From f9aed62a2b12a8e04077737c9942111e14ed738e Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Tue, 21 Aug 2012 16:15:45 -0700 Subject: [PATCH] mm: change nr_ptes BUG_ON to WARN_ON Occasionally an isolated BUG_ON(mm->nr_ptes) gets reported, indicating that not all the page tables allocated could be found and freed when exit_mmap() tore down the user address space. There's usually nothing we can say about it, beyond that it's probably a sign of some bad memory or memory corruption; though it might still indicate a bug in vma or page table management (and did recently reveal a race in THP, fixed a few months ago). But one overdue change we can make is from BUG_ON to WARN_ON. It's fairly likely that the system will crash shortly afterwards in some other way (for example, the BUG_ON(page_mapped(page)) in __delete_from_page_cache(), once an inode mapped into the lost page tables gets evicted); but might tell us more before that. Change the BUG_ON(page_mapped) to WARN_ON too? Later perhaps: I'm less eager, since that one has several times led to fixes. Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/mmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/mmap.c b/mm/mmap.c index e3e86914f11a..9adee9fc0d8a 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2309,7 +2309,7 @@ void exit_mmap(struct mm_struct *mm) } vm_unacct_memory(nr_accounted); - BUG_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT); + WARN_ON(mm->nr_ptes > (FIRST_USER_ADDRESS+PMD_SIZE-1)>>PMD_SHIFT); } /* Insert vm structure into process list sorted by address