1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/fs/nfs/cache_lib.c
4 *
5 * Helper routines for the NFS client caches
6 *
7 * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
8 */
9 #include <linux/kmod.h>
10 #include <linux/module.h>
11 #include <linux/moduleparam.h>
12 #include <linux/mount.h>
13 #include <linux/namei.h>
14 #include <linux/slab.h>
15 #include <linux/sunrpc/cache.h>
16 #include <linux/sunrpc/rpc_pipe_fs.h>
17 #include <net/net_namespace.h>
18
19 #include "cache_lib.h"
20
21 #define NFS_CACHE_UPCALL_PATHLEN 256
22 #define NFS_CACHE_UPCALL_TIMEOUT 15
23
24 static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =
25 "/sbin/nfs_cache_getent";
26 static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT;
27
28 module_param_string(cache_getent, nfs_cache_getent_prog,
29 sizeof(nfs_cache_getent_prog), 0600);
30 MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");
31 module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);
32 MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "
33 "the cache upcall is assumed to have failed");
34
35 int nfs_cache_upcall(struct cache_detail *cd, char *entry_name)
36 {
37 static char *envp[] = { "HOME=/",
38 "TERM=linux",
39 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
40 NULL
41 };
42 char *argv[] = {
43 nfs_cache_getent_prog,
44 cd->name,
45 entry_name,
46 NULL
47 };
48 int ret = -EACCES;
49
50 if (nfs_cache_getent_prog[0] == '\0')
51 goto out;
52 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
53 /*
54 * Disable the upcall mechanism if we're getting an ENOENT or
55 * EACCES error. The admin can re-enable it on the fly by using
56 * sysfs to set the 'cache_getent' parameter once the problem
57 * has been fixed.
58 */
59 if (ret == -ENOENT || ret == -EACCES)
60 nfs_cache_getent_prog[0] = '\0';
61 out:
62 return ret > 0 ? 0 : ret;
63 }
64
65 /*
66 * Deferred request handling
67 */
68 void nfs_cache_defer_req_put(struct nfs_cache_defer_req *dreq)
69 {
70 if (refcount_dec_and_test(&dreq->count))
71 kfree(dreq);
72 }
73
74 static void nfs_dns_cache_revisit(struct cache_deferred_req *d, int toomany)
75 {
76 struct nfs_cache_defer_req *dreq;
77
78 dreq = container_of(d, struct nfs_cache_defer_req, deferred_req);
79
80 complete(&dreq->completion);
81 nfs_cache_defer_req_put(dreq);
82 }
83
84 static struct cache_deferred_req *nfs_dns_cache_defer(struct cache_req *req)
85 {
86 struct nfs_cache_defer_req *dreq;
87
88 dreq = container_of(req, struct nfs_cache_defer_req, req);
89 dreq->deferred_req.revisit = nfs_dns_cache_revisit;
90 refcount_inc(&dreq->count);
91
92 return &dreq->deferred_req;
93 }
94
95 struct nfs_cache_defer_req *nfs_cache_defer_req_alloc(void)
96 {
97 struct nfs_cache_defer_req *dreq;
98
99 dreq = kzalloc(sizeof(*dreq), GFP_KERNEL);
100 if (dreq) {
101 init_completion(&dreq->completion);
102 refcount_set(&dreq->count, 1);
103 dreq->req.defer = nfs_dns_cache_defer;
104 }
105 return dreq;
106 }
107
108 int nfs_cache_wait_for_upcall(struct nfs_cache_defer_req *dreq)
109 {
110 if (wait_for_completion_timeout(&dreq->completion,
111 nfs_cache_getent_timeout * HZ) == 0)
112 return -ETIMEDOUT;
113 return 0;
114 }
115
116 int nfs_cache_register_sb(struct super_block *sb, struct cache_detail *cd)
117 {
118 int ret;
119 struct dentry *dir;
120
121 dir = rpc_d_lookup_sb(sb, "cache");
122 ret = sunrpc_cache_register_pipefs(dir, cd->name, 0600, cd);
123 dput(dir);
124 return ret;
125 }
126
127 int nfs_cache_register_net(struct net *net, struct cache_detail *cd)
128 {
129 struct super_block *pipefs_sb;
130 int ret = 0;
131
132 sunrpc_init_cache_detail(cd);
133 pipefs_sb = rpc_get_sb_net(net);
134 if (pipefs_sb) {
135 ret = nfs_cache_register_sb(pipefs_sb, cd);
136 rpc_put_sb_net(net);
137 if (ret)
138 sunrpc_destroy_cache_detail(cd);
139 }
140 return ret;
141 }
142
143 void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
144 {
145 sunrpc_cache_unregister_pipefs(cd);
146 }
147
148 void nfs_cache_unregister_net(struct net *net, struct cache_detail *cd)
149 {
150 struct super_block *pipefs_sb;
151
152 pipefs_sb = rpc_get_sb_net(net);
153 if (pipefs_sb) {
154 nfs_cache_unregister_sb(pipefs_sb, cd);
155 rpc_put_sb_net(net);
156 }
157 sunrpc_destroy_cache_detail(cd);
158 }
159
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