Re: [PATCH 1/2] cxl/region: fix region leak when attach_target fails in cxl_add_to_region

Alison Schofield
2026-02-23T19:48:56Z

On Fri, Feb 20, 2026 at 11:30:12PM -0500, Gregory Price wrote:
> cxl_add_to_region() ignores the return value of attach_target(). When
> attach_target() fails (e.g. cxl_port_setup_targets() returns -ENXIO),
> the auto-discovered region remains registered with its HPA resource
> consumed but never reaches COMMIT state. Subsequent region creation
> attempts fail with -ENOSPC because the HPA range is already reserved.
>
> Track whether this call to cxl_add_to_region() created the region, and
> call drop_region() on attach_target() failure to unregister it and
> release the HPA resource. Pre-existing regions are left alone since
> other endpoints may already be attached.

I see you dropping this, perhaps just for the moment, because
the drop_region() you wanted to use is not available yet.

This looks a lot like
https://lore.kernel.org/linux-cxl/2a613604c0cdda6d9f838ae9b47ea6d936c5e4ce.1769746294.git.alison.schofield@intel.com/
cxl/region: Unregister auto-created region when assembly fails
When auto-created region assembly fails the region remains registered
but disabled. The region continues to reserve its memory resource,
preventing DAX from registering the memory.
Unregister the region on assembly failure to release the resource.

And the review comments on that one, or at least on that thread in
general, was to leave all the broken things in place.
I didn't agree with that, and hope to see this version move ahead
when you have the drop_region you need.

-- Alison

>
> Signed-off-by: Gregory Price <gourry@gourry.net>
> ---
> drivers/cxl/core/region.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 385be9cb44cd..276046d49f88 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -3923,6 +3923,7 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
> struct cxl_region_context ctx;
> struct cxl_region_params *p;
> bool attach = false;
> + bool newly_created = false;
> int rc;
>
> ctx = (struct cxl_region_context) {
> @@ -3946,15 +3947,23 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
> mutex_lock(&cxlrd->range_lock);
> struct cxl_region *cxlr __free(put_cxl_region) =
> cxl_find_region_by_range(cxlrd, &ctx.hpa_range);
> - if (!cxlr)
> + if (!cxlr) {
> cxlr = construct_region(cxlrd, &ctx);
> + newly_created = !IS_ERR(cxlr);
> + }
> mutex_unlock(&cxlrd->range_lock);
>
> rc = PTR_ERR_OR_ZERO(cxlr);
> if (rc)
> return rc;
>
> - attach_target(cxlr, cxled, -1, TASK_UNINTERRUPTIBLE);
> + rc = attach_target(cxlr, cxled, -1, TASK_UNINTERRUPTIBLE);
> + if (rc) {
> + /* If endpoint was just created, tear it down to release HPA */
> + if (newly_created)
> + drop_region(cxlrd, cxlr);
> + return rc;
> + }
>
> scoped_guard(rwsem_read, &cxl_rwsem.region) {
> p = &cxlr->params;
> @@ -3972,7 +3981,7 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
> p->res);
> }
>
> - return rc;
> + return 0;
> }
> EXPORT_SYMBOL_NS_GPL(cxl_add_to_region, "CXL");
>
> --
> 2.47.3
>