Re: [PATCH v2] dax/kmem: account for partial dis-contiguous resource upon removal

[Jonathan Cameron]

On Wed, 25 Feb 2026 21:01:08 -0800
Alison Schofield <alison.schofield@xxxxxxxxx> wrote:

> On Mon, Feb 23, 2026 at 12:15:16PM -0800, Davidlohr Bueso wrote:
> > When dev_dax_kmem_probe() partially succeeds (at least one range
> > is mapped) but a subsequent range fails request_mem_region()
> > or add_memory_driver_managed(), the probe silently continues,
> > ultimately returning success, but with the corresponding range
> > resource NULL'ed out.
> > 
> > dev_dax_kmem_remove() iterates over all dax_device ranges regardless
> > of if the underlying resource exists. When remove_memory() is
> > called later, it returns 0 because the memory was never added which
> > causes dev_dax_kmem_remove() to incorrectly assume the (nonexistent)
> > resource can be removed and attempts cleanup on a NULL pointer.  
> 
> Do you have a failure signature w Call Trace to paste here?
> If not, maybe just insert the expected signature for grepping:
> "BUG: unable to handle kernel NULL pointer dereference"
> 
> Reviewed-by: Alison Schofield <alison.schofield@xxxxxxxxx>
Reviewed-by: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>