BACKPORT: block: use standard blktrace API to output cgroup info for debug notes

Currently cfq/bfq/blk-throttle output cgroup info in trace in their own
way. Now we have standard blktrace API for this, so convert them to use
it.

Note, this changes the behavior a little bit. cgroup info isn't output
by default, we only do this with 'blk_cgroup' option enabled. cgroup
info isn't output as a string by default too, we only do this with
'blk_cgname' option enabled. Also cgroup info is output in different
position of the note string. I think these behavior changes aren't a big
issue (actually we make trace data shorter which is good), since the
blktrace note is solely for debugging.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sorayukii <sorayukii69@gmail.com>

block/blk-throttle.c

@@ -215,10 +215,8 @@ static struct throtl_data *sq_to_td(struct throtl_service_queue *sq)
 	if (likely(!blk_trace_note_message_enabled(__td->queue)))	\
 		break;							\
 	if ((__tg)) {							\
-		char __pbuf[128];					\
-									\
-		blkg_path(tg_to_blkg(__tg), __pbuf, sizeof(__pbuf));	\
-		blk_add_trace_msg(__td->queue, "throtl %s " fmt, __pbuf, ##args); \
+		blk_add_cgroup_trace_msg(__td->queue,			\
+			tg_to_blkg(__tg)->blkcg, "throtl " fmt, ##args);\
 	} else {							\
 		blk_add_trace_msg(__td->queue, "throtl " fmt, ##args);	\
 	}								\

block/cfq-iosched.c

@@ -656,20 +656,17 @@ static inline void cfqg_put(struct cfq_group *cfqg)
 }
 
 #define cfq_log_cfqq(cfqd, cfqq, fmt, args...)	do {			\
-	char __pbuf[128];						\
-									\
-	blkg_path(cfqg_to_blkg((cfqq)->cfqg), __pbuf, sizeof(__pbuf));	\
-	blk_add_trace_msg((cfqd)->queue, "cfq%d%c%c %s " fmt, (cfqq)->pid, \
+	blk_add_cgroup_trace_msg((cfqd)->queue,				\
+			cfqg_to_blkg((cfqq)->cfqg)->blkcg,		\
+			"cfq%d%c%c " fmt, (cfqq)->pid,			\
 			cfq_cfqq_sync((cfqq)) ? 'S' : 'A',		\
 			cfqq_type((cfqq)) == SYNC_NOIDLE_WORKLOAD ? 'N' : ' ',\
-			  __pbuf, ##args);				\
+			  ##args);					\
 } while (0)
 
 #define cfq_log_cfqg(cfqd, cfqg, fmt, args...)	do {			\
-	char __pbuf[128];						\
-									\
-	blkg_path(cfqg_to_blkg(cfqg), __pbuf, sizeof(__pbuf));		\
-	blk_add_trace_msg((cfqd)->queue, "%s " fmt, __pbuf, ##args);	\
+	blk_add_cgroup_trace_msg((cfqd)->queue,				\
+			cfqg_to_blkg(cfqg)->blkcg, fmt, ##args);	\
 } while (0)
 
 static inline void cfqg_stats_update_io_add(struct cfq_group *cfqg,

include/linux/blktrace_api.h

@@ -28,13 +28,15 @@ struct blk_trace {
 	atomic_t dropped;
 };
 
+struct blkcg;
+
 extern int blk_trace_ioctl(struct block_device *, unsigned, char __user *);
 extern void blk_trace_shutdown(struct request_queue *);
 extern int do_blk_trace_setup(struct request_queue *q, char *name,
 			      dev_t dev, struct block_device *bdev,
 			      struct blk_user_trace_setup *buts);
-extern __printf(2, 3)
-void __trace_note_message(struct blk_trace *, const char *fmt, ...);
+extern __printf(3, 4)
+void __trace_note_message(struct blk_trace *, struct blkcg *blkcg, const char *fmt, ...);
 
 /**
  * blk_add_trace_msg - Add a (simple) message to the blktrace stream
@@ -49,16 +51,18 @@ void __trace_note_message(struct blk_trace *, const char *fmt, ...);
  *     NOTE: Can not use 'static inline' due to presence of var args...
  *
  **/
-#define blk_add_trace_msg(q, fmt, ...)					\
+#define blk_add_cgroup_trace_msg(q, cg, fmt, ...)			\
 	do {								\
 		struct blk_trace *bt;					\
 									\
 		rcu_read_lock();					\
 		bt = rcu_dereference((q)->blk_trace);			\
 		if (unlikely(bt))					\
-			__trace_note_message(bt, fmt, ##__VA_ARGS__);	\
+			__trace_note_message(bt, cg, fmt, ##__VA_ARGS__);\
 		rcu_read_unlock();					\
 	} while (0)
+#define blk_add_trace_msg(q, fmt, ...)					\
+	blk_add_cgroup_trace_msg(q, NULL, fmt, ##__VA_ARGS__)
 #define BLK_TN_MAX_MSG		128
 
 static inline bool blk_trace_note_message_enabled(struct request_queue *q)
@@ -94,6 +98,7 @@ extern struct attribute_group blk_trace_attr_group;
 # define blk_trace_startstop(q, start)			(-ENOTTY)
 # define blk_trace_remove(q)				(-ENOTTY)
 # define blk_add_trace_msg(q, fmt, ...)			do { } while (0)
+# define blk_add_cgroup_trace_msg(q, cg, fmt, ...)	do { } while (0)
 # define blk_trace_remove_sysfs(dev)			do { } while (0)
 # define blk_trace_note_message_enabled(q)		(false)
 static inline int blk_trace_init_sysfs(struct device *dev)

kernel/trace/blktrace.c

@@ -156,7 +156,8 @@ static void trace_note_time(struct blk_trace *bt)
 	local_irq_restore(flags);
 }
 
-void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
+void __trace_note_message(struct blk_trace *bt, struct blkcg *blkcg,
+	const char *fmt, ...)
 {
 	int n;
 	va_list args;
@@ -180,7 +181,14 @@ void __trace_note_message(struct blk_trace *bt, const char *fmt, ...)
 	n = vscnprintf(buf, BLK_TN_MAX_MSG, fmt, args);
 	va_end(args);
 
+	if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))
+		blkcg = NULL;
+#ifdef CONFIG_BLK_CGROUP
+	trace_note(bt, 0, BLK_TN_MESSAGE, buf, n,
+		blkcg ? cgroup_get_kernfs_id(blkcg->css.cgroup) : NULL);
+#else
 	trace_note(bt, 0, BLK_TN_MESSAGE, buf, n, NULL);
+#endif
 	local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(__trace_note_message);
@@ -407,7 +415,7 @@ static ssize_t blk_msg_write(struct file *filp, const char __user *buffer,
 		return PTR_ERR(msg);
 
 	bt = filp->private_data;
-	__trace_note_message(bt, "%s", msg);
+	__trace_note_message(bt, NULL, "%s", msg);
 	kfree(msg);
 
 	return count;