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a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=wMbWURXBKlERnmrf5QHs0kPUbIXlx/juA5w6FY/x4Mo=; b=pQX0zA99VzZEIlAcpAlPuQefUS jy9CjjLBfeNNN1FNJitVD8JqerILO8jjC2fZiCCKiOnZ+AFbjn1TYpqjbQaKf+C8/KRnnpzD3SGrm 1PWJ9D0VnaLF05hqis2S5I41XDL1jyEKDnD+EFR38vRrwM8QPEg3EqDl695fgD/6Ar8xKBHcmKyax 7put0Wn3gyLR7YcoxmrK+vm9eU0JdOvfRB2prGJ/Am84hKoGOlEzX9X79ne8Tfk9prDNrEldtzRiA ijbo3W0+o5oEyQQ0Ds62PvFNcq+zxEq6evP7CKwgfSi+8rKZW1NE7FntT3VSj7fEic6gmCvCHtw/f BXWot+KA==; Received: from hch by bombadil.infradead.org with local (Exim 4.98.2 #2 (Red Hat Linux)) id 1viV0b-00000005EMZ-1e4Z; Wed, 21 Jan 2026 10:00:17 +0000 Date: Wed, 21 Jan 2026 02:00:17 -0800 From: Christoph Hellwig To: Jeff Layton Cc: Christian Brauner , NeilBrown , Christoph Hellwig , 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 Message-ID: References: <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> <20260120-entmilitarisieren-wanken-afd04b910897@brauner> <176890211061.16766.16354247063052030403@noble.neil.brown.name> <20260120-hacken-revision-88209121ac2c@brauner> X-Mailing-List: linux-erofs@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; 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See http://www.infradead.org/rpr.html On Tue, Jan 20, 2026 at 07:50:32AM -0500, Jeff Layton wrote: > > > and it DOES provide stable filehandles. > > > > Across reboot? Not really. > > It's quite possible that we may end up with the same "id" numbers in > cgroupfs on a new incarnation of the filesystem after a reboot. The > files in there are not the same ones as the ones before, but their > filehandles may match because kernfs doesn't factor in an i_generation > number. > > Could we fix it by adding a random i_generation value or something? > Possibly, but there really isn't a good use-case that I can see for > allowing cgroupfs to be exported via nfsd. Best to disallow it until > someone comes up with one. Yeah. And I'm pretty sure everyone here will push back hard on any such use case.