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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 50ADAC433DB for ; Sat, 23 Jan 2021 10:40:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0FA8522D75 for ; Sat, 23 Jan 2021 10:40:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726388AbhAWKkQ (ORCPT ); Sat, 23 Jan 2021 05:40:16 -0500 Received: from rin.romanrm.net ([51.158.148.128]:35012 "EHLO rin.romanrm.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726339AbhAWKkP (ORCPT ); Sat, 23 Jan 2021 05:40:15 -0500 Received: from natsu (unknown [IPv6:fd39::e99e:8f1b:cfc9:ccb8]) by rin.romanrm.net (Postfix) with SMTP id C6C7D893; Sat, 23 Jan 2021 10:39:33 +0000 (UTC) Date: Sat, 23 Jan 2021 15:39:33 +0500 From: Roman Mamedov To: Qu Wenruo Cc: Dave Chinner , linux-btrfs@vger.kernel.org Subject: Re: Unexpected reflink/subvol snapshot behaviour Message-ID: <20210123153933.534a43ea@natsu> In-Reply-To: <58c9d792-5af4-7b54-2072-77230658e677@gmx.com> References: <20210121222051.GB4626@dread.disaster.area> <58c9d792-5af4-7b54-2072-77230658e677@gmx.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Sat, 23 Jan 2021 16:42:33 +0800 Qu Wenruo wrote: > For the worst case, btrfs can allocate a 128 MiB file extent, and have > good luck to write 127MiB into the extent. It will take 127MiB + 128MiB > space, until the last 1MiB of the original extent get freed, the full > 128MiB can be freed. Does it mean enabling compression actually mitigates this issue as a side-effect? Since each extent will be limited to only 128K. What are the typical extent sizes without compression? -- With respect, Roman