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

[Chen Pei <cp0613@linux.alibaba.com>]

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/20260514063234.86439-1-cp0613@linux.alibaba.com/
[2]: https://lore.kernel.org/nvdimm/agtf5uwBJOaCDR6l@aschofie-mobl2.lan/
[3]: https://lore.kernel.org/nvdimm/20260526132251.254476-1-cp0613@linux.alibaba.com/

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

 daxctl/lib/libdaxctl.c | 23 ++++++++++++++++++++--
 util/sysfs.c           | 44 +++++++++++++++++++++++++++++++++++++++++-
 util/sysfs.h           | 16 +++++++++++++++
 3 files changed, 80 insertions(+), 3 deletions(-)

-- 
2.43.0