random: simplify accounting logic (ee1de406) · Commits · 戴 / test

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

+4 −8

Original line number	Diff line number	Diff line
		@@ -984,14 +984,10 @@ retry:
		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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