Re: [PATCH v2] btrfs: use %pe for error code output

On Wed, Jul 22, 2026 at 05:04:07PM +0930, Qu Wenruo wrote:
> During an interrupted mount, I got the following messages:
> 
>  workqueue: Failed to create a rescuer kthread for wq "btrfs-qgroup-rescan": -EINTR
>  BTRFS error (device dm-3): open_ctree failed: -12

Awesome, I didn't know we have a "strerror()" in the kernel now :).

> Workqueue code is outputting a human readable error string, meanwhile
> we're still using a numeric error code.
> 
> So follow the workqueue code to use "%pe" format, which will
> automatically convert an error pointer to the human readable string.
> 
> However this is a minor pitfall, if the return value is not an error
> code, e.g. a positive number, "%pe" with "ERR_PTR(ret)" will output the
> pointer as a hash value, e.g.:
> 
>  ret=1 %pe out=0000000019414716
>  ret=-22 %pe out=-EINVAL
> 
> So we should not use this "%pe" output for callsites that are known to
> return positive values.

Or not blindly print return values that aren't errors.

Reviewed-by: Johannes Thumshirn <[email protected]>