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Date:	Sun, 01 Jul 2007 03:38:10 -0400
From:	Mingming Cao <cmm@...ibm.com>
To:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-ext4@...r.kernel.org
Subject: [EXT4 set 6][PATCH 1/1]Export jbd stats through procfs

[PATCH] jbd2 stats through procfs

The patch below updates the jbd stats patch to 2.6.20/jbd2.
The initial patch was posted by Alex Tomas in December 2005
(http://marc.info/?l=linux-ext4&m=113538565128617&w=2).
It provides statistics via procfs such as transaction lifetime and size.

[ This probably should be rewritten to use debugfs?   -- Ted]

Signed-off-by: Johann Lombardi <johann.lombardi@...l.net>
--

Index: linux-2.6.22-rc4/include/linux/jbd2.h
===================================================================
--- linux-2.6.22-rc4.orig/include/linux/jbd2.h	2007-06-11 17:28:17.000000000 -0700
+++ linux-2.6.22-rc4/include/linux/jbd2.h	2007-06-13 10:45:21.000000000 -0700
@@ -408,6 +408,16 @@
 };
 
 
+/*
+ * Some stats for checkpoint phase
+ */
+struct transaction_chp_stats_s {
+	unsigned long		cs_chp_time;
+	unsigned long		cs_forced_to_close;
+	unsigned long		cs_written;
+	unsigned long		cs_dropped;
+};
+
 /* The transaction_t type is the guts of the journaling mechanism.  It
  * tracks a compound transaction through its various states:
  *
@@ -543,6 +553,21 @@
 	spinlock_t		t_handle_lock;
 
 	/*
+	 * Longest time some handle had to wait for running transaction
+	 */
+	unsigned long		t_max_wait;
+
+	/*
+	 * When transaction started
+	 */
+	unsigned long		t_start;
+
+	/*
+	 * Checkpointing stats [j_checkpoint_sem]
+	 */
+	struct transaction_chp_stats_s t_chp_stats;
+
+	/*
 	 * Number of outstanding updates running on this transaction
 	 * [t_handle_lock]
 	 */
@@ -573,6 +598,57 @@
 
 };
 
+struct transaction_run_stats_s {
+	unsigned long		rs_wait;
+	unsigned long		rs_running;
+	unsigned long		rs_locked;
+	unsigned long		rs_flushing;
+	unsigned long		rs_logging;
+
+	unsigned long		rs_handle_count;
+	unsigned long		rs_blocks;
+	unsigned long		rs_blocks_logged;
+};
+
+struct transaction_stats_s
+{
+	int 			ts_type;
+	unsigned long		ts_tid;
+	union {
+		struct transaction_run_stats_s run;
+		struct transaction_chp_stats_s chp;
+	} u;
+};
+
+#define JBD2_STATS_RUN		1
+#define JBD2_STATS_CHECKPOINT	2
+
+#define ts_wait			u.run.rs_wait
+#define ts_running		u.run.rs_running
+#define ts_locked		u.run.rs_locked
+#define ts_flushing		u.run.rs_flushing
+#define ts_logging		u.run.rs_logging
+#define ts_handle_count		u.run.rs_handle_count
+#define ts_blocks		u.run.rs_blocks
+#define ts_blocks_logged	u.run.rs_blocks_logged
+
+#define ts_chp_time		u.chp.cs_chp_time
+#define ts_forced_to_close	u.chp.cs_forced_to_close
+#define ts_written		u.chp.cs_written
+#define ts_dropped		u.chp.cs_dropped
+
+#define CURRENT_MSECS		(jiffies_to_msecs(jiffies))
+
+static inline unsigned int
+jbd2_time_diff(unsigned int start, unsigned int end)
+{
+	if (unlikely(start > end))
+		end = end + (~0UL - start);
+	else
+		end -= start;
+	return end;
+}
+
 /**
  * struct journal_s - The journal_s type is the concrete type associated with
  *     journal_t.
@@ -634,6 +710,12 @@
  * @j_wbufsize: maximum number of buffer_heads allowed in j_wbuf, the
  *	number that will fit in j_blocksize
  * @j_last_sync_writer: most recent pid which did a synchronous write
+ * @j_history: Buffer storing the transactions statistics history
+ * @j_history_max: Maximum number of transactions in the statistics history
+ * @j_history_cur: Current number of transactions in the statistics history
+ * @j_history_lock: Protect the transactions statistics history
+ * @j_proc_entry: procfs entry for the jbd statistics directory
+ * @j_stats: Overall statistics
  * @j_private: An opaque pointer to fs-private information.
  */
 
@@ -826,6 +908,16 @@
 	pid_t			j_last_sync_writer;
 
 	/*
+	 * Journal statistics
+	 */
+	struct transaction_stats_s *j_history;
+	int			j_history_max;
+	int			j_history_cur;
+	spinlock_t		j_history_lock;
+	struct proc_dir_entry	*j_proc_entry;
+	struct transaction_stats_s j_stats;
+
+	/*
 	 * An opaque pointer to fs-private information.  ext3 puts its
 	 * superblock pointer here
 	 */
Index: linux-2.6.22-rc4/fs/jbd2/transaction.c
===================================================================
--- linux-2.6.22-rc4.orig/fs/jbd2/transaction.c	2007-06-11 17:22:14.000000000 -0700
+++ linux-2.6.22-rc4/fs/jbd2/transaction.c	2007-06-13 10:47:56.000000000 -0700
@@ -59,6 +59,8 @@
 
 	J_ASSERT(journal->j_running_transaction == NULL);
 	journal->j_running_transaction = transaction;
+	transaction->t_max_wait = 0;
+	transaction->t_start = CURRENT_MSECS;
 
 	return transaction;
 }
@@ -85,6 +87,7 @@
 	int nblocks = handle->h_buffer_credits;
 	transaction_t *new_transaction = NULL;
 	int ret = 0;
+	unsigned long ts = CURRENT_MSECS;
 
 	if (nblocks > journal->j_max_transaction_buffers) {
 		printk(KERN_ERR "JBD: %s wants too many credits (%d > %d)\n",
@@ -218,6 +221,12 @@
 	/* OK, account for the buffers that this operation expects to
 	 * use and add the handle to the running transaction. */
 
+	if (time_after(transaction->t_start, ts)) {
+		ts = jbd2_time_diff(ts, transaction->t_start);
+		if (ts > transaction->t_max_wait)
+			transaction->t_max_wait = ts;
+	}
+
 	handle->h_transaction = transaction;
 	transaction->t_outstanding_credits += nblocks;
 	transaction->t_updates++;
Index: linux-2.6.22-rc4/fs/jbd2/checkpoint.c
===================================================================
--- linux-2.6.22-rc4.orig/fs/jbd2/checkpoint.c	2007-06-11 17:22:14.000000000 -0700
+++ linux-2.6.22-rc4/fs/jbd2/checkpoint.c	2007-06-13 10:48:44.000000000 -0700
@@ -232,7 +232,8 @@
  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  */
 static int __process_buffer(journal_t *journal, struct journal_head *jh,
-			struct buffer_head **bhs, int *batch_count)
+			struct buffer_head **bhs, int *batch_count,
+			transaction_t *transaction)
 {
 	struct buffer_head *bh = jh2bh(jh);
 	int ret = 0;
@@ -250,6 +251,7 @@
 		transaction_t *t = jh->b_transaction;
 		tid_t tid = t->t_tid;
 
+		transaction->t_chp_stats.cs_forced_to_close++;
 		spin_unlock(&journal->j_list_lock);
 		jbd_unlock_bh_state(bh);
 		jbd2_log_start_commit(journal, tid);
@@ -279,6 +281,7 @@
 		bhs[*batch_count] = bh;
 		__buffer_relink_io(jh);
 		jbd_unlock_bh_state(bh);
+		transaction->t_chp_stats.cs_written++;
 		(*batch_count)++;
 		if (*batch_count == NR_BATCH) {
 			spin_unlock(&journal->j_list_lock);
@@ -322,6 +325,8 @@
 	if (!journal->j_checkpoint_transactions)
 		goto out;
 	transaction = journal->j_checkpoint_transactions;
+	if (transaction->t_chp_stats.cs_chp_time == 0)
+		transaction->t_chp_stats.cs_chp_time = CURRENT_MSECS;
 	this_tid = transaction->t_tid;
 restart:
 	/*
@@ -346,7 +351,8 @@
 				retry = 1;
 				break;
 			}
-			retry = __process_buffer(journal, jh, bhs,&batch_count);
+			retry = __process_buffer(journal, jh, bhs, &batch_count,
+						 transaction);
 			if (!retry && lock_need_resched(&journal->j_list_lock)){
 				spin_unlock(&journal->j_list_lock);
 				retry = 1;
@@ -668,6 +674,8 @@
 
 void __jbd2_journal_drop_transaction(journal_t *journal, transaction_t *transaction)
 {
+	struct transaction_stats_s stats;
+
 	assert_spin_locked(&journal->j_list_lock);
 	if (transaction->t_cpnext) {
 		transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
@@ -693,5 +701,26 @@
 	J_ASSERT(journal->j_running_transaction != transaction);
 
 	jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
+
+	/*
+	 * File the transaction for history
+	 */
+	if (transaction->t_chp_stats.cs_written != 0 ||
+			transaction->t_chp_stats.cs_chp_time != 0) {
+		stats.ts_type = JBD2_STATS_CHECKPOINT;
+		stats.ts_tid = transaction->t_tid;
+		stats.u.chp = transaction->t_chp_stats;
+		if (stats.ts_chp_time)
+			stats.ts_chp_time =
+				jbd2_time_diff(stats.ts_chp_time,
+						CURRENT_MSECS);
+		spin_lock(&journal->j_history_lock);
+		memcpy(journal->j_history + journal->j_history_cur, &stats,
+				sizeof(stats));
+		if (++journal->j_history_cur == journal->j_history_max)
+			journal->j_history_cur = 0;
+		spin_unlock(&journal->j_history_lock);
+	}
+
 	kfree(transaction);
 }
Index: linux-2.6.22-rc4/fs/jbd2/commit.c
===================================================================
--- linux-2.6.22-rc4.orig/fs/jbd2/commit.c	2007-06-11 17:22:14.000000000 -0700
+++ linux-2.6.22-rc4/fs/jbd2/commit.c	2007-06-13 10:45:21.000000000 -0700
@@ -20,6 +20,7 @@
 #include <linux/slab.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
+#include <linux/jiffies.h>
 
 /*
  * Default IO end handler for temporary BJ_IO buffer_heads.
@@ -290,6 +291,7 @@
  */
 void jbd2_journal_commit_transaction(journal_t *journal)
 {
+	struct transaction_stats_s stats;
 	transaction_t *commit_transaction;
 	struct journal_head *jh, *new_jh, *descriptor;
 	struct buffer_head **wbuf = journal->j_wbuf;
@@ -337,6 +339,11 @@
 	spin_lock(&journal->j_state_lock);
 	commit_transaction->t_state = T_LOCKED;
 
+	stats.ts_wait = commit_transaction->t_max_wait;
+	stats.ts_locked = CURRENT_MSECS;
+	stats.ts_running = jbd2_time_diff(commit_transaction->t_start,
+						stats.ts_locked);
+
 	spin_lock(&commit_transaction->t_handle_lock);
 	while (commit_transaction->t_updates) {
 		DEFINE_WAIT(wait);
@@ -407,6 +414,9 @@
 	 */
 	jbd2_journal_switch_revoke_table(journal);
 
+	stats.ts_flushing = CURRENT_MSECS;
+	stats.ts_locked = jbd2_time_diff(stats.ts_locked, stats.ts_flushing);
+
 	commit_transaction->t_state = T_FLUSH;
 	journal->j_committing_transaction = commit_transaction;
 	journal->j_running_transaction = NULL;
@@ -498,6 +508,11 @@
 	 */
 	commit_transaction->t_state = T_COMMIT;
 
+	stats.ts_logging = CURRENT_MSECS;
+	stats.ts_flushing = jbd2_time_diff(stats.ts_flushing, stats.ts_logging);
+	stats.ts_blocks = commit_transaction->t_outstanding_credits;
+	stats.ts_blocks_logged = 0;
+
 	descriptor = NULL;
 	bufs = 0;
 	while (commit_transaction->t_buffers) {
@@ -646,6 +661,7 @@
 				submit_bh(WRITE, bh);
 			}
 			cond_resched();
+			stats.ts_blocks_logged += bufs;
 
 			/* Force a new descriptor to be generated next
                            time round the loop. */
@@ -816,6 +832,7 @@
 		cp_transaction = jh->b_cp_transaction;
 		if (cp_transaction) {
 			JBUFFER_TRACE(jh, "remove from old cp transaction");
+			cp_transaction->t_chp_stats.cs_dropped++;
 			__jbd2_journal_remove_checkpoint(jh);
 		}
 
@@ -890,6 +907,36 @@
 
 	J_ASSERT(commit_transaction->t_state == T_COMMIT);
 
+	commit_transaction->t_start = CURRENT_MSECS;
+	stats.ts_logging = jbd2_time_diff(stats.ts_logging,
+						commit_transaction->t_start);
+
+	/*
+	 * File the transaction for history
+	 */
+	stats.ts_type = JBD2_STATS_RUN;
+	stats.ts_tid = commit_transaction->t_tid;
+	stats.ts_handle_count = commit_transaction->t_handle_count;
+	spin_lock(&journal->j_history_lock);
+	memcpy(journal->j_history + journal->j_history_cur, &stats,
+			sizeof(stats));
+	if (++journal->j_history_cur == journal->j_history_max)
+		journal->j_history_cur = 0;
+
+	/*
+	 * Calculate overall stats
+	 */
+	journal->j_stats.ts_tid++;
+	journal->j_stats.ts_wait += stats.ts_wait;
+	journal->j_stats.ts_running += stats.ts_running;
+	journal->j_stats.ts_locked += stats.ts_locked;
+	journal->j_stats.ts_flushing += stats.ts_flushing;
+	journal->j_stats.ts_logging += stats.ts_logging;
+	journal->j_stats.ts_handle_count += stats.ts_handle_count;
+	journal->j_stats.ts_blocks += stats.ts_blocks;
+	journal->j_stats.ts_blocks_logged += stats.ts_blocks_logged;
+	spin_unlock(&journal->j_history_lock);
+
 	commit_transaction->t_state = T_FINISHED;
 	J_ASSERT(commit_transaction == journal->j_committing_transaction);
 	journal->j_commit_sequence = commit_transaction->t_tid;
Index: linux-2.6.22-rc4/fs/jbd2/journal.c
===================================================================
--- linux-2.6.22-rc4.orig/fs/jbd2/journal.c	2007-06-11 17:28:17.000000000 -0700
+++ linux-2.6.22-rc4/fs/jbd2/journal.c	2007-06-13 12:11:49.000000000 -0700
@@ -36,6 +36,7 @@
 #include <linux/poison.h>
 #include <linux/proc_fs.h>
 #include <linux/debugfs.h>
+#include <linux/seq_file.h>
 
 #include <asm/uaccess.h>
 #include <asm/page.h>
@@ -641,6 +642,306 @@
 	return jbd2_journal_add_journal_head(bh);
 }
 
+struct jbd2_stats_proc_session {
+	journal_t *journal;
+	struct transaction_stats_s *stats;
+	int start;
+	int max;
+};
+
+static void *jbd2_history_skip_empty(struct jbd2_stats_proc_session *s,
+					struct transaction_stats_s *ts,
+					int first)
+{
+	if (ts == s->stats + s->max)
+		ts = s->stats;
+	if (!first && ts == s->stats + s->start)
+		return NULL;
+	while (ts->ts_type == 0) {
+		ts++;
+		if (ts == s->stats + s->max)
+			ts = s->stats;
+		if (ts == s->stats + s->start)
+			return NULL;
+	}
+	return ts;
+
+}
+
+static void *jbd2_seq_history_start(struct seq_file *seq, loff_t *pos)
+{
+	struct jbd2_stats_proc_session *s = seq->private;
+	struct transaction_stats_s *ts;
+	int l = *pos;
+
+	if (l == 0)
+		return SEQ_START_TOKEN;
+	ts = jbd2_history_skip_empty(s, s->stats + s->start, 1);
+	if (!ts)
+		return NULL;
+	l--;
+	while (l) {
+		ts = jbd2_history_skip_empty(s, ++ts, 0);
+		if (!ts)
+			break;
+		l--;
+	}
+	return ts;
+}
+
+static void *jbd2_seq_history_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct jbd2_stats_proc_session *s = seq->private;
+	struct transaction_stats_s *ts = v;
+
+	++*pos;
+	if (v == SEQ_START_TOKEN)
+		return jbd2_history_skip_empty(s, s->stats + s->start, 1);
+	else
+		return jbd2_history_skip_empty(s, ++ts, 0);
+}
+
+static int jbd2_seq_history_show(struct seq_file *seq, void *v)
+{
+	struct transaction_stats_s *ts = v;
+	if (v == SEQ_START_TOKEN) {
+		seq_printf(seq, "%-4s %-5s %-5s %-5s %-5s %-5s %-5s %-6s %-5s "
+				"%-5s %-5s %-5s %-5s %-5s\n", "R/C", "tid",
+				"wait", "run", "lock", "flush", "log", "hndls",
+				"block", "inlog", "ctime", "write", "drop",
+				"close");
+		return 0;
+	}
+	if (ts->ts_type == JBD2_STATS_RUN)
+		seq_printf(seq, "%-4s %-5lu %-5lu %-5lu %-5lu %-5lu %-5lu "
+				"%-6lu %-5lu %-5lu\n", "R", ts->ts_tid,
+				ts->ts_wait, ts->ts_running, ts->ts_locked,
+				ts->ts_flushing, ts->ts_logging,
+				ts->ts_handle_count, ts->ts_blocks,
+				ts->ts_blocks_logged);
+	else if (ts->ts_type == JBD2_STATS_CHECKPOINT)
+		seq_printf(seq, "%-4s %-5lu %48s %-5lu %-5lu %-5lu %-5lu\n",
+				"C", ts->ts_tid, " ", ts->ts_chp_time,
+				ts->ts_written, ts->ts_dropped,
+				ts->ts_forced_to_close);
+	else
+		J_ASSERT(0);
+	return 0;
+}
+
+static void jbd2_seq_history_stop(struct seq_file *seq, void *v)
+{
+}
+
+static struct seq_operations jbd2_seq_history_ops = {
+	.start  = jbd2_seq_history_start,
+	.next   = jbd2_seq_history_next,
+	.stop   = jbd2_seq_history_stop,
+	.show   = jbd2_seq_history_show,
+};
+
+static int jbd2_seq_history_open(struct inode *inode, struct file *file)
+{
+	journal_t *journal = PDE(inode)->data;
+	struct jbd2_stats_proc_session *s;
+	int rc, size;
+
+	s = kmalloc(sizeof(*s), GFP_KERNEL);
+	if (s == NULL)
+		return -EIO;
+	size = sizeof(struct transaction_stats_s) * journal->j_history_max;
+	s->stats = kmalloc(size, GFP_KERNEL);
+	if (s == NULL) {
+		kfree(s);
+		return -EIO;
+	}
+	spin_lock(&journal->j_history_lock);
+	memcpy(s->stats, journal->j_history, size);
+	s->max = journal->j_history_max;
+	s->start = journal->j_history_cur % s->max;
+	spin_unlock(&journal->j_history_lock);
+
+	rc = seq_open(file, &jbd2_seq_history_ops);
+	if (rc == 0) {
+		struct seq_file *m = (struct seq_file *)file->private_data;
+		m->private = s;
+	} else {
+		kfree(s->stats);
+		kfree(s);
+	}
+	return rc;
+
+}
+
+static int jbd2_seq_history_release(struct inode *inode, struct file *file)
+{
+	struct seq_file *seq = (struct seq_file *)file->private_data;
+	struct jbd2_stats_proc_session *s = seq->private;
+	kfree(s->stats);
+	kfree(s);
+	return seq_release(inode, file);
+}
+
+static struct file_operations jbd2_seq_history_fops = {
+	.owner		= THIS_MODULE,
+	.open           = jbd2_seq_history_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = jbd2_seq_history_release,
+};
+
+static void *jbd2_seq_info_start(struct seq_file *seq, loff_t *pos)
+{
+	return *pos ? NULL : SEQ_START_TOKEN;
+}
+
+static void *jbd2_seq_info_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	return NULL;
+}
+
+static int jbd2_seq_info_show(struct seq_file *seq, void *v)
+{
+	struct jbd2_stats_proc_session *s = seq->private;
+	if (v != SEQ_START_TOKEN)
+		return 0;
+	seq_printf(seq, "%lu transaction, each upto %u blocks\n",
+			s->stats->ts_tid,
+			s->journal->j_max_transaction_buffers);
+	if (s->stats->ts_tid == 0)
+		return 0;
+	seq_printf(seq, "average: \n  %lums waiting for transaction\n",
+			s->stats->ts_wait / s->stats->ts_tid);
+	seq_printf(seq, "  %lums running transaction\n",
+			s->stats->ts_running / s->stats->ts_tid);
+	seq_printf(seq, "  %lums transaction was being locked\n",
+			s->stats->ts_locked / s->stats->ts_tid);
+	seq_printf(seq, "  %lums flushing data (in ordered mode)\n",
+			s->stats->ts_flushing / s->stats->ts_tid);
+	seq_printf(seq, "  %lums logging transaction\n",
+			s->stats->ts_logging / s->stats->ts_tid);
+	seq_printf(seq, "  %lu handles per transaction\n",
+			s->stats->ts_handle_count / s->stats->ts_tid);
+	seq_printf(seq, "  %lu blocks per transaction\n",
+			s->stats->ts_blocks / s->stats->ts_tid);
+	seq_printf(seq, "  %lu logged blocks per transaction\n",
+			s->stats->ts_blocks_logged / s->stats->ts_tid);
+	return 0;
+}
+
+static void jbd2_seq_info_stop(struct seq_file *seq, void *v)
+{
+}
+
+static struct seq_operations jbd2_seq_info_ops = {
+	.start  = jbd2_seq_info_start,
+	.next   = jbd2_seq_info_next,
+	.stop   = jbd2_seq_info_stop,
+	.show   = jbd2_seq_info_show,
+};
+
+static int jbd2_seq_info_open(struct inode *inode, struct file *file)
+{
+	journal_t *journal = PDE(inode)->data;
+	struct jbd2_stats_proc_session *s;
+	int rc, size;
+
+	s = kmalloc(sizeof(*s), GFP_KERNEL);
+	if (s == NULL)
+		return -EIO;
+	size = sizeof(struct transaction_stats_s);
+	s->stats = kmalloc(size, GFP_KERNEL);
+	if (s == NULL) {
+		kfree(s);
+		return -EIO;
+	}
+	spin_lock(&journal->j_history_lock);
+	memcpy(s->stats, &journal->j_stats, size);
+	s->journal = journal;
+	spin_unlock(&journal->j_history_lock);
+
+	rc = seq_open(file, &jbd2_seq_info_ops);
+	if (rc == 0) {
+		struct seq_file *m = (struct seq_file *)file->private_data;
+		m->private = s;
+	} else {
+		kfree(s->stats);
+		kfree(s);
+	}
+	return rc;
+
+}
+
+static int jbd2_seq_info_release(struct inode *inode, struct file *file)
+{
+	struct seq_file *seq = (struct seq_file *)file->private_data;
+	struct jbd2_stats_proc_session *s = seq->private;
+	kfree(s->stats);
+	kfree(s);
+	return seq_release(inode, file);
+}
+
+static struct file_operations jbd2_seq_info_fops = {
+	.owner		= THIS_MODULE,
+	.open           = jbd2_seq_info_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = jbd2_seq_info_release,
+};
+
+static struct proc_dir_entry *proc_jbd2_stats = NULL;
+
+static void jbd2_stats_proc_init(journal_t *journal)
+{
+	char name[64];
+
+	snprintf(name, sizeof(name) - 1, "%s", bdevname(journal->j_dev, name));
+	journal->j_proc_entry = proc_mkdir(name, proc_jbd2_stats);
+	if (journal->j_proc_entry) {
+		struct proc_dir_entry *p;
+		p = create_proc_entry("history", S_IRUGO,
+				journal->j_proc_entry);
+		if (p) {
+			p->proc_fops = &jbd2_seq_history_fops;
+			p->data = journal;
+			p = create_proc_entry("info", S_IRUGO,
+						journal->j_proc_entry);
+			if (p) {
+				p->proc_fops = &jbd2_seq_info_fops;
+				p->data = journal;
+			}
+		}
+	}
+}
+
+static void jbd2_stats_proc_exit(journal_t *journal)
+{
+	char name[64];
+
+	snprintf(name, sizeof(name) - 1, "%s", bdevname(journal->j_dev, name));
+	remove_proc_entry("info", journal->j_proc_entry);
+	remove_proc_entry("history", journal->j_proc_entry);
+	remove_proc_entry(name, proc_jbd2_stats);
+}
+
+static void journal_init_stats(journal_t *journal)
+{
+	int size;
+
+	if (proc_jbd2_stats == NULL)
+		return;
+
+	journal->j_history_max = 100;
+	size = sizeof(struct transaction_stats_s) * journal->j_history_max;
+	journal->j_history = kmalloc(size, GFP_KERNEL);
+	if (journal->j_history == NULL) {
+		journal->j_history_max = 0;
+		return;
+	}
+	memset(journal->j_history, 0, size);
+	spin_lock_init(&journal->j_history_lock);
+}
+
 /*
  * Management for journal control blocks: functions to create and
  * destroy journal_t structures, and to initialise and read existing
@@ -683,6 +984,9 @@
 		kfree(journal);
 		goto fail;
 	}
+
+	journal_init_stats(journal);
+
 	return journal;
 fail:
 	return NULL;
@@ -733,6 +1037,7 @@
 		journal = NULL;
 		goto out;
 	}
+	jbd2_stats_proc_init(journal);
 	journal->j_dev = bdev;
 	journal->j_fs_dev = fs_dev;
 	journal->j_blk_offset = start;
@@ -775,6 +1080,7 @@
 
 	journal->j_maxlen = inode->i_size >> inode->i_sb->s_blocksize_bits;
 	journal->j_blocksize = inode->i_sb->s_blocksize;
+	jbd2_stats_proc_init(journal);
 
 	/* journal descriptor can store up to n blocks -bzzz */
 	n = journal->j_blocksize / sizeof(journal_block_tag_t);
@@ -1162,6 +1468,8 @@
 		brelse(journal->j_sb_buffer);
 	}
 
+	if (journal->j_proc_entry)
+		jbd2_stats_proc_exit(journal);
 	if (journal->j_inode)
 		iput(journal->j_inode);
 	if (journal->j_revoke)
@@ -1989,6 +2297,28 @@
 
 #endif
 
+#if defined(CONFIG_PROC_FS)
+
+#define JBD2_STATS_PROC_NAME "fs/jbd2"
+
+static void __init jbd2_create_jbd_stats_proc_entry(void)
+{
+	proc_jbd2_stats = proc_mkdir(JBD2_STATS_PROC_NAME, NULL);
+}
+
+static void __exit jbd2_remove_jbd_stats_proc_entry(void)
+{
+	if (proc_jbd2_stats)
+		remove_proc_entry(JBD2_STATS_PROC_NAME, NULL);
+}
+
+#else
+
+#define jbd2_create_jbd_stats_proc_entry() do {} while (0)
+#define jbd2_remove_jbd_stats_proc_entry() do {} while (0)
+
+#endif
+
 struct kmem_cache *jbd2_handle_cache;
 
 static int __init journal_init_handle_cache(void)
@@ -2046,6 +2376,7 @@
 	if (ret != 0)
 		jbd2_journal_destroy_caches();
 	jbd2_create_debugfs_entry();
+	jbd2_create_jbd_stats_proc_entry();
 	return ret;
 }
 
@@ -2057,6 +2388,7 @@
 		printk(KERN_EMERG "JBD: leaked %d journal_heads!\n", n);
 #endif
 	jbd2_remove_debugfs_entry();
+	jbd2_remove_jbd_stats_proc_entry();
 	jbd2_journal_destroy_caches();
 }
 


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