xref: /linux/fs/nfs/cache_lib.c (revision 664b0bae0b87f69bc9deb098f5e0158b9cf18e04)
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 
nfs_cache_upcall(struct cache_detail * cd,char * entry_name)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  */
nfs_cache_defer_req_put(struct nfs_cache_defer_req * dreq)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 
nfs_dns_cache_revisit(struct cache_deferred_req * d,int toomany)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 
nfs_dns_cache_defer(struct cache_req * req)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 
nfs_cache_defer_req_alloc(void)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 
nfs_cache_wait_for_upcall(struct nfs_cache_defer_req * dreq)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 
nfs_cache_register_sb(struct super_block * sb,struct cache_detail * cd)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 
nfs_cache_register_net(struct net * net,struct cache_detail * cd)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 
nfs_cache_unregister_sb(struct super_block * sb,struct cache_detail * cd)143 void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
144 {
145 	sunrpc_cache_unregister_pipefs(cd);
146 }
147 
nfs_cache_unregister_net(struct net * net,struct cache_detail * cd)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