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linux-7.2.3/fs/configfs/Kconfig

@@ -0,0 +1,11 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config CONFIGFS_FS
+	tristate "Userspace-driven configuration filesystem"
+	help
+	  configfs is a RAM-based filesystem that provides the converse
+	  of sysfs's functionality. Where sysfs is a filesystem-based
+	  view of kernel objects, configfs is a filesystem-based manager
+	  of kernel objects, or config_items.
+
+	  Both sysfs and configfs can and should exist together on the
+	  same system. One is not a replacement for the other.

linux-7.2.3/fs/configfs/Makefile

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Makefile for the configfs virtual filesystem
+#
+
+obj-$(CONFIG_CONFIGFS_FS)	+= configfs.o
+
+configfs-objs	:= inode.o file.o dir.o symlink.o mount.o item.o

linux-7.2.3/fs/configfs/configfs_internal.h

@@ -0,0 +1,158 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * configfs_internal.h - Internal stuff for configfs
+ *
+ * Based on sysfs:
+ * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
+ *
+ * configfs Copyright (C) 2005 Oracle.  All rights reserved.
+ */
+
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+
+struct configfs_fragment {
+	atomic_t frag_count;
+	struct rw_semaphore frag_sem;
+	bool frag_dead;
+};
+
+void put_fragment(struct configfs_fragment *);
+struct configfs_fragment *get_fragment(struct configfs_fragment *);
+
+struct configfs_dirent {
+	atomic_t		s_count;
+	int			s_dependent_count;
+	struct list_head	s_sibling;
+	struct list_head	s_children;
+	int			s_links;
+	void			* s_element;
+	int			s_type;
+	umode_t			s_mode;
+	struct dentry		* s_dentry;
+	struct iattr		* s_iattr;
+#ifdef CONFIG_LOCKDEP
+	int			s_depth;
+#endif
+	struct configfs_fragment *s_frag;
+};
+
+#define CONFIGFS_ROOT		0x0001
+#define CONFIGFS_DIR		0x0002
+#define CONFIGFS_ITEM_ATTR	0x0004
+#define CONFIGFS_ITEM_BIN_ATTR	0x0008
+#define CONFIGFS_ITEM_LINK	0x0020
+#define CONFIGFS_USET_DIR	0x0040
+#define CONFIGFS_USET_DEFAULT	0x0080
+#define CONFIGFS_USET_DROPPING	0x0100
+#define CONFIGFS_USET_IN_MKDIR	0x0200
+#define CONFIGFS_USET_CREATING	0x0400
+#define CONFIGFS_NOT_PINNED	(CONFIGFS_ITEM_ATTR | CONFIGFS_ITEM_BIN_ATTR)
+#define CONFIGFS_PINNED \
+	(CONFIGFS_ROOT | CONFIGFS_DIR | CONFIGFS_ITEM_LINK)
+
+extern struct mutex configfs_symlink_mutex;
+extern spinlock_t configfs_dirent_lock;
+
+extern struct kmem_cache *configfs_dir_cachep;
+
+extern int configfs_is_root(struct config_item *item);
+
+extern struct inode * configfs_new_inode(umode_t mode, struct configfs_dirent *, struct super_block *);
+extern struct inode *configfs_create(struct dentry *, umode_t mode);
+
+extern int configfs_create_file(struct config_item *, const struct configfs_attribute *);
+extern int configfs_create_bin_file(struct config_item *,
+				    const struct configfs_bin_attribute *);
+extern int configfs_make_dirent(struct configfs_dirent *, struct dentry *,
+				void *, umode_t, int, struct configfs_fragment *);
+extern int configfs_dirent_is_ready(struct configfs_dirent *);
+
+extern const unsigned char * configfs_get_name(struct configfs_dirent *sd);
+extern int configfs_setattr(struct mnt_idmap *idmap,
+			    struct dentry *dentry, struct iattr *iattr);
+
+extern struct dentry *configfs_pin_fs(void);
+extern void configfs_release_fs(void);
+
+extern const struct file_operations configfs_dir_operations;
+extern const struct file_operations configfs_file_operations;
+extern const struct file_operations configfs_bin_file_operations;
+extern const struct inode_operations configfs_dir_inode_operations;
+extern const struct inode_operations configfs_root_inode_operations;
+extern const struct inode_operations configfs_symlink_inode_operations;
+extern const struct dentry_operations configfs_dentry_ops;
+
+extern int configfs_symlink(struct mnt_idmap *idmap,
+			    struct inode *dir, struct dentry *dentry,
+			    const char *symname);
+extern int configfs_unlink(struct inode *dir, struct dentry *dentry);
+
+int configfs_create_link(struct configfs_dirent *target, struct dentry *parent,
+		struct dentry *dentry, char *body);
+
+static inline struct config_item * to_item(struct dentry * dentry)
+{
+	struct configfs_dirent * sd = dentry->d_fsdata;
+	return ((struct config_item *) sd->s_element);
+}
+
+static inline struct configfs_attribute * to_attr(struct dentry * dentry)
+{
+	struct configfs_dirent * sd = dentry->d_fsdata;
+	return ((struct configfs_attribute *) sd->s_element);
+}
+
+static inline struct configfs_bin_attribute *to_bin_attr(struct dentry *dentry)
+{
+	struct configfs_attribute *attr = to_attr(dentry);
+
+	return container_of(attr, struct configfs_bin_attribute, cb_attr);
+}
+
+static inline struct config_item *configfs_get_config_item(struct dentry *dentry)
+{
+	struct config_item * item = NULL;
+
+	spin_lock(&dentry->d_lock);
+	if (!d_unhashed(dentry)) {
+		struct configfs_dirent * sd = dentry->d_fsdata;
+		item = config_item_get(sd->s_element);
+	}
+	spin_unlock(&dentry->d_lock);
+
+	return item;
+}
+
+static inline void release_configfs_dirent(struct configfs_dirent * sd)
+{
+	if (!(sd->s_type & CONFIGFS_ROOT)) {
+		kfree(sd->s_iattr);
+		put_fragment(sd->s_frag);
+		kmem_cache_free(configfs_dir_cachep, sd);
+	}
+}
+
+static inline struct configfs_dirent * configfs_get(struct configfs_dirent * sd)
+{
+	if (sd) {
+		WARN_ON(!atomic_read(&sd->s_count));
+		atomic_inc(&sd->s_count);
+	}
+	return sd;
+}
+
+static inline void configfs_put(struct configfs_dirent * sd)
+{
+	WARN_ON(!atomic_read(&sd->s_count));
+	if (atomic_dec_and_test(&sd->s_count))
+		release_configfs_dirent(sd);
+}
+

linux-7.2.3/fs/configfs/file.c

@@ -0,0 +1,481 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * file.c - operations for regular (text) files.
+ *
+ * Based on sysfs:
+ * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
+ *
+ * configfs Copyright (C) 2005 Oracle.  All rights reserved.
+ */
+
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+#include <linux/vmalloc.h>
+#include <linux/uaccess.h>
+#include <linux/uio.h>
+#include <linux/configfs.h>
+#include "configfs_internal.h"
+
+/*
+ * A simple attribute can only be 4096 characters.  Why 4k?  Because the
+ * original code limited it to PAGE_SIZE.  That's a bad idea, though,
+ * because an attribute of 16k on ia64 won't work on x86.  So we limit to
+ * 4k, our minimum common page size.
+ */
+#define SIMPLE_ATTR_SIZE 4096
+
+struct configfs_buffer {
+	size_t			count;
+	loff_t			pos;
+	char			* page;
+	const struct configfs_item_operations	*ops;
+	struct mutex		mutex;
+	int			needs_read_fill;
+	bool			read_in_progress;
+	bool			write_in_progress;
+	char			*bin_buffer;
+	int			bin_buffer_size;
+	int			cb_max_size;
+	struct config_item	*item;
+	struct module		*owner;
+	union {
+		struct configfs_attribute	*attr;
+		struct configfs_bin_attribute	*bin_attr;
+	};
+};
+
+static inline struct configfs_fragment *to_frag(struct file *file)
+{
+	struct configfs_dirent *sd = file->f_path.dentry->d_fsdata;
+
+	return sd->s_frag;
+}
+
+static int fill_read_buffer(struct file *file, struct configfs_buffer *buffer)
+{
+	struct configfs_fragment *frag = to_frag(file);
+	ssize_t count = -ENOENT;
+
+	if (!buffer->page)
+		buffer->page = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!buffer->page)
+		return -ENOMEM;
+
+	down_read(&frag->frag_sem);
+	if (!frag->frag_dead)
+		count = buffer->attr->show(buffer->item, buffer->page);
+	up_read(&frag->frag_sem);
+
+	if (count < 0)
+		return count;
+	if (WARN_ON_ONCE(count > (ssize_t)SIMPLE_ATTR_SIZE))
+		return -EIO;
+	buffer->needs_read_fill = 0;
+	buffer->count = count;
+	return 0;
+}
+
+static ssize_t configfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct configfs_buffer *buffer = file->private_data;
+	ssize_t retval = 0;
+
+	mutex_lock(&buffer->mutex);
+	if (buffer->needs_read_fill) {
+		retval = fill_read_buffer(file, buffer);
+		if (retval)
+			goto out;
+	}
+	pr_debug("%s: count = %zd, pos = %lld, buf = %s\n",
+		 __func__, iov_iter_count(to), iocb->ki_pos, buffer->page);
+	if (iocb->ki_pos >= buffer->count)
+		goto out;
+	retval = copy_to_iter(buffer->page + iocb->ki_pos,
+			      buffer->count - iocb->ki_pos, to);
+	iocb->ki_pos += retval;
+	if (retval == 0)
+		retval = -EFAULT;
+out:
+	mutex_unlock(&buffer->mutex);
+	return retval;
+}
+
+static ssize_t configfs_bin_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct configfs_fragment *frag = to_frag(file);
+	struct configfs_buffer *buffer = file->private_data;
+	ssize_t retval = 0;
+	ssize_t len;
+
+	mutex_lock(&buffer->mutex);
+
+	/* we don't support switching read/write modes */
+	if (buffer->write_in_progress) {
+		retval = -ETXTBSY;
+		goto out;
+	}
+	buffer->read_in_progress = true;
+
+	if (buffer->needs_read_fill) {
+		/* perform first read with buf == NULL to get extent */
+		down_read(&frag->frag_sem);
+		if (!frag->frag_dead)
+			len = buffer->bin_attr->read(buffer->item, NULL, 0);
+		else
+			len = -ENOENT;
+		up_read(&frag->frag_sem);
+		if (len <= 0) {
+			retval = len;
+			goto out;
+		}
+
+		/* do not exceed the maximum value */
+		if (buffer->cb_max_size && len > buffer->cb_max_size) {
+			retval = -EFBIG;
+			goto out;
+		}
+
+		buffer->bin_buffer = vmalloc(len);
+		if (buffer->bin_buffer == NULL) {
+			retval = -ENOMEM;
+			goto out;
+		}
+		buffer->bin_buffer_size = len;
+
+		/* perform second read to fill buffer */
+		down_read(&frag->frag_sem);
+		if (!frag->frag_dead)
+			len = buffer->bin_attr->read(buffer->item,
+						     buffer->bin_buffer, len);
+		else
+			len = -ENOENT;
+		up_read(&frag->frag_sem);
+		if (len < 0) {
+			retval = len;
+			vfree(buffer->bin_buffer);
+			buffer->bin_buffer_size = 0;
+			buffer->bin_buffer = NULL;
+			goto out;
+		}
+
+		buffer->needs_read_fill = 0;
+	}
+
+	if (iocb->ki_pos >= buffer->bin_buffer_size)
+		goto out;
+	retval = copy_to_iter(buffer->bin_buffer + iocb->ki_pos,
+			      buffer->bin_buffer_size - iocb->ki_pos, to);
+	iocb->ki_pos += retval;
+	if (retval == 0)
+		retval = -EFAULT;
+out:
+	mutex_unlock(&buffer->mutex);
+	return retval;
+}
+
+/* Fill @buffer with data coming from @from. */
+static int fill_write_buffer(struct configfs_buffer *buffer,
+			     struct iov_iter *from)
+{
+	int copied;
+
+	if (!buffer->page)
+		buffer->page = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!buffer->page)
+		return -ENOMEM;
+
+	copied = copy_from_iter(buffer->page, SIMPLE_ATTR_SIZE - 1, from);
+	buffer->needs_read_fill = 1;
+	/* if buf is assumed to contain a string, terminate it by \0,
+	 * so e.g. sscanf() can scan the string easily */
+	buffer->page[copied] = 0;
+	return copied ? : -EFAULT;
+}
+
+static int
+flush_write_buffer(struct file *file, struct configfs_buffer *buffer, size_t count)
+{
+	struct configfs_fragment *frag = to_frag(file);
+	int res = -ENOENT;
+
+	down_read(&frag->frag_sem);
+	if (!frag->frag_dead)
+		res = buffer->attr->store(buffer->item, buffer->page, count);
+	up_read(&frag->frag_sem);
+	return res;
+}
+
+
+/*
+ * There is no easy way for us to know if userspace is only doing a partial
+ * write, so we don't support them. We expect the entire buffer to come on the
+ * first write.
+ * Hint: if you're writing a value, first read the file, modify only the value
+ * you're changing, then write entire buffer back.
+ */
+static ssize_t configfs_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct configfs_buffer *buffer = file->private_data;
+	int len;
+
+	mutex_lock(&buffer->mutex);
+	len = fill_write_buffer(buffer, from);
+	if (len > 0)
+		len = flush_write_buffer(file, buffer, len);
+	if (len > 0)
+		iocb->ki_pos += len;
+	mutex_unlock(&buffer->mutex);
+	return len;
+}
+
+static ssize_t configfs_bin_write_iter(struct kiocb *iocb,
+				       struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct configfs_buffer *buffer = file->private_data;
+	void *tbuf = NULL;
+	size_t end_offset;
+	ssize_t len;
+
+	mutex_lock(&buffer->mutex);
+
+	/* we don't support switching read/write modes */
+	if (buffer->read_in_progress) {
+		len = -ETXTBSY;
+		goto out;
+	}
+	buffer->write_in_progress = true;
+
+	/* buffer grows? */
+	end_offset = iocb->ki_pos + iov_iter_count(from);
+	if (end_offset > buffer->bin_buffer_size) {
+		if (buffer->cb_max_size && end_offset > buffer->cb_max_size) {
+			len = -EFBIG;
+			goto out;
+		}
+
+		tbuf = vmalloc(end_offset);
+		if (tbuf == NULL) {
+			len = -ENOMEM;
+			goto out;
+		}
+
+		/* copy old contents */
+		if (buffer->bin_buffer) {
+			memcpy(tbuf, buffer->bin_buffer,
+				buffer->bin_buffer_size);
+			vfree(buffer->bin_buffer);
+		}
+
+		/* clear the new area */
+		memset(tbuf + buffer->bin_buffer_size, 0,
+			end_offset - buffer->bin_buffer_size);
+		buffer->bin_buffer = tbuf;
+		buffer->bin_buffer_size = end_offset;
+	}
+
+	len = copy_from_iter(buffer->bin_buffer + iocb->ki_pos,
+			     buffer->bin_buffer_size - iocb->ki_pos, from);
+	iocb->ki_pos += len;
+out:
+	mutex_unlock(&buffer->mutex);
+	return len ? : -EFAULT;
+}
+
+static int __configfs_open_file(struct inode *inode, struct file *file, int type)
+{
+	struct dentry *dentry = file->f_path.dentry;
+	struct configfs_fragment *frag = to_frag(file);
+	struct configfs_attribute *attr;
+	struct configfs_buffer *buffer;
+	int error;
+
+	error = -ENOMEM;
+	buffer = kzalloc_obj(struct configfs_buffer);
+	if (!buffer)
+		goto out;
+
+	error = -ENOENT;
+	down_read(&frag->frag_sem);
+	if (unlikely(frag->frag_dead))
+		goto out_free_buffer;
+
+	error = -EINVAL;
+	buffer->item = to_item(dentry->d_parent);
+	if (!buffer->item)
+		goto out_free_buffer;
+
+	attr = to_attr(dentry);
+	if (!attr)
+		goto out_free_buffer;
+
+	if (type & CONFIGFS_ITEM_BIN_ATTR) {
+		buffer->bin_attr = to_bin_attr(dentry);
+		buffer->cb_max_size = buffer->bin_attr->cb_max_size;
+	} else {
+		buffer->attr = attr;
+	}
+
+	buffer->owner = attr->ca_owner;
+	/* Grab the module reference for this attribute if we have one */
+	error = -ENODEV;
+	if (!try_module_get(buffer->owner))
+		goto out_free_buffer;
+
+	error = -EACCES;
+	if (!buffer->item->ci_type)
+		goto out_put_module;
+
+	buffer->ops = buffer->item->ci_type->ct_item_ops;
+
+	/* File needs write support.
+	 * The inode's perms must say it's ok,
+	 * and we must have a store method.
+	 */
+	if (file->f_mode & FMODE_WRITE) {
+		if (!(inode->i_mode & S_IWUGO))
+			goto out_put_module;
+		if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)
+			goto out_put_module;
+		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->write)
+			goto out_put_module;
+	}
+
+	/* File needs read support.
+	 * The inode's perms must say it's ok, and we there
+	 * must be a show method for it.
+	 */
+	if (file->f_mode & FMODE_READ) {
+		if (!(inode->i_mode & S_IRUGO))
+			goto out_put_module;
+		if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)
+			goto out_put_module;
+		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->read)
+			goto out_put_module;
+	}
+
+	mutex_init(&buffer->mutex);
+	buffer->needs_read_fill = 1;
+	buffer->read_in_progress = false;
+	buffer->write_in_progress = false;
+	file->private_data = buffer;
+	up_read(&frag->frag_sem);
+	return 0;
+
+out_put_module:
+	module_put(buffer->owner);
+out_free_buffer:
+	up_read(&frag->frag_sem);
+	kfree(buffer);
+out:
+	return error;
+}
+
+static int configfs_release(struct inode *inode, struct file *filp)
+{
+	struct configfs_buffer *buffer = filp->private_data;
+
+	module_put(buffer->owner);
+	kfree(buffer->page);
+	mutex_destroy(&buffer->mutex);
+	kfree(buffer);
+	return 0;
+}
+
+static int configfs_open_file(struct inode *inode, struct file *filp)
+{
+	return __configfs_open_file(inode, filp, CONFIGFS_ITEM_ATTR);
+}
+
+static int configfs_open_bin_file(struct inode *inode, struct file *filp)
+{
+	return __configfs_open_file(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
+}
+
+static int configfs_release_bin_file(struct inode *inode, struct file *file)
+{
+	struct configfs_buffer *buffer = file->private_data;
+
+	if (buffer->write_in_progress) {
+		struct configfs_fragment *frag = to_frag(file);
+
+		down_read(&frag->frag_sem);
+		if (!frag->frag_dead) {
+			/* result of ->release() is ignored */
+			buffer->bin_attr->write(buffer->item,
+					buffer->bin_buffer,
+					buffer->bin_buffer_size);
+		}
+		up_read(&frag->frag_sem);
+	}
+
+	vfree(buffer->bin_buffer);
+
+	configfs_release(inode, file);
+	return 0;
+}
+
+
+const struct file_operations configfs_file_operations = {
+	.read_iter	= configfs_read_iter,
+	.write_iter	= configfs_write_iter,
+	.llseek		= generic_file_llseek,
+	.open		= configfs_open_file,
+	.release	= configfs_release,
+};
+
+const struct file_operations configfs_bin_file_operations = {
+	.read_iter	= configfs_bin_read_iter,
+	.write_iter	= configfs_bin_write_iter,
+	.llseek		= NULL,		/* bin file is not seekable */
+	.open		= configfs_open_bin_file,
+	.release	= configfs_release_bin_file,
+};
+
+/**
+ *	configfs_create_file - create an attribute file for an item.
+ *	@item:	item we're creating for.
+ *	@attr:	atrribute descriptor.
+ */
+
+int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
+{
+	struct dentry *dir = item->ci_dentry;
+	struct configfs_dirent *parent_sd = dir->d_fsdata;
+	umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
+	int error = 0;
+
+	inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);
+	error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
+				     CONFIGFS_ITEM_ATTR, parent_sd->s_frag);
+	inode_unlock(d_inode(dir));
+
+	return error;
+}
+
+/**
+ *	configfs_create_bin_file - create a binary attribute file for an item.
+ *	@item:	item we're creating for.
+ *	@bin_attr: atrribute descriptor.
+ */
+
+int configfs_create_bin_file(struct config_item *item,
+		const struct configfs_bin_attribute *bin_attr)
+{
+	struct dentry *dir = item->ci_dentry;
+	struct configfs_dirent *parent_sd = dir->d_fsdata;
+	umode_t mode = (bin_attr->cb_attr.ca_mode & S_IALLUGO) | S_IFREG;
+	int error = 0;
+
+	inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);
+	error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
+				     CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);
+	inode_unlock(dir->d_inode);
+
+	return error;
+}

linux-7.2.3/fs/configfs/inode.c

@@ -0,0 +1,194 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * inode.c - basic inode and dentry operations.
+ *
+ * Based on sysfs:
+ * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
+ *
+ * configfs Copyright (C) 2005 Oracle.  All rights reserved.
+ *
+ * Please see Documentation/filesystems/configfs.rst for more
+ * information.
+ */
+
+#undef DEBUG
+
+#include <linux/pagemap.h>
+#include <linux/namei.h>
+#include <linux/backing-dev.h>
+#include <linux/capability.h>
+#include <linux/sched.h>
+#include <linux/lockdep.h>
+#include <linux/slab.h>
+
+#include <linux/configfs.h>
+#include "configfs_internal.h"
+
+#ifdef CONFIG_LOCKDEP
+static struct lock_class_key default_group_class[MAX_LOCK_DEPTH];
+#endif
+
+static const struct inode_operations configfs_inode_operations ={
+	.setattr	= configfs_setattr,
+};
+
+int configfs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+		     struct iattr *iattr)
+{
+	struct inode * inode = d_inode(dentry);
+	struct configfs_dirent * sd = dentry->d_fsdata;
+	struct iattr * sd_iattr;
+	unsigned int ia_valid = iattr->ia_valid;
+	int error;
+
+	if (!sd)
+		return -EINVAL;
+
+	sd_iattr = sd->s_iattr;
+	if (!sd_iattr) {
+		/* setting attributes for the first time, allocate now */
+		sd_iattr = kzalloc_obj(struct iattr);
+		if (!sd_iattr)
+			return -ENOMEM;
+		/* assign default attributes */
+		sd_iattr->ia_mode = sd->s_mode;
+		sd_iattr->ia_uid = GLOBAL_ROOT_UID;
+		sd_iattr->ia_gid = GLOBAL_ROOT_GID;
+		sd_iattr->ia_atime = sd_iattr->ia_mtime =
+			sd_iattr->ia_ctime = current_time(inode);
+		sd->s_iattr = sd_iattr;
+	}
+	/* attributes were changed atleast once in past */
+
+	error = simple_setattr(idmap, dentry, iattr);
+	if (error)
+		return error;
+
+	if (ia_valid & ATTR_UID)
+		sd_iattr->ia_uid = iattr->ia_uid;
+	if (ia_valid & ATTR_GID)
+		sd_iattr->ia_gid = iattr->ia_gid;
+	if (ia_valid & ATTR_ATIME)
+		sd_iattr->ia_atime = iattr->ia_atime;
+	if (ia_valid & ATTR_MTIME)
+		sd_iattr->ia_mtime = iattr->ia_mtime;
+	if (ia_valid & ATTR_CTIME)
+		sd_iattr->ia_ctime = iattr->ia_ctime;
+	if (ia_valid & ATTR_MODE) {
+		umode_t mode = iattr->ia_mode;
+
+		if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
+			mode &= ~S_ISGID;
+		sd_iattr->ia_mode = sd->s_mode = mode;
+	}
+
+	return error;
+}
+
+static inline void set_default_inode_attr(struct inode * inode, umode_t mode)
+{
+	inode->i_mode = mode;
+	simple_inode_init_ts(inode);
+}
+
+static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
+{
+	inode->i_mode = iattr->ia_mode;
+	inode->i_uid = iattr->ia_uid;
+	inode->i_gid = iattr->ia_gid;
+	inode_set_atime_to_ts(inode, iattr->ia_atime);
+	inode_set_mtime_to_ts(inode, iattr->ia_mtime);
+	inode_set_ctime_to_ts(inode, iattr->ia_ctime);
+}
+
+struct inode *configfs_new_inode(umode_t mode, struct configfs_dirent *sd,
+				 struct super_block *s)
+{
+	struct inode * inode = new_inode(s);
+	if (inode) {
+		inode->i_ino = get_next_ino();
+		inode->i_mapping->a_ops = &ram_aops;
+		inode->i_op = &configfs_inode_operations;
+
+		if (sd->s_iattr) {
+			/* sysfs_dirent has non-default attributes
+			 * get them for the new inode from persistent copy
+			 * in sysfs_dirent
+			 */
+			set_inode_attr(inode, sd->s_iattr);
+		} else
+			set_default_inode_attr(inode, mode);
+	}
+	return inode;
+}
+
+#ifdef CONFIG_LOCKDEP
+
+static void configfs_set_inode_lock_class(struct configfs_dirent *sd,
+					  struct inode *inode)
+{
+	int depth = sd->s_depth;
+
+	if (depth > 0) {
+		if (depth <= ARRAY_SIZE(default_group_class)) {
+			lockdep_set_class(&inode->i_rwsem,
+					  &default_group_class[depth - 1]);
+		} else {
+			/*
+			 * In practice the maximum level of locking depth is
+			 * already reached. Just inform about possible reasons.
+			 */
+			pr_info("Too many levels of inodes for the locking correctness validator.\n");
+			pr_info("Spurious warnings may appear.\n");
+		}
+	}
+}
+
+#else /* CONFIG_LOCKDEP */
+
+static void configfs_set_inode_lock_class(struct configfs_dirent *sd,
+					  struct inode *inode)
+{
+}
+
+#endif /* CONFIG_LOCKDEP */
+
+struct inode *configfs_create(struct dentry *dentry, umode_t mode)
+{
+	struct inode *inode = NULL;
+	struct configfs_dirent *sd;
+
+	if (!dentry)
+		return ERR_PTR(-ENOENT);
+
+	if (d_really_is_positive(dentry))
+		return ERR_PTR(-EEXIST);
+
+	sd = dentry->d_fsdata;
+	inode = configfs_new_inode(mode, sd, dentry->d_sb);
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+
+	configfs_set_inode_lock_class(sd, inode);
+	return inode;
+}
+
+/*
+ * Get the name for corresponding element represented by the given configfs_dirent
+ */
+const unsigned char * configfs_get_name(struct configfs_dirent *sd)
+{
+	struct configfs_attribute *attr;
+
+	BUG_ON(!sd || !sd->s_element);
+
+	/* These always have a dentry, so use that */
+	if (sd->s_type & (CONFIGFS_DIR | CONFIGFS_ITEM_LINK))
+		return sd->s_dentry->d_name.name;
+
+	if (sd->s_type & (CONFIGFS_ITEM_ATTR | CONFIGFS_ITEM_BIN_ATTR)) {
+		attr = sd->s_element;
+		return attr->ca_name;
+	}
+	return NULL;
+}

linux-7.2.3/fs/configfs/item.c

@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * item.c - library routines for handling generic config items
+ *
+ * Based on kobject:
+ *	kobject is Copyright (c) 2002-2003 Patrick Mochel
+ *
+ * configfs Copyright (C) 2005 Oracle.  All rights reserved.
+ *
+ * Please see the file Documentation/filesystems/configfs.rst for
+ * critical information about using the config_item interface.
+ */
+
+#include <linux/string.h>
+#include <linux/module.h>
+#include <linux/stat.h>
+#include <linux/slab.h>
+
+#include <linux/configfs.h>
+
+
+static inline struct config_item *to_item(struct list_head *entry)
+{
+	return container_of(entry, struct config_item, ci_entry);
+}
+
+/* Evil kernel */
+static void config_item_release(struct kref *kref);
+
+/**
+ *	config_item_init - initialize item.
+ *	@item:	item in question.
+ */
+static void config_item_init(struct config_item *item)
+{
+	kref_init(&item->ci_kref);
+	INIT_LIST_HEAD(&item->ci_entry);
+}
+
+/**
+ *	config_item_set_name - Set the name of an item
+ *	@item:	item.
+ *	@fmt:  The vsnprintf()'s format string.
+ *
+ *	If strlen(name) >= CONFIGFS_ITEM_NAME_LEN, then use a
+ *	dynamically allocated string that @item->ci_name points to.
+ *	Otherwise, use the static @item->ci_namebuf array.
+ */
+int config_item_set_name(struct config_item *item, const char *fmt, ...)
+{
+	int limit = CONFIGFS_ITEM_NAME_LEN;
+	int need;
+	va_list args;
+	char *name;
+
+	/*
+	 * First, try the static array
+	 */
+	va_start(args, fmt);
+	need = vsnprintf(item->ci_namebuf, limit, fmt, args);
+	va_end(args);
+	if (need < limit)
+		name = item->ci_namebuf;
+	else {
+		va_start(args, fmt);
+		name = kvasprintf(GFP_KERNEL, fmt, args);
+		va_end(args);
+		if (!name)
+			return -ENOMEM;
+	}
+
+	/* Free the old name, if necessary. */
+	if (item->ci_name && item->ci_name != item->ci_namebuf)
+		kfree(item->ci_name);
+
+	/* Now, set the new name */
+	item->ci_name = name;
+	return 0;
+}
+EXPORT_SYMBOL(config_item_set_name);
+
+void config_item_init_type_name(struct config_item *item,
+				const char *name,
+				const struct config_item_type *type)
+{
+	config_item_set_name(item, "%s", name);
+	item->ci_type = type;
+	config_item_init(item);
+}
+EXPORT_SYMBOL(config_item_init_type_name);
+
+void config_group_init_type_name(struct config_group *group, const char *name,
+			 const struct config_item_type *type)
+{
+	config_item_set_name(&group->cg_item, "%s", name);
+	group->cg_item.ci_type = type;
+	config_group_init(group);
+}
+EXPORT_SYMBOL(config_group_init_type_name);
+
+struct config_item *config_item_get(struct config_item *item)
+{
+	if (item)
+		kref_get(&item->ci_kref);
+	return item;
+}
+EXPORT_SYMBOL(config_item_get);
+
+struct config_item *config_item_get_unless_zero(struct config_item *item)
+{
+	if (item && kref_get_unless_zero(&item->ci_kref))
+		return item;
+	return NULL;
+}
+EXPORT_SYMBOL(config_item_get_unless_zero);
+
+static void config_item_cleanup(struct config_item *item)
+{
+	const struct config_item_type *t = item->ci_type;
+	struct config_group *s = item->ci_group;
+	struct config_item *parent = item->ci_parent;
+
+	pr_debug("config_item %s: cleaning up\n", config_item_name(item));
+	if (item->ci_name != item->ci_namebuf)
+		kfree(item->ci_name);
+	item->ci_name = NULL;
+	if (t && t->ct_item_ops && t->ct_item_ops->release)
+		t->ct_item_ops->release(item);
+	if (s)
+		config_group_put(s);
+	if (parent)
+		config_item_put(parent);
+}
+
+static void config_item_release(struct kref *kref)
+{
+	config_item_cleanup(container_of(kref, struct config_item, ci_kref));
+}
+
+/**
+ *	config_item_put - decrement refcount for item.
+ *	@item:	item.
+ *
+ *	Decrement the refcount, and if 0, call config_item_cleanup().
+ */
+void config_item_put(struct config_item *item)
+{
+	if (item)
+		kref_put(&item->ci_kref, config_item_release);
+}
+EXPORT_SYMBOL(config_item_put);
+
+/**
+ *	config_group_init - initialize a group for use
+ *	@group:	config_group
+ */
+void config_group_init(struct config_group *group)
+{
+	config_item_init(&group->cg_item);
+	INIT_LIST_HEAD(&group->cg_children);
+	INIT_LIST_HEAD(&group->default_groups);
+}
+EXPORT_SYMBOL(config_group_init);
+
+/**
+ *	config_group_find_item - search for item in group.
+ *	@group:	group we're looking in.
+ *	@name:	item's name.
+ *
+ *	Iterate over @group->cg_list, looking for a matching config_item.
+ *	If matching item is found take a reference and return the item.
+ *	Caller must have locked group via @group->cg_subsys->su_mtx.
+ */
+struct config_item *config_group_find_item(struct config_group *group,
+					   const char *name)
+{
+	struct list_head *entry;
+	struct config_item *ret = NULL;
+
+	list_for_each(entry, &group->cg_children) {
+		struct config_item *item = to_item(entry);
+		if (config_item_name(item) &&
+		    !strcmp(config_item_name(item), name)) {
+			ret = config_item_get(item);
+			break;
+		}
+	}
+	return ret;
+}
+EXPORT_SYMBOL(config_group_find_item);

linux-7.2.3/fs/configfs/mount.c

@@ -0,0 +1,179 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * mount.c - operations for initializing and mounting configfs.
+ *
+ * Based on sysfs:
+ * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
+ *
+ * configfs Copyright (C) 2005 Oracle.  All rights reserved.
+ */
+
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/mount.h>
+#include <linux/fs_context.h>
+#include <linux/pagemap.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+
+#include <linux/configfs.h>
+#include "configfs_internal.h"
+
+/* Random magic number */
+#define CONFIGFS_MAGIC 0x62656570
+
+static struct vfsmount *configfs_mount = NULL;
+struct kmem_cache *configfs_dir_cachep;
+static int configfs_mnt_count = 0;
+
+
+static void configfs_free_inode(struct inode *inode)
+{
+	if (S_ISLNK(inode->i_mode))
+		kfree(inode->i_link);
+	free_inode_nonrcu(inode);
+}
+
+static const struct super_operations configfs_ops = {
+	.statfs		= simple_statfs,
+	.drop_inode	= inode_just_drop,
+	.free_inode	= configfs_free_inode,
+};
+
+static struct config_group configfs_root_group = {
+	.cg_item = {
+		.ci_namebuf	= "root",
+		.ci_name	= configfs_root_group.cg_item.ci_namebuf,
+	},
+};
+
+int configfs_is_root(struct config_item *item)
+{
+	return item == &configfs_root_group.cg_item;
+}
+
+static struct configfs_dirent configfs_root = {
+	.s_sibling	= LIST_HEAD_INIT(configfs_root.s_sibling),
+	.s_children	= LIST_HEAD_INIT(configfs_root.s_children),
+	.s_element	= &configfs_root_group.cg_item,
+	.s_type		= CONFIGFS_ROOT,
+	.s_iattr	= NULL,
+};
+
+static int configfs_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+	struct inode *inode;
+	struct dentry *root;
+
+	sb->s_blocksize = PAGE_SIZE;
+	sb->s_blocksize_bits = PAGE_SHIFT;
+	sb->s_magic = CONFIGFS_MAGIC;
+	sb->s_op = &configfs_ops;
+	sb->s_time_gran = 1;
+
+	inode = configfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
+				   &configfs_root, sb);
+	if (inode) {
+		inode->i_op = &configfs_root_inode_operations;
+		inode->i_fop = &configfs_dir_operations;
+		/* directory inodes start off with i_nlink == 2 (for "." entry) */
+		inc_nlink(inode);
+	} else {
+		pr_debug("could not get root inode\n");
+		return -ENOMEM;
+	}
+
+	root = d_make_root(inode);
+	if (!root) {
+		pr_debug("%s: could not get root dentry!\n",__func__);
+		return -ENOMEM;
+	}
+	config_group_init(&configfs_root_group);
+	configfs_root_group.cg_item.ci_dentry = root;
+	root->d_fsdata = &configfs_root;
+	sb->s_root = root;
+	set_default_d_op(sb, &configfs_dentry_ops); /* the rest get that */
+	sb->s_d_flags |= DCACHE_DONTCACHE;
+	return 0;
+}
+
+static int configfs_get_tree(struct fs_context *fc)
+{
+	return get_tree_single(fc, configfs_fill_super);
+}
+
+static const struct fs_context_operations configfs_context_ops = {
+	.get_tree	= configfs_get_tree,
+};
+
+static int configfs_init_fs_context(struct fs_context *fc)
+{
+	fc->ops = &configfs_context_ops;
+	return 0;
+}
+
+static struct file_system_type configfs_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "configfs",
+	.init_fs_context = configfs_init_fs_context,
+	.kill_sb	= kill_anon_super,
+};
+MODULE_ALIAS_FS("configfs");
+
+struct dentry *configfs_pin_fs(void)
+{
+	int err = simple_pin_fs(&configfs_fs_type, &configfs_mount,
+			     &configfs_mnt_count);
+	return err ? ERR_PTR(err) : configfs_mount->mnt_root;
+}
+
+void configfs_release_fs(void)
+{
+	simple_release_fs(&configfs_mount, &configfs_mnt_count);
+}
+
+
+static int __init configfs_init(void)
+{
+	int err = -ENOMEM;
+
+	configfs_dir_cachep = kmem_cache_create("configfs_dir_cache",
+						sizeof(struct configfs_dirent),
+						0, 0, NULL);
+	if (!configfs_dir_cachep)
+		goto out;
+
+	err = sysfs_create_mount_point(kernel_kobj, "config");
+	if (err)
+		goto out2;
+
+	err = register_filesystem(&configfs_fs_type);
+	if (err)
+		goto out3;
+
+	return 0;
+out3:
+	pr_err("Unable to register filesystem!\n");
+	sysfs_remove_mount_point(kernel_kobj, "config");
+out2:
+	kmem_cache_destroy(configfs_dir_cachep);
+	configfs_dir_cachep = NULL;
+out:
+	return err;
+}
+
+static void __exit configfs_exit(void)
+{
+	unregister_filesystem(&configfs_fs_type);
+	sysfs_remove_mount_point(kernel_kobj, "config");
+	kmem_cache_destroy(configfs_dir_cachep);
+	configfs_dir_cachep = NULL;
+}
+
+MODULE_AUTHOR("Oracle");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("0.0.2");
+MODULE_DESCRIPTION("Simple RAM filesystem for user driven kernel subsystem configuration.");
+
+core_initcall(configfs_init);
+module_exit(configfs_exit);

linux-7.2.3/fs/configfs/symlink.c

@@ -0,0 +1,262 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * symlink.c - operations for configfs symlinks.
+ *
+ * Based on sysfs:
+ * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
+ *
+ * configfs Copyright (C) 2005 Oracle.  All rights reserved.
+ */
+
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/namei.h>
+#include <linux/slab.h>
+
+#include <linux/configfs.h>
+#include "configfs_internal.h"
+
+/* Protects attachments of new symlinks */
+DEFINE_MUTEX(configfs_symlink_mutex);
+
+static int item_depth(struct config_item * item)
+{
+	struct config_item * p = item;
+	int depth = 0;
+	do { depth++; } while ((p = p->ci_parent) && !configfs_is_root(p));
+	return depth;
+}
+
+static int item_path_length(struct config_item * item)
+{
+	struct config_item * p = item;
+	int length = 1;
+	do {
+		length += strlen(config_item_name(p)) + 1;
+		p = p->ci_parent;
+	} while (p && !configfs_is_root(p));
+	return length;
+}
+
+static void fill_item_path(struct config_item * item, char * buffer, int length)
+{
+	struct config_item * p;
+
+	--length;
+	for (p = item; p && !configfs_is_root(p); p = p->ci_parent) {
+		int cur = strlen(config_item_name(p));
+
+		/* back up enough to print this bus id with '/' */
+		length -= cur;
+		memcpy(buffer + length, config_item_name(p), cur);
+		*(buffer + --length) = '/';
+	}
+}
+
+static int configfs_get_target_path(struct config_item *item,
+		struct config_item *target, char *path)
+{
+	int depth, size;
+	char *s;
+
+	depth = item_depth(item);
+	size = item_path_length(target) + depth * 3 - 1;
+	if (size > PATH_MAX)
+		return -ENAMETOOLONG;
+
+	pr_debug("%s: depth = %d, size = %d\n", __func__, depth, size);
+
+	for (s = path; depth--; s += 3)
+		strcpy(s,"../");
+
+	fill_item_path(target, path, size);
+	pr_debug("%s: path = '%s'\n", __func__, path);
+	return 0;
+}
+
+static int create_link(struct config_item *parent_item,
+		       struct config_item *item,
+		       struct dentry *dentry)
+{
+	struct configfs_dirent *target_sd = item->ci_dentry->d_fsdata;
+	char *body;
+	int ret;
+
+	if (!configfs_dirent_is_ready(target_sd))
+		return -ENOENT;
+
+	body = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!body)
+		return -ENOMEM;
+
+	configfs_get(target_sd);
+	spin_lock(&configfs_dirent_lock);
+	if (target_sd->s_type & CONFIGFS_USET_DROPPING) {
+		spin_unlock(&configfs_dirent_lock);
+		configfs_put(target_sd);
+		kfree(body);
+		return -ENOENT;
+	}
+	target_sd->s_links++;
+	spin_unlock(&configfs_dirent_lock);
+	ret = configfs_get_target_path(parent_item, item, body);
+	if (!ret)
+		ret = configfs_create_link(target_sd, parent_item->ci_dentry,
+					   dentry, body);
+	if (ret) {
+		spin_lock(&configfs_dirent_lock);
+		target_sd->s_links--;
+		spin_unlock(&configfs_dirent_lock);
+		configfs_put(target_sd);
+		kfree(body);
+	}
+	return ret;
+}
+
+
+static int get_target(const char *symname, struct config_item **target,
+		      struct super_block *sb)
+{
+	struct path path __free(path_put) = {};
+	int ret;
+
+	ret = kern_path(symname, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &path);
+	if (ret)
+		return ret;
+	if (path.dentry->d_sb != sb)
+		return -EPERM;
+	*target = configfs_get_config_item(path.dentry);
+	if (!*target)
+		return -ENOENT;
+	return 0;
+}
+
+
+int configfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
+		     struct dentry *dentry, const char *symname)
+{
+	int ret;
+	struct configfs_dirent *sd;
+	struct config_item *parent_item;
+	struct config_item *target_item = NULL;
+	const struct config_item_type *type;
+
+	sd = dentry->d_parent->d_fsdata;
+	/*
+	 * Fake invisibility if dir belongs to a group/default groups hierarchy
+	 * being attached
+	 */
+	if (!configfs_dirent_is_ready(sd))
+		return -ENOENT;
+
+	parent_item = configfs_get_config_item(dentry->d_parent);
+	type = parent_item->ci_type;
+
+	ret = -EPERM;
+	if (!type || !type->ct_item_ops ||
+	    !type->ct_item_ops->allow_link)
+		goto out_put;
+
+	/*
+	 * This is really sick.  What they wanted was a hybrid of
+	 * link(2) and symlink(2) - they wanted the target resolved
+	 * at syscall time (as link(2) would've done), be a directory
+	 * (which link(2) would've refused to do) *AND* be a deep
+	 * fucking magic, making the target busy from rmdir POV.
+	 * symlink(2) is nothing of that sort, and the locking it
+	 * gets matches the normal symlink(2) semantics.  Without
+	 * attempts to resolve the target (which might very well
+	 * not even exist yet) done prior to locking the parent
+	 * directory.  This perversion, OTOH, needs to resolve
+	 * the target, which would lead to obvious deadlocks if
+	 * attempted with any directories locked.
+	 *
+	 * Unfortunately, that garbage is userland ABI and we should've
+	 * said "no" back in 2005.  Too late now, so we get to
+	 * play very ugly games with locking.
+	 *
+	 * Try *ANYTHING* of that sort in new code, and you will
+	 * really regret it.  Just ask yourself - what could a BOFH
+	 * do to me and do I want to find it out first-hand?
+	 *
+	 *  AV, a thoroughly annoyed bastard.
+	 */
+	inode_unlock(dir);
+	ret = get_target(symname, &target_item, dentry->d_sb);
+	inode_lock(dir);
+	if (ret)
+		goto out_put;
+
+	if (dentry->d_inode || d_unhashed(dentry))
+		ret = -EEXIST;
+	else
+		ret = inode_permission(&nop_mnt_idmap, dir,
+				       MAY_WRITE | MAY_EXEC);
+	if (!ret)
+		ret = type->ct_item_ops->allow_link(parent_item, target_item);
+	if (!ret) {
+		mutex_lock(&configfs_symlink_mutex);
+		ret = create_link(parent_item, target_item, dentry);
+		mutex_unlock(&configfs_symlink_mutex);
+		if (ret && type->ct_item_ops->drop_link)
+			type->ct_item_ops->drop_link(parent_item,
+						     target_item);
+	}
+
+	config_item_put(target_item);
+
+out_put:
+	config_item_put(parent_item);
+	return ret;
+}
+
+int configfs_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct configfs_dirent *sd = dentry->d_fsdata, *target_sd;
+	struct config_item *parent_item;
+	const struct config_item_type *type;
+	int ret;
+
+	ret = -EPERM;  /* What lack-of-symlink returns */
+	if (!(sd->s_type & CONFIGFS_ITEM_LINK))
+		goto out;
+
+	target_sd = sd->s_element;
+
+	parent_item = configfs_get_config_item(dentry->d_parent);
+	type = parent_item->ci_type;
+
+	spin_lock(&configfs_dirent_lock);
+	list_del_init(&sd->s_sibling);
+	spin_unlock(&configfs_dirent_lock);
+	configfs_put(sd);
+	simple_unlink(dir, dentry);
+
+	/*
+	 * drop_link() must be called before
+	 * decrementing target's ->s_links, so that the order of
+	 * drop_link(this, target) and drop_item(target) is preserved.
+	 */
+	if (type && type->ct_item_ops &&
+	    type->ct_item_ops->drop_link)
+		type->ct_item_ops->drop_link(parent_item,
+					       target_sd->s_element);
+
+	spin_lock(&configfs_dirent_lock);
+	target_sd->s_links--;
+	spin_unlock(&configfs_dirent_lock);
+	configfs_put(target_sd);
+
+	config_item_put(parent_item);
+
+	ret = 0;
+
+out:
+	return ret;
+}
+
+const struct inode_operations configfs_symlink_inode_operations = {
+	.get_link = simple_get_link,
+	.setattr = configfs_setattr,
+};
+