writeback: Add a 'reason' to wb_writeback_work

This creates a new 'reason' field in a wb_writeback_work
structure, which unambiguously identifies who initiates
writeback activity.  A 'wb_reason' enumeration has been
added to writeback.h, to enumerate the possible reasons.

The 'writeback_work_class' and tracepoint event class and
'writeback_queue_io' tracepoints are updated to include the
symbolic 'reason' in all trace events.

And the 'writeback_inodes_sbXXX' family of routines has had
a wb_stats parameter added to them, so callers can specify
why writeback is being started.

Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 1261db3916cc..b99caa8b780c 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -34,6 +34,7 @@ DECLARE_EVENT_CLASS(writeback_work_class,
                 __field(int, for_kupdate)
                 __field(int, range_cyclic)
                 __field(int, for_background)
+                __field(int, reason)
         ),
         TP_fast_assign(
                 strncpy(__entry->name, dev_name(bdi->dev), 32);
@@ -43,16 +44,18 @@ DECLARE_EVENT_CLASS(writeback_work_class,
                 __entry->for_kupdate = work->for_kupdate;
                 __entry->range_cyclic = work->range_cyclic;
                 __entry->for_background = work->for_background;
+                __entry->reason = work->reason;
         ),
         TP_printk("bdi %s: sb_dev %d:%d nr_pages=%ld sync_mode=%d "
-                  "kupdate=%d range_cyclic=%d background=%d",
+                  "kupdate=%d range_cyclic=%d background=%d reason=%s",
                   __entry->name,
                   MAJOR(__entry->sb_dev), MINOR(__entry->sb_dev),
                   __entry->nr_pages,
                   __entry->sync_mode,
                   __entry->for_kupdate,
                   __entry->range_cyclic,
-                  __entry->for_background
+                  __entry->for_background,
+                  wb_reason_name[__entry->reason]
         )
 );
 #define DEFINE_WRITEBACK_WORK_EVENT(name) \
@@ -165,6 +168,7 @@ TRACE_EVENT(writeback_queue_io,
                 __field(unsigned long,  older)
                 __field(long,           age)
                 __field(int,            moved)
+                __field(int,            reason)
         ),
         TP_fast_assign(
                 unsigned long *older_than_this = work->older_than_this;
@@ -173,12 +177,14 @@ TRACE_EVENT(writeback_queue_io,
                 __entry->age    = older_than_this ?
                                   (jiffies - *older_than_this) * 1000 / HZ : -1;
                 __entry->moved  = moved;
+                __entry->reason = work->reason;
         ),
-        TP_printk("bdi %s: older=%lu age=%ld enqueue=%d",
+        TP_printk("bdi %s: older=%lu age=%ld enqueue=%d reason=%s",
                 __entry->name,
                 __entry->older, /* older_than_this in jiffies */
                 __entry->age,   /* older_than_this in relative milliseconds */
-                __entry->moved)
+                __entry->moved,
+                wb_reason_name[__entry->reason])
 );
 
 TRACE_EVENT(global_dirty_state,