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 C0E09D29B; Wed, 3 Apr 2024 01:26:53 +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=1712107613; cv=none; b=l6L9ArZNqnATDw5d4QDqScsylJFY8FrbwgQHDGsFupRymYtGvhq8AygWfS1HBpIBQWHq/jqGBo1QvFqkHzVWRg4rtu418NrE8PB+dp0N3tGmOGZ9GmdGP4wnPjC43WtciCW5MnipjnL79728g1xO6H9zuSNr4usi/NkMPNMjB7w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712107613; c=relaxed/simple; bh=mF+2sS0dgEpJGvcfOshVPrnAcb2zqkRLy1L+aLs61AE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=EjJClZB297iCTmsC8q5uYcr15MbgKuwbf1mjjhpq+ap9ZLXvIH4jaCIuicOCVzPG6rZ8noTSlvFvqma03G+dtijxbNYjBw6wTE+B+cz0/uBVoqgz1ZwgldbDUakgM69LipHiAFMnZY1PksXOCpKX072ZZ/04wItosD0GoiUWNQM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WxH8p3fM; 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="WxH8p3fM" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 44785C433F1; Wed, 3 Apr 2024 01:26:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1712107613; bh=mF+2sS0dgEpJGvcfOshVPrnAcb2zqkRLy1L+aLs61AE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WxH8p3fMxBq9C+iYnlgbQvwT1lcPUjGJ+Mp7j+s2as1K/B6K5dxTJyzN9iN/a+hzj +Wf8A/v4kKkxi6FoWDq0RWWyMVmQpj6Ueuj9X1UTJxlmryPcVsDLwmpyvp/wcftU+5 6C9F4BfXmoJiOhEAUuTkRrGCrLJIYXhkd5NoXe48T5T9ybw6jTEh9k+VZ5R3tbdh23 wfBo4/VisSLRlAz4h2eGipnvDWPYHPfUGbT0LKtTyZwLoPUAR7EoYlLIYxOzylCzAH 3Uht2hX9HXBCZXXpPgl6L7mfTXYQsBFDFDuqaspICrdBg/G9GPpOos5X8Yk/ebSEXa stK8u3/PXvSFA== Date: Tue, 2 Apr 2024 18:26:52 -0700 From: "Darrick J. Wong" To: Eric Biggers Cc: aalbersh@redhat.com, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, fsverity@lists.linux.dev Subject: Re: [PATCH 27/29] xfs: make it possible to disable fsverity Message-ID: <20240403012652.GE6390@frogsfrogsfrogs> References: <171175868489.1988170.9803938936906955260.stgit@frogsfrogsfrogs> <171175869006.1988170.17755870506078239341.stgit@frogsfrogsfrogs> <20240402232510.GA2576@sol.localdomain> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240402232510.GA2576@sol.localdomain> On Tue, Apr 02, 2024 at 04:25:10PM -0700, Eric Biggers wrote: > On Fri, Mar 29, 2024 at 05:43:06PM -0700, Darrick J. Wong wrote: > > From: Darrick J. Wong > > > > Create an experimental ioctl so that we can turn off fsverity. > > The concept of "experimental ioctls" seems problematic. What if people start > relying on them? Linux tends not to have "experimental" system calls, and > probably for good reason... They're trapped in my enormous backlog of patches. They get this special treatment so that I can show them to developers without anyone getting any fancy ideas about merging them. Once I get close enough to actually consider merging it, I'll move it out from under EXPERIMENTAL. IOWs: I'm not planning to push xfs_fs_staging.h itself to upstream ever. > Also, what is the use case for this ioctl? Is it necessary to have this when > userspace can already just replace a verity file with a copy that has verity > disabled? That's less efficient, but it does not require any kernel support and > does not require CAP_SYS_ADMIN. No, of course it isn't needed if replacing the file is easy. That however assumes that replacing /is/ easy. The use case for this is: "I enabled fsverity on my backup volume so I could detect bitrot, then the primary disk died, and when I went to restore the primary, I got a verity error." Being able to read known-bad corrupted contents are less bad than losing the entire file or having to do surgery with xfs_db to turn off fsverity. Just for my own convenience, this would enable me to try out fsverity in a few places while being able to undo it quickly if we end up changing the ondisk format during review. > And of course, if do we add this ioctl it shouldn't be XFS-specific. Yes, this is a proof of concept. I'd lift it to fs/verity/ if you accept the premise. --D > - Eric >