Re: [BUG/PATCH] md bitmap broken on big endian machines

[Michael Tokarev <mjt@tls.msk.ru>]

Paul Clements wrote:
> Michael Tokarev wrote:
>> Neil Brown wrote:
> 
>>> ffs is closer, but takes an 'int' and we have a 'unsigned long'.
>>> So use ffz(~X) to convert a chunksize into a chunkshift.
>>
>> So we don't use ffs(int) for an unsigned value because of int vs
>> unsigned int, but we use ffz() with negated UNSIGNED.  Looks even
>> more broken to me, even if it happens to work correctly... ;)
> 
> No, it doesn't matter about the signedness, these are just bit
> operations. The problem is the size (int vs. long), even though in
> practice it's very unlikely you'd ever have a bitmap chunk size that
> exceeded 32 bits. But it's better to be correct and not have to worry
> about it.

I understand the point, in the first place (I didn't mentioned long
vs int above, however).  The thing is: when reading the code, it looks
just plain wrong.  Esp. since function prototypes aren't here, but for
those ffs(), ffz() etc they're hidden somewhere in include/asm/* (as
they're architecture-dependent), and it's not at all obvious which is
signed and which is unsigned, which is long or int etc.

At the very least, return -ENOCOMMENT :)

/mjt