diff options
| author | Stanislaw Gruszka <[email protected]> | 2019-03-07 16:28:18 -0800 |
|---|---|---|
| committer | Linus Torvalds <[email protected]> | 2019-03-07 18:32:00 -0800 |
| commit | cdc94a37493135e355dfc0b0e086d84e3eadb50d (patch) | |
| tree | 6ef3fffed75206a1b44d0038d55d0bad914fe497 | |
| parent | 1db604f676b2edb7b18de7881f4d5988e97be616 (diff) | |
lib/div64.c: off by one in shift
fls counts bits starting from 1 to 32 (returns 0 for zero argument). If
we add 1 we shift right one bit more and loose precision from divisor,
what cause function incorect results with some numbers.
Corrected code was tested in user-space, see bugzilla:
https://bugzilla.kernel.org/show_bug.cgi?id=202391
Link: http://lkml.kernel.org/r/[email protected]
Fixes: 658716d19f8f ("div64_u64(): improve precision on 32bit platforms")
Signed-off-by: Stanislaw Gruszka <[email protected]>
Reported-by: Siarhei Volkau <[email protected]>
Tested-by: Siarhei Volkau <[email protected]>
Acked-by: Oleg Nesterov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
| -rw-r--r-- | lib/div64.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/lib/div64.c b/lib/div64.c index 01c8602bb6ff..ee146bb4c558 100644 --- a/lib/div64.c +++ b/lib/div64.c @@ -109,7 +109,7 @@ u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder) quot = div_u64_rem(dividend, divisor, &rem32); *remainder = rem32; } else { - int n = 1 + fls(high); + int n = fls(high); quot = div_u64(dividend >> n, divisor >> n); if (quot != 0) @@ -147,7 +147,7 @@ u64 div64_u64(u64 dividend, u64 divisor) if (high == 0) { quot = div_u64(dividend, divisor); } else { - int n = 1 + fls(high); + int n = fls(high); quot = div_u64(dividend >> n, divisor >> n); if (quot != 0) |