jbd2: remove jbd2_dev_to_name() from jbd2 tracepoints

Using function calls in TP_printk causes perf heartburn, so print the
MAJOR/MINOR device numbers instead.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/jbd2/journal.c

@@ -2390,73 +2390,6 @@ static void __exit journal_exit(void)
 	jbd2_journal_destroy_caches();
 }
 
-/* 
- * jbd2_dev_to_name is a utility function used by the jbd2 and ext4 
- * tracing infrastructure to map a dev_t to a device name.
- *
- * The caller should use rcu_read_lock() in order to make sure the
- * device name stays valid until its done with it.  We use
- * rcu_read_lock() as well to make sure we're safe in case the caller
- * gets sloppy, and because rcu_read_lock() is cheap and can be safely
- * nested.
- */
-struct devname_cache {
-	struct rcu_head	rcu;
-	dev_t		device;
-	char		devname[BDEVNAME_SIZE];
-};
-#define CACHE_SIZE_BITS 6
-static struct devname_cache *devcache[1 << CACHE_SIZE_BITS];
-static DEFINE_SPINLOCK(devname_cache_lock);
-
-static void free_devcache(struct rcu_head *rcu)
-{
-	kfree(rcu);
-}
-
-const char *jbd2_dev_to_name(dev_t device)
-{
-	int	i = hash_32(device, CACHE_SIZE_BITS);
-	char	*ret;
-	struct block_device *bd;
-	static struct devname_cache *new_dev;
-
-	rcu_read_lock();
-	if (devcache[i] && devcache[i]->device == device) {
-		ret = devcache[i]->devname;
-		rcu_read_unlock();
-		return ret;
-	}
-	rcu_read_unlock();
-
-	new_dev = kmalloc(sizeof(struct devname_cache), GFP_KERNEL);
-	if (!new_dev)
-		return "NODEV-ALLOCFAILURE"; /* Something non-NULL */
-	bd = bdget(device);
-	spin_lock(&devname_cache_lock);
-	if (devcache[i]) {
-		if (devcache[i]->device == device) {
-			kfree(new_dev);
-			bdput(bd);
-			ret = devcache[i]->devname;
-			spin_unlock(&devname_cache_lock);
-			return ret;
-		}
-		call_rcu(&devcache[i]->rcu, free_devcache);
-	}
-	devcache[i] = new_dev;
-	devcache[i]->device = device;
-	if (bd) {
-		bdevname(bd, devcache[i]->devname);
-		bdput(bd);
-	} else
-		__bdevname(device, devcache[i]->devname);
-	ret = devcache[i]->devname;
-	spin_unlock(&devname_cache_lock);
-	return ret;
-}
-EXPORT_SYMBOL(jbd2_dev_to_name);
-
 MODULE_LICENSE("GPL");
 module_init(journal_init);
 module_exit(journal_exit);

include/linux/jbd2.h

@@ -1329,12 +1329,6 @@ extern int jbd_blocks_per_page(struct inode *inode);
 #define BUFFER_TRACE2(bh, bh2, info)	do {} while (0)
 #define JBUFFER_TRACE(jh, info)	do {} while (0)
 
-/* 
- * jbd2_dev_to_name is a utility function used by the jbd2 and ext4 
- * tracing infrastructure to map a dev_t to a device name.
- */
-extern const char *jbd2_dev_to_name(dev_t device);
-
 #endif	/* __KERNEL__ */
 
 #endif	/* _LINUX_JBD2_H */

include/trace/events/jbd2.h

@@ -26,8 +26,8 @@ TRACE_EVENT(jbd2_checkpoint,
 		__entry->result		= result;
 	),
 
-	TP_printk("dev %s result %d",
-		  jbd2_dev_to_name(__entry->dev), __entry->result)
+	TP_printk("dev %d,%d result %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->result)
 );
 
 DECLARE_EVENT_CLASS(jbd2_commit,
@@ -48,9 +48,9 @@ DECLARE_EVENT_CLASS(jbd2_commit,
 		__entry->transaction	= commit_transaction->t_tid;
 	),
 
-	TP_printk("dev %s transaction %d sync %d",
-		  jbd2_dev_to_name(__entry->dev), __entry->transaction,
-		  __entry->sync_commit)
+	TP_printk("dev %d,%d transaction %d sync %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->transaction, __entry->sync_commit)
 );
 
 DEFINE_EVENT(jbd2_commit, jbd2_start_commit,
@@ -100,9 +100,9 @@ TRACE_EVENT(jbd2_end_commit,
 		__entry->head		= journal->j_tail_sequence;
 	),
 
-	TP_printk("dev %s transaction %d sync %d head %d",
-		  jbd2_dev_to_name(__entry->dev), __entry->transaction,
-		  __entry->sync_commit, __entry->head)
+	TP_printk("dev %d,%d transaction %d sync %d head %d",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->transaction, __entry->sync_commit, __entry->head)
 );
 
 TRACE_EVENT(jbd2_submit_inode_data,
@@ -120,8 +120,9 @@ TRACE_EVENT(jbd2_submit_inode_data,
 		__entry->ino	= inode->i_ino;
 	),
 
-	TP_printk("dev %s ino %lu",
-		  jbd2_dev_to_name(__entry->dev), (unsigned long) __entry->ino)
+	TP_printk("dev %d,%d ino %lu",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  (unsigned long) __entry->ino)
 );
 
 TRACE_EVENT(jbd2_run_stats,
@@ -156,9 +157,9 @@ TRACE_EVENT(jbd2_run_stats,
 		__entry->blocks_logged	= stats->rs_blocks_logged;
 	),
 
-	TP_printk("dev %s tid %lu wait %u running %u locked %u flushing %u "
+	TP_printk("dev %d,%d tid %lu wait %u running %u locked %u flushing %u "
 		  "logging %u handle_count %u blocks %u blocks_logged %u",
-		  jbd2_dev_to_name(__entry->dev), __entry->tid,
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->tid,
 		  jiffies_to_msecs(__entry->wait),
 		  jiffies_to_msecs(__entry->running),
 		  jiffies_to_msecs(__entry->locked),
@@ -192,9 +193,9 @@ TRACE_EVENT(jbd2_checkpoint_stats,
 		__entry->dropped	= stats->cs_dropped;
 	),
 
-	TP_printk("dev %s tid %lu chp_time %u forced_to_close %u "
+	TP_printk("dev %d,%d tid %lu chp_time %u forced_to_close %u "
 		  "written %u dropped %u",
-		  jbd2_dev_to_name(__entry->dev), __entry->tid,
+		  MAJOR(__entry->dev), MINOR(__entry->dev), __entry->tid,
 		  jiffies_to_msecs(__entry->chp_time),
 		  __entry->forced_to_close, __entry->written, __entry->dropped)
 );
@@ -222,9 +223,10 @@ TRACE_EVENT(jbd2_cleanup_journal_tail,
 		__entry->freed		= freed;
 	),
 
-	TP_printk("dev %s from %u to %u offset %lu freed %lu",
-		  jbd2_dev_to_name(__entry->dev), __entry->tail_sequence,
-		  __entry->first_tid, __entry->block_nr, __entry->freed)
+	TP_printk("dev %d,%d from %u to %u offset %lu freed %lu",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		  __entry->tail_sequence, __entry->first_tid,
+		  __entry->block_nr, __entry->freed)
 );
 
 #endif /* _TRACE_JBD2_H */