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mm: remove bogus warning in copy_huge_pmd()

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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 <mgorman@suse.de>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mel Gorman 2014-01-02 12:58:49 -08:00 committed by Linus Torvalds
parent 695c608307
commit d0319bd52e
1 changed files with 0 additions and 3 deletions
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3
mm/huge_memory.c
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@ -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);