linux-kernel - [PATCH] drivers/char/random.c: remove unused dont_count

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Date:   Sat, 28 Oct 2017 00:30:42 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     "Theodore Ts'o" <tytso@....edu>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] drivers/char/random.c: remove unused dont_count_entropy

Ever since "random: kill dead extract_state struct" [1], the
dont_count_entropy member of struct timer_rand_state has been
effectively unused. Since it hasn't found a new use in 12 years, it's
probably safe to finally kill it.

[1] Pre-git, https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git/commit/?id=c1c48e61c251f57e7a3f1bf11b3c462b2de9dcb5

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 drivers/char/random.c | 53 ++++++++++++++++++++++++---------------------------
 1 file changed, 25 insertions(+), 28 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 8ad92707e45f..cc42392c74dc 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -964,7 +964,6 @@ static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
 struct timer_rand_state {
 	cycles_t last_time;
 	long last_delta, last_delta2;
-	unsigned dont_count_entropy:1;
 };
 
 #define INIT_TIMER_RAND_STATE { INITIAL_JIFFIES, };
@@ -1030,35 +1029,33 @@ static void add_timer_randomness(struct timer_rand_state *state, unsigned num)
 	 * We take into account the first, second and third-order deltas
 	 * in order to make our estimate.
 	 */
+	delta = sample.jiffies - state->last_time;
+	state->last_time = sample.jiffies;
+
+	delta2 = delta - state->last_delta;
+	state->last_delta = delta;
+
+	delta3 = delta2 - state->last_delta2;
+	state->last_delta2 = delta2;
+
+	if (delta < 0)
+		delta = -delta;
+	if (delta2 < 0)
+		delta2 = -delta2;
+	if (delta3 < 0)
+		delta3 = -delta3;
+	if (delta > delta2)
+		delta = delta2;
+	if (delta > delta3)
+		delta = delta3;
 
-	if (!state->dont_count_entropy) {
-		delta = sample.jiffies - state->last_time;
-		state->last_time = sample.jiffies;
-
-		delta2 = delta - state->last_delta;
-		state->last_delta = delta;
-
-		delta3 = delta2 - state->last_delta2;
-		state->last_delta2 = delta2;
-
-		if (delta < 0)
-			delta = -delta;
-		if (delta2 < 0)
-			delta2 = -delta2;
-		if (delta3 < 0)
-			delta3 = -delta3;
-		if (delta > delta2)
-			delta = delta2;
-		if (delta > delta3)
-			delta = delta3;
+	/*
+	 * delta is now minimum absolute delta.
+	 * Round down by 1 bit on general principles,
+	 * and limit entropy entimate to 12 bits.
+	 */
+	credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
 
-		/*
-		 * delta is now minimum absolute delta.
-		 * Round down by 1 bit on general principles,
-		 * and limit entropy entimate to 12 bits.
-		 */
-		credit_entropy_bits(r, min_t(int, fls(delta>>1), 11));
-	}
 	preempt_enable();
 }
 
-- 
2.11.0