linux-kernel - [RFC PATCH 04/41] random: drop 'reserved' parameter from extract

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Date:   Mon, 21 Sep 2020 09:58:20 +0200
From:   Nicolai Stange <nstange@...e.de>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     linux-crypto@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "Alexander E. Patrakov" <patrakov@...il.com>,
        "Ahmed S. Darwish" <darwish.07@...il.com>,
        Willy Tarreau <w@....eu>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Vito Caputo <vcaputo@...garu.com>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jan Kara <jack@...e.cz>, Ray Strode <rstrode@...hat.com>,
        William Jon McCann <mccann@....edu>,
        zhangjs <zachary@...shancloud.com>,
        Andy Lutomirski <luto@...nel.org>,
        Florian Weimer <fweimer@...hat.com>,
        Lennart Poettering <mzxreary@...inter.de>,
        Peter Matthias <matthias.peter@....bund.de>,
        Marcelo Henrique Cerri <marcelo.cerri@...onical.com>,
        Roman Drahtmueller <draht@...altsekun.de>,
        Neil Horman <nhorman@...hat.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Julia Lawall <julia.lawall@...ia.fr>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Andy Lavr <andy.lavr@...il.com>,
        Eric Biggers <ebiggers@...nel.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Stephan Müller <smueller@...onox.de>,
        Torsten Duwe <duwe@...e.de>, Petr Tesarik <ptesarik@...e.cz>,
        Nicolai Stange <nstange@...e.de>
Subject: [RFC PATCH 04/41] random: drop 'reserved' parameter from extract_entropy()

Since commit 43d8a72cd985 ("random: remove variable limit") all call
sites of extract_entropy() pass in zero for the 'reserved' argument
and the corresponding code in account() is effectively dead.

Remove it and the drop the now unused 'reserved' argument from
extract_entropy() as well as from account() called therefrom.

Signed-off-by: Nicolai Stange <nstange@...e.de>
---
 drivers/char/random.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 14c39608cc17..35e381be20fe 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -506,7 +506,7 @@ struct entropy_store {
 };
 
 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
-			       size_t nbytes, int min, int rsvd);
+			       size_t nbytes, int min);
 static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
 				size_t nbytes, int fips);
 
@@ -944,7 +944,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
 	} buf;
 
 	if (r) {
-		num = extract_entropy(r, &buf, 32, 16, 0);
+		num = extract_entropy(r, &buf, 32, 16);
 		if (num == 0)
 			return;
 	} else {
@@ -1330,8 +1330,7 @@ EXPORT_SYMBOL_GPL(add_disk_randomness);
  * This function decides how many bytes to actually take from the
  * given pool, and also debits the entropy count accordingly.
  */
-static size_t account(struct entropy_store *r, size_t nbytes, int min,
-		      int reserved)
+static size_t account(struct entropy_store *r, size_t nbytes, int min)
 {
 	int entropy_count, orig, have_bytes;
 	size_t ibytes, nfrac;
@@ -1345,8 +1344,6 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
 	/* never pull more than available */
 	have_bytes = entropy_count >> (ENTROPY_SHIFT + 3);
 
-	if ((have_bytes -= reserved) < 0)
-		have_bytes = 0;
 	ibytes = min_t(size_t, ibytes, have_bytes);
 	if (ibytes < min)
 		ibytes = 0;
@@ -1469,12 +1466,10 @@ static ssize_t _extract_entropy(struct entropy_store *r, void *buf,
  * returns it in a buffer.
  *
  * The min parameter specifies the minimum amount we can pull before
- * failing to avoid races that defeat catastrophic reseeding while the
- * reserved parameter indicates how much entropy we must leave in the
- * pool after each pull to avoid starving other readers.
+ * failing to avoid races that defeat catastrophic reseeding.
  */
 static ssize_t extract_entropy(struct entropy_store *r, void *buf,
-				 size_t nbytes, int min, int reserved)
+				 size_t nbytes, int min)
 {
 	__u8 tmp[EXTRACT_SIZE];
 	unsigned long flags;
@@ -1495,7 +1490,7 @@ static ssize_t extract_entropy(struct entropy_store *r, void *buf,
 	}
 
 	trace_extract_entropy(r->name, nbytes, ENTROPY_BITS(r), _RET_IP_);
-	nbytes = account(r, nbytes, min, reserved);
+	nbytes = account(r, nbytes, min);
 
 	return _extract_entropy(r, buf, nbytes, fips_enabled);
 }
-- 
2.26.2