Root/fs/jffs2/symlink.c

1/*
2 * JFFS2 -- Journalling Flash File System, Version 2.
3 *
4 * Copyright © 2001-2007 Red Hat, Inc.
5 *
6 * Created by David Woodhouse <dwmw2@infradead.org>
7 *
8 * For licensing information, see the file 'LICENCE' in this directory.
9 *
10 */
11
12#include <linux/kernel.h>
13#include <linux/slab.h>
14#include <linux/fs.h>
15#include <linux/namei.h>
16#include "nodelist.h"
17
18static void *jffs2_follow_link(struct dentry *dentry, struct nameidata *nd);
19
20const struct inode_operations jffs2_symlink_inode_operations =
21{
22    .readlink = generic_readlink,
23    .follow_link = jffs2_follow_link,
24    .permission = jffs2_permission,
25    .setattr = jffs2_setattr,
26    .setxattr = jffs2_setxattr,
27    .getxattr = jffs2_getxattr,
28    .listxattr = jffs2_listxattr,
29    .removexattr = jffs2_removexattr
30};
31
32static void *jffs2_follow_link(struct dentry *dentry, struct nameidata *nd)
33{
34    struct jffs2_inode_info *f = JFFS2_INODE_INFO(dentry->d_inode);
35    char *p = (char *)f->target;
36
37    /*
38     * We don't acquire the f->sem mutex here since the only data we
39     * use is f->target.
40     *
41     * 1. If we are here the inode has already built and f->target has
42     * to point to the target path.
43     * 2. Nobody uses f->target (if the inode is symlink's inode). The
44     * exception is inode freeing function which frees f->target. But
45     * it can't be called while we are here and before VFS has
46     * stopped using our f->target string which we provide by means of
47     * nd_set_link() call.
48     */
49
50    if (!p) {
51        printk(KERN_ERR "jffs2_follow_link(): can't find symlink target\n");
52        p = ERR_PTR(-EIO);
53    }
54    D1(printk(KERN_DEBUG "jffs2_follow_link(): target path is '%s'\n", (char *) f->target));
55
56    nd_set_link(nd, p);
57
58    /*
59     * We will unlock the f->sem mutex but VFS will use the f->target string. This is safe
60     * since the only way that may cause f->target to be changed is iput() operation.
61     * But VFS will not use f->target after iput() has been called.
62     */
63    return NULL;
64}
65
66

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