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bh=/eEJr0vh6Ms092OOq5LENbMjP5M0eUCSzb+gN9R63ZU=; b=ZTOv4MzwyUUuYk68NktEK7BQSFJvRTNOIHMwcx/Z7s0Pf+cRUk/0X4Y/5n+CnNyz+aDzG/ ltlfUENg3BKuW2Dw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id A2C82139B0; Tue, 14 Oct 2025 17:40:33 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id uMX7JhGL7mg3NgAAD6G6ig (envelope-from ); Tue, 14 Oct 2025 17:40:33 +0000 Date: Tue, 14 Oct 2025 19:40:32 +0200 From: David Sterba To: Qu Wenruo Cc: Christoph Hellwig , =?iso-8859-1?Q?Andr=E9?= Almeida , linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, kernel-dev@igalia.com, Miklos Szeredi , Amir Goldstein , Chris Mason , David Sterba , Anand Jain , "Guilherme G . Piccoli" Subject: Re: [RFC PATCH 1/1] ovl: Use fsid as unique identifier for trusted origin Message-ID: <20251014174032.GC13776@suse.cz> Reply-To: dsterba@suse.cz References: <20251014015707.129013-1-andrealmeid@igalia.com> <20251014015707.129013-2-andrealmeid@igalia.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) X-Rspamd-Queue-Id: CB03521293 X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-4.21 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; HAS_REPLYTO(0.30)[dsterba@suse.cz]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; FUZZY_RATELIMITED(0.00)[rspamd.com]; ARC_NA(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCPT_COUNT_TWELVE(0.00)[14]; MIME_TRACE(0.00)[0:+]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; FREEMAIL_CC(0.00)[infradead.org,igalia.com,vger.kernel.org,szeredi.hu,gmail.com,fb.com,suse.com,oracle.com]; DKIM_TRACE(0.00)[suse.cz:+]; REPLYTO_ADDR_EQ_FROM(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RCVD_VIA_SMTP_AUTH(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; REPLYTO_DOM_NEQ_TO_DOM(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns] X-Rspamd-Action: no action X-Spam-Flag: NO X-Spam-Score: -4.21 X-Spam-Level: On Tue, Oct 14, 2025 at 03:43:54PM +1030, Qu Wenruo wrote: > 在 2025/10/14 15:09, Christoph Hellwig 写道: > > On Mon, Oct 13, 2025 at 10:57:07PM -0300, André Almeida wrote: > >> Some filesystem have non-persistent UUIDs, that can change between > >> mounting, even if the filesystem is not modified. To prevent > >> false-positives when mounting overlayfs with index enabled, use the fsid > >> reported from statfs that is persistent across mounts. > > > > Please fix btrfs to not change uuids, as that completely defeats the > > point of uuids. > > > > That is the temp-fsid feature from Anand, introduced by commit > a5b8a5f9f835 ("btrfs: support cloned-device mount capability"). > > I'm not 100% sure if it's really that important to support mounting > cloned devices in the first place, as LVM will reject activating any LVs > if there is even conflicting VGs names, not to mention conflicting UUIDs. > > If temp-fsid is causing problems with overlayfs, I'm happy to remove it, > as this really looks like a niche that no one is asking. What do you mean no one asking? This was specifically asked for by Steam to do A/B root partition mounts for recovery. It is a niche use case but it has its users.