shmem: convert shmem_alloc_hugepage() to use vma_alloc_folio()

Patch series "Folio patches for 5.19", v2.


This patch (of 26):

For now, return the head page of the folio, but remove use of the old
alloc_pages_vma() API.

Link: https://lkml.kernel.org/r/20220504182857.4013401-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20220504182857.4013401-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/shmem.c

@@ -1528,7 +1528,7 @@ static struct page *shmem_alloc_hugepage(gfp_t gfp,
 	struct vm_area_struct pvma;
 	struct address_space *mapping = info->vfs_inode.i_mapping;
 	pgoff_t hindex;
-	struct page *page;
+	struct folio *folio;
 
 	hindex = round_down(index, HPAGE_PMD_NR);
 	if (xa_find(&mapping->i_pages, &hindex, hindex + HPAGE_PMD_NR - 1,
@@ -1536,13 +1536,11 @@ static struct page *shmem_alloc_hugepage(gfp_t gfp,
 		return NULL;
 
 	shmem_pseudo_vma_init(&pvma, info, hindex);
-	page = alloc_pages_vma(gfp, HPAGE_PMD_ORDER, &pvma, 0, true);
+	folio = vma_alloc_folio(gfp, HPAGE_PMD_ORDER, &pvma, 0, true);
 	shmem_pseudo_vma_destroy(&pvma);
-	if (page)
-		prep_transhuge_page(page);
-	else
+	if (!folio)
 		count_vm_event(THP_FILE_FALLBACK);
-	return page;
+	return &folio->page;
 }
 
 static struct page *shmem_alloc_page(gfp_t gfp,