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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,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 84481FA372C for ; Fri, 8 Nov 2019 20:15:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4E85620869 for ; Fri, 8 Nov 2019 20:15:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573244105; bh=O1BIRVTDaJkJXMQzkjL3iwCWkwlABjetWfZ2FZSPKbA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=eatfECTQpx7JREWSiSPnk+qYysRJJA/2iXpODtljN+9jY0YAYlw+HK18IhrXYHfMk Rl0hHeYAitPV+d53hvwmwM0fq0J7CBkr10b0AqbIMtJwW0iiF09r59had/4Ad5gLQ0 BCi93HI0E8AYLsjVR+PRZKoyZvtGBIPJdNjO1jFY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726900AbfKHUPE (ORCPT ); Fri, 8 Nov 2019 15:15:04 -0500 Received: from mail-qt1-f196.google.com ([209.85.160.196]:42965 "EHLO mail-qt1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726294AbfKHUPE (ORCPT ); Fri, 8 Nov 2019 15:15:04 -0500 Received: by mail-qt1-f196.google.com with SMTP id t20so7851219qtn.9 for ; Fri, 08 Nov 2019 12:15:03 -0800 (PST) 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=ahKEYAmk3MOxCrKBQIHmaUXyvSLHCoSr+L2KQf1u5C8=; b=Nbbg7IrL3PfzhyCGr0THB8yOIH5+j5ErbRYut9lt+xM29BvznklYOrU1wR++lTvfH2 UI65Q0lQP4EHNAKJZ/ZkL6cz8E2vvHVPDDAkxV6h0X4kHtOnvVHHJnt275TrmAhqJII4 k/rs1Id3ALxllkmdMbaQZfXh4owo2QwMZfZkiWg8F7ZqOIoN4Wvwivz+Rm1qcsuAhKhF geCUrfRSm/RfLz9y3aMUnicQPymoHmjSEjRCXSMnk7fr0/O1z5wzVRLSxSrNQk25VM8Y Hgecoyameec3tsBNkdjk++YKnVMiZiyAqXMXUBPmK2mbgLit/uGe9sSoyH4iHelU8lp6 vieA== X-Gm-Message-State: APjAAAXVs/12p2eSJaVAflDdRuwR8JKAPI68ZjgzsiDYwoFHO9n/2Thh ndO96C744hto2hz0PxP+eX8= X-Google-Smtp-Source: APXvYqzXpUZicXBbL+sOnB7vk4A4a3tH6LQr/3hcNnhoq/ZevdXdxMyWwZCkeFIO/3BAH2+sCrQybg== X-Received: by 2002:ac8:3168:: with SMTP id h37mr12390599qtb.311.1573244103426; Fri, 08 Nov 2019 12:15:03 -0800 (PST) Received: from dennisz-mbp ([2620:10d:c091:500::1:ac97]) by smtp.gmail.com with ESMTPSA id l62sm3508899qkc.9.2019.11.08.12.15.00 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 08 Nov 2019 12:15:01 -0800 (PST) Date: Fri, 8 Nov 2019 15:14:58 -0500 From: Dennis Zhou To: Josef Bacik Cc: Dennis Zhou , David Sterba , Chris Mason , Omar Sandoval , kernel-team@fb.com, linux-btrfs@vger.kernel.org Subject: Re: [PATCH 18/22] btrfs: only keep track of data extents for async discard Message-ID: <20191108201458.GA51086@dennisz-mbp> References: <28b5064229e24388600f6f776621c6443c3e92b7.1571865775.git.dennis@kernel.org> <20191108194650.tcr5gsfl6vrh7riu@macbook-pro-91.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191108194650.tcr5gsfl6vrh7riu@macbook-pro-91.dhcp.thefacebook.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Fri, Nov 08, 2019 at 02:46:51PM -0500, Josef Bacik wrote: > On Wed, Oct 23, 2019 at 06:53:12PM -0400, Dennis Zhou wrote: > > As mentioned earlier, discarding data can be done either by issuing an > > explicit discard or implicitly by reusing the LBA. Metadata chunks see > > much more frequent reuse due to well it being metadata. So instead of > > explicitly discarding metadata blocks, just leave them be and let the > > latter implicit discarding be done for them. > > > > Hmm now that I look at this, it seems like we won't even discard empty metadata > block groups now, right? Or am I missing something? Thanks, > Empty block groups go through btrfs_add_to_discard_unused_list() which skips that check. So metadata blocks will be discarded here from btrfs_discard_queue_work() which should be called from __btrfs_add_free_space(). We should just skip discarding metadata blocks while they are being used. Thanks, Dennis