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Subject[PATCH] mm/pgtable-generic.c: optimize the VM_BUG_ON condition in pmdp_huge_clear_flush()
Date
The developer will have trouble figuring out why the BUG actually triggered
when there is a complex expression in the VM_BUG_ON. Because we can only
identify the condition triggered BUG via line number provided by VM_BUG_ON.
Optimize this by spliting such a complex expression into two simple
conditions.

Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
mm/pgtable-generic.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index fa1375f3e3b2..c2210e1cdb51 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -135,8 +135,9 @@ pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address,
{
pmd_t pmd;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
- VM_BUG_ON(!pmd_present(*pmdp) || (!pmd_trans_huge(*pmdp) &&
- !pmd_devmap(*pmdp)));
+ VM_BUG_ON(!pmd_present(*pmdp));
+ /* Below assumes pmd_present() is true */
+ VM_BUG_ON(!pmd_trans_huge(*pmdp) && !pmd_devmap(*pmdp));
pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);
flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
return pmd;
--
2.19.1
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