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Mon, 19 Jan 2026 02:22:45 -0500 (EST) Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit MIME-Version: 1.0 From: NeilBrown To: "Christoph Hellwig" Cc: "Jeff Layton" , "Amir Goldstein" , "Christian Brauner" , "Alexander Viro" , "Chuck Lever" , "Olga Kornievskaia" , "Dai Ngo" , "Tom Talpey" , "Hugh Dickins" , "Baolin Wang" , "Andrew Morton" , "Theodore Ts'o" , "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, 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 In-reply-to: References: <20260115-exportfs-nfsd-v1-0-8e80160e3c0c@kernel.org>, , <9c99197dde2eafa55a1b55dce2f0d4d02c77340a.camel@kernel.org>, <176877859306.16766.15009835437490907207@noble.neil.brown.name>, Date: Mon, 19 Jan 2026 18:22:42 +1100 Message-id: <176880736225.16766.4203157325432990313@noble.neil.brown.name> Reply-To: NeilBrown X-Stat-Signature: f66ixhwxhz1da5b4sio7oq85sb8stqtc X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 2A76A40003 X-Rspam-User: X-HE-Tag: 1768807388-233154 X-HE-Meta: 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 cyO4+qSe S7FY3Ag04vGMJdt4ypuBoD7zegmwXZanALIlUjsxixc4Y8sHFbI7v8Mt9ZmOY06zX2CjB2nzPa4A6DKo/KNthuK2IKH6FUL2F8U6CHCIYm3e3Oo4CcCSCN9fmv+EE8EndGnv2oXGpeSSWrxk5ug6AuGW3iEqCX8BOqrMJ/9oumK//XLkkjJoFEggeQUVJ8MiP9Hhaf0f4SbAAbIlnvkPFCQE8ppGC+boQ+VOzAbg8Z7fZYsDrik/kTbYxGecAUo5EhdlKHyWxS3NgtHSfIondsb4rK4ojrnT26WZEt7vAyy01Dsypl3O5ywi/BCN/CJYEPf4+tbY36MjIpMW5y/uxu5dRoickJ1wSiAL4uoLjNwcrYdYhIsH5TO6WVXlYZ3g5leWrLXuC4L+rou8GBZneF31FxG6CrB6ToRDtOkaLGfmK5/MI226SD36G6S6OicNZ9qM1/eYaWDP8/XGxCW+6nHpbYSds38w/gpd2qiPmJ9CKbacl+ej+n9GWMUew94/Y1xPx7p5khjinuuBCheOA+EnnZXGjgiHqonHUmiMYbCXNeARyFsrot0MThcqiBVGtO7MBsEerkJk+A4wrerHt98rcOGiuhQkR8im0ga913jZPrrHeVBSwYHofNk8SzC+VvtFBE9g12W4YSUtzEdJunFfjkbpDy+NsZEAOs2tQpcKb3WmLhne5c4ukEpCnydQ4TXtM X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 19 Jan 2026, Christoph Hellwig wrote: > On Mon, Jan 19, 2026 at 10:23:13AM +1100, NeilBrown wrote: > > > This was Chuck's suggested name. His point was that STABLE means that > > > the FH's don't change during the lifetime of the file. > > > > > > I don't much care about the flag name, so if everyone likes PERSISTENT > > > better I'll roll with that. > > > > I don't like PERSISTENT. > > I'd rather call a spade a spade. > > > > EXPORT_OP_SUPPORTS_NFS_EXPORT > > or > > EXPORT_OP_NOT_NFS_COMPATIBLE > > > > The issue here is NFS export and indirection doesn't bring any benefits. > > No, it absolutely is not. And the whole concept of calling something > after the initial or main use is a recipe for a mess. We are calling it for it's only use. If there was ever another use, we could change the name if that made sense. It is not a public name, it is easy to change. > > Pick a name that conveys what the flag is about, and document those > semantics well. This flag is about the fact that for a given file, > as long as that file exists in the file system the handle is stable. > Both stable and persistent are suitable for that, nfs is everything > but. My understanding is that kernfs would not get the flag. kernfs filehandles do not change as long as the file exist. But this is not sufficient for the files to be usefully exported. I suspect kernfs does re-use filehandles relatively soon after the file/object has been destroyed. Maybe that is the real problem here: filehandle reuse, not filehandle stability. Jeff: could you please give details (and preserve them in future cover letters) of which filesystems are known to have problems and what exactly those problems are? > > Remember nfs also support volatile file handles, and other applications > might rely on this (I know of quite a few user space applications that > do, but they are kinda hardwired to xfs anyway). The NFS protocol supports volatile file handles. knfsd does not. So maybe EXPORT_OP_NOT_NFSD_COMPATIBLE might be better. or EXPORT_OP_NOT_LINUX_NFSD_COMPATIBLE. (I prefer opt-out rather than opt-in because nfsd export was the original purpose of export_operations, but it isn't something I would fight for) NeilBrown