fs/configfs/symlink.c

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

File Facts

System
Linux kernel
Corpus path
fs/configfs/symlink.c
Extension
.c
Size
6763 bytes
Lines
263
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-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;

Annotation

Implementation Notes