From ee1de406ba6eb1e01f143fe3351e70cc772cc63e Mon Sep 17 00:00:00 2001
From: Greg Price <price@MIT.EDU>
Date: Fri, 29 Nov 2013 15:56:16 -0500
Subject: [PATCH] random: simplify accounting logic
This logic is exactly equivalent to the old logic, but it should
be easier to see what it's doing.
The equivalence depends on one fact from outside this function:
when 'r->limit' is false, 'reserved' is zero. (Well, two facts;
the other is that 'reserved' is never negative.)
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Greg Price <price@mit.edu>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
drivers/char/random.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 2c532a6b0a21..9675821b4b5a 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -984,14 +984,10 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
ibytes = 0;
} else {
/* If limited, never pull more than available */
- if (r->limit && ibytes + reserved >= have_bytes)
- ibytes = have_bytes - reserved;
-
- if (have_bytes >= ibytes + reserved)
- entropy_count -= ibytes << (ENTROPY_SHIFT + 3);
- else
- entropy_count = reserved << (ENTROPY_SHIFT + 3);
-
+ if (r->limit)
+ ibytes = min_t(size_t, ibytes, have_bytes - reserved);
+ entropy_count = max_t(int, 0,
+ entropy_count - (ibytes << (ENTROPY_SHIFT + 3)));
if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
goto retry;
--
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