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[49.180.164.75]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-81fa10bda5csm259171b3a.19.2026.01.15.13.09.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Jan 2026 13:09:35 -0800 (PST) Received: from dave by dread.disaster.area with local (Exim 4.99.1) (envelope-from ) id 1vgUai-00000003vHn-2AU2; Fri, 16 Jan 2026 08:09:16 +1100 Date: Fri, 16 Jan 2026 08:09:16 +1100 From: Dave Chinner To: Chuck Lever Cc: Amir Goldstein , Jeff Layton , Christian Brauner , Alexander Viro , Chuck Lever , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey , Hugh Dickins , Baolin Wang , Andrew Morton , Theodore Tso , Andreas Dilger , Jan Kara , Gao Xiang , Chao Yu , Yue Hu , Jeffle Xu , Sandeep Dhavale , Hongbo Li , Chunhai Guo , Carlos Maiolino , Ilya Dryomov , Alex Markuze , Viacheslav Dubeyko , Chris Mason , David Sterba , Luis de Bethencourt , Salah Triki , Phillip Lougher , Steve French , Paulo Alcantara , Ronnie Sahlberg , Shyam Prasad N , Bharath SM , Miklos Szeredi , Mike Marshall , Martin Brandenburg , Mark Fasheh , Joel Becker , Joseph Qi , Konstantin Komarov , Ryusuke Konishi , Trond Myklebust , Anna Schumaker , Dave Kleikamp , David Woodhouse , Richard Weinberger , Jan Kara , Andreas Gruenbacher , OGAWA Hirofumi , Jaegeuk Kim , Christoph Hellwig , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-xfs@vger.kernel.org, ceph-devel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-unionfs@vger.kernel.org, devel@lists.orangefs.org, ocfs2-devel@lists.linux.dev, ntfs3@lists.linux.dev, linux-nilfs@vger.kernel.org, jfs-discussion@lists.sourceforge.net, linux-mtd@lists.infradead.org, gfs2@lists.linux.dev, linux-f2fs-devel@lists.sourceforge.net Subject: Re: [PATCH 00/29] fs: require filesystems to explicitly opt-in to nfsd export support Message-ID: References: <20260115-exportfs-nfsd-v1-0-8e80160e3c0c@kernel.org> <4d9967cc-a454-46cf-909b-b8ab2d18358d@kernel.org> Precedence: bulk X-Mailing-List: linux-ext4@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: <4d9967cc-a454-46cf-909b-b8ab2d18358d@kernel.org> On Thu, Jan 15, 2026 at 02:37:09PM -0500, Chuck Lever wrote: > On 1/15/26 2:14 PM, Amir Goldstein wrote: > > On Thu, Jan 15, 2026 at 7:32 PM Chuck Lever wrote: > >> > >> > >> > >> On Thu, Jan 15, 2026, at 1:17 PM, Amir Goldstein wrote: > >>> On Thu, Jan 15, 2026 at 6:48 PM Jeff Layton wrote: > >>>> > >>>> In recent years, a number of filesystems that can't present stable > >>>> filehandles have grown struct export_operations. They've mostly done > >>>> this for local use-cases (enabling open_by_handle_at() and the like). > >>>> Unfortunately, having export_operations is generally sufficient to make > >>>> a filesystem be considered exportable via nfsd, but that requires that > >>>> the server present stable filehandles. > >>> > >>> Where does the term "stable file handles" come from? and what does it mean? > >>> Why not "persistent handles", which is described in NFS and SMB specs? > >>> > >>> Not to mention that EXPORT_OP_PERSISTENT_HANDLES was Acked > >>> by both Christoph and Christian: > >>> > >>> https://lore.kernel.org/linux-fsdevel/20260115-rundgang-leihgabe-12018e93c00c@brauner/ > >>> > >>> Am I missing anything? > >> > >> PERSISTENT generally implies that the file handle is saved on > >> persistent storage. This is not true of tmpfs. > > > > That's one way of interpreting "persistent". > > Another way is "continuing to exist or occur over a prolonged period." > > which works well for tmpfs that is mounted for a long time. > > I think we can be a lot more precise about the guarantee: The file > handle does not change for the life of the inode it represents. It File handles most definitely change over the life of a /physical/ inode. Unlinking a file does not require ending the life of the physical object that provides the persistent data store for the file. e.g. XFS dynamically allocates physical inodes might in a life cycle that looks somewhat life this: allocate physical inode insert record into allocated inode index mark inode as free while (don't need to free physical inode) { ... allocate inode for a new file update persistent inode metadata to generate new filehandle mark inode in use ... unlink file mark inode free } remove inode from allocated inode index free physical inode i.e. a free inode is still an -allocated, indexed inode- in the filesystem, and until we physically remove it from the filesystem the inode life cycle has not ended. IOWs, the physical (persistent) inode lifetime can span the lifetime of -many- files. However, the filesystem guarantees that the handle generated for that inode is different for each file it represents over the whole inode life time. Hence I think that file handle stability/persistence needs to be defined in terms of -file lifetimes-, not the lifetimes of the filesystem objects implement the file's persistent data store. -Dave. -- Dave Chinner david@fromorbit.com