linux-kernel - [PATCH resend] init/main.c: Simplify initcall

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Date:	Tue, 22 Mar 2016 00:14:25 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Oleg Nesterov <oleg@...hat.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	linux-kernel@...r.kernel.org
Subject: [PATCH resend] init/main.c: Simplify initcall_blacklisted()

Using kasprintf to get the function name makes us look up the name
twice, along with all the vsnprintf overhead of parsing the format
string etc. It also means there is an allocation failure case to deal
with. Since symbol_string in vsprintf.c would anyway allocate an array
of size KSYM_SYMBOL_LEN on the stack, that might as well be done up
here.

Moreover, since this is a debug feature and the blacklisted_initcalls
list is usually empty, we might as well test that and thus avoid
looking up the symbol name even once in the common case.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 init/main.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/init/main.c b/init/main.c
index b3c6e363ae18..d76d94cd537c 100644
--- a/init/main.c
+++ b/init/main.c
@@ -706,21 +706,20 @@ static int __init initcall_blacklist(char *str)
 static bool __init_or_module initcall_blacklisted(initcall_t fn)
 {
 	struct blacklist_entry *entry;
-	char *fn_name;
+	char fn_name[KSYM_SYMBOL_LEN];
 
-	fn_name = kasprintf(GFP_KERNEL, "%pf", fn);
-	if (!fn_name)
+	if (list_empty(&blacklisted_initcalls))
 		return false;
 
+	sprint_symbol_no_offset(fn_name, (unsigned long)fn);
+
 	list_for_each_entry(entry, &blacklisted_initcalls, next) {
 		if (!strcmp(fn_name, entry->buf)) {
 			pr_debug("initcall %s blacklisted\n", fn_name);
-			kfree(fn_name);
 			return true;
 		}
 	}
 
-	kfree(fn_name);
 	return false;
 }
 #else
-- 
2.1.4