From patchwork Wed Aug 14 02:17:53 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wei Yang X-Patchwork-Id: 11093053 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B581E112C for ; Wed, 14 Aug 2019 02:18:27 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9AC762872E for ; Wed, 14 Aug 2019 02:18:27 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8B14E2872A; Wed, 14 Aug 2019 02:18:27 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1EDFC2872A for ; Wed, 14 Aug 2019 02:18:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EB2206B0005; Tue, 13 Aug 2019 22:18:23 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id E62616B0006; Tue, 13 Aug 2019 22:18:23 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D76F76B0007; Tue, 13 Aug 2019 22:18:23 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0190.hostedemail.com [216.40.44.190]) by kanga.kvack.org (Postfix) with ESMTP id B1A066B0005 for ; Tue, 13 Aug 2019 22:18:23 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id 45C7F485F for ; Wed, 14 Aug 2019 02:18:23 +0000 (UTC) X-FDA: 75819424086.05.eyes21_ef3f024fb74e X-HE-Tag: eyes21_ef3f024fb74e X-Filterd-Recvd-Size: 3340 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by imf31.hostedemail.com (Postfix) with ESMTP for ; Wed, 14 Aug 2019 02:18:22 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 13 Aug 2019 19:18:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,382,1559545200"; d="scan'208";a="205293131" Received: from richard.sh.intel.com (HELO localhost) ([10.239.159.54]) by fmsmga002.fm.intel.com with ESMTP; 13 Aug 2019 19:18:19 -0700 From: Wei Yang To: akpm@linux-foundation.org, mgorman@techsingularity.net, vbabka@suse.cz, osalvador@suse.de Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wei Yang Subject: [PATCH 1/3] mm/mmap.c: prev could be retrieved from vma->vm_prev Date: Wed, 14 Aug 2019 10:17:53 +0800 Message-Id: <20190814021755.1977-1-richardw.yang@linux.intel.com> X-Mailer: git-send-email 2.17.1 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP Currently __vma_unlink_common handles two cases: * has_prev * or not When has_prev is false, it is obvious prev is calculated from vma->vm_prev in __vma_unlink_common. When has_prev is true, the prev is passed through from __vma_unlink_prev in __vma_adjust for non-case 8. And at the beginning next is calculated from vma->vm_next, which implies vma is next->vm_prev. The above statement sounds a little complicated, while to think in another point of view, no matter whether vma and next is swapped, the mmap link list still preserves its property. It is proper to access vma->vm_prev. Signed-off-by: Wei Yang --- mm/mmap.c | 20 +++++++------------- 1 file changed, 7 insertions(+), 13 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index b8072630766f..3d56340fea36 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -675,23 +675,17 @@ static void __insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma) static __always_inline void __vma_unlink_common(struct mm_struct *mm, struct vm_area_struct *vma, - struct vm_area_struct *prev, - bool has_prev, struct vm_area_struct *ignore) { - struct vm_area_struct *next; + struct vm_area_struct *prev, *next; vma_rb_erase_ignore(vma, &mm->mm_rb, ignore); next = vma->vm_next; - if (has_prev) + prev = vma->vm_prev; + if (prev) prev->vm_next = next; - else { - prev = vma->vm_prev; - if (prev) - prev->vm_next = next; - else - mm->mmap = next; - } + else + mm->mmap = next; if (next) next->vm_prev = prev; @@ -703,7 +697,7 @@ static inline void __vma_unlink_prev(struct mm_struct *mm, struct vm_area_struct *vma, struct vm_area_struct *prev) { - __vma_unlink_common(mm, vma, prev, true, vma); + __vma_unlink_common(mm, vma, vma); } /* @@ -891,7 +885,7 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start, * "next" (which is stored in post-swap() * "vma"). */ - __vma_unlink_common(mm, next, NULL, false, vma); + __vma_unlink_common(mm, next, vma); if (file) __remove_shared_vm_struct(next, file, mapping); } else if (insert) {