From b16664e44c54525be89dc07ad15a13b4eeec5634 Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Wed, 1 Feb 2006 03:05:36 -0800 Subject: [PATCH] Direct Migration V9: PageSwapCache checks Check for PageSwapCache after looking up and locking a swap page. The page migration code may change a swap pte to point to a different page under lock_page(). If that happens then the vm must retry the lookup operation in the swap space to find the correct page number. There are a couple of locations in the VM where a lock_page() is done on a swap page. In these locations we need to check afterwards if the page was migrated. If the page was migrated then the old page that was looked up before was freed and no longer has the PageSwapCache bit set. Signed-off-by: Hirokazu Takahashi Signed-off-by: Dave Hansen Signed-off-by: Christoph Lameter Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/swapfile.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'mm/swapfile.c') diff --git a/mm/swapfile.c b/mm/swapfile.c index f1e69c30d203..9678182e0eef 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -646,6 +646,7 @@ static int try_to_unuse(unsigned int type) */ swap_map = &si->swap_map[i]; entry = swp_entry(type, i); +again: page = read_swap_cache_async(entry, NULL, 0); if (!page) { /* @@ -680,6 +681,12 @@ static int try_to_unuse(unsigned int type) wait_on_page_locked(page); wait_on_page_writeback(page); lock_page(page); + if (!PageSwapCache(page)) { + /* Page migration has occured */ + unlock_page(page); + page_cache_release(page); + goto again; + } wait_on_page_writeback(page); /* -- cgit v1.2.1