linux-kernel - Re: [PATCH v2 07/13] xfs: Introduce FORCEALIGN inode flag

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240711035956.GA2556@lst.de>
Date: Thu, 11 Jul 2024 05:59:56 +0200
From: Christoph Hellwig <hch@....de>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: John Garry <john.g.garry@...cle.com>, chandan.babu@...cle.com,
	dchinner@...hat.com, hch@....de, viro@...iv.linux.org.uk,
	brauner@...nel.org, jack@...e.cz, linux-xfs@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	catherine.hoang@...cle.com, martin.petersen@...cle.com
Subject: Re: [PATCH v2 07/13] xfs: Introduce FORCEALIGN inode flag

On Wed, Jul 10, 2024 at 07:59:58PM -0700, Darrick J. Wong wrote:
> Hmm.  If we don't support reflink + forcealign ATM, then shouldn't the
> superblock verifier or xfs_fs_fill_super fail the mount so that old
> kernels won't abruptly emit EFSCORRUPTED errors if a future kernel adds
> support for forcealign'd cow and starts writing out files with both
> iflags set?

Yes.

> That said, if the bs>ps patchset lands, then I think forcealign cow is
> a simple matter of setting the min folio order to the forcealign size
> and making sure that we always write out entire folios if any of the
> blocks cached by the folio is shared.  Direct writes to forcealigned
> shared files probably has to be aligned to the forcealign size or fall
> back to buffered writes for cow.

It has all the same problems as rtexsize > 1 + reflink, and suppoting
it will require raiding your patch stack.  Or better just wait until
we've got all that in now that we're actively working on it.