FAILED: patch "[PATCH] mm/damon/sysfs-schemes: kobject_del() scheme dirs" failed to apply to 6.1-stable tree

PATCH Applied [email protected] 4 participants 4 messages Sep 8 – Sep 9

Subsystems (3)

Stable branch Memory management DAMON

lore

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lore

[email protected]

author maintainer

2026-09-08 12:56 UTC #0 lore raw

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x 05fb6ac98c49be870c5f9ccdfdf95f0107e564ae
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090817-livable-sturdily-4c48@gregkh' --subject-prefix 'PATCH 6.1.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 05fb6ac98c49be870c5f9ccdfdf95f0107e564ae Mon Sep 17 00:00:00 2001
From: SJ Park <[email protected]>
Date: Sun, 28 Jun 2026 15:01:12 -0700
Subject: [PATCH] mm/damon/sysfs-schemes: kobject_del() scheme dirs

On CONFIG_DEBUG_KOBJECT_RELEASE enabled kernel, lack of kobject_del() could cause directories creation failures due to the name conflicts. Fix those issues for scheme directories by adding kobject_del() calls.

Link https://lore.kernel.org/[email protected] open here

Fixes 7e84b1f8212a ("mm/damon/sysfs: support DAMON-based Operation Schemes")

Signed-off-by SJ Park <[email protected]>

Cc <[email protected]> # 5.18.x

Signed-off-by Andrew Morton <[email protected]>

mm/damon/sysfs-schemes.c +4 -1

index 3cbeccd436e4..db496d2e493a 100644
@@ -2681,6 +2681,7 @@ void damon_sysfs_schemes_rm_dirs(struct damon_sysfs_schemes *schemes)
 
 	for (i = 0; i < schemes->nr; i++) {
 		damon_sysfs_scheme_rm_dirs(schemes_arr[i]);
+		kobject_del(&schemes_arr[i]->kobj);
 		kobject_put(&schemes_arr[i]->kobj);
 	}
 	schemes->nr = 0;

@@ -2722,13 +2723,15 @@ static int damon_sysfs_schemes_add_dirs(struct damon_sysfs_schemes *schemes,
 			goto out;
 		err = damon_sysfs_scheme_add_dirs(scheme);
 		if (err)
-			goto out;
+			goto del_out;
 
 		schemes_arr[i] = scheme;
 		schemes->nr++;
 	}
 	return 0;
 
+del_out:
+	kobject_del(&scheme->kobj);
 out:
 	damon_sysfs_schemes_rm_dirs(schemes);
 	kobject_put(&scheme->kobj);

SJ Park

maintainer

2026-09-09 03:55 UTC #1 lore raw

PATCH 1/1 mm/damon/sysfs-schemes: kobject_del() scheme dirs

Link https://lore.kernel.org/[email protected] open here

Fixes 7e84b1f8212a ("mm/damon/sysfs: support DAMON-based Operation Schemes")

Signed-off-by SJ Park <[email protected]>

Cc <[email protected]> # 5.18.x

Signed-off-by Andrew Morton <[email protected]>

(cherry picked from commit 05fb6ac98c49be870c5f9ccdfdf95f0107e564ae)

Signed-off-by SJ Park <[email protected]>

---
 mm/damon/sysfs.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

mm/damon/sysfs.c +4 -1

index bb2f4650741fa..7e4fb112d1154 100644
@@ -954,6 +954,7 @@ static void damon_sysfs_schemes_rm_dirs(struct damon_sysfs_schemes *schemes)
 
 	for (i = 0; i < schemes->nr; i++) {
 		damon_sysfs_scheme_rm_dirs(schemes_arr[i]);
+		kobject_del(&schemes_arr[i]->kobj);
 		kobject_put(&schemes_arr[i]->kobj);
 	}
 	schemes->nr = 0;

@@ -991,13 +992,15 @@ static int damon_sysfs_schemes_add_dirs(struct damon_sysfs_schemes *schemes,
 			goto out;
 		err = damon_sysfs_scheme_add_dirs(scheme);
 		if (err)
-			goto out;
+			goto del_out;
 
 		schemes_arr[i] = scheme;
 		schemes->nr++;
 	}
 	return 0;
 
+del_out:
+	kobject_del(&scheme->kobj);
 out:
 	damon_sysfs_schemes_rm_dirs(schemes);
 	kobject_put(&scheme->kobj);

Signature · 1 line

2.47.3

[email protected]

AI review

2026-09-09 04:05 UTC #2 lore raw

Re: [PATCH 6.1.y] mm/damon/sysfs-schemes: kobject_del() scheme dirs

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Incomplete fix: Missing kobject_del() for dynamically sized sysfs array directories (kdamonds, contexts, targets, regions) causes name conflicts on recreation. --

commit 313d3e99fc72ef8df36e0924dc61e045a278961d
Author: SJ Park <[email protected]>

mm/damon/sysfs-schemes: kobject_del() scheme dirs

Link https://lore.kernel.org/[email protected] open here

mm/damon/sysfs.c static void damon_sysfs_schemes_rm_dirs(struct damon_sysfs_schemes *schemes) · line 959

Quoted 11 lines

mm/damon/sysfs.c +1 -0

index bb2f4650741fa..7e4fb112d1154 100644
@@ -954,6 +954,7 @@ static void damon_sysfs_schemes_rm_dirs(struct damon_sysfs_schemes *schemes)
 
 	for (i = 0; i < schemes->nr; i++) {
 		damon_sysfs_scheme_rm_dirs(schemes_arr[i]);
+		kobject_del(&schemes_arr[i]->kobj);
 		kobject_put(&schemes_arr[i]->kobj);
 	}

[Severity: High]
This isn't a bug introduced by this patch, but while reviewing this fix for the schemes directories, it appears the exact same omission of kobject_del() is still present for other dynamically sized sysfs arrays (kdamonds, contexts, targets, and regions).

For instance, in damon_sysfs_kdamonds_rm_dirs():

static void damon_sysfs_kdamonds_rm_dirs(struct damon_sysfs_kdamonds *kdamonds)

{
	...
	for (i = 0; i < kdamonds->nr; i++) {
		damon_sysfs_kdamond_rm_dirs(kdamonds_arr[i]);
		kobject_put(&kdamonds_arr[i]->kobj);
	}
	...
}

When updating these directories, the old directories are dropped using only kobject_put() and new ones are immediately added with kobject_init_and_add() using the same names. If CONFIG_DEBUG_KOBJECT_RELEASE is enabled or a reference is held, won't this deferred removal leave the old directory active and cause the recreation to fail with -EEXIST?

Should kobject_del() also be added to damon_sysfs_kdamonds_rm_dirs(), damon_sysfs_contexts_rm_dirs(), damon_sysfs_targets_rm_dirs(), and damon_sysfs_regions_rm_dirs() to prevent these same name conflicts?

Quoted 7 lines

mm/damon/sysfs.c +1 -1

@@ -991,13 +992,15 @@ static int damon_sysfs_schemes_add_dirs(struct damon_sysfs_schemes *schemes,
 			goto out;
 		err = damon_sysfs_scheme_add_dirs(scheme);
 		if (err)
-			goto out;
+			goto del_out;

mm/damon/sysfs.c static int damon_sysfs_schemes_add_dirs(struct damon_sysfs_schemes *schemes, · line 1006

Quoted 10 lines

mm/damon/sysfs.c +2 -0

 		schemes_arr[i] = scheme;
 		schemes->nr++;
 	}
 	return 0;
 
+del_out:
+	kobject_del(&scheme->kobj);
 out:
 	damon_sysfs_schemes_rm_dirs(schemes);
 	kobject_put(&scheme->kobj);

[Severity: High]
This is also a pre-existing issue, but similar to the rm_dirs() paths, the error paths for adding other array elements appear to be missing kobject_del().

For example, in damon_sysfs_kdamonds_add_dirs():

	for (i = 0; i < nr_kdamonds; i++) {
		...
		err = kobject_init_and_add(&kdamond->kobj,
				&damon_sysfs_kdamond_ktype, &kdamonds->kobj,
				"%d", i);
		if (err)
			goto out;

		err = damon_sysfs_kdamond_add_dirs(kdamond);
		if (err)
			goto out;
		...
out:
	damon_sysfs_kdamonds_rm_dirs(kdamonds);
	kobject_put(&kdamond->kobj);
	return err;

If adding the child directories via damon_sysfs_kdamond_add_dirs() fails, the parent kdamond->kobj has already been added to sysfs. Doesn't branching directly to 'out' leave a lingering sysfs node without calling kobject_del()?

Should a similar 'del_out' error path be added to damon_sysfs_kdamonds_add_dirs(), damon_sysfs_contexts_add_dirs(), and damon_sysfs_targets_add_dirs()?

Signature · 1 line

Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=1

Sasha Levin

maintainer Applied

2026-09-09 20:26 UTC #3 lore raw

Re: [PATCH 6.1.y] mm/damon/sysfs-schemes: kobject_del() scheme dirs

In reply to SJ Park

Quoted 3 lines

On CONFIG_DEBUG_KOBJECT_RELEASE enabled kernel, lack of kobject_del() could cause directories creation failures due to the name conflicts. Fix those issues for scheme directories by adding kobject_del() calls.

Queued for 6.1, thanks.

Signature · 2 lines

Thanks,
Sasha