ftrace: 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.

Link: http://lkml.kernel.org/p/1402474014-28655-2-git-send-email-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index e14ff4c1713eea50c9f73cb0380286435f9511f0..232b898eebbdce632bd55ba251de9d8a15f425a2 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3010,7 +3010,13 @@ 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);
@@ -3019,10 +3025,6 @@ 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;