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

To: Jan Kara <jack@xxxxxxx>
Subject: Re: [PATCH 1/6] fs: add hole punching to fallocate
From: Josef Bacik <josef@xxxxxxxxxx>
Date: Tue, 16 Nov 2010 07:52:50 -0500
Cc: Josef Bacik <josef@xxxxxxxxxx>, david@xxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-btrfs@xxxxxxxxxxxxxxx, linux-ext4@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx, cmm@xxxxxxxxxx, cluster-devel@xxxxxxxxxx, ocfs2-devel@xxxxxxxxxxxxxx
In-reply-to: <20101116114346.GB4757@xxxxxxxxxxxxx>
References: <1289840723-3056-1-git-send-email-josef@xxxxxxxxxx> <1289840723-3056-2-git-send-email-josef@xxxxxxxxxx> <20101116111611.GA4757@xxxxxxxxxxxxx> <20101116114346.GB4757@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.19 (2009-01-05)
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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