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[100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 5BF4160097; Wed, 21 Jan 2026 14:27:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 960D7C4CEF1; Wed, 21 Jan 2026 14:27:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769005666; bh=i5hbrzdp22zDHgYLz86OMwY0w48EYyLnIazFien27/4=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=l4/7iE8/tj2pXG5zknCg4ReuYwfqpqrOXJ1Ek1+CBBwcjIrFrFAsh3OUZD6NyX2gC 8GnPn+a+/lDm9Ub0sXmq1vMq1ziRtpUm/KvJCrFC8MQkE3yUjTa1A8c1lWa2UhuAMw F1KXosNj6EfSZv5WIUnMAH6O/8u/xSTUQnlG9vk9fua1DK0oFe4v2KVPe+DXALpHfR Ytlvn34xTSytWwINfuBvK84VHh0v10umjqXj/Do8jSFk122fZzWzi1yH+bO2QmJc/N i9HI4rmiVVvnnQqTe7kRXccV5wCNLETc1O+xGwbL9wWGE1cYEuej+YUuqPZWutMoy8 irgZTK8S3Cf6A== Message-ID: <364d2fd98af52a2e2c32ca286decbdc1fe1c80d3.camel@kernel.org> Subject: Re: [PATCH 00/29] fs: require filesystems to explicitly opt-in to nfsd export support From: Jeff Layton To: NeilBrown , Christoph Hellwig Cc: Christian Brauner , 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 Date: Wed, 21 Jan 2026 09:27:38 -0500 In-Reply-To: <176899164457.16766.16099772451425825775@noble.neil.brown.name> 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> , <176885553525.16766.291581709413217562@noble.neil.brown.name> , , <176890126683.16766.5241619788613840985@noble.neil.brown.name> , <176899164457.16766.16099772451425825775@noble.neil.brown.name> Autocrypt: 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text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.2 (3.58.2-1.fc43) MIME-Version: 1.0 X-Stat-Signature: kpj6eoipguwmxj4ukqaiw6cd8gmingno X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 1D3CC1C0004 X-Rspam-User: X-HE-Tag: 1769005666-48902 X-HE-Meta: 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 t4VDTJAa yNIu0xwNusZtS9I8+Im1W3Xc4ZUHR9kb+YCxEWEqrSANfkqv7Unnte4uIYNkTSaPvGi+YVOX2snFBIUiuRj2F4eFyHYcE8G9VELsIKqRBj6Fa0mBZmiDfScSOsHhVR8veJs+RL7wk3JTtWi2pILIYEviTUecKlt7YKhWi5+qmBKzJnfkMce5pWthGqEaKGBsWyBLBzV1gbNxfl4p+0oJVGA64vt3+ZAQIlxGex833eeZRcFtg/b4u7wbwgG4rV4ZK6kmxY54EjqCmjkk7hhD3Tlh/rxhyFBiU8e5+TJbrEoHdHqocKlOtvRkjxQ== 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 Wed, 2026-01-21 at 21:34 +1100, NeilBrown wrote: > On Wed, 21 Jan 2026, Christoph Hellwig wrote: >=20 > >=20 > > >=20 > > > It took me a while to sift through the code/patches/comments and come= to > > > this understanding and I apologise if I wasn't as clear earlier. But > > > my intuition was always that file handle stability was never the real > > > issue, and maintainer choice was. Hence my rejection of the > > > "STABLE_HANDLES" name. > >=20 > > Why do you keep ignoring the fat that the stable handles are really > > important for anyone wanting to actually use them for their original > > storage purpose, be that for knfsd, a userland nfs damon, or other > > storage applications in userspace despite explaining this countless > > times? > >=20 >=20 > It isn't that I don't think they are important. It is that I think they > are universally provided (when not connectable). > If we add an EXPORT_OP_STABLE_FILEHANDLES flag, I believe we would need t= o > set it on every export_operations structure. So what would be the > point? >=20 I see your point. Using your definitions, stability is not a problem for Linux filesystems. The filehandles generally don't change after they have been established. Uniqueness however _is_ a problem as we can end up with valid handles for files that have been recreated across a reboot with some filesystems (esp. "synthetic" ones like cgroupfs, pidfs, etc.). Naming the flag STABLE conflates the two. In an earlier email, HCH said: > We'll still need a stable handles flag, and expose it to userspace > to avoid applications being tricked into using broken non-stable > file handles. We should have caught that when they were added, but > didn't unfortunately. >=20 If we assume he meant "unique handles" flag, then I think we're all mostly in agreement here. As far as this patchset goes: what if we were to just rename EXPORT_OP_STABLE_HANDLES to EXPORT_OP_UNIQUE_HANDLES (and clean up the documentation), since that's the main issue for existing filesystems. It would be fairly simple to advertise handle uniqueness using statx or something. Alternately, instead of denying access to these filesystems, we could just fix these filesystems to create unique handles (a'la random i_generation value or something similar). That should mostly prevent filehandles from being reusable across a reboot on these filesystems. That would leave cgroupfs and the like exportable via nfsd, but as you point out, we can't deny export by userland servers. If people want to do this kind of crazy stuff, maybe we shouldn't deny them after all. --=20 Jeff Layton