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Mon, 19 Jan 2026 15:45:39 -0500 (EST) Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 From: NeilBrown To: "Christian Brauner" Cc: "Christoph Hellwig" , "Jeff Layton" , "Amir Goldstein" , "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" , 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: <20260119-kanufahren-meerjungfrau-775048806544@brauner> References: <20260115-exportfs-nfsd-v1-0-8e80160e3c0c@kernel.org>, , <9c99197dde2eafa55a1b55dce2f0d4d02c77340a.camel@kernel.org>, <176877859306.16766.15009835437490907207@noble.neil.brown.name>, , <176880736225.16766.4203157325432990313@noble.neil.brown.name>, <20260119-kanufahren-meerjungfrau-775048806544@brauner> Date: Tue, 20 Jan 2026 07:45:35 +1100 Message-id: <176885553525.16766.291581709413217562@noble.neil.brown.name> Reply-To: NeilBrown X-Rspamd-Queue-Id: B81654000D X-Stat-Signature: eomukjpud7mds4wfo7guhagd83sn8wns X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1768855562-995271 X-HE-Meta: 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 SvcxJQsQ 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 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, Christian Brauner wrote: > On Mon, Jan 19, 2026 at 06:22:42PM +1100, NeilBrown wrote: > > 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 th= at > > > > > the FH's don't change during the lifetime of the file. > > > > >=20 > > > > > I don't much care about the flag name, so if everyone likes PERSIST= ENT > > > > > better I'll roll with that. > > > >=20 > > > > I don't like PERSISTENT. > > > > I'd rather call a spade a spade. > > > >=20 > > > > EXPORT_OP_SUPPORTS_NFS_EXPORT > > > > or > > > > EXPORT_OP_NOT_NFS_COMPATIBLE > > > >=20 > > > > The issue here is NFS export and indirection doesn't bring any benefi= ts. > > >=20 > > > No, it absolutely is not. And the whole concept of calling something > > > after the initial or main use is a recipe for a mess. > >=20 > > 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. > >=20 > > >=20 > > > 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. > >=20 > > 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. > >=20 > > 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. > >=20 > > 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? > >=20 > > >=20 > > > 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). > >=20 > > 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) >=20 > I prefer one of the variants you proposed here but I don't particularly > care. It's not a hill worth dying on. So if Christoph insists on the > other name then I say let's just go with it. >=20 This sounds like you are recommending that we give in to bullying. I would rather the decision be made based on the facts of the case, not the opinions that are stated most bluntly. I actually think that what Christoph wants is actually quite different from what Jeff wants, and maybe two flags are needed. But I don't yet have a clear understanding of what Christoph wants, so I cannot be sure. NeilBrown