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=-5.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 1FA7CC35257 for ; Fri, 2 Oct 2020 23:50:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4F82206B6 for ; Fri, 2 Oct 2020 23:50:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601682612; bh=xjOoOyB0zeZ+Byb9uqgCHneY8/N0FZTLJDNsfNY3F8Q=; h=Subject:To:Cc:References:From:Date:In-Reply-To:List-ID:From; b=TklGG6/2qDW6c37vPe6wJ2RvxbMUAvB/gY+1hMNLcnIQangXxydRCgkbZRNpAX2Of ThpF8yns9sORW1a3AjkgHZpkxf1NQVViobIN0PbV/Z5ZTJia97IkVr2MLDxImoPsIV mamTUNR/lc2cl3Z8gZoIeCmFc9U8uNWLCDcmWwG0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725796AbgJBXuM (ORCPT ); Fri, 2 Oct 2020 19:50:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57010 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725283AbgJBXuL (ORCPT ); Fri, 2 Oct 2020 19:50:11 -0400 Received: from mail-io1-xd29.google.com (mail-io1-xd29.google.com [IPv6:2607:f8b0:4864:20::d29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 291A1C0613D0 for ; Fri, 2 Oct 2020 16:50:11 -0700 (PDT) Received: by mail-io1-xd29.google.com with SMTP id k6so3365935ior.2 for ; Fri, 02 Oct 2020 16:50:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=google; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=y34GUHs7y+dhv/PBEvBFpzMJQXZxzed838y/lOyLkeg=; b=OwYWHVGo0duTZnucRDmSw4KE0SR/5oK6MjUHXkaXaZfKd4ZipqfpuD49mVhiJKjZlv foof3M7EwOlISDCGFPniEcCoGb9R3GMBYpjtj1kdCbWhzCtglUC2Y3AhMXI56dvI4IB3 12EP7mBPUzV7Y/Dkj7rbuTUXufEgWwpYYDz5w= 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=y34GUHs7y+dhv/PBEvBFpzMJQXZxzed838y/lOyLkeg=; b=Xjmu1h9zvk8F0lxt5ycH60g2zlIpa7ggS1y61Ajf53F8Jq6jZsGweZXETTzmKlS9C4 P3Z3RJQfdS9wCSWDSAHvpNGal4/mLtXLvIPdEoh3TDCs8VXpQ1BgVHplEtEz3uvxT4lZ II7ANIgGDNIJMMIqZbojJAHPVXJ6bBxa26Pw9C8mhFPqLaUqfEUVkgRZYgy1H6Z6YmfW mKSzC7qWhwhwFvHGA4/EKX2mXpcgy9YQ++wpPgOg+XtdzFHU37SjsbWqUWg/G18IEPaJ ZTwlR4wRfgIPumFr/fJchLQj98V63pr7TqZkKusrr6GKRcApiQYpPOUcVwFXOjcCsTYh nGsQ== X-Gm-Message-State: AOAM533EkX5i/5zz7Rc+PJjSESq7vQG5O1zXvIRLZ5ca3rbJjGK2tOdi A/tFag3dEHff4rAh2i8VRVRrBA== X-Google-Smtp-Source: ABdhPJzSBEr+9V1AlHXCphfVeGtDS7AVdMlZMDMld9vw+ZO1HhBVd/1CspUbOw5A51Sn4k2ViZQJgQ== X-Received: by 2002:a6b:7909:: with SMTP id i9mr3399241iop.98.1601682610398; Fri, 02 Oct 2020 16:50:10 -0700 (PDT) Received: from [192.168.1.112] (c-24-9-64-241.hsd1.co.comcast.net. [24.9.64.241]) by smtp.gmail.com with ESMTPSA id z13sm1571063ilm.53.2020.10.02.16.50.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 02 Oct 2020 16:50:09 -0700 (PDT) Subject: Re: drivers/block/rbd.c: atomic_inc_return_safe() & atomic_dec_return_safe() To: Jens Axboe , idryomov@gmail.com, dongsheng.yang@easystack.cn Cc: ceph-devel@vger.kernel.org, Linux Kernel Mailing List , Greg Kroah-Hartman , Kees Cook , Shuah Khan References: From: Shuah Khan Message-ID: Date: Fri, 2 Oct 2020 17:50:09 -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; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/2/20 5:44 PM, Jens Axboe wrote: > 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. > Makes sense. Guess these came before refcount_t. I will track this for refcount_t conversion. thanks, -- Shuah