mm/hugetlb: remove unnecessary holding of hugetlb_lock

In isolate_or_dissolve_huge_folio(), after acquiring the hugetlb_lock, it
is only for the purpose of obtaining the correct hstate, which is then
passed to alloc_and_dissolve_hugetlb_folio().

alloc_and_dissolve_hugetlb_folio() itself also acquires the hugetlb_lock. 
We can have alloc_and_dissolve_hugetlb_folio() obtain the hstate by
itself, so that isolate_or_dissolve_huge_folio() no longer needs to
acquire the hugetlb_lock.  In addition, we keep the folio_test_hugetlb()
check within isolate_or_dissolve_huge_folio().  By doing so, we can avoid
disrupting the normal path by vainly holding the hugetlb_lock.

replace_free_hugepage_folios() has the same issue, and we should address
it as well.

Addresses a possible performance problem which was added by the hotfix
113ed54ad276 ("mm/hugetlb: fix kernel NULL pointer dereference when
replacing free hugetlb folios").

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 113ed54ad276 ("mm/hugetlb: fix kernel NULL pointer dereference when replacing free hugetlb folios")
Signed-off-by: Ge Yang <[email protected]>
Suggested-by: Oscar Salvador <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Cc: Baolin Wang <[email protected]>
Cc: Barry Song <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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