From: Miaohe Lin <linmiaohe@xxxxxxxxxx> Subject: mm/pgtable-generic.c: optimize the VM_BUG_ON condition in pmdp_huge_clear_flush() 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. Link: https://lkml.kernel.org/r/20210203084137.25522-1-linmiaohe@xxxxxxxxxx Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx> Suggested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/pgtable-generic.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/mm/pgtable-generic.c~mm-pgtable-genericc-optimize-the-vm_bug_on-condition-in-pmdp_huge_clear_flush +++ a/mm/pgtable-generic.c @@ -135,8 +135,9 @@ pmd_t pmdp_huge_clear_flush(struct vm_ar { 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; _
