linux-kernel - [PATCH 4.9 029/264] drivers/char/random.c: remove unused dont_count

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Date:   Thu, 23 Jun 2022 18:40:22 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Theodore Tso <tytso@....edu>,
        "Jason A. Donenfeld" <Jason@...c4.com>
Subject: [PATCH 4.9 029/264] drivers/char/random.c: remove unused dont_count_entropy

From: Rasmus Villemoes <linux@...musvillemoes.dk>

commit 5e747dd9be54be190dd6ebeebf4a4a01ba765625 upstream.

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>
Signed-off-by: Theodore Ts'o <tytso@....edu>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/char/random.c |   55 +++++++++++++++++++++++---------------------------
 1 file changed, 26 insertions(+), 29 deletions(-)

--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -1130,7 +1130,6 @@ static ssize_t extract_crng_user(void __
 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, };
@@ -1194,35 +1193,33 @@ static void add_timer_randomness(struct
 	 * 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;
+
+	/*
+	 * 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));
 
-	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));
-	}
 	preempt_enable();
 }