linux-kernel - Re: [PATCH v3 04/14] xfs: make EOF allocation simpler

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Message-ID: <20240807002423.GR623936@frogsfrogsfrogs>
Date: Tue, 6 Aug 2024 17:24:23 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: Dave Chinner <david@...morbit.com>
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 v3 04/14] xfs: make EOF allocation simpler

On Wed, Aug 07, 2024 at 10:00:46AM +1000, Dave Chinner wrote:
> On Tue, Aug 06, 2024 at 11:58:53AM -0700, Darrick J. Wong wrote:
> > On Thu, Aug 01, 2024 at 04:30:47PM +0000, John Garry wrote:
> > > @@ -3688,12 +3649,19 @@ xfs_bmap_btalloc_filestreams(
> > >  	}
> > >  
> > >  	args->minlen = xfs_bmap_select_minlen(ap, args, blen);
> > > -	if (ap->aeof)
> > > -		error = xfs_bmap_btalloc_at_eof(ap, args, blen, true);
> > > +	if (ap->aeof && ap->offset)
> > > +		error = xfs_bmap_btalloc_at_eof(ap, args);
> > >  
> > > +	/* This may be an aligned allocation attempt. */
> > >  	if (!error && args->fsbno == NULLFSBLOCK)
> > >  		error = xfs_alloc_vextent_near_bno(args, ap->blkno);
> > >  
> > > +	/* Attempt non-aligned allocation if we haven't already. */
> > > +	if (!error && args->fsbno == NULLFSBLOCK && args->alignment > 1)  {
> > > +		args->alignment = 1;
> > > +		error = xfs_alloc_vextent_near_bno(args, ap->blkno);
> > 
> > Oops, I just replied to the v2 thread instead of this.
> > 
> > From
> > https://lore.kernel.org/linux-xfs/20240621203556.GU3058325@frogsfrogsfrogs/
> > 
> > Do we have to zero args->alignslop here?
> 
> No. It should always be zero here to begin with. It is the
> responsibility of the allocation attempt that modifies
> args->alignment and args->alignslop to reset them to original values
> on allocation failure.
> 
> The only places we use alignslop are xfs_bmap_btalloc_at_eof() and
> xfs_ialloc_ag_alloc(). They both zero it and reset args->alignment
> on allocation failure before falling through to the next allocation
> attempt.

Aha, that's even in this patch.

Reviewed-by: Darrick J. Wong <djwong@...nel.org>

--D


> -Dave.
> -- 
> Dave Chinner
> david@...morbit.com
>