linux/fs/sysfs/symlink.c
Arjan van de Ven c5ef1c42c5 [PATCH] mark struct inode_operations const 3
Many struct inode_operations in the kernel can be "const".  Marking them const
moves these to the .rodata section, which avoids false sharing with potential
dirty data.  In addition it'll catch accidental writes at compile time to
these shared resources.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-12 09:48:46 -08:00

193 lines
4.1 KiB
C

/*
* symlink.c - operations for sysfs symlinks.
*/
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/namei.h>
#include <asm/semaphore.h>
#include "sysfs.h"
static int object_depth(struct kobject * kobj)
{
struct kobject * p = kobj;
int depth = 0;
do { depth++; } while ((p = p->parent));
return depth;
}
static int object_path_length(struct kobject * kobj)
{
struct kobject * p = kobj;
int length = 1;
do {
length += strlen(kobject_name(p)) + 1;
p = p->parent;
} while (p);
return length;
}
static void fill_object_path(struct kobject * kobj, char * buffer, int length)
{
struct kobject * p;
--length;
for (p = kobj; p; p = p->parent) {
int cur = strlen(kobject_name(p));
/* back up enough to print this bus id with '/' */
length -= cur;
strncpy(buffer + length,kobject_name(p),cur);
*(buffer + --length) = '/';
}
}
static int sysfs_add_link(struct dentry * parent, const char * name, struct kobject * target)
{
struct sysfs_dirent * parent_sd = parent->d_fsdata;
struct sysfs_symlink * sl;
int error = 0;
error = -ENOMEM;
sl = kmalloc(sizeof(*sl), GFP_KERNEL);
if (!sl)
goto exit1;
sl->link_name = kmalloc(strlen(name) + 1, GFP_KERNEL);
if (!sl->link_name)
goto exit2;
strcpy(sl->link_name, name);
sl->target_kobj = kobject_get(target);
error = sysfs_make_dirent(parent_sd, NULL, sl, S_IFLNK|S_IRWXUGO,
SYSFS_KOBJ_LINK);
if (!error)
return 0;
kobject_put(target);
kfree(sl->link_name);
exit2:
kfree(sl);
exit1:
return error;
}
/**
* 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)
{
struct dentry *dentry = NULL;
int error = -EEXIST;
BUG_ON(!name);
if (!kobj) {
if (sysfs_mount && sysfs_mount->mnt_sb)
dentry = sysfs_mount->mnt_sb->s_root;
} else
dentry = kobj->dentry;
if (!dentry)
return -EFAULT;
mutex_lock(&dentry->d_inode->i_mutex);
if (!sysfs_dirent_exist(dentry->d_fsdata, name))
error = sysfs_add_link(dentry, name, target);
mutex_unlock(&dentry->d_inode->i_mutex);
return error;
}
/**
* 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)
{
sysfs_hash_and_remove(kobj->dentry,name);
}
static int sysfs_get_target_path(struct kobject * kobj, struct kobject * target,
char *path)
{
char * s;
int depth, size;
depth = object_depth(kobj);
size = object_path_length(target) + depth * 3 - 1;
if (size > PATH_MAX)
return -ENAMETOOLONG;
pr_debug("%s: depth = %d, size = %d\n", __FUNCTION__, depth, size);
for (s = path; depth--; s += 3)
strcpy(s,"../");
fill_object_path(target, path, size);
pr_debug("%s: path = '%s'\n", __FUNCTION__, path);
return 0;
}
static int sysfs_getlink(struct dentry *dentry, char * path)
{
struct kobject *kobj, *target_kobj;
int error = 0;
kobj = sysfs_get_kobject(dentry->d_parent);
if (!kobj)
return -EINVAL;
target_kobj = sysfs_get_kobject(dentry);
if (!target_kobj) {
kobject_put(kobj);
return -EINVAL;
}
down_read(&sysfs_rename_sem);
error = sysfs_get_target_path(kobj, target_kobj, path);
up_read(&sysfs_rename_sem);
kobject_put(kobj);
kobject_put(target_kobj);
return error;
}
static void *sysfs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
int error = -ENOMEM;
unsigned long page = get_zeroed_page(GFP_KERNEL);
if (page)
error = sysfs_getlink(dentry, (char *) page);
nd_set_link(nd, error ? ERR_PTR(error) : (char *)page);
return NULL;
}
static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
{
char *page = nd_get_link(nd);
if (!IS_ERR(page))
free_page((unsigned long)page);
}
const struct inode_operations sysfs_symlink_inode_operations = {
.readlink = generic_readlink,
.follow_link = sysfs_follow_link,
.put_link = sysfs_put_link,
};
EXPORT_SYMBOL_GPL(sysfs_create_link);
EXPORT_SYMBOL_GPL(sysfs_remove_link);