+ mm-damon-sysfs-implement-preps-nr_preps-file.patch added to mm-new branch

+ mm-damon-sysfs-implement-preps-nr_preps-file.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mm/damon/sysfs: implement preps/nr_preps file
has been added to the -mm mm-new branch.  Its filename is
     mm-damon-sysfs-implement-preps-nr_preps-file.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-sysfs-implement-preps-nr_preps-file.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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and is updated there most days

------------------------------------------------------
From: SJ Park <sj@kernel.org>
Subject: mm/damon/sysfs: implement preps/nr_preps file
Date: Tue, 1 Sep 2026 06:24:57 -0700

Implement nr_preps file under the preps directory.  It will be evolved to
be used for generating sub directories that will represent each probe
preparation action.

Link: https://lore.kernel.org/20260901132506.99243-11-sj@kernel.org
Signed-off-by: SJ Park <sj@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/damon/sysfs.c |   53 ++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 52 insertions(+), 1 deletion(-)

--- a/mm/damon/sysfs.c~mm-damon-sysfs-implement-preps-nr_preps-file
+++ a/mm/damon/sysfs.c
@@ -755,6 +755,7 @@ static const struct kobj_type damon_sysf
 
 struct damon_sysfs_preps {
 	struct kobject kobj;
+	int nr;
 };
 
 static struct damon_sysfs_preps *damon_sysfs_preps_alloc(void)
@@ -762,12 +763,60 @@ static struct damon_sysfs_preps *damon_s
 	return kzalloc_obj(struct damon_sysfs_preps);
 }
 
+static void damon_sysfs_preps_rm_dirs(struct damon_sysfs_preps *preps)
+{
+	preps->nr = 0;
+}
+
+static int damon_sysfs_preps_add_dirs(struct damon_sysfs_preps *preps,
+		int nr_preps)
+{
+	preps->nr = nr_preps;
+	return 0;
+}
+
+static ssize_t nr_preps_show(struct kobject *kobj, struct kobj_attribute *attr,
+		char *buf)
+{
+	struct damon_sysfs_preps *preps = container_of(kobj,
+			struct damon_sysfs_preps, kobj);
+
+	return sysfs_emit(buf, "%d\n", preps->nr);
+}
+
+static ssize_t nr_preps_store(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
+{
+	struct damon_sysfs_preps *preps;
+	int nr, err = kstrtoint(buf, 0, &nr);
+
+	if (err)
+		return err;
+	if (nr < 0)
+		return -EINVAL;
+
+	preps = container_of(kobj, struct damon_sysfs_preps, kobj);
+
+	if (!mutex_trylock(&damon_sysfs_lock))
+		return -EBUSY;
+	err = damon_sysfs_preps_add_dirs(preps, nr);
+	mutex_unlock(&damon_sysfs_lock);
+	if (err)
+		return err;
+
+	return count;
+}
+
 static void damon_sysfs_preps_release(struct kobject *kobj)
 {
 	kfree(container_of(kobj, struct damon_sysfs_preps, kobj));
 }
 
+static struct kobj_attribute damon_sysfs_preps_nr_attr =
+		__ATTR_RW_MODE(nr_preps, 0600);
+
 static struct attribute *damon_sysfs_preps_attrs[] = {
+	&damon_sysfs_preps_nr_attr.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(damon_sysfs_preps);
@@ -1149,8 +1198,10 @@ put_preps_out:
 
 static void damon_sysfs_probe_rm_dirs(struct damon_sysfs_probe *probe)
 {
-	if (probe->preps)
+	if (probe->preps) {
+		damon_sysfs_preps_rm_dirs(probe->preps);
 		kobject_put(&probe->preps->kobj);
+	}
 	if (probe->filters) {
 		damon_sysfs_filters_rm_dirs(probe->filters);
 		kobject_put(&probe->filters->kobj);
_

Patches currently in -mm which might be from sj@kernel.org are

mm-damon-core-skip-applying-scheme-if-region-split-for-quota-fails.patch
mm-damon-paddr-respect-folio-end-for-damos_stat.patch
mm-damon-paddr-respect-folio-end-for-damos-actions-except-stat.patch
mm-damon-vaddr-respect-folio-end-for-damos_stat.patch
mm-damon-vaddr-respect-folio-end-for-damos_migrate_hotcold.patch
mm-damon-core-handle-extreme-memory-state-in-damon_get_node_mem_bp.patch
mm-damon-core-handle-extreme-memory-state-in-get_node_memcg_used_bp.patch
mm-damon-core-handle-extreme-memory-state-in-get_in_active_mem_bp.patch
mm-damon-core-introduce-damon_filter_type_pgidle_unset.patch
mm-damon-paddr-support-pgidle_unset-probe-filter-type.patch
mm-damon-sysfs-support-pgidle_unset-probe-filter-type.patch
docs-mm-damon-design-document-pgidle_unset-probe-filter-type.patch
mm-damon-core-introduce-damon_prep-struct.patch
mm-damon-core-commit-preps.patch
mm-damon-core-introduce-damon_operations-prep_probes.patch
mm-damon-paddr-support-damon_prep.patch
mm-damon-sysfs-implement-preps-directory.patch
mm-damon-sysfs-implement-preps-nr_preps-file.patch
mm-damon-sysfs-create-directories-for-nr_preps-writes.patch
mm-damon-sysfs-implement-prep_action-file.patch
mm-damon-sysfs-pass-preps-to-damon-core.patch
selftests-damon-sysfssh-test-probe-prep-sysfs-files.patch
docs-mm-damon-design-document-probe-preps.patch
docs-admin-guide-mm-damon-usage-document-probe-preps-sysfs-files.patch
docs-abi-damon-document-probe-prep-sysfs-files.patch