ext4: add commit tid info in ext4_fc_commit_start/stop trace events

This adds commit_tid info in ext4_fc_commit_start/stop which is helpful
in debugging fast_commit issues.

For e.g. issues where due to jbd2 journal full commit, FC miss to commit
updates to a file.

Also improves TP_prink format string i.e. all ext4 and jbd2 trace events
starts with "dev MAjOR,MINOR". Let's follow the same convention while we
are still at it.

Signed-off-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Link: https://lore.kernel.org/r/ebcd6b9ab5b718db30f90854497886801ce38c63.1647057583.git.riteshh@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: riteshharjani

fs/ext4/fast_commit.c

@@ -1187,7 +1187,7 @@ static void ext4_fc_update_stats(struct super_block *sb, int status,
 	} else {
 		stats->fc_skipped_commits++;
 	}
-	trace_ext4_fc_commit_stop(sb, nblks, status);
+	trace_ext4_fc_commit_stop(sb, nblks, status, commit_tid);
 }
 
 /*
@@ -1208,7 +1208,7 @@ int ext4_fc_commit(journal_t *journal, tid_t commit_tid)
 	if (!test_opt2(sb, JOURNAL_FAST_COMMIT))
 		return jbd2_complete_transaction(journal, commit_tid);
 
-	trace_ext4_fc_commit_start(sb);
+	trace_ext4_fc_commit_start(sb, commit_tid);
 
 	start_time = ktime_get();
 

include/trace/events/ext4.h

@@ -2686,26 +2686,29 @@ TRACE_EVENT(ext4_fc_replay,
 );
 
 TRACE_EVENT(ext4_fc_commit_start,
-	TP_PROTO(struct super_block *sb),
+	TP_PROTO(struct super_block *sb, tid_t commit_tid),
 
-	TP_ARGS(sb),
+	TP_ARGS(sb, commit_tid),
 
 	TP_STRUCT__entry(
 		__field(dev_t, dev)
+		__field(tid_t, tid)
 	),
 
 	TP_fast_assign(
 		__entry->dev = sb->s_dev;
+		__entry->tid = commit_tid;
 	),
 
-	TP_printk("fast_commit started on dev %d,%d",
-		  MAJOR(__entry->dev), MINOR(__entry->dev))
+	TP_printk("dev %d,%d tid %u", MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->tid)
 );
 
 TRACE_EVENT(ext4_fc_commit_stop,
-	    TP_PROTO(struct super_block *sb, int nblks, int reason),
+	    TP_PROTO(struct super_block *sb, int nblks, int reason,
+		     tid_t commit_tid),
 
-	TP_ARGS(sb, nblks, reason),
+	TP_ARGS(sb, nblks, reason, commit_tid),
 
 	TP_STRUCT__entry(
 		__field(dev_t, dev)
@@ -2714,6 +2717,7 @@ TRACE_EVENT(ext4_fc_commit_stop,
 		__field(int, num_fc)
 		__field(int, num_fc_ineligible)
 		__field(int, nblks_agg)
+		__field(tid_t, tid)
 	),
 
 	TP_fast_assign(
@@ -2724,12 +2728,13 @@ TRACE_EVENT(ext4_fc_commit_stop,
 		__entry->num_fc_ineligible =
 			EXT4_SB(sb)->s_fc_stats.fc_ineligible_commits;
 		__entry->nblks_agg = EXT4_SB(sb)->s_fc_stats.fc_numblks;
+		__entry->tid = commit_tid;
 	),
 
-	TP_printk("fc on [%d,%d] nblks %d, reason %d, fc = %d, ineligible = %d, agg_nblks %d",
+	TP_printk("dev %d,%d nblks %d, reason %d, fc = %d, ineligible = %d, agg_nblks %d, tid %u",
 		  MAJOR(__entry->dev), MINOR(__entry->dev),
 		  __entry->nblks, __entry->reason, __entry->num_fc,
-		  __entry->num_fc_ineligible, __entry->nblks_agg)
+		  __entry->num_fc_ineligible, __entry->nblks_agg, __entry->tid)
 );
 
 #define FC_REASON_NAME_STAT(reason)					\