I've hit the "address >= vma->vm_end" check in do_page_add_anon_rmap() just once. The stack showed khugepaged allocation trying to compact pages: the call to page_add_anon_rmap() coming from remove_migration_pte(). That path holds anon_vma lock, but does not hold mmap_sem: it can therefore race with a split_vma(), and in commit 5f70b962ccc2 "mmap: avoid unnecessary anon_vma lock" we just took away the anon_vma lock protection when adjusting vma->vm_end. I don't think that particular BUG_ON ever caught anything interesting, so better replace it by a comment, than reinstate the anon_vma locking. Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> --- mm/rmap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- linux.orig/mm/rmap.c 2011-05-27 19:05:27.000000000 -0700 +++ linux/mm/rmap.c 2011-05-27 20:07:44.601361236 -0700 @@ -1014,7 +1014,7 @@ void do_page_add_anon_rmap(struct page * return; VM_BUG_ON(!PageLocked(page)); - VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end); + /* address might be in next vma when migration races vma_adjust */ if (first) __page_set_anon_rmap(page, vma, address, exclusive); else @@ -1709,7 +1709,7 @@ void hugepage_add_anon_rmap(struct page BUG_ON(!PageLocked(page)); BUG_ON(!anon_vma); - BUG_ON(address < vma->vm_start || address >= vma->vm_end); + /* address might be in next vma when migration races vma_adjust */ first = atomic_inc_and_test(&page->_mapcount); if (first) __hugepage_set_anon_rmap(page, vma, address, 0); -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>