Re: [PATCH 1/9] exofs: osd Swiss army knife

Boaz Harrosh
2009-01-05T09:02:32Z

Pavel Machek wrote:
> On Sun 2009-01-04 10:43:09, Boaz Harrosh wrote:
>> Pavel Machek wrote:
>>> Hi!
>>>
>>>>> +#ifdef ARCH_HAS_ATOMIC_UNSIGNED
>>>> This doesn't exist, and it would be fairly bad to introduce it. Please
>>>> kill the ifdefs.
>>>>
>>>>> +typedef unsigned exofs_iflags_t;
>>>>> +#else
>>>>> +typedef unsigned long exofs_iflags_t;
>>>>> +#endif
>>>> Then please kill the typedef altogether and replace it with `unsigned
>>>> long' everywhere
>>> Hmmm.. .and at a note somewhere that we assume unsigned long to be atomic...?
>>>
>> I think I'll just use unsigned. It's more then enough I'm not using more then 3
>> bits for now. Is unsigned workable for all ARCHs?

<added>
> /*
> * our extension to the in-memory inode
> */
> struct exofs_i_info {
> unsigned long i_flags; /* various atomic flags */
<snip>
>
> /*
> * our inode flags
> */
> #define OBJ_2BCREATED 0 /* object will be created soon*/
> #define OBJ_CREATED 1 /* object has been created on the osd*/
>
> static inline int obj_2bcreated(struct exofs_i_info *oi)
> {
> return test_bit(OBJ_2BCREATED, &(oi->i_flags));
> }
>
> static inline void set_obj_2bcreated(struct exofs_i_info *oi)
> {
> set_bit(OBJ_2BCREATED, &(oi->i_flags));
> }
>
> static inline int obj_created(struct exofs_i_info *oi)
> {
> return test_bit(OBJ_CREATED, &(oi->i_flags));
> }
>
> static inline void set_obj_created(struct exofs_i_info *oi)
> {
> set_bit(OBJ_CREATED, &(oi->i_flags));
> }
</added>

>
> Please just use atomic_t.
>
> (see "atomics: document that linux expects certain atomic behaviour"
> thread for discussion)
> Pavel

I have a problem with this. The context of i_flags is to be used with
set_bit() and test_bit(). In some ARCHs like x86_64 they take an
"unsigned long *" in most others they take a "void *" and cast internally
to a "u32 *". (for x86_64 I must use "unsigned long", anything else warns)

I think if I declare "unsigned long" but only use 32 bits flags then
I should be in the clear with ALL archs, I'll see if that works once
this code sits in linux-next. (That's real ugly I think)

Is set_bit() and test_bit() should only be used from arch/ code? What
can regular kernel code use?

Thanks
Boaz