mm/hugetlb: convert isolate_or_dissolve_huge_page to folios

Removes a call to compound_head() by using a folio when operating on the
head page of a hugetlb compound page.

Link: https://lkml.kernel.org/r/20221101223059.460937-6-sidhartha.kumar@oracle.comSigned-off-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Bui Quang Minh <minhquangbui99@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mina Almasry <almasrymina@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/hugetlb.c

@@ -2832,7 +2832,7 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page,
 int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list)
 {
 	struct hstate *h;
-	struct page *head;
+	struct folio *folio = page_folio(page);
 	int ret = -EBUSY;
 
 	/*
@@ -2841,9 +2841,8 @@ int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list)
 	 * Return success when racing as if we dissolved the page ourselves.
 	 */
 	spin_lock_irq(&hugetlb_lock);
-	if (PageHuge(page)) {
-		head = compound_head(page);
-		h = page_hstate(head);
+	if (folio_test_hugetlb(folio)) {
+		h = folio_hstate(folio);
 	} else {
 		spin_unlock_irq(&hugetlb_lock);
 		return 0;
@@ -2858,10 +2857,10 @@ int isolate_or_dissolve_huge_page(struct page *page, struct list_head *list)
 	if (hstate_is_gigantic(h))
 		return -ENOMEM;
 
-	if (page_count(head) && !isolate_hugetlb(head, list))
+	if (folio_ref_count(folio) && !isolate_hugetlb(&folio->page, list))
 		ret = 0;
-	else if (!page_count(head))
-		ret = alloc_and_dissolve_huge_page(h, head, list);
+	else if (!folio_ref_count(folio))
+		ret = alloc_and_dissolve_huge_page(h, &folio->page, list);
 
 	return ret;
 }