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Re: [PATCH 2/2] xfs: add FALLOC_FL_ZERO_RANGE to fallocate

To: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Subject: Re: [PATCH 2/2] xfs: add FALLOC_FL_ZERO_RANGE to fallocate
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 14 Jun 2012 09:52:56 +1000
Cc: linux-kernel@xxxxxxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx, Dave Chinner <dchinner@xxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <4FD8320C.1060308@xxxxxxxxxx>
References: <1339515364-17374-1-git-send-email-pbonzini@xxxxxxxxxx> <1339515364-17374-3-git-send-email-pbonzini@xxxxxxxxxx> <20120613021610.GQ22848@dastard> <4FD8320C.1060308@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
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@xxxxxxxxxxxxx

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