symlink.c

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/*
 * JFFS2 -- Journalling Flash File System, Version 2.
 *
 * Copyright © 2001-2007 Red Hat, Inc.
 *
 * Created by David Woodhouse <[email protected]>
 *
 * For licensing information, see the file 'LICENCE' in this directory.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include "nodelist.h"

static void *jffs2_follow_link(struct dentry *dentry, struct nameidata *nd);

const struct inode_operations jffs2_symlink_inode_operations =
{
    .readlink = generic_readlink,
    .follow_link =  jffs2_follow_link,
    .get_acl =  jffs2_get_acl,
    .setattr =  jffs2_setattr,
    .setxattr = jffs2_setxattr,
    .getxattr = jffs2_getxattr,
    .listxattr =    jffs2_listxattr,
    .removexattr =  jffs2_removexattr
};

static void *jffs2_follow_link(struct dentry *dentry, struct nameidata *nd)
{
    struct jffs2_inode_info *f = JFFS2_INODE_INFO(dentry->d_inode);
    char *p = (char *)f->target;

    /*
     * We don't acquire the f->sem mutex here since the only data we
     * use is f->target.
     *
     * 1. If we are here the inode has already built and f->target has
     * to point to the target path.
     * 2. Nobody uses f->target (if the inode is symlink's inode). The
     * exception is inode freeing function which frees f->target. But
     * it can't be called while we are here and before VFS has
     * stopped using our f->target string which we provide by means of
     * nd_set_link() call.
     */

    if (!p) {
        pr_err("%s(): can't find symlink target\n", __func__);
        p = ERR_PTR(-EIO);
    }
    jffs2_dbg(1, "%s(): target path is '%s'\n",
          __func__, (char *)f->target);

    nd_set_link(nd, p);

    /*
     * We will unlock the f->sem mutex but VFS will use the f->target string. This is safe
     * since the only way that may cause f->target to be changed is iput() operation.
     * But VFS will not use f->target after iput() has been called.
     */
    return NULL;
}