Re: REGRESSION on linux-next (next-20251201)

[Aaron Thompson]

On 12/3/25 01:10, Borah, Chaitanya Kumar wrote:
> 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
>
> `````````````````````````````````````````````````````````````````````````````````
> 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.
> `````````````````````````````````````````````````````````````````````````````````
>
> I see some other drivers also failing to create their debugfs entries.
>
> `````````````````````````````````````````````````````````````````````````````````
> [    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
>
> `````````````````````````````````````````````````````````````````````````````````````````````````````````
> commit f278809475f6835b56de78b28dc2cc0c7e2c20a4
> Author: Aaron Thompson dev@xxxxxxxxxx
> Date:   Thu Nov 20 10:26:33 2025 +0000
>
>      debugfs: Remove broken no-mount mode
> `````````````````````````````````````````````````````````````````````````````````````````````````````````
>
> 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@xxxxxxxxx
> [4] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/ 
> commit/?h=next-20251201&id=f278809475f6835b56de78b28dc2cc0c7e2c20a4

Hi Chaitanya,

This is fixed in next-20251203 (commit d3666c1f8a31). For next-20251201 
and next-20251202, you can also work around the bug by specifying the 
kernel parameter "debugfs=on". Sorry for the inconvenience.

https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/fs/debugfs?h=next-20251203&id=d3666c1f8a31b7ff6805effcfedfac22454c6517

-- Aaron