1 /*
2 * linux/fs/nfs/symlink.c
3 *
4 * Copyright (C) 1992 Rick Sladkey
5 *
6 * Optimization changes Copyright (C) 1994 Florian La Roche
7 *
8 * Jun 7 1999, cache symlink lookups in the page cache. -DaveM
9 *
10 * nfs symlink handling code
11 */
12
13 #define NFS_NEED_XDR_TYPES
14 #include <linux/sched.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/malloc.h>
24 #include <linux/string.h>
25 #include <linux/smp_lock.h>
26
27 /* Symlink caching in the page cache is even more simplistic
28 * and straight-forward than readdir caching.
29 */
30 static int nfs_symlink_filler(struct inode *inode, struct page *page)
31 {
32 void *buffer = kmap(page);
33 int error;
34
35 /* We place the length at the beginning of the page,
36 * in host byte order, followed by the string. The
37 * XDR response verification will NULL terminate it.
38 */
39 lock_kernel();
40 error = NFS_PROTO(inode)->readlink(inode, buffer,
41 PAGE_CACHE_SIZE - sizeof(u32)-4);
42 unlock_kernel();
43 if (error < 0)
44 goto error;
45 SetPageUptodate(page);
46 kunmap(page);
47 UnlockPage(page);
48 return 0;
49
50 error:
51 SetPageError(page);
52 kunmap(page);
53 UnlockPage(page);
54 return -EIO;
55 }
56
57 static char *nfs_getlink(struct inode *inode, struct page **ppage)
58 {
59 struct page *page;
60 u32 *p;
61
62 /* Caller revalidated the directory inode already. */
63 page = read_cache_page(&inode->i_data, 0,
64 (filler_t *)nfs_symlink_filler, inode);
65 if (IS_ERR(page))
66 goto read_failed;
67 if (!Page_Uptodate(page))
68 goto getlink_read_error;
69 *ppage = page;
70 p = kmap(page);
71 return (char*)(p+1);
72
73 getlink_read_error:
74 page_cache_release(page);
75 return ERR_PTR(-EIO);
76 read_failed:
77 return (char*)page;
78 }
79
80 static int nfs_readlink(struct dentry *dentry, char *buffer, int buflen)
81 {
82 struct inode *inode = dentry->d_inode;
83 struct page *page = NULL;
84 int res = vfs_readlink(dentry,buffer,buflen,nfs_getlink(inode,&page));
85 if (page) {
86 kunmap(page);
87 page_cache_release(page);
88 }
89 return res;
90 }
91
92 static int nfs_follow_link(struct dentry *dentry, struct nameidata *nd)
93 {
94 struct inode *inode = dentry->d_inode;
95 struct page *page = NULL;
96 int res = vfs_follow_link(nd, nfs_getlink(inode,&page));
97 if (page) {
98 kunmap(page);
99 page_cache_release(page);
100 }
101 return res;
102 }
103
104 /*
105 * symlinks can't do much...
106 */
107 struct inode_operations nfs_symlink_inode_operations = {
108 readlink: nfs_readlink,
109 follow_link: nfs_follow_link,
110 revalidate: nfs_revalidate,
111 setattr: nfs_notify_change,
112 };
113
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