres = res->tr_logres;
+		__entry->logcount = res->tr_logcount;
+	),
+	TP_printk("dev %d:%d logres %u logcount %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->logres,
+		  __entry->logcount)
+);
+
 DECLARE_EVENT_CLASS(xfs_trans_class,
 	TP_PROTO(struct xfs_trans *tp, unsigned long caller_ip),
 	TP_ARGS(tp, caller_ip),

fs/xfs/xfs_trans.c

@@ -32,7 +32,6 @@ static void
 xfs_trans_trace_reservations(
 	struct xfs_mount	*mp)
 {
-	struct xfs_trans_res	resv;
 	struct xfs_trans_res	*res;
 	struct xfs_trans_res	*end_res;
 	int			i;
@@ -41,8 +40,6 @@ xfs_trans_trace_reservations(
 	end_res = (struct xfs_trans_res *)(M_RES(mp) + 1);
 	for (i = 0; res < end_res; i++, res++)
 		trace_xfs_trans_resv_calc(mp, i, res);
-	xfs_log_get_max_trans_res(mp, &resv);
-	trace_xfs_trans_resv_calc(mp, -1, &resv);
 }
 #else
 # define xfs_trans_trace_reservations(mp)