linux-kernel - [PATCH 2/2] pstore: Use global ftrace filters for function trace filtering

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Date:   Wed, 19 Oct 2016 18:31:43 -0700
From:   Joel Fernandes <joelaf@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Kees Cook <keescook@...omium.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>
Subject: [PATCH 2/2] pstore: Use global ftrace filters for function trace filtering

Currently, pstore doesn't have any filters setup for function tracing.  This
has the associated overhead and may not be useful for users looking for tracing
specific set of functions.

ftrace's regular function trace filtering is done writing to
tracing/set_ftrace_filter however this is not available if not requested.
Inorder to be able to use this feature, the support to request global filtering
introduced earlier in the series should be requested before registering the
ftrace ops. Here we do the same.

Signed-off-by: Joel Fernandes <joelaf@...gle.com>
---
 fs/pstore/ftrace.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
index 1c6cf86..bcdcbcd 100644
--- a/fs/pstore/ftrace.c
+++ b/fs/pstore/ftrace.c
@@ -74,10 +74,13 @@ static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
 	if (!on ^ pstore_ftrace_enabled)
 		goto out;
 
-	if (on)
+	if (on) {
+		ftrace_ops_set_global_filter(&pstore_ftrace_ops);
 		ret = register_ftrace_function(&pstore_ftrace_ops);
-	else
+	} else {
 		ret = unregister_ftrace_function(&pstore_ftrace_ops);
+	}
+
 	if (ret) {
 		pr_err("%s: unable to %sregister ftrace ops: %zd\n",
 		       __func__, on ? "" : "un", ret);
-- 
2.7.4