hugetlbfs: New huge_add_to_page_cache helper routine

Currently, there is only a single place where hugetlbfs pages are added
to the page cache.  The new fallocate code be adding a second one, so
break the functionality out into its own helper.
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Aneesh Kumar <aneesh.kumar@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/hugetlb.h

@@ -333,6 +333,8 @@ struct huge_bootmem_page {
 struct page *alloc_huge_page_node(struct hstate *h, int nid);
 struct page *alloc_huge_page_noerr(struct vm_area_struct *vma,
 				unsigned long addr, int avoid_reserve);
+int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
+			pgoff_t idx);
 
 /* arch callback */
 int __init alloc_bootmem_huge_page(struct hstate *h);

mm/hugetlb.c

@@ -3375,6 +3375,23 @@ static bool hugetlbfs_pagecache_present(struct hstate *h,
 	return page != NULL;
 }
 
+int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
+			   pgoff_t idx)
+{
+	struct inode *inode = mapping->host;
+	struct hstate *h = hstate_inode(inode);
+	int err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
+
+	if (err)
+		return err;
+	ClearPagePrivate(page);
+
+	spin_lock(&inode->i_lock);
+	inode->i_blocks += blocks_per_huge_page(h);
+	spin_unlock(&inode->i_lock);
+	return 0;
+}
+
 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 			   struct address_space *mapping, pgoff_t idx,
 			   unsigned long address, pte_t *ptep, unsigned int flags)
@@ -3422,21 +3439,13 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		set_page_huge_active(page);
 
 		if (vma->vm_flags & VM_MAYSHARE) {
-			int err;
-			struct inode *inode = mapping->host;
-
-			err = add_to_page_cache(page, mapping, idx, GFP_KERNEL);
+			int err = huge_add_to_page_cache(page, mapping, idx);
 			if (err) {
 				put_page(page);
 				if (err == -EEXIST)
 					goto retry;
 				goto out;
 			}
-			ClearPagePrivate(page);
-
-			spin_lock(&inode->i_lock);
-			inode->i_blocks += blocks_per_huge_page(h);
-			spin_unlock(&inode->i_lock);
 		} else {
 			lock_page(page);
 			if (unlikely(anon_vma_prepare(vma))) {