linux-kernel - Re: [PATCH 1/6] fs: add hole punching to fallocate

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Message-ID: <20101116125249.GB31957@dhcp231-156.rdu.redhat.com>
Date:	Tue, 16 Nov 2010 07:52:50 -0500
From:	Josef Bacik <josef@...hat.com>
To:	Jan Kara <jack@...e.cz>
Cc:	Josef Bacik <josef@...hat.com>, david@...morbit.com,
	linux-kernel@...r.kernel.org, linux-btrfs@...r.kernel.org,
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	xfs@....sgi.com, cmm@...ibm.com, cluster-devel@...hat.com,
	ocfs2-devel@....oracle.com
Subject: Re: [PATCH 1/6] fs: add hole punching to fallocate

On Tue, Nov 16, 2010 at 12:43:46PM +0100, Jan Kara wrote:
> On Tue 16-11-10 12:16:11, Jan Kara wrote:
> > On Mon 15-11-10 12:05:18, Josef Bacik wrote:
> > > diff --git a/fs/open.c b/fs/open.c
> > > index 4197b9e..ab8dedf 100644
> > > --- a/fs/open.c
> > > +++ b/fs/open.c
> > > @@ -223,7 +223,7 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
> > >  		return -EINVAL;
> > >  
> > >  	/* Return error if mode is not supported */
> > > -	if (mode && !(mode & FALLOC_FL_KEEP_SIZE))
> > > +	if (mode && (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE)))
> >   Why not just:
> > if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE)) ?
>   And BTW, since FALLOC_FL_PUNCH_HOLE does not change the file size, should
> not we enforce that FALLOC_FL_KEEP_SIZE is / is not set? I don't mind too
> much which way but keeping it ambiguous (ignored) in the interface usually
> proves as a bad idea in future when we want to further extend the interface...
>

Yeah I went back and forth on this.  KEEP_SIZE won't change the behavior of
PUNCH_HOLE since PUNCH_HOLE implicitly means keep the size.  I figured since its
"mode" and not "flags" it would be ok to make either way accepted, but if you
prefer PUNCH_HOLE means you have to have KEEP_SIZE set then I'm cool with that,
just let me know one way or the other.  Thanks,

Josef
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