From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f54.google.com ([74.125.82.54]:42112 "EHLO mail-wm0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750772AbdKUP3D (ORCPT ); Tue, 21 Nov 2017 10:29:03 -0500 Received: by mail-wm0-f54.google.com with SMTP id l188so2438951wma.1 for ; Tue, 21 Nov 2017 07:29:03 -0800 (PST) Message-ID: <1511278140.1680.41.camel@gmail.com> Subject: Re: quotas: failure on removing a file via SFTP/SSH From: ST To: Qu Wenruo Cc: linux-btrfs@vger.kernel.org Date: Tue, 21 Nov 2017 17:29:00 +0200 In-Reply-To: <09f4e574-8cab-26fd-d7ea-64a0cee2b20b@gmx.com> References: <1511266131.1680.27.camel@gmail.com> <093ee7e4-91f1-7d23-1ef1-81230d07b405@gmx.com> <1511270292.1680.35.camel@gmail.com> <09f4e574-8cab-26fd-d7ea-64a0cee2b20b@gmx.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-btrfs-owner@vger.kernel.org List-ID: > >>> I'm trying to use quotas for a simple chrooted sftp setup, limiting > >>> space for each user's subvolume (now for testing to 1M). > >>> > >>> I tried to hit the limit by uploading files and once it comes to the > >>> limit I face following problem: if I try to free space by removing a > >>> file via Linux sftp client (or Filezilla) - I get error: > >>> "Couldn't delete file: Failure" > >>> > >>> Sometimes, but not always, if I repeat it for 3-5 times it does removes > >>> the file at the end. > >>> If I login as root and try to remove the file via SSH I get the error: > >>> "rm: cannot remove 'example.txt': Disk quota exceeded" > >>> > >>> What is the problem? And how can I solve it? > >> > >> Kernel version first. > >> > >> If it's possible, please use latest kernel, at least newer than v4.10, > >> since we have a lot of qgroup reservation related fixes in newer kernel. > >> > >> Then, for small quota, due to the nature of btrfs metadata CoW and > >> relative large default node size (16K), it's quite easy to hit disk > >> quota for metadata. > > > > Yes, but why I get the error specifically on REMOVING a file? Even if I > > hit disk quota - if I free up space - it should be possible, isn't it? > > It's only true for fs modifying its metadata in-place (and use journal > to protect it). > > For fs using metadata CoW, even freeing space needs extra space for new > metadata. > Wait, it doesn't sound like a bug, but rather like a flaw in design. This means - each time a user hits his quota limit he will get stuck without being able to free space?!! Thank you.