[PATCH 06/18] mm, hugetlb: remove vma_need_reservation()

[Joonsoo Kim]

vma_need_reservation() can be substituted by vma_has_reserves()
with minor change. These function do almost same thing,
so unifying them is better to maintain.

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

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index bf2ee11..ff46a2c 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -451,8 +451,18 @@ void reset_vma_resv_huge_pages(struct vm_area_struct *vma)
 		vma->vm_private_data = (void *)0;
 }
 
-/* Returns true if the VMA has associated reserve pages */
-static int vma_has_reserves(struct vm_area_struct *vma, long chg)
+/*
+ * Determine if the huge page at addr within the vma has an associated
+ * reservation.  Where it does not we will need to logically increase
+ * reservation and actually increase subpool usage before an allocation
+ * can occur.  Where any new reservation would be required the
+ * reservation change is prepared, but not committed.  Once the page
+ * has been allocated from the subpool and instantiated the change should
+ * be committed via vma_commit_reservation.  No action is required on
+ * failure.
+ */
+static int vma_has_reserves(struct hstate *h,
+			struct vm_area_struct *vma, unsigned long addr)
 {
 	if (vma->vm_flags & VM_NORESERVE) {
 		/*
@@ -464,10 +474,22 @@ static int vma_has_reserves(struct vm_area_struct *vma, long chg)
 		 * step. Currently, we don't have any other solution to deal
 		 * with this situation properly, so add work-around here.
 		 */
-		if (vma->vm_flags & VM_MAYSHARE && chg == 0)
-			return 1;
-		else
-			return 0;
+		if (vma->vm_flags & VM_MAYSHARE) {
+			struct address_space *mapping = vma->vm_file->f_mapping;
+			struct inode *inode = mapping->host;
+			pgoff_t idx = vma_hugecache_offset(h, vma, addr);
+			struct resv_map *resv = inode->i_mapping->private_data;
+			long chg;
+
+			chg = region_chg(resv, idx, idx + 1);
+			if (chg < 0)
+				return -ENOMEM;
+
+			if (chg == 0)
+				return 1;
+		}
+
+		return 0;
 	}
 
 	/* Shared mappings always use reserves */
@@ -478,8 +500,16 @@ static int vma_has_reserves(struct vm_area_struct *vma, long chg)
 	 * Only the process that called mmap() has reserves for
 	 * private mappings.
 	 */
-	if (is_vma_resv_set(vma, HPAGE_RESV_OWNER))
+	if (is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
+		pgoff_t idx = vma_hugecache_offset(h, vma, addr);
+		struct resv_map *resv = vma_resv_map(vma);
+
+		/* Just for allocating region structure */
+		if (region_chg(resv, idx, idx + 1) < 0)
+			return -ENOMEM;
+
 		return 1;
+	}
 
 	return 0;
 }
@@ -542,8 +572,7 @@ static struct page *dequeue_huge_page_node(struct hstate *h, int nid)
 
 static struct page *dequeue_huge_page_vma(struct hstate *h,
 				struct vm_area_struct *vma,
-				unsigned long address, int avoid_reserve,
-				long chg)
+				unsigned long address, int avoid_reserve)
 {
 	struct page *page = NULL;
 	struct mempolicy *mpol;
@@ -558,7 +587,7 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
 	 * have no page reserves. This check ensures that reservations are
 	 * not "stolen". The child may still get SIGKILLed
 	 */
-	if (!vma_has_reserves(vma, chg) &&
+	if (!vma_has_reserves(h, vma, address) &&
 			h->free_huge_pages - h->resv_huge_pages == 0)
 		return NULL;
 
@@ -578,7 +607,7 @@ retry_cpuset:
 			if (page) {
 				if (avoid_reserve)
 					break;
-				if (!vma_has_reserves(vma, chg))
+				if (!vma_has_reserves(h, vma, address))
 					break;
 
 				h->resv_huge_pages--;
@@ -1077,42 +1106,6 @@ static void return_unused_surplus_pages(struct hstate *h,
 	}
 }
 
-/*
- * Determine if the huge page at addr within the vma has an associated
- * reservation.  Where it does not we will need to logically increase
- * reservation and actually increase subpool usage before an allocation
- * can occur.  Where any new reservation would be required the
- * reservation change is prepared, but not committed.  Once the page
- * has been allocated from the subpool and instantiated the change should
- * be committed via vma_commit_reservation.  No action is required on
- * failure.
- */
-static long vma_needs_reservation(struct hstate *h,
-			struct vm_area_struct *vma, unsigned long addr)
-{
-	struct address_space *mapping = vma->vm_file->f_mapping;
-	struct inode *inode = mapping->host;
-
-	if (vma->vm_flags & VM_MAYSHARE) {
-		pgoff_t idx = vma_hugecache_offset(h, vma, addr);
-		struct resv_map *resv = inode->i_mapping->private_data;
-
-		return region_chg(resv, idx, idx + 1);
-
-	} else if (!is_vma_resv_set(vma, HPAGE_RESV_OWNER)) {
-		return 1;
-
-	} else  {
-		long err;
-		pgoff_t idx = vma_hugecache_offset(h, vma, addr);
-		struct resv_map *resv = vma_resv_map(vma);
-
-		err = region_chg(resv, idx, idx + 1);
-		if (err < 0)
-			return err;
-		return 0;
-	}
-}
 static void vma_commit_reservation(struct hstate *h,
 			struct vm_area_struct *vma, unsigned long addr)
 {
@@ -1140,8 +1133,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
 	struct hugepage_subpool *spool = subpool_vma(vma);
 	struct hstate *h = hstate_vma(vma);
 	struct page *page;
-	long chg;
-	int ret, idx;
+	int ret, idx, has_reserve;
 	struct hugetlb_cgroup *h_cg;
 
 	idx = hstate_index(h);
@@ -1153,20 +1145,21 @@ 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)
+	has_reserve = vma_has_reserves(h, vma, addr);
+	if (has_reserve < 0)
 		return ERR_PTR(-ENOMEM);
-	if (chg)
-		if (hugepage_subpool_get_pages(spool, chg))
+
+	if (!has_reserve && (hugepage_subpool_get_pages(spool, 1) < 0))
 			return ERR_PTR(-ENOSPC);
 
 	ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
 	if (ret) {
-		hugepage_subpool_put_pages(spool, chg);
+		if (!has_reserve)
+			hugepage_subpool_put_pages(spool, 1);
 		return ERR_PTR(-ENOSPC);
 	}
 	spin_lock(&hugetlb_lock);
-	page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, chg);
+	page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve);
 	if (!page) {
 		spin_unlock(&hugetlb_lock);
 		page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
@@ -1174,7 +1167,8 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
 			hugetlb_cgroup_uncharge_cgroup(idx,
 						       pages_per_huge_page(h),
 						       h_cg);
-			hugepage_subpool_put_pages(spool, chg);
+			if (!has_reserve)
+				hugepage_subpool_put_pages(spool, 1);
 			return ERR_PTR(-ENOSPC);
 		}
 		spin_lock(&hugetlb_lock);
@@ -2769,7 +2763,7 @@ retry:
 	 * the spinlock.
 	 */
 	if ((flags & FAULT_FLAG_WRITE) && !(vma->vm_flags & VM_SHARED))
-		if (vma_needs_reservation(h, vma, address) < 0) {
+		if (vma_has_reserves(h, vma, address) < 0) {
 			ret = VM_FAULT_OOM;
 			goto backout_unlocked;
 		}
@@ -2860,7 +2854,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * consumed.
 	 */
 	if ((flags & FAULT_FLAG_WRITE) && !huge_pte_write(entry)) {
-		if (vma_needs_reservation(h, vma, address) < 0) {
+		if (vma_has_reserves(h, vma, address) < 0) {
 			ret = VM_FAULT_OOM;
 			goto out_mutex;
 		}
-- 
1.7.9.5

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