From c76aaef04194fdaad83dc6c27eb5edce77d4a7f9 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Mon, 18 Oct 2004 08:54:48 -0700 Subject: [PATCH] [PATCH] __set_page_dirty_nobuffers mappings Marcelo noticed that the BUG_ON in __set_page_dirty_nobuffers doesn't make much sense: it lost its way in 2.6.7, amidst so many page_mappings! It's supposed to be checking that, although page->mapping may suddenly go NULL from truncation, and although tmpfs swizzles page_mapping(page) between tmpfs inode address_space and swapper_space, there's sufficient stabilization while here in __set_page_dirty_nobuffers that the mapping after we locked mapping->tree_lock is the same as the mapping before we locked mapping->tree_lock i.e. the lock we hold is the right one. Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page-writeback.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 343998d46bb03..a3f185e9fc2f1 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -580,12 +580,13 @@ int __set_page_dirty_nobuffers(struct page *page) if (!TestSetPageDirty(page)) { struct address_space *mapping = page_mapping(page); + struct address_space *mapping2; if (mapping) { spin_lock_irq(&mapping->tree_lock); - mapping = page_mapping(page); - if (page_mapping(page)) { /* Race with truncate? */ - BUG_ON(page_mapping(page) != mapping); + mapping2 = page_mapping(page); + if (mapping2) { /* Race with truncate? */ + BUG_ON(mapping2 != mapping); if (!mapping->backing_dev_info->memory_backed) inc_page_state(nr_dirty); radix_tree_tag_set(&mapping->page_tree, -- 2.53.0