jbd2: add tracepoints which provide per-handle statistics

Handles which stay open a long time are problematic when it comes time
to close down a transaction so it can be committed. These tracepoints
will help us determine which ones are the problematic ones, and to
validate whether changes makes things better or worse.

Signed-off-by: "Theodore Ts'o" <[e-mail]>

fs/jbd2/transaction.c

···
 #include <linux/bug.h>
 #include <linux/module.h>
 
+#include <trace/events/jbd2.h>
+
 static void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh);
 static void __jbd2_journal_unfile_buffer(struct journal_head *jh);
 
···
 	 */
 	update_t_max_wait(transaction, ts);
 	handle->h_transaction = transaction;
+	handle->h_requested_credits = nblocks;
+	handle->h_start_jiffies = jiffies;
 	atomic_inc(&transaction->t_updates);
 	atomic_inc(&transaction->t_handle_count);
 	jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
···
  * Return a pointer to a newly allocated handle, or an ERR_PTR() value
  * on failure.
  */
-handle_t *jbd2__journal_start(journal_t *journal, int nblocks, gfp_t gfp_mask)
+handle_t *jbd2__journal_start(journal_t *journal, int nblocks, gfp_t gfp_mask,
+			      unsigned int type, unsigned int line_no)
 {
 	handle_t *handle = journal_current_handle();
 	int err;
···
 		current->journal_info = NULL;
 		handle = ERR_PTR(err);
 	}
+	handle->h_type = type;
+	handle->h_line_no = line_no;
+	trace_jbd2_handle_start(journal->j_fs_dev->bd_dev,
+				handle->h_transaction->t_tid, type,
+				line_no, nblocks);
 	return handle;
 }
 EXPORT_SYMBOL(jbd2__journal_start);
···
 
 handle_t *jbd2_journal_start(journal_t *journal, int nblocks)
 {
-	return jbd2__journal_start(journal, nblocks, GFP_NOFS);
+	return jbd2__journal_start(journal, nblocks, GFP_NOFS, 0, 0);
 }
 EXPORT_SYMBOL(jbd2_journal_start);
 
···
 		goto unlock;
 	}
 
+	trace_jbd2_handle_extend(journal->j_fs_dev->bd_dev,
+				 handle->h_transaction->t_tid,
+				 handle->h_type, handle->h_line_no,
+				 handle->h_buffer_credits,
+				 nblocks);
+
 	handle->h_buffer_credits += nblocks;
+	handle->h_requested_credits += nblocks;
 	atomic_add(nblocks, &transaction->t_outstanding_credits);
 	result = 0;
 
···
 	}
 
 	jbd_debug(4, "Handle %p going down\n", handle);
+	trace_jbd2_handle_stats(journal->j_fs_dev->bd_dev,
+				handle->h_transaction->t_tid,
+				handle->h_type, handle->h_line_no,
+				jiffies - handle->h_start_jiffies,
+				handle->h_sync, handle->h_requested_credits,
+				(handle->h_requested_credits -
+				 handle->h_buffer_credits));
 
 	/*
 	 * Implement synchronous transaction batching.  If the handle

include/linux/jbd2.h

···
 	unsigned int	h_sync:		1;	/* sync-on-close */
 	unsigned int	h_jdata:	1;	/* force data journaling */
 	unsigned int	h_aborted:	1;	/* fatal error on handle */
+	unsigned int	h_type:		8;	/* for handle statistics */
+	unsigned int	h_line_no:	16;	/* for handle statistics */
+
+	unsigned long		h_start_jiffies;
+	unsigned int		h_requested_credits;
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 	struct lockdep_map	h_lockdep_map;
···
  */
 
 extern handle_t *jbd2_journal_start(journal_t *, int nblocks);
-extern handle_t *jbd2__journal_start(journal_t *, int nblocks, gfp_t gfp_mask);
+extern handle_t *jbd2__journal_start(journal_t *, int nblocks, gfp_t gfp_mask,
+				     unsigned int type, unsigned int line_no);
 extern int	 jbd2_journal_restart(handle_t *, int nblocks);
 extern int	 jbd2__journal_restart(handle_t *, int nblocks, gfp_t gfp_mask);
 extern int	 jbd2_journal_extend (handle_t *, int nblocks);

include/trace/events/jbd2.h

···
 		  (unsigned long) __entry->ino)
 );
 
+TRACE_EVENT(jbd2_handle_start,
+	TP_PROTO(dev_t dev, unsigned long tid, unsigned int type,
+		 unsigned int line_no, int requested_blocks),
+
+	TP_ARGS(dev, tid, type, line_no, requested_blocks),
+
+	TP_STRUCT__entry(
+		__field(		dev_t,	dev		)
+		__field(	unsigned long,	tid		)
+		__field(	 unsigned int,	type		)
+		__field(	 unsigned int,	line_no		)
+		__field(		  int,	requested_blocks)
+	),
+
+	TP_fast_assign(
+		__entry->dev		  = dev;
+		__entry->tid		  = tid;
+		__entry->type		  = type;
+		__entry->line_no	  = line_no;
+		__entry->requested_blocks = requested_blocks;
+	),
+
+	TP_printk("dev %d,%d tid %lu type %u line_no %u "
+		  "requested_blocks %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->tid,
+		  __entry->type, __entry->line_no, __entry->requested_blocks)
+);
+
+TRACE_EVENT(jbd2_handle_extend,
+	TP_PROTO(dev_t dev, unsigned long tid, unsigned int type,
+		 unsigned int line_no, int buffer_credits,
+		 int requested_blocks),
+
+	TP_ARGS(dev, tid, type, line_no, buffer_credits, requested_blocks),
+
+	TP_STRUCT__entry(
+		__field(		dev_t,	dev		)
+		__field(	unsigned long,	tid		)
+		__field(	 unsigned int,	type		)
+		__field(	 unsigned int,	line_no		)
+		__field(		  int,	buffer_credits  )
+		__field(		  int,	requested_blocks)
+	),
+
+	TP_fast_assign(
+		__entry->dev		  = dev;
+		__entry->tid		  = tid;
+		__entry->type		  = type;
+		__entry->line_no	  = line_no;
+		__entry->buffer_credits   = buffer_credits;
+		__entry->requested_blocks = requested_blocks;
+	),
+
+	TP_printk("dev %d,%d tid %lu type %u line_no %u "
+		  "buffer_credits %d requested_blocks %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->tid,
+		  __entry->type, __entry->line_no, __entry->buffer_credits,
+		  __entry->requested_blocks)
+);
+
+TRACE_EVENT(jbd2_handle_stats,
+	TP_PROTO(dev_t dev, unsigned long tid, unsigned int type,
+		 unsigned int line_no, int interval, int sync,
+		 int requested_blocks, int dirtied_blocks),
+
+	TP_ARGS(dev, tid, type, line_no, interval, sync,
+		requested_blocks, dirtied_blocks),
+
+	TP_STRUCT__entry(
+		__field(		dev_t,	dev		)
+		__field(	unsigned long,	tid		)
+		__field(	 unsigned int,	type		)
+		__field(	 unsigned int,	line_no		)
+		__field(		  int,	interval	)
+		__field(		  int,	sync		)
+		__field(		  int,	requested_blocks)
+		__field(		  int,	dirtied_blocks	)
+	),
+
+	TP_fast_assign(
+		__entry->dev		  = dev;
+		__entry->tid		  = tid;
+		__entry->type		  = type;
+		__entry->line_no	  = line_no;
+		__entry->interval	  = interval;
+		__entry->sync		  = sync;
+		__entry->requested_blocks = requested_blocks;
+		__entry->dirtied_blocks	  = dirtied_blocks;
+	),
+
+	TP_printk("dev %d,%d tid %lu type %u line_no %u interval %d "
+		  "sync %d requested_blocks %d dirtied_blocks %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->tid,
+		  __entry->type, __entry->line_no, __entry->interval,
+		  __entry->sync, __entry->requested_blocks,
+		  __entry->dirtied_blocks)
+);
+
 TRACE_EVENT(jbd2_run_stats,
 	TP_PROTO(dev_t dev, unsigned long tid,
 		 struct transaction_run_stats_s *stats),