Commit 374437a2 authored by Miaohe Lin's avatar Miaohe Lin Committed by Linus Torvalds
Browse files

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@huawei.com


Signed-off-by: default avatarMiaohe Lin <linmiaohe@huawei.com>
Suggested-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c045c72c

mm/pgtable-generic.c

+3 −2
Original line number Diff line number Diff line
@@ -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;