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Wysocki" , Danilo Krummrich , Jonathan Corbet , Andrew Morton , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Aishwarya.TCV@arm.com Subject: Re: [PATCH 2/2] debugfs: Remove broken no-mount mode Message-ID: <20251202060117.GA2268011@google.com> References: <20251120102222.18371-1-dev@null.aaront.org> <20251120102222.18371-3-dev@null.aaront.org> <8c2a2753-145e-4de5-84fe-9a900af6a2ee@sirena.org.uk> <0101019adbfd6b56-c13ab9c4-a0dd-483c-a6fd-a6ea0d110604-000000@us-west-2.amazonses.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0101019adbfd6b56-c13ab9c4-a0dd-483c-a6fd-a6ea0d110604-000000@us-west-2.amazonses.com> On Mon, Dec 01, 2025 at 10:16:49PM +0000, Aaron Thompson wrote: > On 12/1/25 09:15, Mark Brown wrote: > > On Thu, Nov 20, 2025 at 10:26:33AM +0000, Aaron Thompson wrote: > > > > > debugfs access modes were added in Linux 5.10 (Dec 2020) [1], but the > > > no-mount mode has behaved effectively the same as the off mode since > > > Linux 5.12 (Apr 2021) [2]. The only difference is the specific error > > > code returned by the debugfs_create_* functions, which is -ENOENT in > > > no-mount mode and -EPERM in off mode. > > > > I'm seeing regressions in -next in a lot of testing stuff which bisect > > to this patch. I've got a test that looks at the deferred probe list to > > see if it's empty, and the mm split_huge_page_test which uses a debugfs > > file called split_huge_pages. Neither of these mount debugfs for > > themselves, they just assume it'll be there - it looks like that's not > > happening any more but I didn't investigate properly. > > > > I don't immediately see what's getting confused, DEBUG_FS_ALLOW_ALL is > > the default and not overridden by anything in any defconfig so > > debugfs_enabled still ought to be being set, but I didn't actually try > > to debug this yet. > > > > Sample bisect: > > > > git bisect start > > # status: waiting for both good and bad commits > > ... > > # bad: [f278809475f6835b56de78b28dc2cc0c7e2c20a4] debugfs: Remove broken no-mount mode > > git bisect bad f278809475f6835b56de78b28dc2cc0c7e2c20a4 > > # first bad commit: [f278809475f6835b56de78b28dc2cc0c7e2c20a4] debugfs: Remove broken no-mount mode > > I am terribly sorry, this was a sloppy mistake on my part. The IS_ENABLED() > check is missing the CONFIG_ prefix. The fix patch is attached. I see it wasn't my local stuff acting up. > Greg, should I send a v2 of the patch series, or a separate patch with just > the fix? Or something else? Again, sorry for the trouble. > > -- Aaron > commit 92dcc0b68643955317fa4174442a6376df5a8c97 > Author: Aaron Thompson > Date: Mon Dec 1 22:15:24 2025 +0000 > > debugfs: Fix IS_ENABLED check > > diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c > index 930d66911fcd..4b263c328ed2 100644 > --- a/fs/debugfs/inode.c > +++ b/fs/debugfs/inode.c > @@ -35,7 +35,7 @@ > static struct vfsmount *debugfs_mount; > static int debugfs_mount_count; > static bool debugfs_registered; > -static bool debugfs_enabled __ro_after_init = IS_ENABLED(DEBUG_FS_ALLOW_ALL); > +static bool debugfs_enabled __ro_after_init = IS_ENABLED(CONFIG_DEBUG_FS_ALLOW_ALL); > > /* > * Don't allow access attributes to be changed whilst the kernel is locked down Tested-by: Chen-Yu Tsai