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=-3.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_NEOMUTT 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 0D866C04E84 for ; Thu, 16 May 2019 14:43:29 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BFB5020815 for ; Thu, 16 May 2019 14:43:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BFB5020815 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3B4D06B000A; Thu, 16 May 2019 10:43:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3633E6B000C; Thu, 16 May 2019 10:43:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 22D3D6B000D; Thu, 16 May 2019 10:43:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) by kanga.kvack.org (Postfix) with ESMTP id CD6CD6B000A for ; Thu, 16 May 2019 10:43:27 -0400 (EDT) Received: by mail-wm1-f69.google.com with SMTP id b85so777003wme.3 for ; Thu, 16 May 2019 07:43:27 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:date:from:to :cc:subject:message-id:references:mime-version:content-disposition :in-reply-to:user-agent; bh=Cj+rXNfNlUN3r4Yp7FC3w8W2jv87lre7M4pXy1RJygg=; b=RWcglj1XZivKGPCK+025CXFcMfCEpYeMXXiNx1F9AAvRsFeOE6PatK7CKNU0ijadOZ yRrwBtU8T2L3O9tGiDPEIsSh/QAnOIOwJwwIgl5+Fspy5yTUeaMFmgAAazqLe8cEz8gX RQhMKSUdCWh4pQ2i5qdkPwMUyyPLk9q3xjWSu68gYKY0vw4o1lBeoWFJE+B5VafrVxxg VqsuPAaYEqBoF9N+u44PN0PV/K+BtdZNxC+iBEKqGeFTECHyPsQTkxuddIHEiA1TBjuu Gef5Q+NUJ8+hTh2J1aovNjjC703xS4COjqM/Qw9J8JWHHXPVaxluMR+rQRchYVvCf5/l G5cQ== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of oleksandr@redhat.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=oleksandr@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com X-Gm-Message-State: APjAAAV22C4rPYQCBla/fBimZ0L9SnLfJ9UxKrlkzxrE4aqsvKc9Nf7X aYin0YWSG2ljgcmM+vymseblbFFI0no69SJaUr6FTQmLqm4lgDWgYktXRTyzGRVc1uCjC5ma8i7 cshHazxClnbPetSb12ISEWgxb22MV92sWCR73aZyoJHROXBPI+cV5mn4PrcAbNl+VKA== X-Received: by 2002:adf:e711:: with SMTP id c17mr8937636wrm.227.1558017807415; Thu, 16 May 2019 07:43:27 -0700 (PDT) X-Received: by 2002:adf:e711:: with SMTP id c17mr8937573wrm.227.1558017806410; Thu, 16 May 2019 07:43:26 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1558017806; cv=none; d=google.com; s=arc-20160816; b=YoMg3O3imYSAVqw/PtuNEjZjsV6SmdshqD+jUSAl/HjsY5Zp4p7TY7ccuZegTaGNwu 637anze7b5nUm4SNvmKohf3dY5T/EwSQEcqRwCGAYo9ZHQiJqYM4TgyTvSKdp3q0F2DO fE9jFDzcDizkrG4zkamnwp8cReJNY/rP0xxQbjgPUwOP8OS4nz4fgq7/syR1x3a0HCTq J4ufU5EokCKvxKUJmkZAn5GRODIBJnhUPrH7aqw9GFsEuPF8PifTuHziZUPKKsaFYx5B urteRXOyWzLMbGOZV1Qz35pmIn5y8/49zY7Mmr+g2bxffUtJX0cXSYp8Pj7YgwhcGN28 hG9g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date; bh=Cj+rXNfNlUN3r4Yp7FC3w8W2jv87lre7M4pXy1RJygg=; b=SVVaiHIawLinRcmeeDQV0CF2wkkNp8pecrjPUtIt0/JA7voSbu/1uPpA3waw3tYCBI 1IqNxCGVClkqIS4ksfjQhWZCCKqLGCCb2PjOcOI/gSiqywI0DwsJgNPLsv/LTsmK3pl0 qccbC/pOt5OTjCw/zTvzNjAkJFJnDbI1GWIhUQh7Z/w1a3Nocsq0Nxi7K12ToHRhG/Um bVnpREbQC5uXRHaZ6pu0y9h9ZKY4eJPUPFdEN3DH8HmOBOyZ4q3NidNm4yU74tfvnF/S QDSVaWbadcW04159vszSLFlcoq9WGtJ+h8EGvuda7C7Zq9m4PoD8vvkVcw8hnhzUpWOc xwIg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of oleksandr@redhat.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=oleksandr@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id v4sor4756239wrq.18.2019.05.16.07.43.26 for (Google Transport Security); Thu, 16 May 2019 07:43:26 -0700 (PDT) Received-SPF: pass (google.com: domain of oleksandr@redhat.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; spf=pass (google.com: domain of oleksandr@redhat.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=oleksandr@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com X-Google-Smtp-Source: APXvYqzKDhdhn0sTfAQMEnf2Z3MPEpDPMQ1RAoC5i7RhAcgllW8ck8oD5TGkmgzragiiRcn+PESIqQ== X-Received: by 2002:a5d:4206:: with SMTP id n6mr17691401wrq.58.1558017806003; Thu, 16 May 2019 07:43:26 -0700 (PDT) Received: from localhost (nat-pool-brq-t.redhat.com. [213.175.37.10]) by smtp.gmail.com with ESMTPSA id q13sm6113444wrn.27.2019.05.16.07.43.24 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 16 May 2019 07:43:25 -0700 (PDT) Date: Thu, 16 May 2019 16:43:24 +0200 From: Oleksandr Natalenko To: Jann Horn Cc: kernel list , Kirill Tkhai , Hugh Dickins , Alexey Dobriyan , Vlastimil Babka , Michal Hocko , Matthew Wilcox , Pavel Tatashin , Greg KH , Suren Baghdasaryan , Minchan Kim , Timofey Titovets , Aaron Tomlin , Grzegorz Halat , Linux-MM , Linux API Subject: Re: [PATCH RFC 4/5] mm/ksm, proc: introduce remote merge Message-ID: <20190516144323.pzkvs6hapf3czorz@butterfly.localdomain> References: <20190516094234.9116-1-oleksandr@redhat.com> <20190516094234.9116-5-oleksandr@redhat.com> <20190516142013.sf2vitmksvbkb33f@butterfly.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190516142013.sf2vitmksvbkb33f@butterfly.localdomain> User-Agent: NeoMutt/20180716 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: On Thu, May 16, 2019 at 04:20:13PM +0200, Oleksandr Natalenko wrote: > > [...] > > > @@ -2960,15 +2962,63 @@ static int proc_stack_depth(struct seq_file *m, struct pid_namespace *ns, > > > static ssize_t madvise_write(struct file *file, const char __user *buf, > > > size_t count, loff_t *ppos) > > > { > > > + /* For now, only KSM hints are implemented */ > > > +#ifdef CONFIG_KSM > > > + char buffer[PROC_NUMBUF]; > > > + int behaviour; > > > struct task_struct *task; > > > + struct mm_struct *mm; > > > + int err = 0; > > > + struct vm_area_struct *vma; > > > + > > > + memset(buffer, 0, sizeof(buffer)); > > > + if (count > sizeof(buffer) - 1) > > > + count = sizeof(buffer) - 1; > > > + if (copy_from_user(buffer, buf, count)) > > > + return -EFAULT; > > > + > > > + if (!memcmp("merge", buffer, min(sizeof("merge")-1, count))) > > > > This means that you also match on something like "mergeblah". Just use strcmp(). > > I agree. Just to make it more interesting I must say that > > /sys/kernel/mm/transparent_hugepage/enabled > > uses memcmp in the very same way, and thus echoing "alwaysssss" or > "madviseeee" works perfectly there, and it was like that from the very > beginning, it seems. Should we fix it, or it became (zomg) a public API? Actually, maybe, the reason for using memcmp is to handle "echo" properly: by default it puts a newline character at the end, so if we use just strcmp, echo should be called with -n, otherwise strcmp won't match the string. Huh? > [...] -- Best regards, Oleksandr Natalenko (post-factum) Senior Software Maintenance Engineer