linux-kernel - Re: [PATCH v7 5/8] xfs: Support FS_XFLAG

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Message-ID: <20241007054229.GA307@lst.de>
Date: Mon, 7 Oct 2024 07:42:29 +0200
From: Christoph Hellwig <hch@....de>
To: John Garry <john.g.garry@...cle.com>
Cc: Christoph Hellwig <hch@....de>, axboe@...nel.dk, brauner@...nel.org,
	djwong@...nel.org, viro@...iv.linux.org.uk, jack@...e.cz,
	dchinner@...hat.com, 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 v7 5/8] xfs: Support FS_XFLAG_ATOMICWRITES

On Fri, Oct 04, 2024 at 02:07:05PM +0100, John Garry wrote:
> Sure, that is true (about being able to atomically write 1x FS block if the 
> bdev support it).
>
> But if we are going to add forcealign or similar later, then it would make 
> sense (to me) to have FS_XFLAG_ATOMICWRITES (and its other flags) from the 
> beginning. I mean, for example, if FS_XFLAG_FORCEALIGN were enabled and we 
> want atomic writes, setting FS_XFLAG_ATOMICWRITES would be rejected if AG 
> count is not aligned with extsize, or extsize is not a power-of-2, or 
> extsize exceeds bdev limits. So FS_XFLAG_ATOMICWRITES could have some value 
> there.
>
> As such, it makes sense to have a consistent user experience and require 
> FS_XFLAG_ATOMICWRITES from the beginning.

Well, even with forcealign we're not going to lose support for atomic
writes <= block size, are we?