mm: hugetlb: improve the handling of hugetlb allocation failure for freed or in-use hugetlb

alloc_and_dissolve_hugetlb_folio() preallocates a new hugetlb page before
it takes hugetlb_lock.  In 3 out of 4 cases the page is not really used
and therefore the newly allocated page is just freed right away.  This is
wasteful and it might cause pre-mature failures in those cases.

Address that by moving the allocation down to the only case (hugetlb page
is really in the free pages pool).  We need to drop hugetlb_lock to do so
and therefore need to recheck the page state after regaining it.

The patch is more of a cleanup than an actual fix to an existing problem. 
There are no known reports about pre-mature failures.

Link: https://lkml.kernel.org/r/62890fd60b1ecd5bf1cdc476c973f60fe37aa0cb.1707181934.git.baolin.wang@linux.alibaba.com
Signed-off-by: Baolin Wang <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Oscar Salvador <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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