linux-kernel - Re: [PATCH 2/2] xfs: add FALLOC_FL_ZERO

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Message-ID: <20120613235256.GX22848@dastard>
Date:	Thu, 14 Jun 2012 09:52:56 +1000
From:	Dave Chinner <david@...morbit.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Dave Chinner <dchinner@...hat.com>, xfs@....sgi.com
Subject: Re: [PATCH 2/2] xfs: add FALLOC_FL_ZERO_RANGE to fallocate

On Wed, Jun 13, 2012 at 08:24:12AM +0200, Paolo Bonzini wrote:
> Il 13/06/2012 04:16, Dave Chinner ha scritto:
> >> > +	BUG_ON((mode & FALLOC_FL_PUNCH_HOLE) && (mode & FALLOC_FL_ZERO_RANGE));
> > Never put BUG_ON() or BUG() in XFS code that can return an error.
> > Return EINVAL if we chose not to support it, and if it's really
> > something we consider bad, emit a warning to syslog (i.e.
> > xfs_warn()) and potentially add a ASSERT() case so that debug
> > kernels will trip over it. Nobody should be panicing a production
> > system just because a user supplied a set of incorrect syscall
> > paramters....
> 
> I know, the BUG_ON() is because it is ruled out in VFS code.  Of course
> if I remove that code, this will not be a BUG_ON() anymore.

If we put a BUG_ON() for every condition the VFS checked in every
filesystem, we'd have so many BUG_ON checks we wouldn't be able to
find the code. If it's banned at the VFS, there's no need to assert
that inthe filesystem code....

Cheers,

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