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

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

[Jiri Olsa]

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 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 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8df69e702706..71dcbfeac86c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6608,7 +6608,7 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, b
 
 	/* Enable the tmp_ops to have the same functions as the direct ops */
 	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

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

[bot+bpf-ci]

[-- Attachment #1: Type: text/plain, Size: 1158 bytes --]

> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 8df69e702706..71dcbfeac86c 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -6608,7 +6608,7 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, b
>
>  	/* Enable the tmp_ops to have the same functions as the direct ops */
>  	ftrace_ops_init(&tmp_ops);
> -	tmp_ops.func_hash = ops->func_hash;
> +	tmp_ops.func_hash->filter_hash = hash;

The comment above says "Enable the tmp_ops to have the same functions
as the direct ops", but after this change tmp_ops only gets the
modified subset via the hash argument, not all of the direct ops
functions.  Should the comment be updated to reflect this?

Also, the commit message has a minor grammar issue:

> which contains only the modified sites is always a subset of the
> ops->func_hash.

Reads like it is missing an "and" between "sites" and "is".


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/23000924618

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

[Jiri Olsa]

On Thu, Mar 12, 2026 at 12:24:24PM +0000, bot+bpf-ci@kernel.org wrote:
> > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > index 8df69e702706..71dcbfeac86c 100644
> > --- a/kernel/trace/ftrace.c
> > +++ b/kernel/trace/ftrace.c
> > @@ -6608,7 +6608,7 @@ int update_ftrace_direct_mod(struct ftrace_ops *ops, struct ftrace_hash *hash, b
> >
> >  	/* Enable the tmp_ops to have the same functions as the direct ops */
> >  	ftrace_ops_init(&tmp_ops);
> > -	tmp_ops.func_hash = ops->func_hash;
> > +	tmp_ops.func_hash->filter_hash = hash;
> 
> The comment above says "Enable the tmp_ops to have the same functions
> as the direct ops", but after this change tmp_ops only gets the
> modified subset via the hash argument, not all of the direct ops
> functions.  Should the comment be updated to reflect this?
> 
> Also, the commit message has a minor grammar issue:
> 
> > which contains only the modified sites is always a subset of the
> > ops->func_hash.
> 
> Reads like it is missing an "and" between "sites" and "is".

yep, sent v2 

jirka