mm: vmalloc: use trace_free_vmap_area_noflush event

It is for debug purposes and is called when a vmap area gets freed.  This
event gives some indication about:

- a start address of released area;
- a current number of outstanding pages;
- a maximum number of allowed outstanding pages.

Link: https://lkml.kernel.org/r/20221018181053.434508-7-urezki@gmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Oleksiy Avramchenko <oleksiy.avramchenko@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/vmalloc.c

@@ -1821,6 +1821,8 @@ static void drain_vmap_area_work(struct work_struct *work)
  */
 static void free_vmap_area_noflush(struct vmap_area *va)
 {
+	unsigned long nr_lazy_max = lazy_max_pages();
+	unsigned long va_start = va->va_start;
 	unsigned long nr_lazy;
 
 	spin_lock(&vmap_area_lock);
@@ -1838,8 +1840,10 @@ static void free_vmap_area_noflush(struct vmap_area *va)
 		&purge_vmap_area_root, &purge_vmap_area_list);
 	spin_unlock(&purge_vmap_area_lock);
 
+	trace_free_vmap_area_noflush(va_start, nr_lazy, nr_lazy_max);
+
 	/* After this point, we may free va at any time */
-	if (unlikely(nr_lazy > lazy_max_pages()))
+	if (unlikely(nr_lazy > nr_lazy_max))
 		schedule_work(&drain_vmap_work);
 }