diff --git a/mm/shmem.c b/mm/shmem.c
index 8fa27e4e582a236886eba7d875e6c612130468fc..262d7117344794e28a73e1440c39f0ade96bb44b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1039,6 +1039,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 	struct address_space *mapping;
 	unsigned long index;
 	struct inode *inode;
+	bool unlock_mutex = false;
 
 	BUG_ON(!PageLocked(page));
 	mapping = page->mapping;
@@ -1064,7 +1065,26 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 	else
 		swap.val = 0;
 
+	/*
+	 * Add inode to shmem_unuse()'s list of swapped-out inodes,
+	 * if it's not already there.  Do it now because we cannot take
+	 * mutex while holding spinlock, and must do so before the page
+	 * is moved to swap cache, when its pagelock no longer protects
+	 * the inode from eviction.  But don't unlock the mutex until
+	 * we've taken the spinlock, because shmem_unuse_inode() will
+	 * prune a !swapped inode from the swaplist under both locks.
+	 */
+	if (swap.val && list_empty(&info->swaplist)) {
+		mutex_lock(&shmem_swaplist_mutex);
+		/* move instead of add in case we're racing */
+		list_move_tail(&info->swaplist, &shmem_swaplist);
+		unlock_mutex = true;
+	}
+
 	spin_lock(&info->lock);
+	if (unlock_mutex)
+		mutex_unlock(&shmem_swaplist_mutex);
+
 	if (index >= info->next_index) {
 		BUG_ON(!(info->flags & SHMEM_TRUNCATE));
 		goto unlock;
@@ -1084,21 +1104,10 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 		delete_from_page_cache(page);
 		shmem_swp_set(info, entry, swap.val);
 		shmem_swp_unmap(entry);
-		if (list_empty(&info->swaplist))
-			inode = igrab(inode);
-		else
-			inode = NULL;
 		spin_unlock(&info->lock);
 		swap_shmem_alloc(swap);
 		BUG_ON(page_mapped(page));
 		swap_writepage(page, wbc);
-		if (inode) {
-			mutex_lock(&shmem_swaplist_mutex);
-			/* move instead of add in case we're racing */
-			list_move_tail(&info->swaplist, &shmem_swaplist);
-			mutex_unlock(&shmem_swaplist_mutex);
-			iput(inode);
-		}
 		return 0;
 	}