On 7/14/20 11:57 AM, Wei Yang wrote: > On Tue, Jul 14, 2020 at 11:22:03AM +0200, Vlastimil Babka wrote: >>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@xxxxxxxxxxxxxxxxx> >>>> --- >>>> 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 > > Hmm... I tried what you suggested, but compiler complains. > > 'for' loop initial declarations are only allowed in C99 or C11 mode Yes, by "we should switch to C99" I meant that the kernel kbuild system would need to switch. Not a trivial change... Without that, I don't see how your patch is possible to do safely.
