REGRESSION on linux-next (next-20251201)

["Borah, Chaitanya Kumar" <chaitanya.kumar.borah@intel.com>]

Hello Aaron,

Hope you are doing well. I am Chaitanya from the linux graphics team in 
Intel.

This mail is regarding a regression we are seeing in our CI runs[1] on
linux-next repository.

Since the version next-20251201 [2], we are seeing the following regression

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Starting subtest: load
(i915_module_load:1280) igt_debugfs-CRITICAL: Test assertion failure 
function igt_debugfs_path, file ../lib/igt_debugfs.c:121:
(i915_module_load:1280) igt_debugfs-CRITICAL: Failed assertion: debugfs_root
(i915_module_load:1280) igt_debugfs-CRITICAL: Last errno: 2, No such 
file or directory
Subtest load failed.
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I see some other drivers also failing to create their debugfs entries.

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[    0.134437] pinctrl core: failed to create debugfs directory
[    3.488263] intel-lpss 0000:00:15.0: Failed to create debugfs entries
[    3.563494] intel-lpss 0000:00:15.1: Failed to create debugfs entries
[    3.631076] intel-lpss 0000:00:15.2: Failed to create debugfs entries
[    3.697366] intel-lpss 0000:00:15.3: Failed to create debugfs entries
[    3.764351] intel-lpss 0000:00:19.0: Failed to create debugfs entries
[    3.841824] intel-lpss 0000:00:19.1: Failed to create debugfs entries
[    3.909492] nvme0: failed to create debugfs directory
[    3.937845] nvme0n1: failed to create debugfs directory
[    5.636042] pinctrl core: failed to create debugfs directory for 
INTC105E:00
[  177.973628] cec: Failed to create debugfs cec dir
`````````````````````````````````````````````````````````````````````````````````
Detailed log can be found in [3].

After bisecting the tree, the following patch [4] seems to be the first 
"bad" commit

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commit f278809475f6835b56de78b28dc2cc0c7e2c20a4
Author: Aaron Thompson dev@aaront.org
Date:   Thu Nov 20 10:26:33 2025 +0000

     debugfs: Remove broken no-mount mode
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We also verified that if we revert the patch the issue is not seen.

Could you please check why the patch causes this regression and provide 
a fix if necessary?

Thank you.

Regards

Chaitanya

[1]
https://intel-gfx-ci.01.org/tree/linux-next/combined-alt.html?
[2] 
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20251201
[3]
https://intel-gfx-ci.01.org/tree/linux-next/next-20251201/bat-arlh-2/igt@i915_module_load@load.html
[4] 
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?h=next-20251201&id=f278809475f6835b56de78b28dc2cc0c7e2c20a4