fs/kernfs/symlink.c

Source file repositories/reference/linux-study-clean/fs/kernfs/symlink.c

File Facts

System
Linux kernel
Corpus path
fs/kernfs/symlink.c
Extension
.c
Size
3547 bytes
Lines
156
Domain
Core OS
Bucket
VFS And Filesystem Core
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-only
/*
 * fs/kernfs/symlink.c - kernfs symlink implementation
 *
 * Copyright (c) 2001-3 Patrick Mochel
 * Copyright (c) 2007 SUSE Linux Products GmbH
 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
 */

#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/namei.h>

#include "kernfs-internal.h"

/**
 * kernfs_create_link - create a symlink
 * @parent: directory to create the symlink in
 * @name: name of the symlink
 * @target: target node for the symlink to point to
 *
 * Return: the created node on success, ERR_PTR() value on error.
 * Ownership of the link matches ownership of the target.
 */
struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
				       const char *name,
				       struct kernfs_node *target)
{
	struct kernfs_node *kn;
	int error;
	kuid_t uid = GLOBAL_ROOT_UID;
	kgid_t gid = GLOBAL_ROOT_GID;

	if (target->iattr) {
		uid = target->iattr->ia_uid;
		gid = target->iattr->ia_gid;
	}

	kn = kernfs_new_node(parent, name, S_IFLNK|0777, uid, gid, KERNFS_LINK);
	if (!kn)
		return ERR_PTR(-ENOMEM);

	if (kernfs_ns_enabled(parent))
		kn->ns = target->ns;
	kn->symlink.target_kn = target;
	kernfs_get(target);	/* ref owned by symlink */

	error = kernfs_add_one(kn);
	if (!error)
		return kn;

	kernfs_put(kn);
	return ERR_PTR(error);
}

static int kernfs_get_target_path(struct kernfs_node *parent,
				  struct kernfs_node *target, char *path)
{
	struct kernfs_node *base, *kn;
	char *s = path;
	int len = 0;

	/* go up to the root, stop at the base */
	base = parent;
	while (kernfs_parent(base)) {
		kn = kernfs_parent(target);
		while (kernfs_parent(kn) && base != kn)
			kn = kernfs_parent(kn);

		if (base == kn)
			break;

		if ((s - path) + 3 >= PATH_MAX)
			return -ENAMETOOLONG;

		strcpy(s, "../");
		s += 3;
		base = kernfs_parent(base);
	}

	/* determine end of target string for reverse fillup */
	kn = target;
	while (kernfs_parent(kn) && kn != base) {
		len += strlen(kernfs_rcu_name(kn)) + 1;
		kn = kernfs_parent(kn);
	}

	/* check limits */
	if (len < 2)
		return -EINVAL;

Annotation

Implementation Notes