[PATCHv6 bpf-next 02/29] ftrace: Add ftrace_hash_remove function

[Jiri Olsa <jolsa@kernel.org>]

Adding ftrace_hash_remove function that removes all entries
from struct ftrace_hash object without freeing them.

It will be used in following changes where entries are allocated
as part of another structure and are free-ed separately.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 include/linux/ftrace.h |  1 +
 kernel/trace/ftrace.c  | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 282da661f131..d3acfac4f8a7 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -415,6 +415,7 @@ struct ftrace_hash *alloc_ftrace_hash(int size_bits);
 void free_ftrace_hash(struct ftrace_hash *hash);
 struct ftrace_func_entry *add_ftrace_hash_entry_direct(struct ftrace_hash *hash,
 						       unsigned long ip, unsigned long direct);
+void ftrace_hash_remove(struct ftrace_hash *hash);
 
 /* The hash used to know what functions callbacks trace */
 struct ftrace_ops_hash {
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 57ab01fd00bd..45548b0200eb 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1249,6 +1249,25 @@ remove_hash_entry(struct ftrace_hash *hash,
 	hash->count--;
 }
 
+void ftrace_hash_remove(struct ftrace_hash *hash)
+{
+	struct ftrace_func_entry *entry;
+	struct hlist_head *hhd;
+	struct hlist_node *tn;
+	int size;
+	int i;
+
+	if (!hash || !hash->count)
+		return;
+	size = 1 << hash->size_bits;
+	for (i = 0; i < size; i++) {
+		hhd = &hash->buckets[i];
+		hlist_for_each_entry_safe(entry, tn, hhd, hlist)
+			remove_hash_entry(hash, entry);
+	}
+	FTRACE_WARN_ON(hash->count);
+}
+
 static void ftrace_hash_clear(struct ftrace_hash *hash)
 {
 	struct hlist_head *hhd;
-- 
2.54.0