ata: libata-scsi: fix ata_dsm_trim_pages() kernel-docgrafted

make htmldocs fails with:

  Documentation/driver-api/libata:604: ./drivers/ata/libata-scsi.c:2301:
  ERROR: Unexpected indentation. [docutils]

The Return: section of ata_dsm_trim_pages() ends its first sentence with
a colon and continues with an indented bullet list. reStructuredText
requires a blank line before an indented block, so docutils chokes on
the list.

Simply adding the missing blank line does not work either: Return: is a
kernel-doc "special section", which is terminated by the first blank
line, so the bullet list would end up in the Description section,
detached from the sentence introducing it.

Spell the two bounds out as prose instead, so that the Return: section
stays self-contained. Documentation-only change.

Fixes: e64e6b5dc867 ("ata: libata-scsi: scale DSM TRIM payload by MAX PAGES PER DSM COMMAND")
Reported-by: Thomas Huth <thuth@redhat.com>
Closes: https://lore.kernel.org/linux-ide/b0a0b8e8-cc4f-4c7b-8bc5-fee0712d405a@redhat.com/
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Link: https://lore.kernel.org/r/20260916130031.29990-2-cassel@kernel.org
Signed-off-by: Niklas Cassel <cassel@kernel.org>

8 files changed, 1996 insertions, 0 deletions

diff --git a/fs/sysfs/Kconfig b/fs/sysfs/Kconfig
new file mode 100644
index 000000000..b0fe1cce3
--- /dev/null
+++ b/fs/sysfs/Kconfig
@@ -0,0 +1,25 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config SYSFS
+	bool "sysfs file system support" if EXPERT
+	default y
+	select KERNFS
+	help
+	The sysfs filesystem is a virtual filesystem that the kernel uses to
+	export internal kernel objects, their attributes, and their
+	relationships to one another.
+
+	Users can use sysfs to ascertain useful information about the running
+	kernel, such as the devices the kernel has discovered on each bus and
+	which driver each is bound to. sysfs can also be used to tune devices
+	and other kernel subsystems.
+
+	Some system agents rely on the information in sysfs to operate.
+	/sbin/hotplug uses device and object attributes in sysfs to assist in
+	delegating policy decisions, like persistently naming devices.
+
+	sysfs is currently used by the block subsystem to mount the root
+	partition.  If sysfs is disabled you must specify the boot device on
+	the kernel boot command line via its major and minor numbers.  For
+	example, "root=03:01" for /dev/hda1.
+
+	Designers of embedded systems may wish to say N here to conserve space.
diff --git a/fs/sysfs/Makefile b/fs/sysfs/Makefile
new file mode 100644
index 000000000..0906b9e52
--- /dev/null
+++ b/fs/sysfs/Makefile
@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the sysfs virtual filesystem
+#
+
+obj-y		:= file.o dir.o symlink.o mount.o group.o
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
new file mode 100644
index 000000000..ffdcd4153
--- /dev/null
+++ b/fs/sysfs/dir.c
@@ -0,0 +1,161 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fs/sysfs/dir.c - sysfs core and dir operation implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * Please see Documentation/filesystems/sysfs.rst for more information.
+ */
+
+#define pr_fmt(fmt)	"sysfs: " fmt
+
+#include <linux/fs.h>
+#include <linux/kobject.h>
+#include <linux/slab.h>
+#include "sysfs.h"
+
+DEFINE_SPINLOCK(sysfs_symlink_target_lock);
+
+void sysfs_warn_dup(struct kernfs_node *parent, const char *name)
+{
+	char *buf;
+
+	buf = kzalloc(PATH_MAX, GFP_KERNEL);
+	if (buf)
+		kernfs_path(parent, buf, PATH_MAX);
+
+	pr_warn("cannot create duplicate filename '%s/%s'\n", buf, name);
+	dump_stack();
+
+	kfree(buf);
+}
+
+/**
+ * sysfs_create_dir_ns - create a directory for an object with a namespace tag
+ * @kobj: object we're creating directory for
+ * @ns: the namespace tag to use
+ */
+int sysfs_create_dir_ns(struct kobject *kobj, const struct ns_common *ns)
+{
+	struct kernfs_node *parent, *kn;
+	kuid_t uid;
+	kgid_t gid;
+
+	if (WARN_ON(!kobj))
+		return -EINVAL;
+
+	if (kobj->parent)
+		parent = kobj->parent->sd;
+	else
+		parent = sysfs_root_kn;
+
+	if (!parent)
+		return -ENOENT;
+
+	kobject_get_ownership(kobj, &uid, &gid);
+
+	kn = kernfs_create_dir_ns(parent, kobject_name(kobj), 0755, uid, gid,
+				  kobj, ns);
+	if (IS_ERR(kn)) {
+		if (PTR_ERR(kn) == -EEXIST)
+			sysfs_warn_dup(parent, kobject_name(kobj));
+		return PTR_ERR(kn);
+	}
+
+	kobj->sd = kn;
+	return 0;
+}
+
+/**
+ *	sysfs_remove_dir - remove an object's directory.
+ *	@kobj:	object.
+ *
+ *	The only thing special about this is that we remove any files in
+ *	the directory before we remove the directory, and we've inlined
+ *	what used to be sysfs_rmdir() below, instead of calling separately.
+ */
+void sysfs_remove_dir(struct kobject *kobj)
+{
+	struct kernfs_node *kn = kobj->sd;
+
+	/*
+	 * In general, kobject owner is responsible for ensuring removal
+	 * doesn't race with other operations and sysfs doesn't provide any
+	 * protection; however, when @kobj is used as a symlink target, the
+	 * symlinking entity usually doesn't own @kobj and thus has no
+	 * control over removal.  @kobj->sd may be removed anytime
+	 * and symlink code may end up dereferencing an already freed node.
+	 *
+	 * sysfs_symlink_target_lock synchronizes @kobj->sd
+	 * disassociation against symlink operations so that symlink code
+	 * can safely dereference @kobj->sd.
+	 */
+	spin_lock(&sysfs_symlink_target_lock);
+	kobj->sd = NULL;
+	spin_unlock(&sysfs_symlink_target_lock);
+
+	if (kn) {
+		WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
+		kernfs_remove(kn);
+	}
+}
+
+int sysfs_rename_dir_ns(struct kobject *kobj, const char *new_name,
+			const struct ns_common *new_ns)
+{
+	struct kernfs_node *parent;
+	int ret;
+
+	parent = kernfs_get_parent(kobj->sd);
+	ret = kernfs_rename_ns(kobj->sd, parent, new_name, new_ns);
+	kernfs_put(parent);
+	return ret;
+}
+
+int sysfs_move_dir_ns(struct kobject *kobj, struct kobject *new_parent_kobj,
+		      const struct ns_common *new_ns)
+{
+	struct kernfs_node *kn = kobj->sd;
+	struct kernfs_node *new_parent;
+
+	new_parent = new_parent_kobj && new_parent_kobj->sd ?
+		new_parent_kobj->sd : sysfs_root_kn;
+
+	return kernfs_rename_ns(kn, new_parent, NULL, new_ns);
+}
+
+/**
+ * sysfs_create_mount_point - create an always empty directory
+ * @parent_kobj:  kobject that will contain this always empty directory
+ * @name: The name of the always empty directory to add
+ */
+int sysfs_create_mount_point(struct kobject *parent_kobj, const char *name)
+{
+	struct kernfs_node *kn, *parent = parent_kobj->sd;
+
+	kn = kernfs_create_empty_dir(parent, name);
+	if (IS_ERR(kn)) {
+		if (PTR_ERR(kn) == -EEXIST)
+			sysfs_warn_dup(parent, name);
+		return PTR_ERR(kn);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(sysfs_create_mount_point);
+
+/**
+ *	sysfs_remove_mount_point - remove an always empty directory.
+ *	@parent_kobj: kobject that will contain this always empty directory
+ *	@name: The name of the always empty directory to remove
+ *
+ */
+void sysfs_remove_mount_point(struct kobject *parent_kobj, const char *name)
+{
+	struct kernfs_node *parent = parent_kobj->sd;
+
+	kernfs_remove_by_name_ns(parent, name, NULL);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_mount_point);
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
new file mode 100644
index 000000000..cd5bb0f9f
--- /dev/null
+++ b/fs/sysfs/file.c
@@ -0,0 +1,821 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fs/sysfs/file.c - sysfs regular (text) file implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * Please see Documentation/filesystems/sysfs.rst for more information.
+ */
+
+#include <linux/module.h>
+#include <linux/kobject.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/seq_file.h>
+#include <linux/mm.h>
+
+#include "sysfs.h"
+
+static struct kobject *sysfs_file_kobj(struct kernfs_node *kn)
+{
+	guard(rcu)();
+	return rcu_dereference(kn->__parent)->priv;
+}
+
+/*
+ * Determine ktype->sysfs_ops for the given kernfs_node.  This function
+ * must be called while holding an active reference.
+ */
+static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
+{
+	struct kobject *kobj = sysfs_file_kobj(kn);
+
+	if (kn->flags & KERNFS_LOCKDEP)
+		lockdep_assert_held(kn);
+	return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
+}
+
+/*
+ * Reads on sysfs are handled through seq_file, which takes care of hairy
+ * details like buffering and seeking.  The following function pipes
+ * sysfs_ops->show() result through seq_file.
+ */
+static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
+{
+	struct kernfs_open_file *of = sf->private;
+	struct kobject *kobj = sysfs_file_kobj(of->kn);
+	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
+	ssize_t count;
+	char *buf;
+
+	if (WARN_ON_ONCE(!ops->show))
+		return -EINVAL;
+
+	/* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
+	count = seq_get_buf(sf, &buf);
+	if (count < PAGE_SIZE) {
+		seq_commit(sf, -1);
+		return 0;
+	}
+	memset(buf, 0, PAGE_SIZE);
+
+	count = ops->show(kobj, of->kn->priv, buf);
+	if (count < 0)
+		return count;
+
+	/*
+	 * The code works fine with PAGE_SIZE return but it's likely to
+	 * indicate truncated result or overflow in normal use cases.
+	 */
+	if (count >= PAGE_SIZE) {
+		WARN(1, "OOB write or bad count %zd at %pS\n", count, ops->show);
+		/* Try to struggle along */
+		count = PAGE_SIZE - 1;
+	}
+	seq_commit(sf, count);
+	return 0;
+}
+
+static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
+				 size_t count, loff_t pos)
+{
+	const struct bin_attribute *battr = of->kn->priv;
+	struct kobject *kobj = sysfs_file_kobj(of->kn);
+	loff_t size = file_inode(of->file)->i_size;
+
+	if (!count)
+		return 0;
+
+	if (size) {
+		if (pos >= size)
+			return 0;
+		if (pos + count > size)
+			count = size - pos;
+	}
+
+	if (!battr->read)
+		return -EIO;
+
+	return battr->read(of->file, kobj, battr, buf, pos, count);
+}
+
+/* kernfs read callback for regular sysfs files with pre-alloc */
+static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
+			     size_t count, loff_t pos)
+{
+	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
+	struct kobject *kobj = sysfs_file_kobj(of->kn);
+	ssize_t len;
+
+	/*
+	 * If buf != of->prealloc_buf, we don't know how
+	 * large it is, so cannot safely pass it to ->show
+	 */
+	if (WARN_ON_ONCE(buf != of->prealloc_buf))
+		return 0;
+	len = ops->show(kobj, of->kn->priv, buf);
+	if (len < 0)
+		return len;
+	if (len >= (ssize_t)PAGE_SIZE) {
+		printk("fill_read_buffer: %pS returned bad count\n", ops->show);
+		len = PAGE_SIZE - 1;
+	}
+	if (pos) {
+		if (len <= pos)
+			return 0;
+		len -= pos;
+		memmove(buf, buf + pos, len);
+	}
+	return min_t(ssize_t, count, len);
+}
+
+/* kernfs write callback for regular sysfs files */
+static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
+			      size_t count, loff_t pos)
+{
+	const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
+	struct kobject *kobj = sysfs_file_kobj(of->kn);
+
+	if (!count)
+		return 0;
+
+	return ops->store(kobj, of->kn->priv, buf, count);
+}
+
+/* kernfs write callback for bin sysfs files */
+static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
+				  size_t count, loff_t pos)
+{
+	const struct bin_attribute *battr = of->kn->priv;
+	struct kobject *kobj = sysfs_file_kobj(of->kn);
+	loff_t size = file_inode(of->file)->i_size;
+
+	if (size) {
+		if (size <= pos)
+			return -EFBIG;
+		count = min_t(ssize_t, count, size - pos);
+	}
+	if (!count)
+		return 0;
+
+	if (!battr->write)
+		return -EIO;
+
+	return battr->write(of->file, kobj, battr, buf, pos, count);
+}
+
+static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
+			     struct vm_area_struct *vma)
+{
+	const struct bin_attribute *battr = of->kn->priv;
+	struct kobject *kobj = sysfs_file_kobj(of->kn);
+
+	return battr->mmap(of->file, kobj, battr, vma);
+}
+
+static loff_t sysfs_kf_bin_llseek(struct kernfs_open_file *of, loff_t offset,
+				  int whence)
+{
+	const struct bin_attribute *battr = of->kn->priv;
+	struct kobject *kobj = sysfs_file_kobj(of->kn);
+
+	if (battr->llseek)
+		return battr->llseek(of->file, kobj, battr, offset, whence);
+	else
+		return generic_file_llseek(of->file, offset, whence);
+}
+
+static int sysfs_kf_bin_open(struct kernfs_open_file *of)
+{
+	const struct bin_attribute *battr = of->kn->priv;
+
+	if (battr->f_mapping)
+		of->file->f_mapping = battr->f_mapping();
+
+	return 0;
+}
+
+void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
+{
+	struct kernfs_node *kn = kobj->sd, *tmp;
+
+	if (kn && dir)
+		kn = kernfs_find_and_get(kn, dir);
+	else
+		kernfs_get(kn);
+
+	if (kn && attr) {
+		tmp = kernfs_find_and_get(kn, attr);
+		kernfs_put(kn);
+		kn = tmp;
+	}
+
+	if (kn) {
+		kernfs_notify(kn);
+		kernfs_put(kn);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_notify);
+
+static const struct kernfs_ops sysfs_file_kfops_empty = {
+};
+
+static const struct kernfs_ops sysfs_file_kfops_ro = {
+	.seq_show	= sysfs_kf_seq_show,
+};
+
+static const struct kernfs_ops sysfs_file_kfops_wo = {
+	.write		= sysfs_kf_write,
+};
+
+static const struct kernfs_ops sysfs_file_kfops_rw = {
+	.seq_show	= sysfs_kf_seq_show,
+	.write		= sysfs_kf_write,
+};
+
+static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
+	.read		= sysfs_kf_read,
+	.prealloc	= true,
+};
+
+static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
+	.write		= sysfs_kf_write,
+	.prealloc	= true,
+};
+
+static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
+	.read		= sysfs_kf_read,
+	.write		= sysfs_kf_write,
+	.prealloc	= true,
+};
+
+static const struct kernfs_ops sysfs_bin_kfops_ro = {
+	.read		= sysfs_kf_bin_read,
+};
+
+static const struct kernfs_ops sysfs_bin_kfops_wo = {
+	.write		= sysfs_kf_bin_write,
+};
+
+static const struct kernfs_ops sysfs_bin_kfops_rw = {
+	.read		= sysfs_kf_bin_read,
+	.write		= sysfs_kf_bin_write,
+};
+
+static const struct kernfs_ops sysfs_bin_kfops_mmap = {
+	.read		= sysfs_kf_bin_read,
+	.write		= sysfs_kf_bin_write,
+	.mmap		= sysfs_kf_bin_mmap,
+	.open		= sysfs_kf_bin_open,
+	.llseek		= sysfs_kf_bin_llseek,
+};
+
+int sysfs_add_file_mode_ns(struct kernfs_node *parent,
+		const struct attribute *attr, umode_t mode, kuid_t uid,
+		kgid_t gid, const struct ns_common *ns)
+{
+	struct kobject *kobj = parent->priv;
+	const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
+	struct lock_class_key *key = NULL;
+	const struct kernfs_ops *ops = NULL;
+	struct kernfs_node *kn;
+
+	/* every kobject with an attribute needs a ktype assigned */
+	if (WARN(!sysfs_ops, KERN_ERR
+			"missing sysfs attribute operations for kobject: %s\n",
+			kobject_name(kobj)))
+		return -EINVAL;
+
+	if (mode & SYSFS_PREALLOC) {
+		if (sysfs_ops->show && sysfs_ops->store)
+			ops = &sysfs_prealloc_kfops_rw;
+		else if (sysfs_ops->show)
+			ops = &sysfs_prealloc_kfops_ro;
+		else if (sysfs_ops->store)
+			ops = &sysfs_prealloc_kfops_wo;
+	} else {
+		if (sysfs_ops->show && sysfs_ops->store)
+			ops = &sysfs_file_kfops_rw;
+		else if (sysfs_ops->show)
+			ops = &sysfs_file_kfops_ro;
+		else if (sysfs_ops->store)
+			ops = &sysfs_file_kfops_wo;
+	}
+
+	if (!ops)
+		ops = &sysfs_file_kfops_empty;
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	if (!attr->ignore_lockdep)
+		key = attr->key ?: (struct lock_class_key *)&attr->skey;
+#endif
+
+	kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
+				  PAGE_SIZE, ops, (void *)attr, ns, key);
+	if (IS_ERR(kn)) {
+		if (PTR_ERR(kn) == -EEXIST)
+			sysfs_warn_dup(parent, attr->name);
+		return PTR_ERR(kn);
+	}
+	return 0;
+}
+
+int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
+		const struct bin_attribute *battr, umode_t mode, size_t size,
+		kuid_t uid, kgid_t gid, const struct ns_common *ns)
+{
+	const struct attribute *attr = &battr->attr;
+	struct lock_class_key *key = NULL;
+	const struct kernfs_ops *ops;
+	struct kernfs_node *kn;
+
+	if (battr->mmap)
+		ops = &sysfs_bin_kfops_mmap;
+	else if (battr->read && battr->write)
+		ops = &sysfs_bin_kfops_rw;
+	else if (battr->read)
+		ops = &sysfs_bin_kfops_ro;
+	else if (battr->write)
+		ops = &sysfs_bin_kfops_wo;
+	else
+		ops = &sysfs_file_kfops_empty;
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	if (!attr->ignore_lockdep)
+		key = attr->key ?: (struct lock_class_key *)&attr->skey;
+#endif
+
+	kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
+				  size, ops, (void *)attr, ns, key);
+	if (IS_ERR(kn)) {
+		if (PTR_ERR(kn) == -EEXIST)
+			sysfs_warn_dup(parent, attr->name);
+		return PTR_ERR(kn);
+	}
+	return 0;
+}
+
+/**
+ * sysfs_create_file_ns - create an attribute file for an object with custom ns
+ * @kobj: object we're creating for
+ * @attr: attribute descriptor
+ * @ns: namespace the new file should belong to
+ */
+int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
+			 const struct ns_common *ns)
+{
+	kuid_t uid;
+	kgid_t gid;
+
+	if (WARN_ON(!kobj || !kobj->sd || !attr))
+		return -EINVAL;
+
+	kobject_get_ownership(kobj, &uid, &gid);
+	return sysfs_add_file_mode_ns(kobj->sd, attr, attr->mode, uid, gid, ns);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
+
+int sysfs_create_files(struct kobject *kobj, const struct attribute * const *ptr)
+{
+	int err = 0;
+	int i;
+
+	for (i = 0; ptr[i] && !err; i++)
+		err = sysfs_create_file(kobj, ptr[i]);
+	if (err)
+		while (--i >= 0)
+			sysfs_remove_file(kobj, ptr[i]);
+	return err;
+}
+EXPORT_SYMBOL_GPL(sysfs_create_files);
+
+/**
+ * sysfs_add_file_to_group - add an attribute file to a pre-existing group.
+ * @kobj: object we're acting for.
+ * @attr: attribute descriptor.
+ * @group: group name.
+ */
+int sysfs_add_file_to_group(struct kobject *kobj,
+		const struct attribute *attr, const char *group)
+{
+	struct kernfs_node *parent;
+	kuid_t uid;
+	kgid_t gid;
+	int error;
+
+	if (group) {
+		parent = kernfs_find_and_get(kobj->sd, group);
+	} else {
+		parent = kobj->sd;
+		kernfs_get(parent);
+	}
+
+	if (!parent)
+		return -ENOENT;
+
+	kobject_get_ownership(kobj, &uid, &gid);
+	error = sysfs_add_file_mode_ns(parent, attr, attr->mode, uid, gid,
+				       NULL);
+	kernfs_put(parent);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
+
+/**
+ * sysfs_chmod_file - update the modified mode value on an object attribute.
+ * @kobj: object we're acting for.
+ * @attr: attribute descriptor.
+ * @mode: file permissions.
+ *
+ */
+int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
+		     umode_t mode)
+{
+	struct kernfs_node *kn;
+	struct iattr newattrs;
+	int rc;
+
+	kn = kernfs_find_and_get(kobj->sd, attr->name);
+	if (!kn)
+		return -ENOENT;
+
+	newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
+	newattrs.ia_valid = ATTR_MODE;
+
+	rc = kernfs_setattr(kn, &newattrs);
+
+	kernfs_put(kn);
+	return rc;
+}
+EXPORT_SYMBOL_GPL(sysfs_chmod_file);
+
+/**
+ * sysfs_break_active_protection - break "active" protection
+ * @kobj: The kernel object @attr is associated with.
+ * @attr: The attribute to break the "active" protection for.
+ *
+ * With sysfs, just like kernfs, deletion of an attribute is postponed until
+ * all active .show() and .store() callbacks have finished unless this function
+ * is called. Hence this function is useful in methods that implement self
+ * deletion.
+ */
+struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
+						  const struct attribute *attr)
+{
+	struct kernfs_node *kn;
+
+	kobject_get(kobj);
+	kn = kernfs_find_and_get(kobj->sd, attr->name);
+	if (kn)
+		kernfs_break_active_protection(kn);
+	else
+		kobject_put(kobj);
+	return kn;
+}
+EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
+
+/**
+ * sysfs_unbreak_active_protection - restore "active" protection
+ * @kn: Pointer returned by sysfs_break_active_protection().
+ *
+ * Undo the effects of sysfs_break_active_protection(). Since this function
+ * calls kernfs_put() on the kernfs node that corresponds to the 'attr'
+ * argument passed to sysfs_break_active_protection() that attribute may have
+ * been removed between the sysfs_break_active_protection() and
+ * sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
+ * this function has returned.
+ */
+void sysfs_unbreak_active_protection(struct kernfs_node *kn)
+{
+	struct kobject *kobj = sysfs_file_kobj(kn);
+
+	kernfs_unbreak_active_protection(kn);
+	kernfs_put(kn);
+	kobject_put(kobj);
+}
+EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
+
+/**
+ * sysfs_remove_file_ns - remove an object attribute with a custom ns tag
+ * @kobj: object we're acting for
+ * @attr: attribute descriptor
+ * @ns: namespace tag of the file to remove
+ *
+ * Hash the attribute name and namespace tag and kill the victim.
+ */
+void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
+			  const struct ns_common *ns)
+{
+	struct kernfs_node *parent = kobj->sd;
+
+	kernfs_remove_by_name_ns(parent, attr->name, ns);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
+
+/**
+ * sysfs_remove_file_self - remove an object attribute from its own method
+ * @kobj: object we're acting for
+ * @attr: attribute descriptor
+ *
+ * See kernfs_remove_self() for details.
+ */
+bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
+{
+	struct kernfs_node *parent = kobj->sd;
+	struct kernfs_node *kn;
+	bool ret;
+
+	kn = kernfs_find_and_get(parent, attr->name);
+	if (WARN_ON_ONCE(!kn))
+		return false;
+
+	ret = kernfs_remove_self(kn);
+
+	kernfs_put(kn);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_file_self);
+
+void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
+{
+	int i;
+
+	for (i = 0; ptr[i]; i++)
+		sysfs_remove_file(kobj, ptr[i]);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_files);
+
+/**
+ * sysfs_remove_file_from_group - remove an attribute file from a group.
+ * @kobj: object we're acting for.
+ * @attr: attribute descriptor.
+ * @group: group name.
+ */
+void sysfs_remove_file_from_group(struct kobject *kobj,
+		const struct attribute *attr, const char *group)
+{
+	struct kernfs_node *parent;
+
+	if (group) {
+		parent = kernfs_find_and_get(kobj->sd, group);
+	} else {
+		parent = kobj->sd;
+		kernfs_get(parent);
+	}
+
+	if (parent) {
+		kernfs_remove_by_name(parent, attr->name);
+		kernfs_put(parent);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
+
+/**
+ *	sysfs_create_bin_file - create binary file for object.
+ *	@kobj:	object.
+ *	@attr:	attribute descriptor.
+ */
+int sysfs_create_bin_file(struct kobject *kobj,
+			  const struct bin_attribute *attr)
+{
+	kuid_t uid;
+	kgid_t gid;
+
+	if (WARN_ON(!kobj || !kobj->sd || !attr))
+		return -EINVAL;
+
+	kobject_get_ownership(kobj, &uid, &gid);
+	return sysfs_add_bin_file_mode_ns(kobj->sd, attr, attr->attr.mode,
+					  attr->size, uid, gid, NULL);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
+
+/**
+ *	sysfs_remove_bin_file - remove binary file for object.
+ *	@kobj:	object.
+ *	@attr:	attribute descriptor.
+ */
+void sysfs_remove_bin_file(struct kobject *kobj,
+			   const struct bin_attribute *attr)
+{
+	kernfs_remove_by_name(kobj->sd, attr->attr.name);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
+
+static int internal_change_owner(struct kernfs_node *kn, kuid_t kuid,
+				 kgid_t kgid)
+{
+	struct iattr newattrs = {
+		.ia_valid = ATTR_UID | ATTR_GID,
+		.ia_uid = kuid,
+		.ia_gid = kgid,
+	};
+	return kernfs_setattr(kn, &newattrs);
+}
+
+/**
+ *	sysfs_link_change_owner - change owner of a sysfs file.
+ *	@kobj:	object of the kernfs_node the symlink is located in.
+ *	@targ:	object of the kernfs_node the symlink points to.
+ *	@name:	name of the link.
+ *	@kuid:	new owner's kuid
+ *	@kgid:	new owner's kgid
+ *
+ * This function looks up the sysfs symlink entry @name under @kobj and changes
+ * the ownership to @kuid/@kgid. The symlink is looked up in the namespace of
+ * @targ.
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
+			    const char *name, kuid_t kuid, kgid_t kgid)
+{
+	struct kernfs_node *kn = NULL;
+	int error;
+
+	if (!name || !kobj->state_in_sysfs || !targ->state_in_sysfs)
+		return -EINVAL;
+
+	error = -ENOENT;
+	kn = kernfs_find_and_get_ns(kobj->sd, name, targ->sd->ns);
+	if (!kn)
+		goto out;
+
+	error = -EINVAL;
+	if (kernfs_type(kn) != KERNFS_LINK)
+		goto out;
+	if (kn->symlink.target_kn->priv != targ)
+		goto out;
+
+	error = internal_change_owner(kn, kuid, kgid);
+
+out:
+	kernfs_put(kn);
+	return error;
+}
+
+/**
+ *	sysfs_file_change_owner - change owner of a sysfs file.
+ *	@kobj:	object.
+ *	@name:	name of the file to change.
+ *	@kuid:	new owner's kuid
+ *	@kgid:	new owner's kgid
+ *
+ * This function looks up the sysfs entry @name under @kobj and changes the
+ * ownership to @kuid/@kgid.
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
+			    kgid_t kgid)
+{
+	struct kernfs_node *kn;
+	int error;
+
+	if (!name)
+		return -EINVAL;
+
+	if (!kobj->state_in_sysfs)
+		return -EINVAL;
+
+	kn = kernfs_find_and_get(kobj->sd, name);
+	if (!kn)
+		return -ENOENT;
+
+	error = internal_change_owner(kn, kuid, kgid);
+
+	kernfs_put(kn);
+
+	return error;
+}
+
+/**
+ *	sysfs_change_owner - change owner of the given object.
+ *	@kobj:	object.
+ *	@kuid:	new owner's kuid
+ *	@kgid:	new owner's kgid
+ *
+ * Change the owner of the default directory, files, groups, and attributes of
+ * @kobj to @kuid/@kgid. Note that sysfs_change_owner mirrors how the sysfs
+ * entries for a kobject are added by driver core. In summary,
+ * sysfs_change_owner() takes care of the default directory entry for @kobj,
+ * the default attributes associated with the ktype of @kobj and the default
+ * attributes associated with the ktype of @kobj.
+ * Additional properties not added by driver core have to be changed by the
+ * driver or subsystem which created them. This is similar to how
+ * driver/subsystem specific entries are removed.
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid)
+{
+	int error;
+	const struct kobj_type *ktype;
+
+	if (!kobj->state_in_sysfs)
+		return -EINVAL;
+
+	/* Change the owner of the kobject itself. */
+	error = internal_change_owner(kobj->sd, kuid, kgid);
+	if (error)
+		return error;
+
+	ktype = get_ktype(kobj);
+	if (ktype) {
+		/*
+		 * Change owner of the default groups associated with the
+		 * ktype of @kobj.
+		 */
+		error = sysfs_groups_change_owner(kobj, ktype->default_groups,
+						  kuid, kgid);
+		if (error)
+			return error;
+	}
+
+	return 0;
+}
+
+/**
+ *	sysfs_emit - scnprintf equivalent, aware of PAGE_SIZE buffer.
+ *	@buf:	start of PAGE_SIZE buffer.
+ *	@fmt:	format
+ *	@...:	optional arguments to @format
+ *
+ *
+ * Returns number of characters written to @buf.
+ */
+int sysfs_emit(char *buf, const char *fmt, ...)
+{
+	va_list args;
+	int len;
+
+	if (WARN(!buf || offset_in_page(buf),
+		 "invalid sysfs_emit: buf:%p\n", buf))
+		return 0;
+
+	va_start(args, fmt);
+	len = vscnprintf(buf, PAGE_SIZE, fmt, args);
+	va_end(args);
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(sysfs_emit);
+
+/**
+ *	sysfs_emit_at - scnprintf equivalent, aware of PAGE_SIZE buffer.
+ *	@buf:	start of PAGE_SIZE buffer.
+ *	@at:	offset in @buf to start write in bytes
+ *		@at must be >= 0 && < PAGE_SIZE
+ *	@fmt:	format
+ *	@...:	optional arguments to @fmt
+ *
+ *
+ * Returns number of characters written starting at &@buf[@at].
+ */
+int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
+{
+	va_list args;
+	int len;
+
+	if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
+		 "invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
+		return 0;
+
+	va_start(args, fmt);
+	len = vscnprintf(buf + at, PAGE_SIZE - at, fmt, args);
+	va_end(args);
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(sysfs_emit_at);
+
+/**
+ *	sysfs_bin_attr_simple_read - read callback to simply copy from memory.
+ *	@file:	attribute file which is being read.
+ *	@kobj:	object to which the attribute belongs.
+ *	@attr:	attribute descriptor.
+ *	@buf:	destination buffer.
+ *	@off:	offset in bytes from which to read.
+ *	@count:	maximum number of bytes to read.
+ *
+ * Simple ->read() callback for bin_attributes backed by a buffer in memory.
+ * The @private and @size members in struct bin_attribute must be set to the
+ * buffer's location and size before the bin_attribute is created in sysfs.
+ *
+ * Bounds check for @off and @count is done in sysfs_kf_bin_read().
+ * Negative value check for @off is done in vfs_setpos() and default_llseek().
+ *
+ * Returns number of bytes written to @buf.
+ */
+ssize_t sysfs_bin_attr_simple_read(struct file *file, struct kobject *kobj,
+				   const struct bin_attribute *attr, char *buf,
+				   loff_t off, size_t count)
+{
+	memcpy(buf, attr->private + off, count);
+	return count;
+}
+EXPORT_SYMBOL_GPL(sysfs_bin_attr_simple_read);
diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
new file mode 100644
index 000000000..4e1e4f18a
--- /dev/null
+++ b/fs/sysfs/group.c
@@ -0,0 +1,638 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fs/sysfs/group.c - Operations for adding/removing multiple files at once.
+ *
+ * Copyright (c) 2003 Patrick Mochel
+ * Copyright (c) 2003 Open Source Development Lab
+ * Copyright (c) 2013 Greg Kroah-Hartman
+ * Copyright (c) 2013 The Linux Foundation
+ */
+
+#include <linux/kobject.h>
+#include <linux/module.h>
+#include <linux/dcache.h>
+#include <linux/namei.h>
+#include <linux/err.h>
+#include <linux/fs.h>
+#include "sysfs.h"
+
+
+static void remove_files(struct kernfs_node *parent,
+			 const struct attribute_group *grp)
+{
+	struct attribute *const *attr;
+	const struct bin_attribute *const *bin_attr;
+
+	if (grp->attrs)
+		for (attr = grp->attrs; *attr; attr++)
+			kernfs_remove_by_name(parent, (*attr)->name);
+	if (grp->bin_attrs)
+		for (bin_attr = grp->bin_attrs; *bin_attr; bin_attr++)
+			kernfs_remove_by_name(parent, (*bin_attr)->attr.name);
+}
+
+static umode_t __first_visible(const struct attribute_group *grp, struct kobject *kobj)
+{
+	if (grp->attrs && grp->attrs[0] && grp->is_visible)
+		return grp->is_visible(kobj, grp->attrs[0], 0);
+
+	if (grp->attrs && grp->attrs[0] && grp->is_visible_const)
+		return grp->is_visible_const(kobj, grp->attrs[0], 0);
+
+	if (grp->bin_attrs && grp->bin_attrs[0] && grp->is_bin_visible)
+		return grp->is_bin_visible(kobj, grp->bin_attrs[0], 0);
+
+	return 0;
+}
+
+static int create_files(struct kernfs_node *parent, struct kobject *kobj,
+			kuid_t uid, kgid_t gid,
+			const struct attribute_group *grp, int update)
+{
+	struct attribute *const *attr;
+	const struct bin_attribute *const *bin_attr;
+	int error = 0, i;
+
+	if (grp->attrs) {
+		for (i = 0, attr = grp->attrs; *attr && !error; i++, attr++) {
+			umode_t mode = (*attr)->mode;
+
+			/*
+			 * In update mode, we're changing the permissions or
+			 * visibility.  Do this by first removing then
+			 * re-adding (if required) the file.
+			 */
+			if (update)
+				kernfs_remove_by_name(parent, (*attr)->name);
+			if (grp->is_visible || grp->is_visible_const) {
+				if (grp->is_visible)
+					mode = grp->is_visible(kobj, *attr, i);
+				else
+					mode = grp->is_visible_const(kobj, *attr, i);
+				mode &= ~SYSFS_GROUP_INVISIBLE;
+				if (!mode)
+					continue;
+			}
+
+			WARN(mode & ~(SYSFS_PREALLOC | 0664),
+			     "Attribute %s: Invalid permissions 0%o\n",
+			     (*attr)->name, mode);
+
+			mode &= SYSFS_PREALLOC | 0664;
+			error = sysfs_add_file_mode_ns(parent, *attr, mode, uid,
+						       gid, NULL);
+			if (unlikely(error))
+				break;
+		}
+		if (error) {
+			remove_files(parent, grp);
+			goto exit;
+		}
+	}
+
+	if (grp->bin_attrs) {
+		for (i = 0, bin_attr = grp->bin_attrs; *bin_attr; i++, bin_attr++) {
+			umode_t mode = (*bin_attr)->attr.mode;
+			size_t size = (*bin_attr)->size;
+
+			if (update)
+				kernfs_remove_by_name(parent,
+						(*bin_attr)->attr.name);
+			if (grp->is_bin_visible) {
+				mode = grp->is_bin_visible(kobj, *bin_attr, i);
+				mode &= ~SYSFS_GROUP_INVISIBLE;
+				if (!mode)
+					continue;
+			}
+			if (grp->bin_size)
+				size = grp->bin_size(kobj, *bin_attr, i);
+
+			WARN(mode & ~(SYSFS_PREALLOC | 0664),
+			     "Attribute %s: Invalid permissions 0%o\n",
+			     (*bin_attr)->attr.name, mode);
+
+			mode &= SYSFS_PREALLOC | 0664;
+			error = sysfs_add_bin_file_mode_ns(parent, *bin_attr,
+							   mode, size, uid, gid,
+							   NULL);
+			if (error)
+				break;
+		}
+		if (error)
+			remove_files(parent, grp);
+	}
+exit:
+	return error;
+}
+
+
+static int internal_create_group(struct kobject *kobj, int update,
+				 const struct attribute_group *grp)
+{
+	struct kernfs_node *kn;
+	kuid_t uid;
+	kgid_t gid;
+	int error;
+
+	if (WARN_ON(!kobj || (!update && !kobj->sd)))
+		return -EINVAL;
+
+	/* Updates may happen before the object has been instantiated */
+	if (unlikely(update && !kobj->sd))
+		return -EINVAL;
+
+	if (!grp->attrs && !grp->bin_attrs) {
+		pr_debug("sysfs: (bin_)attrs not set by subsystem for group: %s/%s, skipping\n",
+			 kobj->name, grp->name ?: "");
+		return 0;
+	}
+
+	kobject_get_ownership(kobj, &uid, &gid);
+	if (grp->name) {
+		umode_t mode = __first_visible(grp, kobj);
+
+		if (mode & SYSFS_GROUP_INVISIBLE)
+			mode = 0;
+		else
+			mode = S_IRWXU | S_IRUGO | S_IXUGO;
+
+		if (update) {
+			kn = kernfs_find_and_get(kobj->sd, grp->name);
+			if (!kn) {
+				pr_debug("attr grp %s/%s not created yet\n",
+					 kobj->name, grp->name);
+				/* may have been invisible prior to this update */
+				update = 0;
+			} else if (!mode) {
+				sysfs_remove_group(kobj, grp);
+				kernfs_put(kn);
+				return 0;
+			}
+		}
+
+		if (!update) {
+			if (!mode)
+				return 0;
+			kn = kernfs_create_dir_ns(kobj->sd, grp->name, mode,
+						  uid, gid, kobj, NULL);
+			if (IS_ERR(kn)) {
+				if (PTR_ERR(kn) == -EEXIST)
+					sysfs_warn_dup(kobj->sd, grp->name);
+				return PTR_ERR(kn);
+			}
+		}
+	} else {
+		kn = kobj->sd;
+	}
+
+	kernfs_get(kn);
+	error = create_files(kn, kobj, uid, gid, grp, update);
+	if (error) {
+		if (grp->name && !update)
+			kernfs_remove(kn);
+	}
+	kernfs_put(kn);
+
+	if (grp->name && update)
+		kernfs_put(kn);
+
+	return error;
+}
+
+/**
+ * sysfs_create_group - given a directory kobject, create an attribute group
+ * @kobj:	The kobject to create the group on
+ * @grp:	The attribute group to create
+ *
+ * This function creates a group for the first time.  It will explicitly
+ * warn and error if any of the attribute files being created already exist.
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_create_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	return internal_create_group(kobj, 0, grp);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_group);
+
+static int internal_create_groups(struct kobject *kobj, int update,
+				  const struct attribute_group *const *groups)
+{
+	int error = 0;
+	int i;
+
+	if (!groups)
+		return 0;
+
+	for (i = 0; groups[i]; i++) {
+		error = internal_create_group(kobj, update, groups[i]);
+		if (error) {
+			while (--i >= 0)
+				sysfs_remove_group(kobj, groups[i]);
+			break;
+		}
+	}
+	return error;
+}
+
+/**
+ * sysfs_create_groups - given a directory kobject, create a bunch of attribute groups
+ * @kobj:	The kobject to create the group on
+ * @groups:	The attribute groups to create, NULL terminated
+ *
+ * This function creates a bunch of attribute groups.  If an error occurs when
+ * creating a group, all previously created groups will be removed, unwinding
+ * everything back to the original state when this function was called.
+ * It will explicitly warn and error if any of the attribute files being
+ * created already exist.
+ *
+ * Returns 0 on success or error code from sysfs_create_group on failure.
+ */
+int sysfs_create_groups(struct kobject *kobj,
+			const struct attribute_group *const *groups)
+{
+	return internal_create_groups(kobj, 0, groups);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_groups);
+
+/**
+ * sysfs_update_groups - given a directory kobject, create a bunch of attribute groups
+ * @kobj:	The kobject to update the group on
+ * @groups:	The attribute groups to update, NULL terminated
+ *
+ * This function update a bunch of attribute groups.  If an error occurs when
+ * updating a group, all previously updated groups will be removed together
+ * with already existing (not updated) attributes.
+ *
+ * Returns 0 on success or error code from sysfs_update_group on failure.
+ */
+int sysfs_update_groups(struct kobject *kobj,
+			const struct attribute_group *const *groups)
+{
+	return internal_create_groups(kobj, 1, groups);
+}
+EXPORT_SYMBOL_GPL(sysfs_update_groups);
+
+/**
+ * sysfs_update_group - given a directory kobject, update an attribute group
+ * @kobj:	The kobject to update the group on
+ * @grp:	The attribute group to update
+ *
+ * This function updates an attribute group.  Unlike
+ * sysfs_create_group(), it will explicitly not warn or error if any
+ * of the attribute files being created already exist.  Furthermore,
+ * if the visibility of the files has changed through the is_visible()
+ * callback, it will update the permissions and add or remove the
+ * relevant files. Changing a group's name (subdirectory name under
+ * kobj's directory in sysfs) is not allowed.
+ *
+ * The primary use for this function is to call it after making a change
+ * that affects group visibility.
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_update_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	return internal_create_group(kobj, 1, grp);
+}
+EXPORT_SYMBOL_GPL(sysfs_update_group);
+
+/**
+ * sysfs_remove_group: remove a group from a kobject
+ * @kobj:	kobject to remove the group from
+ * @grp:	group to remove
+ *
+ * This function removes a group of attributes from a kobject.  The attributes
+ * previously have to have been created for this group, otherwise it will fail.
+ */
+void sysfs_remove_group(struct kobject *kobj,
+			const struct attribute_group *grp)
+{
+	struct kernfs_node *parent = kobj->sd;
+	struct kernfs_node *kn;
+
+	if (grp->name) {
+		kn = kernfs_find_and_get(parent, grp->name);
+		if (!kn) {
+			pr_debug("sysfs group '%s' not found for kobject '%s'\n",
+				 grp->name, kobject_name(kobj));
+			return;
+		}
+	} else {
+		kn = parent;
+		kernfs_get(kn);
+	}
+
+	remove_files(kn, grp);
+	if (grp->name)
+		kernfs_remove(kn);
+
+	kernfs_put(kn);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_group);
+
+/**
+ * sysfs_remove_groups - remove a list of groups
+ *
+ * @kobj:	The kobject for the groups to be removed from
+ * @groups:	NULL terminated list of groups to be removed
+ *
+ * If groups is not NULL, remove the specified groups from the kobject.
+ */
+void sysfs_remove_groups(struct kobject *kobj,
+			 const struct attribute_group *const *groups)
+{
+	int i;
+
+	if (!groups)
+		return;
+	for (i = 0; groups[i]; i++)
+		sysfs_remove_group(kobj, groups[i]);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_groups);
+
+/**
+ * sysfs_merge_group - merge files into a pre-existing named attribute group.
+ * @kobj:	The kobject containing the group.
+ * @grp:	The files to create and the attribute group they belong to.
+ *
+ * This function returns an error if the group doesn't exist, the .name field is
+ * NULL or any of the files already exist in that group, in which case none of
+ * the new files are created.
+ */
+int sysfs_merge_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	struct kernfs_node *parent;
+	kuid_t uid;
+	kgid_t gid;
+	int error = 0;
+	struct attribute *const *attr;
+	int i;
+
+	parent = kernfs_find_and_get(kobj->sd, grp->name);
+	if (!parent)
+		return -ENOENT;
+
+	kobject_get_ownership(kobj, &uid, &gid);
+
+	for ((i = 0, attr = grp->attrs); *attr && !error; (++i, ++attr))
+		error = sysfs_add_file_mode_ns(parent, *attr, (*attr)->mode,
+					       uid, gid, NULL);
+	if (error) {
+		while (--i >= 0)
+			kernfs_remove_by_name(parent, (*--attr)->name);
+	}
+	kernfs_put(parent);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_merge_group);
+
+/**
+ * sysfs_unmerge_group - remove files from a pre-existing named attribute group.
+ * @kobj:	The kobject containing the group.
+ * @grp:	The files to remove and the attribute group they belong to.
+ */
+void sysfs_unmerge_group(struct kobject *kobj,
+		       const struct attribute_group *grp)
+{
+	struct kernfs_node *parent;
+	struct attribute *const *attr;
+
+	parent = kernfs_find_and_get(kobj->sd, grp->name);
+	if (parent) {
+		for (attr = grp->attrs; *attr; ++attr)
+			kernfs_remove_by_name(parent, (*attr)->name);
+		kernfs_put(parent);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_unmerge_group);
+
+/**
+ * sysfs_add_link_to_group - add a symlink to an attribute group.
+ * @kobj:	The kobject containing the group.
+ * @group_name:	The name of the group.
+ * @target:	The target kobject of the symlink to create.
+ * @link_name:	The name of the symlink to create.
+ */
+int sysfs_add_link_to_group(struct kobject *kobj, const char *group_name,
+			    struct kobject *target, const char *link_name)
+{
+	struct kernfs_node *parent;
+	int error = 0;
+
+	parent = kernfs_find_and_get(kobj->sd, group_name);
+	if (!parent)
+		return -ENOENT;
+
+	error = sysfs_create_link_sd(parent, target, link_name);
+	kernfs_put(parent);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_add_link_to_group);
+
+/**
+ * sysfs_remove_link_from_group - remove a symlink from an attribute group.
+ * @kobj:	The kobject containing the group.
+ * @group_name:	The name of the group.
+ * @link_name:	The name of the symlink to remove.
+ */
+void sysfs_remove_link_from_group(struct kobject *kobj, const char *group_name,
+				  const char *link_name)
+{
+	struct kernfs_node *parent;
+
+	parent = kernfs_find_and_get(kobj->sd, group_name);
+	if (parent) {
+		kernfs_remove_by_name(parent, link_name);
+		kernfs_put(parent);
+	}
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_link_from_group);
+
+/**
+ * compat_only_sysfs_link_entry_to_kobj - add a symlink to a kobject pointing
+ * to a group or an attribute
+ * @kobj:		The kobject containing the group.
+ * @target_kobj:	The target kobject.
+ * @target_name:	The name of the target group or attribute.
+ * @symlink_name:	The name of the symlink file (target_name will be
+ *			considered if symlink_name is NULL).
+ */
+int compat_only_sysfs_link_entry_to_kobj(struct kobject *kobj,
+					 struct kobject *target_kobj,
+					 const char *target_name,
+					 const char *symlink_name)
+{
+	struct kernfs_node *target;
+	struct kernfs_node *entry;
+	struct kernfs_node *link;
+
+	/*
+	 * We don't own @target_kobj and it may be removed at any time.
+	 * Synchronize using sysfs_symlink_target_lock. See sysfs_remove_dir()
+	 * for details.
+	 */
+	spin_lock(&sysfs_symlink_target_lock);
+	target = target_kobj->sd;
+	if (target)
+		kernfs_get(target);
+	spin_unlock(&sysfs_symlink_target_lock);
+	if (!target)
+		return -ENOENT;
+
+	entry = kernfs_find_and_get(target, target_name);
+	if (!entry) {
+		kernfs_put(target);
+		return -ENOENT;
+	}
+
+	if (!symlink_name)
+		symlink_name = target_name;
+
+	link = kernfs_create_link(kobj->sd, symlink_name, entry);
+	if (PTR_ERR(link) == -EEXIST)
+		sysfs_warn_dup(kobj->sd, symlink_name);
+
+	kernfs_put(entry);
+	kernfs_put(target);
+	return PTR_ERR_OR_ZERO(link);
+}
+EXPORT_SYMBOL_GPL(compat_only_sysfs_link_entry_to_kobj);
+
+static int sysfs_group_attrs_change_owner(struct kobject *kobj,
+					  struct kernfs_node *grp_kn,
+					  const struct attribute_group *grp,
+					  struct iattr *newattrs)
+{
+	struct kernfs_node *kn;
+	int error, i;
+	umode_t mode;
+
+	if (grp->attrs) {
+		struct attribute *const *attr;
+
+		for (i = 0, attr = grp->attrs; *attr; i++, attr++) {
+			if (grp->is_visible || grp->is_visible_const) {
+				if (grp->is_visible)
+					mode = grp->is_visible(kobj, *attr, i);
+				else
+					mode = grp->is_visible_const(kobj, *attr, i);
+				if (mode & SYSFS_GROUP_INVISIBLE)
+					break;
+				if (!mode)
+					continue;
+			}
+			kn = kernfs_find_and_get(grp_kn, (*attr)->name);
+			if (!kn)
+				return -ENOENT;
+
+			error = kernfs_setattr(kn, newattrs);
+			kernfs_put(kn);
+			if (error)
+				return error;
+		}
+	}
+
+	if (grp->bin_attrs) {
+		const struct bin_attribute *const *bin_attr;
+
+		for (i = 0, bin_attr = grp->bin_attrs; *bin_attr; i++, bin_attr++) {
+			if (grp->is_bin_visible) {
+				mode = grp->is_bin_visible(kobj, *bin_attr, i);
+				if (mode & SYSFS_GROUP_INVISIBLE)
+					break;
+				if (!mode)
+					continue;
+			}
+			kn = kernfs_find_and_get(grp_kn, (*bin_attr)->attr.name);
+			if (!kn)
+				return -ENOENT;
+
+			error = kernfs_setattr(kn, newattrs);
+			kernfs_put(kn);
+			if (error)
+				return error;
+		}
+	}
+
+	return 0;
+}
+
+/**
+ * sysfs_group_change_owner - change owner of an attribute group.
+ * @kobj:	The kobject containing the group.
+ * @grp:	The attribute group.
+ * @kuid:	new owner's kuid
+ * @kgid:	new owner's kgid
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_group_change_owner(struct kobject *kobj,
+			     const struct attribute_group *grp, kuid_t kuid,
+			     kgid_t kgid)
+{
+	struct kernfs_node *grp_kn;
+	int error;
+	struct iattr newattrs = {
+		.ia_valid = ATTR_UID | ATTR_GID,
+		.ia_uid = kuid,
+		.ia_gid = kgid,
+	};
+
+	if (!kobj->state_in_sysfs)
+		return -EINVAL;
+
+	if (grp->name) {
+		grp_kn = kernfs_find_and_get(kobj->sd, grp->name);
+	} else {
+		kernfs_get(kobj->sd);
+		grp_kn = kobj->sd;
+	}
+	if (!grp_kn)
+		return -ENOENT;
+
+	error = kernfs_setattr(grp_kn, &newattrs);
+	if (!error)
+		error = sysfs_group_attrs_change_owner(kobj, grp_kn, grp, &newattrs);
+
+	kernfs_put(grp_kn);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_group_change_owner);
+
+/**
+ * sysfs_groups_change_owner - change owner of a set of attribute groups.
+ * @kobj:	The kobject containing the groups.
+ * @groups:	The attribute groups.
+ * @kuid:	new owner's kuid
+ * @kgid:	new owner's kgid
+ *
+ * Returns 0 on success or error code on failure.
+ */
+int sysfs_groups_change_owner(struct kobject *kobj,
+			      const struct attribute_group *const *groups,
+			      kuid_t kuid, kgid_t kgid)
+{
+	int error = 0, i;
+
+	if (!kobj->state_in_sysfs)
+		return -EINVAL;
+
+	if (!groups)
+		return 0;
+
+	for (i = 0; groups[i]; i++) {
+		error = sysfs_group_change_owner(kobj, groups[i], kuid, kgid);
+		if (error)
+			break;
+	}
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(sysfs_groups_change_owner);
diff --git a/fs/sysfs/mount.c b/fs/sysfs/mount.c
new file mode 100644
index 000000000..88c10823f
--- /dev/null
+++ b/fs/sysfs/mount.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fs/sysfs/symlink.c - operations for initializing and mounting sysfs
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * Please see Documentation/filesystems/sysfs.rst for more information.
+ */
+
+#include <linux/fs.h>
+#include <linux/magic.h>
+#include <linux/mount.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/user_namespace.h>
+#include <linux/fs_context.h>
+#include <net/net_namespace.h>
+
+#include "sysfs.h"
+
+static struct kernfs_root *sysfs_root;
+struct kernfs_node *sysfs_root_kn;
+
+static void sysfs_fs_context_free(struct fs_context *fc)
+{
+	struct kernfs_fs_context *kfc = fc->fs_private;
+
+	if (kfc->ns_tag)
+		kobj_ns_drop(KOBJ_NS_TYPE_NET, kfc->ns_tag);
+	kernfs_free_fs_context(fc);
+	kfree(kfc);
+}
+
+static const struct fs_context_operations sysfs_fs_context_ops = {
+	.free		= sysfs_fs_context_free,
+	.get_tree	= kernfs_get_tree,
+};
+
+static int sysfs_init_fs_context(struct fs_context *fc)
+{
+	struct kernfs_fs_context *kfc;
+	struct ns_common *ns;
+
+	if (!(fc->sb_flags & SB_KERNMOUNT)) {
+		if (!kobj_ns_current_may_mount(KOBJ_NS_TYPE_NET))
+			return -EPERM;
+	}
+
+	kfc = kzalloc_obj(struct kernfs_fs_context);
+	if (!kfc)
+		return -ENOMEM;
+
+	kfc->ns_tag = ns = kobj_ns_grab_current(KOBJ_NS_TYPE_NET);
+	kfc->root = sysfs_root;
+	kfc->magic = SYSFS_MAGIC;
+	fc->fs_private = kfc;
+	fc->ops = &sysfs_fs_context_ops;
+	if (ns) {
+		struct net *netns = to_net_ns(ns);
+
+		put_user_ns(fc->user_ns);
+		fc->user_ns = get_user_ns(netns->user_ns);
+	}
+	fc->global = true;
+	return 0;
+}
+
+static void sysfs_kill_sb(struct super_block *sb)
+{
+	struct ns_common *ns = (struct ns_common *)kernfs_super_ns(sb);
+
+	kernfs_kill_sb(sb);
+	kobj_ns_drop(KOBJ_NS_TYPE_NET, ns);
+}
+
+static struct file_system_type sysfs_fs_type = {
+	.name			= "sysfs",
+	.init_fs_context	= sysfs_init_fs_context,
+	.kill_sb		= sysfs_kill_sb,
+	.fs_flags		= FS_USERNS_MOUNT | FS_USERNS_MOUNT_RESTRICTED,
+};
+
+int __init sysfs_init(void)
+{
+	int err;
+
+	sysfs_root = kernfs_create_root(NULL, KERNFS_ROOT_EXTRA_OPEN_PERM_CHECK,
+					NULL);
+	if (IS_ERR(sysfs_root))
+		return PTR_ERR(sysfs_root);
+
+	sysfs_root_kn = kernfs_root_to_node(sysfs_root);
+
+	err = register_filesystem(&sysfs_fs_type);
+	if (err) {
+		kernfs_destroy_root(sysfs_root);
+		return err;
+	}
+
+	return 0;
+}
diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
new file mode 100644
index 000000000..5f9c05fb1
--- /dev/null
+++ b/fs/sysfs/symlink.c
@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fs/sysfs/symlink.c - sysfs symlink implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * Please see Documentation/filesystems/sysfs.rst for more information.
+ */
+
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/kobject.h>
+#include <linux/mutex.h>
+#include <linux/security.h>
+
+#include "sysfs.h"
+
+static int sysfs_do_create_link_sd(struct kernfs_node *parent,
+				   struct kobject *target_kobj,
+				   const char *name, int warn)
+{
+	struct kernfs_node *kn, *target = NULL;
+
+	if (WARN_ON(!name || !parent))
+		return -EINVAL;
+
+	/*
+	 * We don't own @target_kobj and it may be removed at any time.
+	 * Synchronize using sysfs_symlink_target_lock.  See
+	 * sysfs_remove_dir() for details.
+	 */
+	spin_lock(&sysfs_symlink_target_lock);
+	if (target_kobj->sd) {
+		target = target_kobj->sd;
+		kernfs_get(target);
+	}
+	spin_unlock(&sysfs_symlink_target_lock);
+
+	if (!target)
+		return -ENOENT;
+
+	kn = kernfs_create_link(parent, name, target);
+	kernfs_put(target);
+
+	if (!IS_ERR(kn))
+		return 0;
+
+	if (warn && PTR_ERR(kn) == -EEXIST)
+		sysfs_warn_dup(parent, name);
+	return PTR_ERR(kn);
+}
+
+/**
+ *	sysfs_create_link_sd - create symlink to a given object.
+ *	@kn:		directory we're creating the link in.
+ *	@target:	object we're pointing to.
+ *	@name:		name of the symlink.
+ */
+int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
+			 const char *name)
+{
+	return sysfs_do_create_link_sd(kn, target, name, 1);
+}
+
+static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
+				const char *name, int warn)
+{
+	struct kernfs_node *parent = NULL;
+
+	if (!kobj)
+		parent = sysfs_root_kn;
+	else
+		parent = kobj->sd;
+
+	if (!parent)
+		return -EFAULT;
+
+	return sysfs_do_create_link_sd(parent, target, name, warn);
+}
+
+/**
+ *	sysfs_create_link - create symlink between two objects.
+ *	@kobj:	object whose directory we're creating the link in.
+ *	@target:	object we're pointing to.
+ *	@name:		name of the symlink.
+ */
+int sysfs_create_link(struct kobject *kobj, struct kobject *target,
+		      const char *name)
+{
+	return sysfs_do_create_link(kobj, target, name, 1);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_link);
+
+/**
+ *	sysfs_create_link_nowarn - create symlink between two objects.
+ *	@kobj:	object whose directory we're creating the link in.
+ *	@target:	object we're pointing to.
+ *	@name:		name of the symlink.
+ *
+ *	This function does the same as sysfs_create_link(), but it
+ *	doesn't warn if the link already exists.
+ */
+int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
+			     const char *name)
+{
+	return sysfs_do_create_link(kobj, target, name, 0);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_link_nowarn);
+
+/**
+ *	sysfs_delete_link - remove symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@targ:	object we're pointing to.
+ *	@name:	name of the symlink to remove.
+ *
+ *	Unlike sysfs_remove_link sysfs_delete_link has enough information
+ *	to successfully delete symlinks in tagged directories.
+ */
+void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
+			const char *name)
+{
+	const struct ns_common *ns = NULL;
+
+	/*
+	 * We don't own @target and it may be removed at any time.
+	 * Synchronize using sysfs_symlink_target_lock.  See
+	 * sysfs_remove_dir() for details.
+	 */
+	spin_lock(&sysfs_symlink_target_lock);
+	if (targ->sd && kernfs_ns_enabled(kobj->sd))
+		ns = targ->sd->ns;
+	spin_unlock(&sysfs_symlink_target_lock);
+	kernfs_remove_by_name_ns(kobj->sd, name, ns);
+}
+
+/**
+ *	sysfs_remove_link - remove symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@name:	name of the symlink to remove.
+ */
+void sysfs_remove_link(struct kobject *kobj, const char *name)
+{
+	struct kernfs_node *parent = NULL;
+
+	if (!kobj)
+		parent = sysfs_root_kn;
+	else
+		parent = kobj->sd;
+
+	kernfs_remove_by_name(parent, name);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_link);
+
+/**
+ *	sysfs_rename_link_ns - rename symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@targ:	object we're pointing to.
+ *	@old:	previous name of the symlink.
+ *	@new:	new name of the symlink.
+ *	@new_ns: new namespace of the symlink.
+ *
+ *	A helper function for the common rename symlink idiom.
+ */
+int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
+			 const char *old, const char *new,
+			 const struct ns_common *new_ns)
+{
+	struct kernfs_node *parent, *kn = NULL;
+	const struct ns_common *old_ns = NULL;
+	int result;
+
+	if (!kobj)
+		parent = sysfs_root_kn;
+	else
+		parent = kobj->sd;
+
+	if (targ->sd)
+		old_ns = targ->sd->ns;
+
+	result = -ENOENT;
+	kn = kernfs_find_and_get_ns(parent, old, old_ns);
+	if (!kn)
+		goto out;
+
+	result = -EINVAL;
+	if (kernfs_type(kn) != KERNFS_LINK)
+		goto out;
+	if (kn->symlink.target_kn->priv != targ)
+		goto out;
+
+	result = kernfs_rename_ns(kn, parent, new, new_ns);
+
+out:
+	kernfs_put(kn);
+	return result;
+}
+EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
new file mode 100644
index 000000000..f4583dcaf
--- /dev/null
+++ b/fs/sysfs/sysfs.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * fs/sysfs/sysfs.h - sysfs internal header file
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ */
+
+#ifndef __SYSFS_INTERNAL_H
+#define __SYSFS_INTERNAL_H
+
+#include <linux/sysfs.h>
+
+/*
+ * mount.c
+ */
+extern struct kernfs_node *sysfs_root_kn;
+
+/*
+ * dir.c
+ */
+extern spinlock_t sysfs_symlink_target_lock;
+
+void sysfs_warn_dup(struct kernfs_node *parent, const char *name);
+
+/*
+ * file.c
+ */
+int sysfs_add_file_mode_ns(struct kernfs_node *parent,
+		const struct attribute *attr, umode_t amode, kuid_t uid,
+		kgid_t gid, const struct ns_common *ns);
+int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
+		const struct bin_attribute *battr, umode_t mode, size_t size,
+		kuid_t uid, kgid_t gid, const struct ns_common *ns);
+
+/*
+ * symlink.c
+ */
+int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
+			 const char *name);
+
+#endif	/* __SYSFS_INTERNAL_H */