xref: /openbmc/linux/fs/nfs/symlink.c (revision 113094f7)
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  
29  static 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  
41  error:
42  	SetPageError(page);
43  	unlock_page(page);
44  	return -EIO;
45  }
46  
47  static 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   */
81  const struct inode_operations nfs_symlink_inode_operations = {
82  	.get_link	= nfs_get_link,
83  	.getattr	= nfs_getattr,
84  	.setattr	= nfs_setattr,
85  };
86