linux-kernel - [PATCH 2/2] tracing: Do not copy hash if O

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Date:	Wed, 11 Jun 2014 17:06:54 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung.kim@....com>,
	Namhyung Kim <namhyung@...nel.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 2/2] tracing: Do not copy hash if O_TRUNC is set

When a filter file is open for writing and O_TRUNC is set, there's no
need to copy and free the filter entries.

Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 kernel/trace/ftrace.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index ddfda763ded7..13885590a184 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2759,7 +2759,13 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
 		hash = ops->filter_hash;
 
 	if (file->f_mode & FMODE_WRITE) {
-		iter->hash = alloc_and_copy_ftrace_hash(FTRACE_HASH_DEFAULT_BITS, hash);
+		const int size_bits = FTRACE_HASH_DEFAULT_BITS;
+
+		if (file->f_flags & O_TRUNC)
+			iter->hash = alloc_ftrace_hash(size_bits);
+		else
+			iter->hash = alloc_and_copy_ftrace_hash(size_bits, hash);
+
 		if (!iter->hash) {
 			trace_parser_put(&iter->parser);
 			kfree(iter);
@@ -2768,10 +2774,6 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
 		}
 	}
 
-	if ((file->f_mode & FMODE_WRITE) &&
-	    (file->f_flags & O_TRUNC))
-		ftrace_filter_reset(iter->hash);
-
 	if (file->f_mode & FMODE_READ) {
 		iter->pg = ftrace_pages_start;
 
-- 
2.0.0

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