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 606CD218845; Tue, 25 Nov 2025 17:06:25 +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=1764090385; cv=none; b=IALHCGNfKnVX+I/UrDxhnM/bvOJfdcx03j8j8nsMNlPuP/03XwQTtP5d/o0pRFShZ8ypunx0m9QC/dDr5u1Q5rMJ+ro87NiTCjwiMgHAJyau714oxYJ8gi3la1pMck4IH1WKtx/qP1h1u2Tq7idWb62/2LhGM5vlpFefnDcDFqY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764090385; c=relaxed/simple; bh=Bh0B/kyPNC1+OWM9/m3mEthutUZz0Rx1kc11ORF7ocU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OIJEoDAIP3vvFLp3V1jqokN8mNa2jRl1jjKKFK1gTV+pQcNP69L7mKObiB6krqj8W07tUJduRzASATd2m1xfVRoztRVoLevoDuBb5qjNymkrecPtwqU7Yt4ps4LSO5d1daVsaID20UDtuoFWkp0lgTfrHldxNrpggag9djYJ4Q0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Hv2YP3DV; 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="Hv2YP3DV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CDF1EC116B1; Tue, 25 Nov 2025 17:06:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764090384; bh=Bh0B/kyPNC1+OWM9/m3mEthutUZz0Rx1kc11ORF7ocU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Hv2YP3DV6rBMnNsnU9TCxxacbVo3Cvu7SmFUbjpS45YJZZRz1T8eQKn3JO2pwxVFD GUlbOzlFzxqH0uENw4/ciilhStBgoGySR9g7SPZcDPjvtYlNyZjXl9UCVyYvxI1Mdt 1SU4k1Jhr+nhNj988M+Cq4YLbvRRVV7ZwNA8+cyOUcnrB0AGEx4GpkULxBRreHrd8B GCF5ebbpG2uFilVfvTMWyZ8DL0REUEz5nCE4ioL/mZUSSC7DOl4kAplOjE0j5JAQsY 7XokgHvCmGL9jLdG1Cpg4s8Z3EWcJZUd2snCrLTKS7IZDx/P9jpPpnZVnIIFk+fb8W rzyy8Larubksg== Date: Tue, 25 Nov 2025 09:06:24 -0800 From: "Darrick J. Wong" To: Christoph Hellwig Cc: Raphael Pinsonneault-Thibeault , cem@kernel.org, chandanbabu@kernel.org, bfoster@redhat.com, david@fromorbit.com, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linux.dev, syzbot+9f6d080dece587cfdd4c@syzkaller.appspotmail.com Subject: Re: [PATCH v5] xfs: validate log record version against superblock log version Message-ID: <20251125170624.GA23380@frogsfrogsfrogs> References: <20251124174658.59275-3-rpthibeault@gmail.com> <20251124185203.GA6076@frogsfrogsfrogs> 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: On Mon, Nov 24, 2025 at 10:31:22PM -0800, Christoph Hellwig wrote: > > Hrmm maybe we ought to reserve XLOG_VERSION==0x3 so that whenever we do > > log v3 we don't accidentally write logs with bits that won't be > > validated quite right on old kernels? > > Why do we need to reserve that? The code checks for either 1 or 2 > right now based on the log feature flag. If we add a v3 log we'll > have to ammend this, but reservations won't help with that. Yeah, I suppose you're right -- log v3 will require a new sb feature bit, and that's good enough. --D > > > + if (xfs_has_logv2(mp)) { > > > + if (XFS_IS_CORRUPT(mp, h_version != XLOG_VERSION_2)) > > > > Being pedantic here, but the kernel cpu_to_be32 wrappers are magic in > > that they compile to byteswapped constants so you can avoid the runtime > > overhead of byteswapping rhead->h_version by doing: > > > > if (XFS_IS_CORRUPT(mp, > > rhead->h_version != cpu_to_be32(XLOG_VERSION_2))) > > return -EFSCORRUPTED; > > > > But seeing as this is log validation for recovery, I think the > > performance implications are vanishingly small. > > Yes. > >