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
24static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =
25				"/sbin/nfs_cache_getent";
26static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT;
27
28module_param_string(cache_getent, nfs_cache_getent_prog,
29		sizeof(nfs_cache_getent_prog), 0600);
30MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");
31module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);
32MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "
33		"the cache upcall is assumed to have failed");
34
35int 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';
61out:
62	return ret > 0 ? 0 : ret;
63}
64
65/*
66 * Deferred request handling
67 */
68void 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
74static 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
84static 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
95struct 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
108int 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
116int 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
127int 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
143void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
144{
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