From 22eca178b9835532d829231ff6dd526deacc92bd Mon Sep 17 00:00:00 2001
From: Andrew Morton <akpm@zip.com.au>
Date: Sun, 5 May 2002 01:09:21 -0700
Subject: [PATCH] [PATCH] radix-tree locking fix

__delete_from_swap_cache modifies the radix tree.  We need to take the
lock for writing.
---
 mm/swapfile.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 67bedbf68446..2ced3aaa6a46 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -308,13 +308,13 @@ int remove_exclusive_swap_page(struct page *page)
 	retval = 0;
 	if (p->swap_map[SWP_OFFSET(entry)] == 1) {
 		/* Recheck the page count with the pagecache lock held.. */
-		read_lock(&swapper_space.page_lock);
+		write_lock(&swapper_space.page_lock);
 		if (page_count(page) - !!PagePrivate(page) == 2) {
 			__delete_from_swap_cache(page);
 			SetPageDirty(page);
 			retval = 1;
 		}
-		read_unlock(&swapper_space.page_lock);
+		write_unlock(&swapper_space.page_lock);
 	}
 	swap_info_put(p);
 
-- 
2.39.5