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

[Christoph Hellwig <hch@infradead.org>]

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.