diff options
Diffstat (limited to 'fs/sysfs/symlink.c')
| -rw-r--r-- | fs/sysfs/symlink.c | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c new file mode 100644 index 000000000000..dfdf70174354 --- /dev/null +++ b/fs/sysfs/symlink.c @@ -0,0 +1,180 @@ +/* + * symlink.c - operations for sysfs symlinks. + */ + +#include <linux/fs.h> +#include <linux/module.h> +#include <linux/kobject.h> +#include <linux/namei.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, 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; + + 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, char * name) +{ + struct dentry * dentry = kobj->dentry; + int error = 0; + + BUG_ON(!kobj || !kobj->dentry || !name); + + down(&dentry->d_inode->i_sem); + error = sysfs_add_link(dentry, name, target); + up(&dentry->d_inode->i_sem); + 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, 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 int 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 0; +} + +static void sysfs_put_link(struct dentry *dentry, struct nameidata *nd) +{ + char *page = nd_get_link(nd); + if (!IS_ERR(page)) + free_page((unsigned long)page); +} + +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); + |