Re: [PATCH v2] mm/hugetlb: initialize hugetlb_usage in mm_init

[Mike Kravetz <mike.kravetz@oracle.com>]

On 8/26/21 12:17 AM, Liu Zixian wrote:
> After fork, the child process will get incorrect (2x) hugetlb_usage.
> If a process uses 5 2MB hugetlb pages in an anonymous mapping,
> 	HugetlbPages:	   10240 kB
> and then forks, the child will show,
> 	HugetlbPages:	   20480 kB
> The reason for double the amount is because hugetlb_usage will be
> copied from the parent and then increased when we copy page tables
> from parent to child. Child will have 2x actual usage.
> 
> Fix this by adding hugetlb_count_init in mm_init.
> 
> Fixes: 5d317b2b6536 ("mm: hugetlb: proc: add HugetlbPages field to
> /proc/PID/status")
> Signed-off-by: Liu Zixian <liuzixian4@huawei.com>
> ---
> v2:
> 1. Create two hugetlb_count_init in hugetlb.h instead of using #ifdef
>   in fork.c
> 2. Add an example to clearify this issue.
> ---
>  include/linux/hugetlb.h | 9 +++++++++
>  kernel/fork.c           | 1 +
>  2 files changed, 10 insertions(+)

Thanks,

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>

Andrew, can you add a CC stable?
-- 
Mike Kravetz