[PATCHv2 bpf-next] ftrace: Use hash argument for tmp_ops in update_ftrace_direct_mod

[Jiri Olsa <jolsa@kernel.org>]

The modify logic registers temporary ftrace_ops object (tmp_ops) to trigger
the slow path for all direct callers to be able to safely modify attached
addresses.

At the moment we use ops->func_hash for tmp_ops filter, which represents all
the systems attachments. It's faster to use just the passed hash filter, which
contains only the modified sites and is always a subset of the ops->func_hash.

Fixes: e93672f770d7 ("ftrace: Add update_ftrace_direct_mod function")
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 kernel/trace/ftrace.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

v2 changes:
- updated comment and changelog [ci]

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8df69e702706..413310912609 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6606,9 +6606,9 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, b
 	if (!orig_hash)
 		goto unlock;
 
-	/* Enable the tmp_ops to have the same functions as the direct ops */
+	/* Enable the tmp_ops to have the same functions as the hash object. */
 	ftrace_ops_init(&tmp_ops);
-	tmp_ops.func_hash = ops->func_hash;
+	tmp_ops.func_hash->filter_hash = hash;
 
 	err = register_ftrace_function_nolock(&tmp_ops);
 	if (err)
-- 
2.53.0