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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 4F8F7C43387 for ; Thu, 27 Dec 2018 02:28:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 179692148E for ; Thu, 27 Dec 2018 02:28:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ln51Lwqh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728250AbeL0C0a (ORCPT ); Wed, 26 Dec 2018 21:26:30 -0500 Received: from mail-pg1-f196.google.com ([209.85.215.196]:35575 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727914AbeL0C03 (ORCPT ); Wed, 26 Dec 2018 21:26:29 -0500 Received: by mail-pg1-f196.google.com with SMTP id s198so8202547pgs.2 for ; Wed, 26 Dec 2018 18:26:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=XZVJF33WWtZ08jZQnJ9EkbvdmFLn3TdWvwfbT+MtXAk=; b=ln51LwqhK7Lj6BmYqOXrOmUO9PpjZlHI0BceupfESszb43Giryq9C5iRNrLkTKDEiD uYm17I5dUDTAo/jSJ1LtHyNIyESaHBWByNrn1RACuUOyBliYK9V6chl1OTflc10nne8C j97uxMLn7C0IldsPsbg8BNs2f+/PdoGiKx75q68M0RaJ4e5MibXA8zflkx5XuGuuOT/+ 0r9vZ6JY5FkIIiNEdsw9Tx7GQ4aed8bYKd9D7jSbjijlTqIxV/dYoyqgeeLGVrXnbW6Y JK/tXwXAKjBY11W9nBvtO3GLJY1FDHANgNJ5qW+32UP8d4KVzqv3PQ/HIQhFacTtcXiK lh5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=XZVJF33WWtZ08jZQnJ9EkbvdmFLn3TdWvwfbT+MtXAk=; b=fYbsRdA1IyVwlXPqfutrv/k8M0nXL4dTduizFu+ICDSvQzyR/VP6t3FUVltJQrtRcG uDmJo1dY71ymTpj0EtgjyJ7wxvn6ahr10H+nvC4RdizAaNm5zTNrA6mgKbVvSdlVo8j0 QVznpdTK/VjswtEyuejlSolgIMuGtvpiWyu3GBD3493oVJMTT0nXMUecuUTMtl6QlXI4 9hC530IKSs7oGwzgEezzxUIlJWVQwoXvs0/jYXYHz6Cr+BP8zojDaNgKHx04LrxnT+VD P56VFIRSnFs6Ze0c3TiAdOHtOPw+Yf5V1CnAWFJ1PXOSUbsBseNxUWowGkRQQQpaJ1a2 /4Zg== X-Gm-Message-State: AJcUukfqqVwNsQX4cyZTH1k36ARZaGXJptZMjMdhmeIHBJGn0e8HFZ3T jol/JEsPRIkzr7hY9/ZrOJg= X-Google-Smtp-Source: ALg8bN4cm2VM7lxtuioeoAKo5AZ+V7dSsQcHMNUGNt7Fp4POKLVqdBRGmwKsEwOrnBn9OLEU4D/RBQ== X-Received: by 2002:a63:8c2:: with SMTP id 185mr21406815pgi.26.1545877588692; Wed, 26 Dec 2018 18:26:28 -0800 (PST) Received: from localhost ([110.70.51.196]) by smtp.gmail.com with ESMTPSA id b4sm41144670pgq.65.2018.12.26.18.26.26 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 26 Dec 2018 18:26:27 -0800 (PST) Date: Thu, 27 Dec 2018 11:26:24 +0900 From: Sergey Senozhatsky To: Minchan Kim Cc: Andrew Morton , LKML , Sergey Senozhatsky , joaodias@google.com, srnvs@google.com Subject: Re: [PATCH] zram: idle writeback fixes and cleanup Message-ID: <20181227022624.GA30091@jagdpanzerIV> References: <20181224033529.19450-1-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181224033529.19450-1-minchan@kernel.org> User-Agent: Mutt/1.11.1 (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (12/24/18 12:35), Minchan Kim wrote: [..] > @@ -645,10 +680,13 @@ static ssize_t writeback_store(struct device *dev, > bvec.bv_len = PAGE_SIZE; > bvec.bv_offset = 0; > > - if (zram->stop_writeback) { > + spin_lock(&zram->wb_limit_lock); > + if (zram->wb_limit_enable && !zram->bd_wb_limit) { > + spin_unlock(&zram->wb_limit_lock); > ret = -EIO; > break; > } > + spin_unlock(&zram->wb_limit_lock); [..] > @@ -732,11 +771,10 @@ static ssize_t writeback_store(struct device *dev, > zram_set_element(zram, index, blk_idx); > blk_idx = 0; > atomic64_inc(&zram->stats.pages_stored); > - if (atomic64_add_unless(&zram->stats.bd_wb_limit, > - -1 << (PAGE_SHIFT - 12), 0)) { > - if (atomic64_read(&zram->stats.bd_wb_limit) == 0) > - zram->stop_writeback = true; > - } > + spin_lock(&zram->wb_limit_lock); > + if (zram->wb_limit_enable && zram->bd_wb_limit > 0) > + zram->bd_wb_limit -= 1UL << (PAGE_SHIFT - 12); > + spin_unlock(&zram->wb_limit_lock); Do we really need ->wb_limit_lock spinlock? We kinda punch it twice in this loop. If someone clears ->wb_limit_enable somewhere in between then the worst thing to happen is that we will just write extra page to the backing device; not a very big deal to me. Am I missing something? -ss