[PATCH 2/4] fs: Prevent doing FALLOC_FL_ZERO_RANGE on append only file

[Lukáš Czerner]

On Sat, 12 Apr 2014, Christoph Hellwig wrote:

> Date: Sat, 12 Apr 2014 08:19:35 -0700
> From: Christoph Hellwig <hch at infradead.org>
> To: Lukas Czerner <lczerner at redhat.com>
> Cc: linux-fsdevel at vger.kernel.org, ceph-devel at vger.kernel.org,
>     linux-ext4 at vger.kernel.org, xfs at oss.sgi.com
> Subject: Re: [PATCH 2/4] fs: Prevent doing FALLOC_FL_ZERO_RANGE on append only
>      file
> 
> On Fri, Apr 11, 2014 at 08:57:43PM +0200, Lukas Czerner wrote:
> >  	/*
> > -	 * It's not possible to punch hole or perform collapse range
> > -	 * on append only file
> > +	 * It's not possible to punch hole, perform collapse range
> > +	 * or zero range on append only file
> >  	 */
> > -	if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_COLLAPSE_RANGE)
> > +	if (mode & (FALLOC_FL_PUNCH_HOLE | FALLOC_FL_COLLAPSE_RANGE |
> > +		    FALLOC_FL_ZERO_RANGE)
> 
> Might be better to make this a negative test fo the operation that is
> allowed on an appen only file.  That's also much better future proof.
> 

True, it might be better to do it this way:

if (mode & ~FALLOC_FL_KEEP_SIZE && IS_APPEND(inode))

this makes FALLOC_FL_NO_HIDE_STALE (reserved, not implemented)
potentially not work on the append only file since it could change
the content of the file.

Will resend.

Thanks!
-Lukas