linux-kernel - [RFC PATCH 30/41] random: add a queued_entropy instance to struct fast

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Date:   Mon, 21 Sep 2020 09:58:46 +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 30/41] random: add a queued_entropy instance to struct fast_pool

When health tests are introduced with upcoming patches, it will become
necessary to keep entropy queued across add_interrupt_randomness()
invocations for later dispatch to the global balance.

Prepare for this by adding a struct queued_entropy member to the per-CPU
fast_pool. Use it in place of that queue with automatic storage duration
in add_interrupt_randomness().

Signed-off-by: Nicolai Stange <nstange@...e.de>
---
 drivers/char/random.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 55e784a5a2ec..37746df53acf 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -885,6 +885,7 @@ struct fast_pool {
 	unsigned short	reg_idx;
 	unsigned char	count;
 	int		event_entropy_shift;
+	struct queued_entropy	q;
 };
 
 /*
@@ -1655,7 +1656,7 @@ void add_interrupt_randomness(int irq, int irq_flags)
 	__u32			c_high, j_high;
 	__u64			ip;
 	bool			reseed;
-	struct queued_entropy	q = { 0 };
+	struct queued_entropy	*q = &fast_pool->q;
 	unsigned int		nfrac;
 
 	if (cycles == 0)
@@ -1700,9 +1701,9 @@ void add_interrupt_randomness(int irq, int irq_flags)
 		nfrac = fast_pool_entropy(fast_pool->count,
 					  fast_pool->event_entropy_shift);
 	}
-	__queue_entropy(r, &q, nfrac);
+	__queue_entropy(r, q, nfrac);
 	__mix_pool_bytes(r, &fast_pool->pool, sizeof(fast_pool->pool));
-	reseed = __dispatch_queued_entropy_fast(r, &q);
+	reseed = __dispatch_queued_entropy_fast(r, q);
 	spin_unlock(&r->lock);
 
 	fast_pool->last = now;
-- 
2.26.2