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@xxxxxxx>
---
fs/ext4/balloc.c | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index d0f13ea..5833939 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -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)
--
1.7.12.rc0.22.gcdd159b
--
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