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1 /*
2 * linux/fs/nfs/cache_lib.c
3 *
4 * Helper routines for the NFS client caches
5 *
6 * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
7 */
8 #include <linux/kmod.h>
9 #include <linux/module.h>
10 #include <linux/moduleparam.h>
11 #include <linux/mount.h>
12 #include <linux/namei.h>
13 #include <linux/slab.h>
14 #include <linux/sunrpc/cache.h>
15 #include <linux/sunrpc/rpc_pipe_fs.h>
16 #include <net/net_namespace.h>
17
18 #include "cache_lib.h"
19
20 #define NFS_CACHE_UPCALL_PATHLEN 256
21 #define NFS_CACHE_UPCALL_TIMEOUT 15
22
23 static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =
24 "/sbin/nfs_cache_getent";
25 static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT;
26
27 module_param_string(cache_getent, nfs_cache_getent_prog,
28 sizeof(nfs_cache_getent_prog), 0600);
29 MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");
30 module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);
31 MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "
32 "the cache upcall is assumed to have failed");
33
34 int nfs_cache_upcall(struct cache_detail *cd, char *entry_name)
35 {
36 static char *envp[] = { "HOME=/",
37 "TERM=linux",
38 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
39 NULL
40 };
41 char *argv[] = {
42 nfs_cache_getent_prog,
43 cd->name,
44 entry_name,
45 NULL
46 };
47 int ret = -EACCES;
48
49 if (nfs_cache_getent_prog[0] == '\0')
50 goto out;
51 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
52 /*
53 * Disable the upcall mechanism if we're getting an ENOENT or
54 * EACCES error. The admin can re-enable it on the fly by using
55 * sysfs to set the 'cache_getent' parameter once the problem
56 * has been fixed.
57 */
58 if (ret == -ENOENT || ret == -EACCES)
59 nfs_cache_getent_prog[0] = '\0';
60 out:
61 return ret > 0 ? 0 : ret;
62 }
63
64 /*
65 * Deferred request handling
66 */
67 void nfs_cache_defer_req_put(struct nfs_cache_defer_req *dreq)
68 {
69 if (atomic_dec_and_test(&dreq->count))
70 kfree(dreq);
71 }
72
73 static void nfs_dns_cache_revisit(struct cache_deferred_req *d, int toomany)
74 {
75 struct nfs_cache_defer_req *dreq;
76
77 dreq = container_of(d, struct nfs_cache_defer_req, deferred_req);
78
79 complete(&dreq->completion);
80 nfs_cache_defer_req_put(dreq);
81 }
82
83 static struct cache_deferred_req *nfs_dns_cache_defer(struct cache_req *req)
84 {
85 struct nfs_cache_defer_req *dreq;
86
87 dreq = container_of(req, struct nfs_cache_defer_req, req);
88 dreq->deferred_req.revisit = nfs_dns_cache_revisit;
89 atomic_inc(&dreq->count);
90
91 return &dreq->deferred_req;
92 }
93
94 struct nfs_cache_defer_req *nfs_cache_defer_req_alloc(void)
95 {
96 struct nfs_cache_defer_req *dreq;
97
98 dreq = kzalloc(sizeof(*dreq), GFP_KERNEL);
99 if (dreq) {
100 init_completion(&dreq->completion);
101 atomic_set(&dreq->count, 1);
102 dreq->req.defer = nfs_dns_cache_defer;
103 }
104 return dreq;
105 }
106
107 int nfs_cache_wait_for_upcall(struct nfs_cache_defer_req *dreq)
108 {
109 if (wait_for_completion_timeout(&dreq->completion,
110 nfs_cache_getent_timeout * HZ) == 0)
111 return -ETIMEDOUT;
112 return 0;
113 }
114
115 int nfs_cache_register_sb(struct super_block *sb, struct cache_detail *cd)
116 {
117 int ret;
118 struct dentry *dir;
119
120 dir = rpc_d_lookup_sb(sb, "cache");
121 ret = sunrpc_cache_register_pipefs(dir, cd->name, 0600, cd);
122 dput(dir);
123 return ret;
124 }
125
126 int nfs_cache_register_net(struct net *net, struct cache_detail *cd)
127 {
128 struct super_block *pipefs_sb;
129 int ret = 0;
130
131 sunrpc_init_cache_detail(cd);
132 pipefs_sb = rpc_get_sb_net(net);
133 if (pipefs_sb) {
134 ret = nfs_cache_register_sb(pipefs_sb, cd);
135 rpc_put_sb_net(net);
136 if (ret)
137 sunrpc_destroy_cache_detail(cd);
138 }
139 return ret;
140 }
141
142 void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
143 {
144 sunrpc_cache_unregister_pipefs(cd);
145 }
146
147 void nfs_cache_unregister_net(struct net *net, struct cache_detail *cd)
148 {
149 struct super_block *pipefs_sb;
150
151 pipefs_sb = rpc_get_sb_net(net);
152 if (pipefs_sb) {
153 nfs_cache_unregister_sb(pipefs_sb, cd);
154 rpc_put_sb_net(net);
155 }
156 sunrpc_destroy_cache_detail(cd);
157 }