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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15DD6C369DC for ; Wed, 30 Apr 2025 00:47:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DC7F48E0002; Tue, 29 Apr 2025 20:47:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D78308E0001; Tue, 29 Apr 2025 20:47:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C3FB18E0002; Tue, 29 Apr 2025 20:47:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id A1A788E0001 for ; Tue, 29 Apr 2025 20:47:07 -0400 (EDT) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 06EF2BCC27 for ; Wed, 30 Apr 2025 00:47:08 +0000 (UTC) X-FDA: 83388870936.09.B0A5EDA Received: from mail-ej1-f51.google.com (mail-ej1-f51.google.com [209.85.218.51]) by imf16.hostedemail.com (Postfix) with ESMTP id 063B6180004 for ; Wed, 30 Apr 2025 00:47:05 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=QEMzOtvQ; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf16.hostedemail.com: domain of richard.weiyang@gmail.com designates 209.85.218.51 as permitted sender) smtp.mailfrom=richard.weiyang@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1745974026; a=rsa-sha256; cv=none; b=i6BWPZUAr02jjV08om/0Ix26NRdxtlm5G6NNJ7+k3AgTMEdbPap5xyqwE8fnSps+3TongN BQrPnBB3gmQEbEqwNpM8OSgAJ1MGlDwVCZsXljSz6M5PrgmkuMp+vlDwLDiTs5CvWTx52d pTGM3Ga9o+MoCgHganI3enlt/hCDLGk= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=QEMzOtvQ; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf16.hostedemail.com: domain of richard.weiyang@gmail.com designates 209.85.218.51 as permitted sender) smtp.mailfrom=richard.weiyang@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1745974026; h=from:from:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=NSgadnBmFdrxH2lG8ysxhENfLPEy41WjvEBPxZFhovg=; b=2sktSVK3hhilzfOkC1eLdeMEGlrz1lBmld+DaaMWytVaEf19l8YG09TX3KZDBODMJvN1Rn /UZJSBNBicgspngxmpZ1ALWelaHf2/cxgWxF/2l28yWg9ETs120qcCtocJbB5hro3M3XC8 gmkj7cl3jFn8z6YfxurDNQ4xSeWe/l4= Received: by mail-ej1-f51.google.com with SMTP id a640c23a62f3a-ac6e8cf9132so1308649066b.2 for ; Tue, 29 Apr 2025 17:47:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1745974024; x=1746578824; darn=kvack.org; h=user-agent:in-reply-to:content-disposition:mime-version:references :reply-to:message-id:subject:cc:to:from:date:from:to:cc:subject:date :message-id:reply-to; bh=NSgadnBmFdrxH2lG8ysxhENfLPEy41WjvEBPxZFhovg=; b=QEMzOtvQlf1Em68xoNUIRV2d+I3W9G2/zhlVHjUcq/8EFYa1woIBGGqC35untHWs6N 3GnzB2eZRzCWhGEjw5ShU/yS75AizEKcyHt6EakZ7qAcu3a5ubetsJwVvLsnxMChA/Y/ b/vRZhs7xC/5v0rYR7VYMQegQKr0qM7cubzHa+Sejw4+acejm0lvxlpuAfW+KP+mHlhA h1BXy/XTiCpbSUWAGAkm7EZ+nXnV7pBlAPNoU9CTTlKIEzerrC8pwLfSXliGWCSoQK7d noRPqcTGduiHQ3USGU+2xmtJTqjCfH0+yYSu6XjuOeA6H2bQV74OoaJ7HWEpEIKiMlat S6XQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1745974024; x=1746578824; h=user-agent:in-reply-to:content-disposition:mime-version:references :reply-to:message-id:subject:cc:to:from:date:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=NSgadnBmFdrxH2lG8ysxhENfLPEy41WjvEBPxZFhovg=; b=QVHNfGV2I47auGiHK5FIs9T/W1ThRPt9tRaaeAGGlvPxv9x2ZJrg3euwYqn/zHceaW KHAGFqoUpzSGETQ38Up4ydDVRX7Ic2zG2hIrx4LwhSmSBzCL9MRuNXNBT7oNhi7OxwaC kwz4LVGUSO/tZ5K/v/2Txg/xuXFG5/vh0c6WkoF0J8xyW4h1aQ/lxVjRfBtn0NHNfoGO 8cD+KmbypxuVVhlN4NdbgJTWh0HaZYj9wzSOE/Mk41ybcQXjPLFetBuinnpuHA/CrnBs Tce4/32GMD20s/H51mVQsI9FhLHeMAe7IV724ZfzO67dk0RhNzMd6AHnEy0IISVeZjZ6 bJqg== X-Forwarded-Encrypted: i=1; AJvYcCU9/NpRSOFuXmP3IswkOIVSp2Xqw/oOOX+xdZo171k8n4fEd96bVyKflF+CQ+ZRZrs5V6cngtEcgA==@kvack.org X-Gm-Message-State: AOJu0YzcDp8vLHnbPlQGX9ym0f/yvad19gMaqSDiX86p6vAkoa4C0EzD c0qzbhCJWr8L3v31882dBrewevCzrOmCNz2MpZ4+p5fz1Jisf0dF X-Gm-Gg: ASbGncvDF5s5NXD3RNLo8nd5kWUpjb2jtRmAelifdZOZkyvREy0lhoRwsMtExaQPNnF B3OTG9zxxk+Pdus92lAL8ulwrDwnnScMG1mlR1KKcISRthaOqQGh5IJTfbxTKSwPlOfHUz+tCm/ U15VBymWvGXd8gxwHPMUAuw2RhOJgLQ9cFvH0mmf5r7HxN5VBztpt7H0684A19AioN/fVvLdAeh tLr5/+a5bUqYMm4Xc1pU+FaZh02BdtlBZbnv3xl6CfOiRrrdrTzbyIeIWjspTGSQjHYqsAmfKrO gX7lUfg5HiIUeHp+gMLnTFIXvVT0iR5qc9JPJ1mT X-Google-Smtp-Source: AGHT+IHONlCCM64wd/nRA8RJxkqOAPFt/TljZ4Y/sOCGYF0ww/K9M13/z4WHBEfBSYmCJg+CXOCEpA== X-Received: by 2002:a17:907:6e86:b0:ace:82a6:b938 with SMTP id a640c23a62f3a-acedc673c5cmr131805566b.36.1745974024087; Tue, 29 Apr 2025 17:47:04 -0700 (PDT) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ace6e41c491sm846098566b.34.2025.04.29.17.47.03 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Tue, 29 Apr 2025 17:47:03 -0700 (PDT) Date: Wed, 30 Apr 2025 00:47:03 +0000 From: Wei Yang To: Lorenzo Stoakes Cc: Andrew Morton , Vlastimil Babka , Jann Horn , "Liam R . Howlett" , Suren Baghdasaryan , Matthew Wilcox , David Hildenbrand , Pedro Falcato , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v2 01/10] mm/mremap: introduce more mergeable mremap via MREMAP_RELOCATE_ANON Message-ID: <20250430004703.63rumj4znewlbc2h@master> Reply-To: Wei Yang References: <87e668d54927bb4ccdb7d374275e0662de667697.1745307301.git.lorenzo.stoakes@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87e668d54927bb4ccdb7d374275e0662de667697.1745307301.git.lorenzo.stoakes@oracle.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Queue-Id: 063B6180004 X-Stat-Signature: 3919nt8x5s9hzwyxninaxmesxxw31113 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1745974025-434503 X-HE-Meta: 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 5Y4+IN7f 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 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: List-Subscribe: List-Unsubscribe: On Tue, Apr 22, 2025 at 09:09:20AM +0100, Lorenzo Stoakes wrote: [...] >+bool vma_had_uncowed_children(struct vm_area_struct *vma) >+{ >+ struct anon_vma *anon_vma = vma ? vma->anon_vma : NULL; >+ bool ret; >+ >+ if (!anon_vma) >+ return false; >+ >+ /* >+ * If we're mmap locked then there's no way for this count to change, as >+ * any such change would require this lock not be held. >+ */ >+ if (rwsem_is_locked(&vma->vm_mm->mmap_lock)) >+ return anon_vma->num_children > 1; Hi, Lorenzo May I have a question here? >+ >+ /* >+ * Any change that would increase the number of children would be >+ * prevented by a read lock. >+ */ >+ anon_vma_lock_read(anon_vma); >+ ret = anon_vma->num_children > 1; >+ anon_vma_unlock_read(anon_vma); >+ >+ return ret; >+} -- Wei Yang Help you, Help me