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Date: Wed, 19 Aug 2026 16:24:45 -0700
From: "Darrick J. Wong" <djwong@kernel.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: hch@lst.de, cem@kernel.org, stable@vger.kernel.org,
	linux-xfs@vger.kernel.org
Subject: Re: [PATCH 5/6] xfs: don't modify file attributes or poke fsnotify
 for dry runs
Message-ID: <20260819232445.GE6072@frogsfrogsfrogs>
References: <178659861838.833922.2269351780488724470.stgit@frogsfrogsfrogs>
 <178659861983.833922.10991178975977666480.stgit@frogsfrogsfrogs>
 <aoVMFaHJoBl-xYAb@infradead.org>
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In-Reply-To: <aoVMFaHJoBl-xYAb@infradead.org>

On Tue, Aug 18, 2026 at 11:24:21PM -0700, Christoph Hellwig wrote:
> On Wed, Aug 12, 2026 at 10:26:43PM -0700, Darrick J. Wong wrote:
> > From: Darrick J. Wong <djwong@kernel.org>
> > 
> > LOLLM points out that a dry run shouldn't poke fsnotify because we don't
> > actually change the files.  I noticed that we also shouldn't be removing
> > file privileges when doing a dry run.
> 
> > +++ b/fs/xfs/xfs_exchrange.c
> > @@ -701,6 +701,9 @@ xfs_exchrange_contents(
> >  	if (error)
> >  		goto out_unlock;
> >  
> > +	if (fxr->flags & XFS_EXCHANGE_RANGE_DRY_RUN)
> > +		goto out_unlock;
> > +
> >  	/*
> >  	 * Finish the exchange by removing special file privileges like any
> >  	 * other file write would do.  This may involve turning on support for
> 
> This just skip removing the privileges.  I guess the commit mentions
> this on the side, but this is probably the important part, so my
> emphasis it?  It would also seem easier to move the check into
> xfs_exchange_range_finish next to the code that it guards.

Yeah, I'll move it, and rearrange the commit message.

> > @@ -783,6 +786,9 @@ xfs_exchange_range(
> >  	if (ret)
> >  		return ret;
> >  
> > +	if (fxr->flags & XFS_EXCHANGE_RANGE_DRY_RUN)
> > +		return 0;
> > +
> >  	fsnotify_modify(fxr->file1);
> >  	if (fxr->file2 != fxr->file1)
> >  		fsnotify_modify(fxr->file2);
> 
> Move the fsnotify calls into an if statement instead of the
> early return?

Done.

--D