From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f51.google.com (mail-ej1-f51.google.com [209.85.218.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 429E3A5A for ; Thu, 2 Jun 2022 14:56:26 +0000 (UTC) Received: by mail-ej1-f51.google.com with SMTP id m20so10447454ejj.10 for ; Thu, 02 Jun 2022 07:56:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=xHh+H7BQlsfCtAThje/xIUlqgtGS6GOCshB5FBGaRKo=; b=Xh4ANWAuyg1cGJ+Dc3w4iprlH+ngwcPVcnneCJIhSUiAvDORma8aDPn+jO+RerLhrD WQOw4rwXU3QNw1K8AKEt4d+PZA7qERjd99V7OhPKdQsNjMdr6fyz4mz88nOKJ4nMWW5r PfVMkS7Q2ZIiWJ1TcouljeNAz58TyHZZbg2zarFPk44XO9QCZWGU7wLrn7NhnSgjXDEm Ve4QHydnVC83yUg2pkJc6wmb+VdAkwcoyB9dzUGjFHICuB/OwFiFrb3dLd32vT97O6A0 HTrTO22GsYmirQRf1EPplon/oZqfyKAVGMB3h4DzpjCe8jkTt8L/4w19GbLaM8/ndhPq a0UQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=xHh+H7BQlsfCtAThje/xIUlqgtGS6GOCshB5FBGaRKo=; b=gTr/53xVAveFhySmhqeQq5xSSHhyH3jWSDTQke9Bat32fh0PAs/grCh0ENenF+BKp3 8D7JX99gO8VOSoFfNwgFZnxR+hi99MFj5RNvhD8wdrXcaWR74pMPzNWFV0DyMIHq5woG 3u8Nw1e0HEB4f0fl70MpUCpQuHNkVIUowiUFyMnfDzhUTaHJila0e1DX0Vc8/gHT0joK 6m16fnNrDUKpXJu/CuKP85Id+0Stnpn15cF7kj8C/dX4VmKt+CYpxYkPOFzhlnjDYAiS 7KAkBhmPD9rO6Vzarrtq2kS5sBlPHYQOU9r1oi7x+OLtoK2UgyJGAqQiWrH2iwQnGv0w WpDg== X-Gm-Message-State: AOAM532mPmLqO5qzWhvwj4w4/4mBkb4e0QoomDxqfDUdLQZ3JunKp8xe y2ldinkacm73CWT06zIFSpY= X-Google-Smtp-Source: ABdhPJzFpDSOoca0Grhs4EW9ifXaEdKhAsPuLn92ZsZoqiBqc/ljbC4VpVXsTCJR4BkYygkcveUQcg== X-Received: by 2002:a17:906:7254:b0:6fe:5637:cbe6 with SMTP id n20-20020a170906725400b006fe5637cbe6mr4645754ejk.612.1654181784247; Thu, 02 Jun 2022 07:56:24 -0700 (PDT) Received: from orion.localdomain ([93.99.228.15]) by smtp.gmail.com with ESMTPSA id x9-20020a1709064a8900b006f3ef214e2csm1873452eju.146.2022.06.02.07.56.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Jun 2022 07:56:23 -0700 (PDT) Received: by orion.localdomain (Postfix, from userid 1003) id 2A742A0886; Thu, 2 Jun 2022 16:56:57 +0200 (CEST) From: =?UTF-8?q?Jakub=20Mat=C4=9Bna?= To: akpm@linux-foundation.org Cc: linux-mm@kvack.org, patches@lists.linux.dev, linux-kernel@vger.kernel.org, vbabka@suse.cz, mhocko@kernel.org, mgorman@techsingularity.net, willy@infradead.org, liam.howlett@oracle.com, hughd@google.com, kirill@shutemov.name, riel@surriel.com, rostedt@goodmis.org, peterz@infradead.org, =?UTF-8?q?Jakub=20Mat=C4=9Bna?= Subject: [PATCH 1/2] [PATCH 1/2] mm: refactor of vma_merge() Date: Thu, 2 Jun 2022 16:56:41 +0200 Message-Id: <20220602145642.16948-2-matenajakub@gmail.com> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220602145642.16948-1-matenajakub@gmail.com> References: <20220602145642.16948-1-matenajakub@gmail.com> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Refactor vma_merge() to make it shorter and more understandable. Main change is the elimination of code duplicity in the case of merge next check. This is done by first doing checks and caching the results before executing the merge itself. The variable 'area' is divided into 'mid' and 'res' as previously it was used for two purposes, as the middle VMA between prev and next and also as the result of the merge itself. Exit paths are also unified. Signed-off-by: Jakub Matěna --- mm/mmap.c | 87 +++++++++++++++++++++++-------------------------------- 1 file changed, 37 insertions(+), 50 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index 313b57d55a63..91100fdc400a 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1170,8 +1170,10 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, struct anon_vma_name *anon_name) { pgoff_t pglen = (end - addr) >> PAGE_SHIFT; - struct vm_area_struct *area, *next; - int err; + struct vm_area_struct *mid, *next, *res; + int err = -1; + bool merge_prev = false; + bool merge_next = false; /* * We later require that vma->vm_flags == vm_flags, @@ -1181,75 +1183,60 @@ struct vm_area_struct *vma_merge(struct mm_struct *mm, return NULL; next = vma_next(mm, prev); - area = next; - if (area && area->vm_end == end) /* cases 6, 7, 8 */ + mid = next; + if (next && next->vm_end == end) /* cases 6, 7, 8 */ next = next->vm_next; /* verify some invariant that must be enforced by the caller */ VM_WARN_ON(prev && addr <= prev->vm_start); - VM_WARN_ON(area && end > area->vm_end); + VM_WARN_ON(mid && end > mid->vm_end); VM_WARN_ON(addr >= end); - /* - * Can it merge with the predecessor? - */ + /* Can we merge the predecessor? */ if (prev && prev->vm_end == addr && mpol_equal(vma_policy(prev), policy) && can_vma_merge_after(prev, vm_flags, anon_vma, file, pgoff, vm_userfaultfd_ctx, anon_name)) { - /* - * OK, it can. Can we now merge in the successor as well? - */ - if (next && end == next->vm_start && - mpol_equal(policy, vma_policy(next)) && - can_vma_merge_before(next, vm_flags, - anon_vma, file, - pgoff+pglen, - vm_userfaultfd_ctx, anon_name) && - is_mergeable_anon_vma(prev->anon_vma, - next->anon_vma, NULL)) { - /* cases 1, 6 */ - err = __vma_adjust(prev, prev->vm_start, - next->vm_end, prev->vm_pgoff, NULL, - prev); - } else /* cases 2, 5, 7 */ - err = __vma_adjust(prev, prev->vm_start, - end, prev->vm_pgoff, NULL, prev); - if (err) - return NULL; - khugepaged_enter_vma_merge(prev, vm_flags); - return prev; + merge_prev = true; } - - /* - * Can this new request be merged in front of next? - */ + /* Can we merge the successor? */ if (next && end == next->vm_start && mpol_equal(policy, vma_policy(next)) && can_vma_merge_before(next, vm_flags, anon_vma, file, pgoff+pglen, vm_userfaultfd_ctx, anon_name)) { + merge_next = true; + } + /* 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)) { /* cases 1, 6 */ + err = __vma_adjust(prev, prev->vm_start, + next->vm_end, prev->vm_pgoff, NULL, + prev); + res = prev; + } else if (merge_prev) { /* cases 2, 5, 7 */ + err = __vma_adjust(prev, prev->vm_start, + end, prev->vm_pgoff, NULL, prev); + res = prev; + } else if (merge_next) { if (prev && addr < prev->vm_end) /* case 4 */ err = __vma_adjust(prev, prev->vm_start, - addr, prev->vm_pgoff, NULL, next); - else { /* cases 3, 8 */ - err = __vma_adjust(area, addr, next->vm_end, - next->vm_pgoff - pglen, NULL, next); - /* - * In case 3 area is already equal to next and - * this is a noop, but in case 8 "area" has - * been removed and next was expanded over it. - */ - area = next; - } - if (err) - return NULL; - khugepaged_enter_vma_merge(area, vm_flags); - return area; + addr, prev->vm_pgoff, NULL, next); + else /* cases 3, 8 */ + err = __vma_adjust(mid, addr, next->vm_end, + next->vm_pgoff - pglen, NULL, next); + res = next; } - return NULL; + /* + * Cannot merge with predecessor or successor or error in __vma_adjust? + */ + if (err) + return NULL; + khugepaged_enter_vma_merge(res, vm_flags); + return res; } /* -- 2.35.1