[PATCH] mm, swap: fix reclaim offset calculation error during allocation

[Kairui Song <ryncsn@gmail.com>]

From: Kairui Song <kasong@tencent.com>

There is a code error that will cause the swap entry allocator to
reclaim and check the whole cluster with an unexpected tail offset
instead of the part that needs to be reclaimed. This may cause
corruption of the swap map, so fix it.

Fixes: 3b644773eefd ("mm, swap: reduce contention on device lock")
Signed-off-by: Kairui Song <kasong@tencent.com>
---
 mm/swapfile.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 6e867c16ea93..ba19430dd4ea 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -794,7 +794,7 @@ static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si,
 		if (!cluster_scan_range(si, ci, offset, nr_pages, &need_reclaim))
 			continue;
 		if (need_reclaim) {
-			ret = cluster_reclaim_range(si, ci, start, end);
+			ret = cluster_reclaim_range(si, ci, offset, offset + nr_pages);
 			/*
 			 * Reclaim drops ci->lock and cluster could be used
 			 * by another order. Not checking flag as off-list
-- 
2.48.1