Re: [ndctl PATCH v3 0/2] daxctl, util/sysfs: fix builtin-driver false failure on enable

On Thu, Jun 18, 2026 at 05:06:51PM +0800, Chen Pei wrote:
> When a DAX / ndctl driver is builtin (not a loadable module),
> daxctl_insert_kmod_for_mode() and __util_bind() still call
> kmod_module_probe_insert_module() unconditionally. libkmod only
> short-circuits builtin modules when it can find the modules.builtin
> index; otherwise it falls through to init_module() and returns -ENOENT,
> surfacing as a spurious "insert failure".
> 
> Pre-check kmod_module_get_initstate() and skip probe-insert when the
> module is already BUILTIN or LIVE, matching the pattern used by ndctl's
> own test/core.c.
> 
> Changes since v2 [3]:
>   - Patch 2/2: Add a Reviewed-by tag.
> 
> Changes since v1 [1]:
>   - Patch 1/2: unchanged; collected Reviewed-by from Dave and Alison.
>   - Patch 2/2: factored the state check into a new helper
>     util_kmod_skip_probe_insert() in util/sysfs.{c,h} so both
>     daxctl_insert_kmod_for_mode() and __util_bind() share it. The
>     helper also returns the observed libkmod state via an out
>     parameter so the caller does not re-read /sys/module/<name>/
>     initstate to distinguish LIVE from BUILTIN.
>   - Patch 2/2: additionally treat KMOD_MODULE_COMING as builtin when
>     /sys/module/<name>/ exists but the initstate file does not. This
>     is the pattern libkmod's sysfs fallback emits for builtin drivers
>     when the modules.builtin index is missing (e.g. a kernel installed
>     without running modules_install). This was the case Jonathan hit
>     on a builtin DAX VM setup; rather than rely on a libkmod fix, ndctl
>     handles the corner case directly. Suggested by Alison [2].
> 
> [1]: https://lore.kernel.org/nvdimm/[email protected]/
> [2]: https://lore.kernel.org/nvdimm/[email protected]/
> [3]: https://lore.kernel.org/nvdimm/[email protected]/
> 
> Chen Pei (2):
>   daxctl: fix kmod reference leak on probe-insert failure
>   daxctl, util/sysfs: skip module probe-insert when driver is builtin or
>     live

Thanks!

Applied to pending for NDCTL v86
https://github.com/pmem/ndctl/commits/pending/