linux-kernel - Re: [PATCH v7 11/14] xfs: add xfs_file_dio_write

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Message-ID: <20250423145116.GY25675@frogsfrogsfrogs>
Date: Wed, 23 Apr 2025 07:51:16 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: Christoph Hellwig <hch@....de>
Cc: John Garry <john.g.garry@...cle.com>, brauner@...nel.org,
	viro@...iv.linux.org.uk, jack@...e.cz, cem@...nel.org,
	linux-fsdevel@...r.kernel.org, dchinner@...hat.com,
	linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	ojaswin@...ux.ibm.com, ritesh.list@...il.com,
	martin.petersen@...cle.com, linux-ext4@...r.kernel.org,
	linux-block@...r.kernel.org, catherine.hoang@...cle.com,
	linux-api@...r.kernel.org
Subject: Re: [PATCH v7 11/14] xfs: add xfs_file_dio_write_atomic()

On Wed, Apr 23, 2025 at 10:19:02AM +0200, Christoph Hellwig wrote:
> On Wed, Apr 23, 2025 at 07:42:51AM +0200, Christoph Hellwig wrote:
> > On Mon, Apr 21, 2025 at 09:42:41AM -0700, Darrick J. Wong wrote:
> > > Well it turns out that was a stupid question -- zoned=1 can't be enabled
> > > with reflink, which means there's no cow fallback so atomic writes just
> > > plain don't work:
> > 
> > Exactly.  It is still on my todo list to support it, but there are a
> > few higher priority items on it as well, in addition to constant
> > interruptions for patch reviews :)
> 
> Actually, for zoned we don't need reflink support - as we always write
> out place only the stuffing of multiple remaps into a single transaction
> is needed.  Still no need to force John to do this work, I can look into
> this (probably fairly trivial) work once we have good enough test cases
> in xfstests that I can trust them to verify I got things right.

<nod> I think we'll need a new fstest to set an error trap on a step
midway through a multi-extent ioend completion to make sure that's
actually working properly.  And probably new write commands for fsx and
fsstress to exercise RWF_ATOMIC.

(Catherine: please send the accumulated atomic writes fstests)

--D