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SubjectRe: [PATCH] hugetlbfs: remove meaningless variable avoid_reserve
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Hi:
On 2021/1/20 2:41, Mike Kravetz wrote:
> Please CC Andrew on hugetlb patches as they need to go through his tree.
>
> On 1/16/21 1:26 AM, Miaohe Lin wrote:
>> The variable avoid_reserve is meaningless because we never changed its
>> value and just passed it to alloc_huge_page(). So remove it to make code
>> more clear that in hugetlbfs_fallocate, we never avoid reserve when alloc
>> hugepage yet.
>
> One might argue that using a named variable makes the call to alloc_huge_page
> more clear. I do not disagree with the change, However, there are some
> subtle reasons why alloc_huge_page is called with 'avoid_reserve = 0' from
> fallocate. Therefore, I would prefer that a comment be added above the call
> in addition to this change. See below.
>
>>
>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>> ---
>> fs/hugetlbfs/inode.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
>> index 88751e35e69d..23ad6ed8b75f 100644
>> --- a/fs/hugetlbfs/inode.c
>> +++ b/fs/hugetlbfs/inode.c
>> @@ -680,7 +680,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
>> */
>> struct page *page;
>> unsigned long addr;
>> - int avoid_reserve = 0;
>>
>> cond_resched();
>>
>> @@ -717,7 +716,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
>> }
>>
>> /* Allocate page and add to page cache */
>
> Perhaps, change comment to read:
>
> /*
> * Allocate page without setting the avoid_reserve argument.
> * There certainly are no reserves associated with the
> * pseudo_vma. However, there could be shared mappings with
> * reserves for the file at the inode level. If we fallocate
> * pages in these areas, we need to consume the reserves
> * to keep reservation accounting consistent.
> */
>

Many thanks for detailed and excellent comment. Will do it in v2.
Thanks again.

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