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=-5.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 3EA66C35257 for ; Fri, 2 Oct 2020 23:44:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E9A38206A2 for ; Fri, 2 Oct 2020 23:44:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20150623.gappssmtp.com header.i=@kernel-dk.20150623.gappssmtp.com header.b="B7XEXV9M" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725788AbgJBXo0 (ORCPT ); Fri, 2 Oct 2020 19:44:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56124 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725562AbgJBXoZ (ORCPT ); Fri, 2 Oct 2020 19:44:25 -0400 Received: from mail-pf1-x429.google.com (mail-pf1-x429.google.com [IPv6:2607:f8b0:4864:20::429]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9499AC0613E2 for ; Fri, 2 Oct 2020 16:44:25 -0700 (PDT) Received: by mail-pf1-x429.google.com with SMTP id z19so2442059pfn.8 for ; Fri, 02 Oct 2020 16:44:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=T60HK5Q7D6JLnVa3qZA2HNweMkJrSWboQgR5a+8Fct8=; b=B7XEXV9M0OT5GTpwanKbTTtkEHvMmPsHY4Kc7Ve698U93E0ptn3c8qz/HZJolqb9WW ZVXA20ktYRV7UVpQawMwuWelUEcX+xC5JKh8aB516hjPPBcN1KwSA27VRE4+zDeNS+oj RlsLXbKdeqaVViYts3zepnnC2hXkvPT5vdR6tV888MJcNz37BhMLDa+lE8xC6wDZPDov jI4faa4jzKxRdl+NJwTrTA1PAwqghUpmKqtN/O8BIZP6pPhAqepFrk3Gilya1OzYOe7r BIE93gUTaxKkNfr9d4oJ++Sgmf9+RqqsdpL+4qRi8lPllSkY3Hw0lKvP27gAXblL5l5a OmVA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=T60HK5Q7D6JLnVa3qZA2HNweMkJrSWboQgR5a+8Fct8=; b=raKbtPEioVzFfjmIoKT7UdxKQ+RJWqFvePkQoD8lN+Uzy6wyp1UIpmtWxFsJXF/tRC DWJb9EGQDf2JM6ywyUsEheL08VCK6B1WL7ZHdmEsIgV0na+YkewRrS7BDSOtwGp6EKR7 Aou9wQZGn8otVYxPKvD0sBotzBGyZBMaS3nHbYnjsodLtdzM4NHTA9ujP13QasLF7xwH TmF9s3v8hO5Wq+slPgIh+k+3vOh+uUmZ9c6hyixM7tWjFnMIzi7WPBEqc8hIMuG7FtOt cgksm/R+sscq412wOV3tEt8TQvG1m9/2wt9rtSzmBpxL12jNDljZyLB2DDGvSowE12Dv HzWw== X-Gm-Message-State: AOAM533mClNGfgXNtanChpJvTfzWBWAk4m32Nt5M0HrBQqA2NdWXbzY1 prP2QHLv3YjJSoHynFZQG/8tIw== X-Google-Smtp-Source: ABdhPJy0ZnLQs/bW0VZEl2sOXT3MyOLLZHiNoz0Wo/r5F+upgVHDHgaFm1w6+JvrEjyJBICPM3MyXA== X-Received: by 2002:a63:f006:: with SMTP id k6mr4331497pgh.88.1601682264925; Fri, 02 Oct 2020 16:44:24 -0700 (PDT) Received: from [192.168.1.134] ([66.219.217.173]) by smtp.gmail.com with ESMTPSA id gw1sm2783871pjb.36.2020.10.02.16.44.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 02 Oct 2020 16:44:24 -0700 (PDT) Subject: Re: drivers/block/rbd.c: atomic_inc_return_safe() & atomic_dec_return_safe() To: Shuah Khan , idryomov@gmail.com, dongsheng.yang@easystack.cn Cc: ceph-devel@vger.kernel.org, Linux Kernel Mailing List , Greg Kroah-Hartman , Kees Cook References: From: Jens Axboe Message-ID: Date: Fri, 2 Oct 2020 17:44:22 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org On 10/2/20 4:34 PM, Shuah Khan wrote: > All, > > I came across these atomic_inc_return_safe() & atomic_dec_return_safe() > functions that hold the counters at safe values. > > atomic_inc_return_safe() > > If the counter is already 0 it will not be incremented. > If the counter is already at its maximum value returns > -EINVAL without updating it. > > atomic_dec_return_safe() > > Decrement the counter. Return the resulting value, or -EINVAL > > These two routines are static and only used in rbd.c. > > Can these become part of atomic_t ops? I think you just want to use refcount_t for this use case. They have safe guards for under/overflow. -- Jens Axboe