On 8/26/2016 9:35 AM, Doug Ledford wrote:
> On 8/26/2016 12:49 AM, Christophe JAILLET wrote:
>> The 2nd parameter of 'find_first_bit' is the number of bits to search.
>> In this case, we are passing 'sizeof(unsigned long)' which is likely to
>> be 4 or 8.
>
> If the size can be 4 or 8, then using 64 universally is not correct.
> Why not use sizeof() * 8 (or << 3)?
Better yet, why not put this patch in the kernel first:
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d96a6118d26a..a8838c87668e 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -52,6 +52,8 @@
#define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) +
__must_be_array(arr))
+#define bitsizeof(x) (sizeof((x)) << 3)
+
#define u64_to_user_ptr(x) ( \
{ \
typecheck(u64, x); \
then start going around replacing all these hard coded numbers with the
use of bitsizeof(). It can be applied not just to the find_first*bit()
routines, but to a bunch of other routines too. Just look at
include/linux/bitmap.h and any that have nbits as an argument are
candidates.
--
Doug Ledford <dledford@xxxxxxxxxx>
GPG Key ID: 0E572FDD
Attachment:
signature.asc
Description: OpenPGP digital signature
