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
23static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =
24				"/sbin/nfs_cache_getent";
25static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT;
26
27module_param_string(cache_getent, nfs_cache_getent_prog,
28		sizeof(nfs_cache_getent_prog), 0600);
29MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");
30module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);
31MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "
32		"the cache upcall is assumed to have failed");
33
34int 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';
60out:
61	return ret > 0 ? 0 : ret;
62}
63
64/*
65 * Deferred request handling
66 */
67void 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
73static 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_all(&dreq->completion);
80	nfs_cache_defer_req_put(dreq);
81}
82
83static 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
94struct 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
107int 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
115int 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
126int 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
142void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
143{
144	if (cd->u.pipefs.dir)
145		sunrpc_cache_unregister_pipefs(cd);
146}
147
148void 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