From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DDA051547D4 for ; Mon, 7 Oct 2024 12:22:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728303738; cv=none; b=e49ivBzxHJAqy3w14ZDXd2UCxVeUStsF1rpH3Qjv+XUKH4yinrg2WI75RAsgB4cbpJpNfdV/vFXxal0Yj5Fs9IZnDz+OgNWmYRqXiQ0D5DC6ODIlg9bu9VdskQ4S9cIi7NDoALcTYd5IwnNSsoB+hYpi6PLAU496rkqiLNhGEE4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728303738; c=relaxed/simple; bh=IJQNFySLxAIaTfUFMogP9emrb56T0cIi+kRHkgWBeHk=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=dr62C4ia5mC635hLG4VK2pRHKrVpRYVFJvr8tA1AfW3akKyit4jvbId9/IdAkWNvnNUCXF0fedRyIMDTB9YJo8sJFpAO/1vMJp4H/R87knHL90X5MGqTVv4eKyay+5LPv4LZaTue5UzPgMwjockR2DXWV7hJDsn79YT/oN7VuB0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YXKa7jEg; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YXKa7jEg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0ACF5C4CEC6; Mon, 7 Oct 2024 12:22:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728303737; bh=IJQNFySLxAIaTfUFMogP9emrb56T0cIi+kRHkgWBeHk=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=YXKa7jEgg3W08FtyhqaEmEUI1q7G4+nV3h2QHduEt27mJxJJ5cAJ2JFRem08wla7C ttjUZQ8sKBZQEKIVZb3OcMFQ6Qox73qE8nG+Ej0FWQlortohjys49STS3ZkqSVaOvr mHyMoSoFVGaL/f9bhNYSNI/xyr/j/bpQoF7OtY/AQ74zFNi4WGdUWGpnSuEu0oXtj4 t0hjfQR9DdLtzo3vUwlyn34vjm3vfQBETXOT2EprgIdviNguorlk8u/ne3JO8fUXQJ LZxq4ZOrW0Myt6oUs//VwUsrCH7789jqpGM0el+8BH4WjWYDmPe9jvX2XZbeVwcOp6 TuqOwCaRfzZ8A== Message-ID: <6e66fc44ecd98b86ae400715a2720fd28079a6ae.camel@kernel.org> Subject: Re: New NFSv4 export option "HideFilesBeginningInDot"? From: Jeff Layton To: Chuck Lever III , Cedric Blancher Cc: Linux NFS Mailing List , Volker Lendecke Date: Mon, 07 Oct 2024 08:22:15 -0400 In-Reply-To: References: Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ cDEsvv5IMmeMe1/qLZ6NaVkNuL3WOXvxaVT9USW1+/SGipO2IpKJjeDZfehlB/kpfF24+RrK+seQf CBYyUE8QJpvTZyfUHNYldXlrjO6n5MdOempLqWpfOmcGkwnyNRBR46g/jf8KnPRwXs509yAqDB6sE 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AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.52.4 (3.52.4-1.fc40) Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Sun, 2024-10-06 at 16:45 +0000, Chuck Lever III wrote: > Copying Volker; maybe he has some thoughts about how > this might work with Samba on Linux. >=20 >=20 > > On Oct 6, 2024, at 2:53=E2=80=AFAM, Cedric Blancher wrote: > >=20 > > Good morning! > >=20 > > Windows Server 2022 has a NFS export option called > > "HideFilesBeginningInDot", which sets the NFS WORD0_HIDDEN flag if a > > file starts with a '.' character. > > https://learn.microsoft.com/en-us/powershell/module/nfs/set-nfsserverco= nfiguration?view=3Dwindowsserver2022-ps > > has some documentation on this. > >=20 > > We'd like to get the same functionality for Linux nfsd, enabled by > > default ("NoHideFilesBeginningInDot" to turn it off), as a mount > > option. >=20 > I'm assuming you mean "export option" here, not "mount > option." >=20 > I'm not sure whether enabling the new behavior by > default is OK, by Linux rules of not introducing > behavior regressions. Will ponder. > It's a change in behavior, but I'd expect that the Linux client (and probably other unix clients like BSD) just ignores this attribute. >=20 > > Before I start writing a patch, are there any objections? >=20 > Not an objection, but here are some things to consider > as you prototype. >=20 > You might be planning to store this not as an actual file > attribute (retrieved via vfs_getattr or vfs_getxattr) but > instead NFSD would construct attribute 25 based on whether > the file name begins with dot and the new export option is > set. >=20 > On Linux, file names are kept in the parent directory, not > with the file; and note that a file can have more than one > name (directory entry) that refers to it. >=20 > Thus it might be difficult to retrieve the file's name > inside of nfsd4_getattr(), let alone retrieve it > efficiently, since GETATTR is a frequent operation. >=20 > You will need a deterministic mechanism to resolve the > ambiguity if the file has multiple names, only some of > which begin with a dot. Maybe -- only if all of the file's > names begin with a dot, then it is marked HIDDEN? >=20 > You will have to do something about SETATTR. RFC 8881 shows > that HIDDEN is a r/w attribute, and IIUC what you are > proposing is a r/o attribute -- clients cannot change this > setting via SETATTR. I'm not sure, but probably NFSD's > SETATTR will need to clear the HIDDEN bit and otherwise > ignore it. I haven't found any spec language that addresses > how a server needs to behave if it supports a RECOMMENDED > r/w attribute but does not permit it to be modified by > clients. >=20 > Given these issues, perhaps that explains why the Microsoft > documentation you provided says only: >=20 > "Specifies whether an NFS server creates files that have > names that begin with a dot (.) as hidden files." >=20 > That is, it appears that the Windows server sets the > HIDDEN attribute on the file inode at creation time. That > has it's own set of issues for Linux, since our file > systems don't implement a HIDDEN attribute (that I know > of). >=20 Windows has also traditionally not supported hardlinks, so it's fairly simple to set this attribute correctly there. Hiddenness on unix-like operating systems is really a characteristic of the filename and not an inode-level attribute like you're trying to make the server report, so this is conceptually more difficult. I think Chuck raises some interesting questions. In particular, if I have a file that has one hardlink "foo" and another of ".foo", should it be considered HIDDEN? =20 --=20 Jeff Layton