1// SPDX-License-Identifier: GPL-2.0
2/*
3 *  linux/fs/nfs/symlink.c
4 *
5 *  Copyright (C) 1992  Rick Sladkey
6 *
7 *  Optimization changes Copyright (C) 1994 Florian La Roche
8 *
9 *  Jun 7 1999, cache symlink lookups in the page cache.  -DaveM
10 *
11 *  nfs symlink handling code
12 */
13
14#include <linux/time.h>
15#include <linux/errno.h>
16#include <linux/sunrpc/clnt.h>
17#include <linux/nfs.h>
18#include <linux/nfs2.h>
19#include <linux/nfs_fs.h>
20#include <linux/pagemap.h>
21#include <linux/stat.h>
22#include <linux/mm.h>
23#include <linux/string.h>
24
25/* Symlink caching in the page cache is even more simplistic
26 * and straight-forward than readdir caching.
27 */
28
29static int nfs_symlink_filler(void *data, struct page *page)
30{
31	struct inode *inode = data;
32	int error;
33
34	error = NFS_PROTO(inode)->readlink(inode, page, 0, PAGE_SIZE);
35	if (error < 0)
36		goto error;
37	SetPageUptodate(page);
38	unlock_page(page);
39	return 0;
40
41error:
42	SetPageError(page);
43	unlock_page(page);
44	return -EIO;
45}
46
47static const char *nfs_get_link(struct dentry *dentry,
48				struct inode *inode,
49				struct delayed_call *done)
50{
51	struct page *page;
52	void *err;
53
54	if (!dentry) {
55		err = ERR_PTR(nfs_revalidate_mapping_rcu(inode));
56		if (err)
57			return err;
58		page = find_get_page(inode->i_mapping, 0);
59		if (!page)
60			return ERR_PTR(-ECHILD);
61		if (!PageUptodate(page)) {
62			put_page(page);
63			return ERR_PTR(-ECHILD);
64		}
65	} else {
66		err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
67		if (err)
68			return err;
69		page = read_cache_page(&inode->i_data, 0, nfs_symlink_filler,
70				inode);
71		if (IS_ERR(page))
72			return ERR_CAST(page);
73	}
74	set_delayed_call(done, page_put_link, page);
75	return page_address(page);
76}
77
78/*
79 * symlinks can't do much...
80 */
81const struct inode_operations nfs_symlink_inode_operations = {
82	.get_link	= nfs_get_link,
83	.getattr	= nfs_getattr,
84	.setattr	= nfs_setattr,
85};
86