linux-kernel - Re: [PATCH v6 5/7] xfs: Support atomic write for statx

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: <20241001084302.GD20648@lst.de>
Date: Tue, 1 Oct 2024 10:43:02 +0200
From: Christoph Hellwig <hch@....de>
To: "Darrick J. Wong" <djwong@...nel.org>
Cc: John Garry <john.g.garry@...cle.com>, axboe@...nel.dk,
	brauner@...nel.org, viro@...iv.linux.org.uk, jack@...e.cz,
	dchinner@...hat.com, hch@....de, cem@...nel.org,
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	hare@...e.de, martin.petersen@...cle.com,
	catherine.hoang@...cle.com, mcgrof@...nel.org,
	ritesh.list@...il.com, ojaswin@...ux.ibm.com
Subject: Re: [PATCH v6 5/7] xfs: Support atomic write for statx

On Mon, Sep 30, 2024 at 09:37:16AM -0700, Darrick J. Wong wrote:
> Ok, so we're only supporting untorn writes if they're exactly the fs
> blocksize, and 1 fsblock is between awu_min/max.  That simplifies a lot
> of things. :)
> 
> Not supporting sub-fsblock atomic writes means that we'll never hit the
> directio COW fallback code, which uses the pagecache.
> 
> Not supporting multi-fsblock atomic writes means that you don't have to
> figure out how to ensure that we always do cow on forcealign
> granularity.  Though as I pointed out elsewhere in this thread, that's a
> forcealign problem.

It does simplify things a lot, and is probably a good idea for
the initial version.  But I suspect support for atomic writes
smaller than the block size will be really useful and we should
eventually support them, but maybe now on reflinked files or
alwayscow.