[PATCH V4 12/12] block: use standard blktrace API to output cgroup info for debug notes

Shaohua Li
2017-06-28T16:31:20Z

From: Shaohua Li <shli@fb.com>

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>
---
block/bfq-iosched.h | 13 ++++++++-----
block/blk-throttle.c | 6 ++----
block/cfq-iosched.c | 15 ++++++---------
include/linux/blktrace_api.h | 13 +++++++++----
kernel/trace/blktrace.c | 12 ++++++++++--
5 files changed, 35 insertions(+), 24 deletions(-)

diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 5c3bf98..ea6a6eb 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -916,13 +916,16 @@ void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq);
struct bfq_group *bfqq_group(struct bfq_queue *bfqq);

#define bfq_log_bfqq(bfqd, bfqq, fmt, args...) do { \
- blk_add_trace_msg((bfqd)->queue, "bfq%d%c %s " fmt, (bfqq)->pid,\
- bfq_bfqq_sync((bfqq)) ? 'S' : 'A', \
- bfqq_group(bfqq)->blkg_path, ##args); \
+ blk_add_cgroup_trace_msg((bfqd)->queue, \
+ bfqg_to_blkg(bfqq_group(bfqq))->blkcg, \
+ "bfq%d%c " fmt, (bfqq)->pid, \
+ bfq_bfqq_sync((bfqq)) ? 'S' : 'A', ##args); \
} while (0)

-#define bfq_log_bfqg(bfqd, bfqg, fmt, args...) \
- blk_add_trace_msg((bfqd)->queue, "%s " fmt, (bfqg)->blkg_path, ##args)
+#define bfq_log_bfqg(bfqd, bfqg, fmt, args...) do { \
+ blk_add_cgroup_trace_msg((bfqd)->queue, \
+ bfqg_to_blkg(bfqg)->blkcg, fmt, ##args); \
+} while (0)

#else /* CONFIG_BFQ_GROUP_IOSCHED */

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index a6ebd2b..6a4c4c4 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -373,10 +373,8 @@ static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
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); \
} \
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 3d5c289..0fb78fb 100644
--- a/block/cfq-iosched.c
+++ b/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,
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index d2e9085..67b4d4d 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -28,10 +28,12 @@ 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 __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
@@ -46,12 +48,14 @@ 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 = (q)->blk_trace; \
if (unlikely(bt)) \
- __trace_note_message(bt, fmt, ##__VA_ARGS__); \
+ __trace_note_message(bt, cg, fmt, ##__VA_ARGS__);\
} 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)
@@ -82,6 +86,7 @@ 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)
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index e90974e..7724de1 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -154,7 +154,8 @@ 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;
@@ -178,7 +179,14 @@ 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);
@@ -375,7 +383,7 @@ 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;
--
2.9.3