From: Steven Rostedt <rostedt@goodmis.org>

The ftrace_lock is taken for most of the ftrace_graph_set_hash() function
throughout the end. Use guard to take the ftrace_lock to simplify the exit
paths.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/ftrace.c | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c0fabd7da5b2..b4ef469f4fd2 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -6816,12 +6816,10 @@ ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
 
 	func_g.len = strlen(func_g.search);
 
-	mutex_lock(&ftrace_lock);
+	guard(mutex)(&ftrace_lock);
 
-	if (unlikely(ftrace_disabled)) {
-		mutex_unlock(&ftrace_lock);
+	if (unlikely(ftrace_disabled))
 		return -ENODEV;
-	}
 
 	do_for_each_ftrace_rec(pg, rec) {
 
@@ -6837,7 +6835,7 @@ ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
 				if (entry)
 					continue;
 				if (add_hash_entry(hash, rec->ip) == NULL)
-					goto out;
+					return 0;
 			} else {
 				if (entry) {
 					free_hash_entry(hash, entry);
@@ -6846,13 +6844,8 @@ ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
 			}
 		}
 	} while_for_each_ftrace_rec();
-out:
-	mutex_unlock(&ftrace_lock);
 
-	if (fail)
-		return -EINVAL;
-
-	return 0;
+	return fail ? -EINVAL : 0;
 }
 
 static ssize_t
-- 
2.45.2

On Mon, Oct 28, 2024 at 03:12:33AM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
> 
> The ftrace_lock is taken for most of the ftrace_graph_set_hash() function
> throughout the end. Use guard to take the ftrace_lock to simplify the exit
> paths.
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
> ---
>  kernel/trace/ftrace.c | 15 ++++-----------
>  1 file changed, 4 insertions(+), 11 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index c0fabd7da5b2..b4ef469f4fd2 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -6816,12 +6816,10 @@ ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
>  
>  	func_g.len = strlen(func_g.search);
>  
> -	mutex_lock(&ftrace_lock);
> +	guard(mutex)(&ftrace_lock);
>  
> -	if (unlikely(ftrace_disabled)) {
> -		mutex_unlock(&ftrace_lock);
> +	if (unlikely(ftrace_disabled))
>  		return -ENODEV;
> -	}
>  
>  	do_for_each_ftrace_rec(pg, rec) {
>  
> @@ -6837,7 +6835,7 @@ ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
>  				if (entry)
>  					continue;
>  				if (add_hash_entry(hash, rec->ip) == NULL)
> -					goto out;
> +					return 0;
>  			} else {
>  				if (entry) {
>  					free_hash_entry(hash, entry);
> @@ -6846,13 +6844,8 @@ ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
>  			}
>  		}
>  	} while_for_each_ftrace_rec();
> -out:
> -	mutex_unlock(&ftrace_lock);
>  
> -	if (fail)
> -		return -EINVAL;
> -
> -	return 0;
> +	return fail ? -EINVAL : 0;
>  }

Isn't the fail case more a case of -ESRCH / -ENOENT rather than -EINVAL?

Anyway, that's orthogonal, the patch preserves existing semantics and
looks okay (as do the others fwiw).

On Mon, 28 Oct 2024 10:16:56 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> > @@ -6846,13 +6844,8 @@ ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer)
> >  			}
> >  		}
> >  	} while_for_each_ftrace_rec();
> > -out:
> > -	mutex_unlock(&ftrace_lock);
> >  
> > -	if (fail)
> > -		return -EINVAL;
> > -
> > -	return 0;
> > +	return fail ? -EINVAL : 0;
> >  }  
> 
> Isn't the fail case more a case of -ESRCH / -ENOENT rather than -EINVAL?

Could be. Although this is mostly for internal use. I should check to
see if this gets back to user space. And yeah, it probably should be
changed.

> 
> Anyway, that's orthogonal, the patch preserves existing semantics and
> looks okay (as do the others fwiw).

Thanks for the review!

-- Steve