[PATCH 5/7] mm/vmalloc: Use a trace_purge_vmap_area_lazy event

["Uladzislau Rezki (Sony)" <urezki@xxxxxxxxx>]

This is for debug purpose and is called when all outstanding
areas are removed back to the vmap space. It gives some extra
information about:
- a start:end range where set of vmap ares were freed;
- a number of purged areas which were backed off.

Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
---
 mm/vmalloc.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index f4397817ccd7..912abcd6e8b4 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1731,6 +1731,7 @@ static void purge_fragmented_blocks_allcpus(void);
 static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
 {
 	unsigned long resched_threshold;
+	unsigned int num_purged_areas = 0;
 	struct list_head local_purge_list;
 	struct vmap_area *va, *n_va;
 
@@ -1742,7 +1743,7 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
 	spin_unlock(&purge_vmap_area_lock);
 
 	if (unlikely(list_empty(&local_purge_list)))
-		return false;
+		goto out;
 
 	start = min(start,
 		list_first_entry(&local_purge_list,
@@ -1777,12 +1778,16 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end)
 					      va->va_start, va->va_end);
 
 		atomic_long_sub(nr, &vmap_lazy_nr);
+		num_purged_areas++;
 
 		if (atomic_long_read(&vmap_lazy_nr) < resched_threshold)
 			cond_resched_lock(&free_vmap_area_lock);
 	}
 	spin_unlock(&free_vmap_area_lock);
-	return true;
+
+out:
+	trace_purge_vmap_area_lazy(start, end, num_purged_areas);
+	return num_purged_areas > 0 ? true:false;
 }
 
 /*
-- 
2.30.2