1 files changed, 19 insertions, 3 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 9c85bd46ab7f..b0a9071cfe1d 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -664,12 +664,15 @@ static bool cluster_scan_range(struct swap_info_struct *si,
 	return true;
 }
 
-static void cluster_alloc_range(struct swap_info_struct *si, struct swap_cluster_info *ci,
+static bool cluster_alloc_range(struct swap_info_struct *si, struct swap_cluster_info *ci,
 				unsigned int start, unsigned char usage,
 				unsigned int order)
 {
 	unsigned int nr_pages = 1 << order;
 
+	if (!(si->flags & SWP_WRITEOK))
+		return false;
+
 	if (cluster_is_free(ci)) {
 		if (nr_pages < SWAPFILE_CLUSTER) {
 			list_move_tail(&ci->list, &si->nonfull_clusters[order]);
@@ -690,6 +693,8 @@ static void cluster_alloc_range(struct swap_info_struct *si, struct swap_cluster
 		list_move_tail(&ci->list, &si->full_clusters);
 		ci->flags = CLUSTER_FLAG_FULL;
 	}
+
+	return true;
 }
 
 static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si, unsigned long offset,
@@ -713,7 +718,10 @@ static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si, unsigne
 
 	while (offset <= end) {
 		if (cluster_scan_range(si, ci, offset, nr_pages)) {
-			cluster_alloc_range(si, ci, offset, usage, order);
+			if (!cluster_alloc_range(si, ci, offset, usage, order)) {
+				offset = SWAP_NEXT_INVALID;
+				goto done;
+			}
 			*foundp = offset;
 			if (ci->count == SWAPFILE_CLUSTER) {
 				offset = SWAP_NEXT_INVALID;
@@ -805,7 +813,11 @@ new_cluster:
 	if (!list_empty(&si->free_clusters)) {
 		ci = list_first_entry(&si->free_clusters, struct swap_cluster_info, list);
 		offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci), &found, order, usage);
-		VM_BUG_ON(!found);
+		/*
+		 * Either we didn't touch the cluster due to swapoff,
+		 * or the allocation must success.
+		 */
+		VM_BUG_ON((si->flags & SWP_WRITEOK) && !found);
 		goto done;
 	}
 
@@ -1041,6 +1053,8 @@ static int cluster_alloc_swap(struct swap_info_struct *si,
 
 	VM_BUG_ON(!si->cluster_info);
 
+	si->flags += SWP_SCANNING;
+
 	while (n_ret < nr) {
 		unsigned long offset = cluster_alloc_swap_entry(si, order, usage);
 
@@ -1049,6 +1063,8 @@ static int cluster_alloc_swap(struct swap_info_struct *si,
 		slots[n_ret++] = swp_entry(si->type, offset);
 	}
 
+	si->flags -= SWP_SCANNING;
+
 	return n_ret;
 }