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);
+