2 files changed, 38 insertions, 0 deletions

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index c80dea7c69af..b8ead8dc2ebe 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -551,6 +551,9 @@ int btrfs_add_extent_mapping(struct extent_map_tree *em_tree,
                 ret = 0;
 
                 existing = search_extent_mapping(em_tree, start, len);
+
+                trace_btrfs_handle_em_exist(existing, em, start, len);
+
                 /*
                  * existing will always be non-NULL, since there must be
                  * extent causing the -EEXIST.
diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h
index c3ac5ec86519..486771e3f4cb 100644
--- a/include/trace/events/btrfs.h
+++ b/include/trace/events/btrfs.h
@@ -248,6 +248,41 @@ TRACE_EVENT_CONDITION(btrfs_get_extent,
                   __entry->refs, __entry->compress_type)
 );
 
+TRACE_EVENT(btrfs_handle_em_exist,
+
+        TP_PROTO(const struct extent_map *existing, const struct extent_map *map, u64 start, u64 len),
+
+        TP_ARGS(existing, map, start, len),
+
+        TP_STRUCT__entry(
+                __field(        u64,  e_start           )
+                __field(        u64,  e_len             )
+                __field(        u64,  map_start         )
+                __field(        u64,  map_len           )
+                __field(        u64,  start             )
+                __field(        u64,  len               )
+        ),
+
+        TP_fast_assign(
+                __entry->e_start        = existing->start;
+                __entry->e_len          = existing->len;
+                __entry->map_start      = map->start;
+                __entry->map_len        = map->len;
+                __entry->start          = start;
+                __entry->len            = len;
+        ),
+
+        TP_printk("start=%llu len=%llu "
+                  "existing(start=%llu len=%llu) "
+                  "em(start=%llu len=%llu)",
+                  (unsigned long long)__entry->start,
+                  (unsigned long long)__entry->len,
+                  (unsigned long long)__entry->e_start,
+                  (unsigned long long)__entry->e_len,
+                  (unsigned long long)__entry->map_start,
+                  (unsigned long long)__entry->map_len)
+);
+
 /* file extent item */
 DECLARE_EVENT_CLASS(btrfs__file_extent_item_regular,