From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4370EC433DB for ; Wed, 24 Feb 2021 20:06:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EC27564F2C for ; Wed, 24 Feb 2021 20:06:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235216AbhBXUGi (ORCPT ); Wed, 24 Feb 2021 15:06:38 -0500 Received: from mail.kernel.org ([198.145.29.99]:55514 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235306AbhBXUFy (ORCPT ); Wed, 24 Feb 2021 15:05:54 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3397364F2D; Wed, 24 Feb 2021 20:04:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1614197080; bh=gTjnI4BIkQ1GHRRNKlBFUJ5q0apX1+RAnlPsE3l1wrM=; h=Date:From:To:Subject:In-Reply-To:From; b=rxojsoa+cRx2XPRA9Tgq0RbmX4T5PVc6bvMRulNKxb0w/nPJQsLKp7Ult8N7TQXop Qt+mvrAgu50RxT+RJDHuvr1MhuMgHYO4eZZaAdg0JUbbE8X6m8enKLyhQJpBiN0Jrd CYKIz+y1sHvZGBFBe2zhvLpjLVA8OxlBIpFOER6A= Date: Wed, 24 Feb 2021 12:04:39 -0800 From: Andrew Morton To: akpm@linux-foundation.org, linmiaohe@huawei.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 079/173] mm/pgtable-generic.c: optimize the VM_BUG_ON condition in pmdp_huge_clear_flush() Message-ID: <20210224200439.0k6rJzU8V%akpm@linux-foundation.org> In-Reply-To: <20210224115824.1e289a6895087f10c41dd8d6@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Miaohe Lin 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@huawei.com Signed-off-by: Miaohe Lin Suggested-by: Andrew Morton Signed-off-by: Andrew Morton --- 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; _