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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7DD4AC6FD1C for ; Wed, 22 Mar 2023 20:35:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232001AbjCVUf5 (ORCPT ); Wed, 22 Mar 2023 16:35:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50700 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230148AbjCVUfm (ORCPT ); Wed, 22 Mar 2023 16:35:42 -0400 Received: from mail-ed1-x535.google.com (mail-ed1-x535.google.com [IPv6:2a00:1450:4864:20::535]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E3B58A54D6 for ; Wed, 22 Mar 2023 13:27:16 -0700 (PDT) Received: by mail-ed1-x535.google.com with SMTP id b20so45030727edd.1 for ; Wed, 22 Mar 2023 13:27:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1679516831; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=Y03ABEGM1iKLlme/gXEiM5NZEzoEuVUqbJDwPp/dx0w=; b=AieqBZhZMkpzi7l8Xgosf+G/LZdAL0XEMXs4cyJOInXcfpx9+8LiBmQhK9QkxTdCr/ Ze7zOBvK5HyUg+blniEH7fx2zlA9be/AaWA72NcaS0PauUJyFpavYmxGMynNDTzRfotU qqVsXgYwm7ePZoj1caewYJiPn8cW89WRes4Y2GgXkvk0tBSyKrjM5VfMz0JzzSIVFFZc MsHex2914d5u+bX8mPH8itnPhFMoDylKRiq36dOF60WY6XyC13GOhVnZWaoX/LZk3OMs Jdnn6JRlNH7jv0WhI8Nml/sTJyBGN+Cv99v8VLQWGojPGrH4eIkMak2R8rFQbaRAYKBt O6Uw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679516831; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=Y03ABEGM1iKLlme/gXEiM5NZEzoEuVUqbJDwPp/dx0w=; b=qHVn9zQ1V50Opuwg8FrHQUApYzLC+zqp7RVtJyVTQp+mOcyJowlYJmZqehsOSeMRUu wTqcWCzmRdKshNT6jVLyCO6/ByIxTHHxzVcz+4VVFWgzd/YK20wrHotisu60GBPEz1e3 Is92dlg8PkFSCSemEuWGrMh1lAwccRraDjsb1lwfdDApz2hVPJAfJOZ+OaR1oaEAvcmN WHptSKc+OIn1R/i8A1GqOE2cXucwlLyXBQMFZQd1FQ2nruKS+xLIh61+sVPgk8E0HWsL BitQRafXQXrChlg68ZuUWlqOApJABZx4/cbhczugiC4XAcvHt1QuYVqYY5wD3ZRf+Sit LCGA== X-Gm-Message-State: AO0yUKUWAULHEjv8RapMKbnuKP5pdRnadvwahaXbBFb4aicW0QdrAnQ3 xlSaFUXOAgtKAcevPiuaBK0coVJ8BsM= X-Google-Smtp-Source: AK7set+ATbzj/eQLxtCrE9dHPBKvwKXL3pNhGaIh1/xzV/CmmQiXekthknCewslVcVuOxIMnzPtpcQ== X-Received: by 2002:a1c:6a08:0:b0:3ed:8780:f265 with SMTP id f8-20020a1c6a08000000b003ed8780f265mr561473wmc.21.1679515772745; Wed, 22 Mar 2023 13:09:32 -0700 (PDT) Received: from lucifer.home ([2a00:23c5:dc8c:8701:1663:9a35:5a7b:1d76]) by smtp.googlemail.com with ESMTPSA id a7-20020adff7c7000000b002c70ce264bfsm14664342wrq.76.2023.03.22.13.09.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Mar 2023 13:09:31 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton Cc: David Hildenbrand , Matthew Wilcox , Vlastimil Babka , "Liam R . Howlett" , maple-tree@lists.infradead.org, Vernon Yang , Lorenzo Stoakes Subject: [PATCH v4 4/4] mm/mmap/vma_merge: init cleanup, be explicit about the non-mergeable case Date: Wed, 22 Mar 2023 20:09:22 +0000 Message-Id: X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Rather than setting err = -1 and only resetting if we hit merge cases, explicitly check the non-mergeable case to make it abundantly clear that we only proceed with the rest if something is mergeable, default err to 0 and only update if an error might occur. Move the merge_prev, merge_next cases closer to the logic determining curr, next and reorder initial variables so they are more logically grouped. This has no functional impact. Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka --- mm/mmap.c | 47 ++++++++++++++++++++++------------------------- 1 file changed, 22 insertions(+), 25 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 2a4f63716231..1064e6341a7a 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -909,18 +909,18 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, struct vm_userfaultfd_ctx vm_userfaultfd_ctx, struct anon_vma_name *anon_name) { - pgoff_t pglen = (end - addr) >> PAGE_SHIFT; - pgoff_t vma_pgoff; struct vm_area_struct *curr, *next, *res; struct vm_area_struct *vma, *adjust, *remove, *remove2; - int err = -1; + struct vma_prepare vp; + pgoff_t vma_pgoff; + int err = 0; bool merge_prev = false; bool merge_next = false; bool vma_expanded = false; - struct vma_prepare vp; + unsigned long vma_start = addr; unsigned long vma_end = end; + pgoff_t pglen = (end - addr) >> PAGE_SHIFT; long adj_start = 0; - unsigned long vma_start = addr; validate_mm(mm); /* @@ -939,24 +939,14 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, else next = NULL; /* case 5 */ - /* - * By default, we return prev. Cases 3, 4, 8 will instead return next - * and cases 3, 8 will also update vma to point at next. - */ - res = vma = prev; - - /* Verify some invariant that must be enforced by the caller. */ - VM_WARN_ON(prev && addr <= prev->vm_start); - VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); - VM_WARN_ON(addr >= end); - if (prev) { vma_start = prev->vm_start; vma_pgoff = prev->vm_pgoff; + /* Can we merge the predecessor? */ - if (prev->vm_end == addr && mpol_equal(vma_policy(prev), policy) + if (addr == prev->vm_end && mpol_equal(vma_policy(prev), policy) && can_vma_merge_after(prev, vm_flags, anon_vma, file, - pgoff, vm_userfaultfd_ctx, anon_name)) { + pgoff, vm_userfaultfd_ctx, anon_name)) { merge_prev = true; vma_prev(vmi); } @@ -964,13 +954,22 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, /* Can we merge the successor? */ if (next && mpol_equal(policy, vma_policy(next)) && - can_vma_merge_before(next, vm_flags, - anon_vma, file, pgoff+pglen, + can_vma_merge_before(next, vm_flags, anon_vma, file, pgoff+pglen, vm_userfaultfd_ctx, anon_name)) { merge_next = true; } + if (!merge_prev && !merge_next) + return NULL; /* Not mergeable. */ + + res = vma = prev; remove = remove2 = adjust = NULL; + + /* Verify some invariant that must be enforced by the caller. */ + VM_WARN_ON(prev && addr <= prev->vm_start); + VM_WARN_ON(curr && (addr != curr->vm_start || end > curr->vm_end)); + VM_WARN_ON(addr >= end); + /* Can we merge both the predecessor and the successor? */ if (merge_prev && merge_next && is_mergeable_anon_vma(prev->anon_vma, next->anon_vma, NULL)) { @@ -983,8 +982,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, if (!next->anon_vma) err = dup_anon_vma(prev, curr); } - } else if (merge_prev) { - err = 0; /* case 2 */ + } else if (merge_prev) { /* case 2 */ if (curr) { err = dup_anon_vma(prev, curr); if (end == curr->vm_end) { /* case 7 */ @@ -994,7 +992,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, adj_start = (end - curr->vm_start); } } - } else if (merge_next) { + } else { /* merge_next */ res = next; if (prev && addr < prev->vm_end) { /* case 4 */ vma_end = addr; @@ -1010,7 +1008,6 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, vma_start = addr; vma_end = next->vm_end; vma_pgoff = next->vm_pgoff; - err = 0; if (curr) { /* case 8 */ vma_pgoff = curr->vm_pgoff; remove = curr; @@ -1019,7 +1016,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, } } - /* Cannot merge or error in anon_vma clone */ + /* Error in anon_vma clone. */ if (err) return NULL; -- 2.39.2