Re: [PATCH] iomap: Make sure iomap_end is called after iomap_begin

From: Christoph Hellwig <hch@infradead.org>
To: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Christoph Hellwig <hch@infradead.org>,
	linux-xfs@vger.kernel.org,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Bob Peterson <rpeterso@redhat.com>
Subject: Re: [PATCH] iomap: Make sure iomap_end is called after iomap_begin
Date: Thu, 18 Jun 2020 06:56:39 -0700	[thread overview]
Message-ID: <20200618135639.GA15658@infradead.org> (raw)
In-Reply-To: <CAHc6FU5x8+54zX5NWEDdsf5HV5qXLnjS1SM+oYmX1yMrh_mDfA@mail.gmail.com>

On Thu, Jun 18, 2020 at 02:37:37PM +0200, Andreas Gruenbacher wrote:
> On Thu, Jun 18, 2020 at 2:32 PM Matthew Wilcox <willy@infradead.org> wrote:
> > On Wed, Jun 17, 2020 at 06:39:01PM -0700, Darrick J. Wong wrote:
> > > > -   if (WARN_ON(iomap.offset > pos))
> > > > -           return -EIO;
> > > > -   if (WARN_ON(iomap.length == 0))
> > > > -           return -EIO;
> > > > +   if (WARN_ON(iomap.offset > pos) || WARN_ON(iomap.length == 0)) {
> > >
> > > Why combine these WARN_ON?  Before, you could distinguish between your
> > > iomap_begin method returning zero length vs. bad offset.
> >
> > Does it matter?  They're both the same problem -- the filesystem has
> > returned an invalid iomap.  I'd go further and combine the two:
> >
> >         if (WARN_ON(iomap.offset > pos || iomap.length == 0)) {
> >
> > that'll save a few bytes of .text
> 
> That would be fine by me as well. Christoph may have wanted separate
> warnings for a particular reason though.

Yes.  The line number in the WARN_ON will tell you which condition
you if they are separate, which is really useful to diagnose what is
going on.