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
17#include "cache_lib.h"
18
19#define NFS_CACHE_UPCALL_PATHLEN 256
20#define NFS_CACHE_UPCALL_TIMEOUT 15
21
22static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =
23				"/sbin/nfs_cache_getent";
24static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT;
25
26module_param_string(cache_getent, nfs_cache_getent_prog,
27		sizeof(nfs_cache_getent_prog), 0600);
28MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");
29module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);
30MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "
31		"the cache upcall is assumed to have failed");
32
33int nfs_cache_upcall(struct cache_detail *cd, char *entry_name)
34{
35	static char *envp[] = { "HOME=/",
36		"TERM=linux",
37		"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
38		NULL
39	};
40	char *argv[] = {
41		nfs_cache_getent_prog,
42		cd->name,
43		entry_name,
44		NULL
45	};
46	int ret = -EACCES;
47
48	if (nfs_cache_getent_prog[0] == '\0')
49		goto out;
50	ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
51	/*
52	 * Disable the upcall mechanism if we're getting an ENOENT or
53	 * EACCES error. The admin can re-enable it on the fly by using
54	 * sysfs to set the 'cache_getent' parameter once the problem
55	 * has been fixed.
56	 */
57	if (ret == -ENOENT || ret == -EACCES)
58		nfs_cache_getent_prog[0] = '\0';
59out:
60	return ret > 0 ? 0 : ret;
61}
62
63/*
64 * Deferred request handling
65 */
66void nfs_cache_defer_req_put(struct nfs_cache_defer_req *dreq)
67{
68	if (atomic_dec_and_test(&dreq->count))
69		kfree(dreq);
70}
71
72static void nfs_dns_cache_revisit(struct cache_deferred_req *d, int toomany)
73{
74	struct nfs_cache_defer_req *dreq;
75
76	dreq = container_of(d, struct nfs_cache_defer_req, deferred_req);
77
78	complete_all(&dreq->completion);
79	nfs_cache_defer_req_put(dreq);
80}
81
82static struct cache_deferred_req *nfs_dns_cache_defer(struct cache_req *req)
83{
84	struct nfs_cache_defer_req *dreq;
85
86	dreq = container_of(req, struct nfs_cache_defer_req, req);
87	dreq->deferred_req.revisit = nfs_dns_cache_revisit;
88	atomic_inc(&dreq->count);
89
90	return &dreq->deferred_req;
91}
92
93struct nfs_cache_defer_req *nfs_cache_defer_req_alloc(void)
94{
95	struct nfs_cache_defer_req *dreq;
96
97	dreq = kzalloc(sizeof(*dreq), GFP_KERNEL);
98	if (dreq) {
99		init_completion(&dreq->completion);
100		atomic_set(&dreq->count, 1);
101		dreq->req.defer = nfs_dns_cache_defer;
102	}
103	return dreq;
104}
105
106int nfs_cache_wait_for_upcall(struct nfs_cache_defer_req *dreq)
107{
108	if (wait_for_completion_timeout(&dreq->completion,
109			nfs_cache_getent_timeout * HZ) == 0)
110		return -ETIMEDOUT;
111	return 0;
112}
113
114int nfs_cache_register(struct cache_detail *cd)
115{
116	struct nameidata nd;
117	struct vfsmount *mnt;
118	int ret;
119
120	mnt = rpc_get_mount();
121	if (IS_ERR(mnt))
122		return PTR_ERR(mnt);
123	ret = vfs_path_lookup(mnt->mnt_root, mnt, "/cache", 0, &nd);
124	if (ret)
125		goto err;
126	ret = sunrpc_cache_register_pipefs(nd.path.dentry,
127			cd->name, 0600, cd);
128	path_put(&nd.path);
129	if (!ret)
130		return ret;
131err:
132	rpc_put_mount();
133	return ret;
134}
135
136void nfs_cache_unregister(struct cache_detail *cd)
137{
138	sunrpc_cache_unregister_pipefs(cd);
139	rpc_put_mount();
140}
141