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

James Bottomley <[email protected]> Thu, 12 Mar 2026 11:32:37 -0400
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Message-ID <f5688b895eaebabae6545a0d9baf8f1404e8454e.camel@HansenPartnership.com> 
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.

Regards,

James