From d0319bd52e373c661f9bc0c04dec85d6f87ac517 Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Thu, 2 Jan 2014 12:58:49 -0800 Subject: [PATCH] mm: remove bogus warning in copy_huge_pmd() Sasha Levin reported the following warning being triggered WARNING: CPU: 28 PID: 35287 at mm/huge_memory.c:887 copy_huge_pmd+0x145/ 0x3a0() Call Trace: copy_huge_pmd+0x145/0x3a0 copy_page_range+0x3f2/0x560 dup_mmap+0x2c9/0x3d0 dup_mm+0xad/0x150 copy_process+0xa68/0x12e0 do_fork+0x96/0x270 SyS_clone+0x16/0x20 stub_clone+0x69/0x90 This warning was introduced by "mm: numa: Avoid unnecessary disruption of NUMA hinting during migration" for paranoia reasons but the warning is bogus. I was thinking of parallel races between NUMA hinting faults and forks but this warning would also be triggered by a parallel reclaim splitting a THP during a fork. Remote the bogus warning. Signed-off-by: Mel Gorman Reported-by: Sasha Levin Cc: Alex Thorlton Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/huge_memory.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 7de1bf8..9c0b172 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -883,9 +883,6 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, goto out_unlock; } - /* mmap_sem prevents this happening but warn if that changes */ - WARN_ON(pmd_trans_migrating(pmd)); - if (unlikely(pmd_trans_splitting(pmd))) { /* split huge page running from under us */ spin_unlock(src_ptl); -- 2.7.4