linux-kernel - [PATCH] mm: simplify the VM_BUG_ON condition in pmdp_huge_clear

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Date:   Mon, 1 Feb 2021 06:43:19 -0500
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] mm: simplify the VM_BUG_ON condition in pmdp_huge_clear_flush()

The condition (A && !C && !D) || !A is equivalent to !A || (A && !C && !D)
and can be further simplified to !A || (!C && !D).

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 mm/pgtable-generic.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index 9578db83e312..fa1375f3e3b2 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -135,8 +135,8 @@ 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)) || !pmd_present(*pmdp));
+	VM_BUG_ON(!pmd_present(*pmdp) || (!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