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SubjectRe: [PATCH] mm/hugetlb: hide nr_nodes in the internal of for_each_node_mask_to_[alloc|free]
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On 7/14/20 11:13 AM, Vlastimil Babka wrote:
> On 7/14/20 9:34 AM, Wei Yang wrote:
>> The second parameter of for_each_node_mask_to_[alloc|free] is a loop
>> variant, which is not used outside of loop iteration.
>>
>> Let's hide this.
>>
>> Signed-off-by: Wei Yang <richard.weiyang@linux.alibaba.com>
>> ---
>> mm/hugetlb.c | 38 ++++++++++++++++++++------------------
>> 1 file changed, 20 insertions(+), 18 deletions(-)
>>
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index 57ece74e3aae..9c3d15fb317e 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -1196,17 +1196,19 @@ static int hstate_next_node_to_free(struct hstate *h, nodemask_t *nodes_allowed)
>> return nid;
>> }
>>
>> -#define for_each_node_mask_to_alloc(hs, nr_nodes, node, mask) \
>> - for (nr_nodes = nodes_weight(*mask); \
>> - nr_nodes > 0 && \
>> +#define for_each_node_mask_to_alloc(hs, node, mask) \
>> + int __nr_nodes; \
>> + for (__nr_nodes = nodes_weight(*mask); \
>
> The problem with this is that if I use the macro twice in the same block, this
> will redefine __nr_nodes and fail to compile, no?
> In that case it's better to avoid setting up this trap, IMHO.

Ah, and it will also generate the following warning, if the use of for_each*
macro is not the first thing after variable declarations, but there's another
statement before:

warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]

Instead we should switch to C99 and declare it as "for (int __nr_nodes" :P

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