linux-kernel - [PATCH] ftrace: simplify ftrace hash lookup code

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Date:   Sun,  8 Sep 2019 20:05:45 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        Changbin Du <changbin.du@...il.com>
Subject: [PATCH] ftrace: simplify ftrace hash lookup code

Function ftrace_lookup_ip() will check empty hash table. So we don't
need extra check outside.

Signed-off-by: Changbin Du <changbin.du@...il.com>
---
 kernel/trace/ftrace.c | 15 ++++-----------
 kernel/trace/trace.h  |  6 ------
 2 files changed, 4 insertions(+), 17 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f9821a3374e9..85115deca667 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1461,10 +1461,8 @@ static bool hash_contains_ip(unsigned long ip,
 	 * considered a match for the filter hash, but an empty
 	 * notrace hash is considered not in the notrace hash.
 	 */
-	return (ftrace_hash_empty(hash->filter_hash) ||
-		__ftrace_lookup_ip(hash->filter_hash, ip)) &&
-		(ftrace_hash_empty(hash->notrace_hash) ||
-		 !__ftrace_lookup_ip(hash->notrace_hash, ip));
+	return ftrace_lookup_ip(hash->filter_hash, ip) &&
+	       !ftrace_lookup_ip(hash->notrace_hash, ip);
 }
 
 /*
@@ -2890,8 +2888,7 @@ ops_references_rec(struct ftrace_ops *ops, struct dyn_ftrace *rec)
 		return true;
 
 	/* The function must be in the filter */
-	if (!ftrace_hash_empty(ops->func_hash->filter_hash) &&
-	    !__ftrace_lookup_ip(ops->func_hash->filter_hash, rec->ip))
+	if (!ftrace_lookup_ip(ops->func_hash->filter_hash, rec->ip))
 		return false;
 
 	/* If in notrace hash, we ignore it too */
@@ -6036,11 +6033,7 @@ clear_func_from_hash(struct ftrace_init_func *func, struct ftrace_hash *hash)
 {
 	struct ftrace_func_entry *entry;
 
-	if (ftrace_hash_empty(hash))
-		return;
-
-	entry = __ftrace_lookup_ip(hash, func->ip);
-
+	entry = ftrace_lookup_ip(hash, func->ip);
 	/*
 	 * Do not allow this rec to match again.
 	 * Yeah, it may waste some memory, but will be removed
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 005f08629b8b..74162bc4024d 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -941,11 +941,6 @@ static inline int ftrace_graph_addr(struct ftrace_graph_ent *trace)
 
 	preempt_disable_notrace();
 
-	if (ftrace_hash_empty(ftrace_graph_hash)) {
-		ret = 1;
-		goto out;
-	}
-
 	if (ftrace_lookup_ip(ftrace_graph_hash, addr)) {
 
 		/*
@@ -967,7 +962,6 @@ static inline int ftrace_graph_addr(struct ftrace_graph_ent *trace)
 		ret = 1;
 	}
 
-out:
 	preempt_enable_notrace();
 	return ret;
 }
-- 
2.20.1