Commit f4afb4f4 authored Jun 06, 2013 by Theodore Ts'o

ext4: optimize test_root()



The test_root() function could potentially loop forever due to
overflow issues.  So rewrite test_root() to avoid this issue; as a
bonus, it is 38% faster when benchmarked via a test loop:

int main(int argc, char **argv)
{
	int  i;

	for (i = 0; i < 1 << 24; i++) {
		if (test_root(i, 7))
			printf("%d\n", i);
	}
}

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

parent 2f2e09eb

fs/ext4/balloc.c

+9 −5

Original line number	Diff line number	Diff line
		@@ -682,11 +682,15 @@ ext4_fsblk_t ext4_count_free_clusters(struct super_block *sb)

		static inline int test_root(ext4_group_t a, int b)
		{
		int num = b;

		while (a > num)
		num *= b;
		return num == a;
		while (1) {
		if (a < b)
		return 0;
		if (a == b)
		return 1;
		if ((a % b) != 0)
		return 0;
		a = a / b;
		}
		}

		static int ext4_group_sparse(ext4_group_t group)

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