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Mon, 23 Mar 2026 09:43:26 +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 DsiIID4LwWn7bwAAD6G6ig (envelope-from ); Mon, 23 Mar 2026 09:43:26 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 438D8A0B2E; Mon, 23 Mar 2026 10:43:22 +0100 (CET) Date: Mon, 23 Mar 2026 10:43:22 +0100 From: Jan Kara To: Gao Xiang Cc: Demi Marie Obenour , "Darrick J. Wong" , Miklos Szeredi , linux-fsdevel@vger.kernel.org, Joanne Koong , John Groves , Bernd Schubert , Amir Goldstein , Luis Henriques , Horst Birthelmer , Gao Xiang , lsf-pc@lists.linux-foundation.org Subject: Re: [Lsf-pc] [LSF/MM/BPF TOPIC] Where is fuse going? API cleanup, restructuring and more Message-ID: References: <20260204190649.GB7693@frogsfrogsfrogs> <20260206053835.GD7693@frogsfrogsfrogs> <20260221004752.GE11076@frogsfrogsfrogs> <7de8630d-b6f5-406e-809a-bc2a2d945afb@linux.alibaba.com> <20260318215140.GL1742010@frogsfrogsfrogs> <361d312b-9706-45ca-8943-b655a75c765b@gmail.com> <4a1fd8dd-6c8a-43bd-877d-c37720ac1e21@linux.alibaba.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=us-ascii Content-Disposition: inline In-Reply-To: <4a1fd8dd-6c8a-43bd-877d-c37720ac1e21@linux.alibaba.com> X-Rspamd-Action: no action X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-4.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; 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)[]; FUZZY_RATELIMITED(0.00)[rspamd.com]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; RCPT_COUNT_TWELVE(0.00)[13]; MIME_TRACE(0.00)[0:+]; RCVD_COUNT_THREE(0.00)[3]; URIBL_BLOCKED(0.00)[suse.cz:dkim,suse.com:email,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; ARC_NA(0.00)[]; RCVD_TLS_LAST(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TO_DN_SOME(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.cz:dkim]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:106:10:150:64:167:received,2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; FREEMAIL_CC(0.00)[gmail.com,kernel.org,szeredi.hu,vger.kernel.org,groves.net,bsbernd.com,igalia.com,birthelmer.de,lists.linux-foundation.org]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; DKIM_TRACE(0.00)[suse.cz:+]; MISSING_XM_UA(0.00)[]; SUBJECT_HAS_QUESTION(0.00)[] X-Rspamd-Queue-Id: 928095BD63 X-Spam-Flag: NO X-Spam-Score: -4.01 X-Spam-Level: On Sun 22-03-26 13:14:55, Gao Xiang wrote: > > > On 2026/3/22 11:25, Demi Marie Obenour wrote: > > > The only exceptions are if the filesystem is incredibly simple > > or formal methods are used, and neither is the case for existing > > filesystems in the Linux kernel. > > Again, first, I don't think "simple" is a helpful and descriptive > word out of this kind of area: > > "simple" formats are all formats just archive the filesystem > data and metadata, but without any more use cases. No simpler > than that, because you need to tell vfs the file (meta)data > (even the file data is the garbage data), otherwise they won't > be called as filesystems. > > So why we always fall into comparing which archive filesystem > is simpler than others unless some bad buggy designs in those > "simple" filesystems. > > Here, I can definitely say _EROFS uncompressed format_ fits > this kind of area, and I will write down formally later if each > on-disk field has unexpected values like garbage numbers, what > the outcome. And the final goal is to allow EROFS uncompressed > format can be mounted as the "root" into totally isolated > user/mount namespaces since it's really useful and no practical > risk. > > If any other kernel filesystem maintainers say that they can do > the same , why not also allow them do the same thing? I don't > think it's a reasonable policy that "due to EXT4, XFS, BtrFS > communities say that they cannot tolerate the inconsistent > consequence, any other kernel filesystem should follow the > same policy even they don't have such issue by design." > > In other words, does TCP/IP protocol simple? and is there no > simplier protocol for network data? I don't think so, but why > untrusted network data can be parsed in the kernel? Does > TCP/IP kernel implementation already bugless? So the amount of state TCP/IP needs to keep around is very small (I'd say kilobytes) compared to the amount of state a filesystem needs to maintain (gigabytes). This leads to very fundamental differences in the complexity of data structures, their verification, etc. So yes, it is much easier to harden TCP/IP against untrusted input than a filesystem implementation. And yes, when you have immutable filesystem, things are much simpler because the data structures and algorithms can be much simpler and as you wrote a lot of these inconsistencies don't matter (at least for the kernel). But once you add ability to modify the filesystem - here I don't think it matters whether through CoW or other means - things get complicated quickly and it gets much more complex to make your code resilient to all kinds of inconsistencies... Honza -- Jan Kara SUSE Labs, CR