From c8a8f3b4a95ace7683b615ad9c9aa0eac59013ae Mon Sep 17 00:00:00 2001 From: David Stevens Date: Wed, 7 Jun 2023 14:31:35 +0900 Subject: mm/khugepaged: fix iteration in collapse_file Remove an unnecessary call to xas_set(index) when iterating over the target range in collapse_file. The extra call to xas_set reset the xas cursor to the top of the tree, causing the xas_next call on the next iteration to walk the tree to index instead of advancing to index+1. This returned the same page again, which would cause collapse_file to fail because the page is already locked. This bug was hidden when CONFIG_DEBUG_VM was set. When that config was used, the xas_load in a subsequent VM_BUG_ON assert would walk xas from the top of the tree to index, causing the xas_next call on the next loop iteration to advance the cursor as expected. Link: https://lkml.kernel.org/r/20230607053135.2087354-1-stevensd@google.com Fixes: a2e17cc2efc7 ("mm/khugepaged: maintain page cache uptodate flag") Signed-off-by: David Stevens Reviewed-by: Peter Xu Cc: David Hildenbrand Cc: Hugh Dickins Cc: Jiaqi Yan Cc: Kirill A . Shutemov Cc: Matthew Wilcox Cc: Yang Shi Cc: Mike Kravetz Signed-off-by: Andrew Morton --- mm/khugepaged.c | 1 - 1 file changed, 1 deletion(-) (limited to 'mm/khugepaged.c') diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 6b9d39d65b73..2d0d58fb4e7f 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -2070,7 +2070,6 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr, TTU_IGNORE_MLOCK | TTU_BATCH_FLUSH); xas_lock_irq(&xas); - xas_set(&xas, index); VM_BUG_ON_PAGE(page != xas_load(&xas), page); -- cgit v1.2.3