Btrfs: add tracepoint for em's EEXIST case
This is adding a tracepoint 'btrfs_handle_em_exist' to help debug the
subtle bugs around merge_extent_mapping.
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index c80dea7..b8ead8d 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 c3ac5ec..486771e 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,