[PATCH v2 14/20] mm, hugetlb: call vma_needs_reservation before entering alloc_huge_page()

[Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>]

In order to validate that this failure is reasonable, we need to know
whether allocation request is for reserved or not on caller function.
So moving vma_needs_reservation() up to the caller of alloc_huge_page().
There is no functional change in this patch and following patch use
this information.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 8dff972..bc666cf 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1110,13 +1110,11 @@ static void vma_commit_reservation(struct hstate *h,
 }
 
 static struct page *alloc_huge_page(struct vm_area_struct *vma,
-				    unsigned long addr, int avoid_reserve)
+				    unsigned long addr, int use_reserve)
 {
 	struct hugepage_subpool *spool = subpool_vma(vma);
 	struct hstate *h = hstate_vma(vma);
 	struct page *page;
-	long chg;
-	bool use_reserve;
 	int ret, idx;
 	struct hugetlb_cgroup *h_cg;
 
@@ -1129,10 +1127,6 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
 	 * need pages and subpool limit allocated allocated if no reserve
 	 * mapping overlaps.
 	 */
-	chg = vma_needs_reservation(h, vma, addr);
-	if (chg < 0)
-		return ERR_PTR(-ENOMEM);
-	use_reserve = (!chg && !avoid_reserve);
 	if (!use_reserve)
 		if (hugepage_subpool_get_pages(spool, 1))
 			return ERR_PTR(-ENOSPC);
@@ -2504,6 +2498,8 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
 	struct hstate *h = hstate_vma(vma);
 	struct page *old_page, *new_page;
 	int outside_reserve = 0;
+	long chg;
+	bool use_reserve;
 	unsigned long mmun_start;	/* For mmu_notifiers */
 	unsigned long mmun_end;		/* For mmu_notifiers */
 
@@ -2535,7 +2531,17 @@ retry_avoidcopy:
 
 	/* Drop page_table_lock as buddy allocator may be called */
 	spin_unlock(&mm->page_table_lock);
-	new_page = alloc_huge_page(vma, address, outside_reserve);
+	chg = vma_needs_reservation(h, vma, address);
+	if (chg == -ENOMEM) {
+		page_cache_release(old_page);
+
+		/* Caller expects lock to be held */
+		spin_lock(&mm->page_table_lock);
+		return VM_FAULT_OOM;
+	}
+	use_reserve = !chg && !outside_reserve;
+
+	new_page = alloc_huge_page(vma, address, use_reserve);
 
 	if (IS_ERR(new_page)) {
 		long err = PTR_ERR(new_page);
@@ -2664,6 +2670,8 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
 	struct page *page;
 	struct address_space *mapping;
 	pte_t new_pte;
+	long chg;
+	bool use_reserve;
 
 	/*
 	 * Currently, we are forced to kill the process in the event the
@@ -2689,7 +2697,15 @@ retry:
 		size = i_size_read(mapping->host) >> huge_page_shift(h);
 		if (idx >= size)
 			goto out;
-		page = alloc_huge_page(vma, address, 0);
+
+		chg = vma_needs_reservation(h, vma, address);
+		if (chg == -ENOMEM) {
+			ret = VM_FAULT_OOM;
+			goto out;
+		}
+		use_reserve = !chg;
+
+		page = alloc_huge_page(vma, address, use_reserve);
 		if (IS_ERR(page)) {
 			ret = PTR_ERR(page);
 			if (ret == -ENOMEM)
-- 
1.7.9.5

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