mm/hugetlb: update nr_huge_pages and surplus_huge_pages together

In alloc_surplus_hugetlb_folio(), we increase nr_huge_pages and
surplus_huge_pages separately.  In the middle window, if we set
nr_hugepages to smaller and satisfy count < persistent_huge_pages(h), the
surplus_huge_pages will be increased by adjust_pool_surplus().

After adding delay in the middle window, we can reproduce the problem
easily by following step:

 1. echo 3 > /proc/sys/vm/nr_overcommit_hugepages
 2. mmap two hugepages. When nr_huge_pages=2 and surplus_huge_pages=1,
    goto step 3.
 3. echo 0 > /proc/sys/vm/nr_huge_pages

Finally, nr_huge_pages is less than surplus_huge_pages.

To fix the problem, call only_alloc_fresh_hugetlb_folio() instead and
move down __prep_account_new_huge_page() into the hugetlb_lock.

Link: https://lkml.kernel.org/r/20250305035409.2391344-1-liushixin2@huawei.com
Fixes: 0c397daea1d4 ("mm, hugetlb: further simplify hugetlb allocation API")
Signed-off-by: Liu Shixin <liushixin2@huawei.com>
Acked-by: Peter Xu <peterx@redhat.com>
Acked-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liu Shixin <liushixin2@huawei.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions