Re: [PATCH 00/61] treewide: Use IS_ERR_OR_NULL over manual NULL check - refactor

Jason Gunthorpe
2026-03-12T16:54:51Z

On Thu, Mar 12, 2026 at 11:32:37AM -0400, James Bottomley wrote:
> On Thu, 2026-03-12 at 09:57 -0300, Jason Gunthorpe wrote:
> > On Wed, Mar 11, 2026 at 02:40:36AM +0800, Kuan-Wei Chiu wrote:
> >
> > > IMHO, the necessity of IS_ERR_OR_NULL() often highlights a
> > > confusing or flawed API design. It usually implies that the caller
> > > is unsure whether a failure results in an error pointer or a NULL
> > > pointer.
> >
> > +1
> >
> > IS_ERR_OR_NULL() should always be looked on with suspicion. Very
> > little should be returning some tri-state 'ERR' 'NULL' 'SUCCESS'
> > pointer. What does the middle condition even mean? IS_ERR_OR_NULL()
> > implies ERR and NULL are semanticly the same, so fix the things to
> > always use ERR.
>
> Not in any way supporting the original patch. However, the pattern
> ERR, NULL, PTR is used extensively in the dentry code of filesystems.
> See the try_lookup..() set of functions in fs/namei.c
>
> The meaning is
>
> PTR - I found it
> NULL - It definitely doesn't exist
> ERR - something went wrong during the lookup.
>
> So I don't think you can blanket say this pattern is wrong.

Lots of places also would return ENOENT, I'd argue that is easier to
use..

But yes, I did use the word "suspicion" not blanket wrong :)

Jason