On 02/16/2015 04:20 PM, Kirill A. Shutemov wrote:
> On Thu, Feb 12, 2015 at 04:10:21PM -0500, Rik van Riel wrote:
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>> On 02/12/2015 11:18 AM, Kirill A. Shutemov wrote:
>>
>>> +++ b/include/linux/rmap.h @@ -168,16 +168,24 @@ static inline void
>>> anon_vma_merge(struct vm_area_struct *vma,
>>>
>>> struct anon_vma *page_get_anon_vma(struct page *page);
>>>
>>> +/* flags for do_page_add_anon_rmap() */ +enum { + RMAP_EXCLUSIVE =
>>> 1, + RMAP_COMPOUND = 2, +};
>>
>> Always a good idea to name things. However, "exclusive" is
>> not that clear to me. Given that the argument is supposed
>> to indicate whether we map a single or a compound page,
>> maybe the names in the enum could just be SINGLE and COMPOUND?
>>
>> Naming the enum should make it clear enough what it does:
>>
>> enum rmap_page {
>> SINGLE = 0,
>> COMPOUND
>> }
>
> Okay, this is probably confusing: do_page_add_anon_rmap() already had one
> of arguments called 'exclusive'. It indicates if the page is exclusively
> owned by the current process. And I needed also to indicate if we need to
> handle the page as a compound or not. I've reused the same argument and
> converted it to set bit-flags: bit 0 is exclusive, bit 1 - compound.AFAICT, this is not a common use of enum and probably the reason why Rik was confused (I know I find it confusing). Bit-flags members are usually define by macros. Jerome > >> >>> +++ b/kernel/events/uprobes.c @@ -183,7 +183,7 @@ static int >>> __replace_page(struct vm_area_struct *vma, unsigned long addr, goto >>> unlock; >>> >>> get_page(kpage); - page_add_new_anon_rmap(kpage, vma, addr); + >>> page_add_new_anon_rmap(kpage, vma, addr, false); >>> mem_cgroup_commit_charge(kpage, memcg, false); >>> lru_cache_add_active_or_unevictable(kpage, vma); >> >> Would it make sense to use the name in the argument to that function, >> too? >> >> I often find it a lot easier to see what things do if they use symbolic >> names, rather than by trying to remember what each boolean argument to >> a function does. > > I can convert these compound booleans to enums if you want. I'm personally > not sure that if will bring much value. >
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