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 23 static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] = 24 "/sbin/nfs_cache_getent"; 25 static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT; 26 27 module_param_string(cache_getent, nfs_cache_getent_prog, 28 sizeof(nfs_cache_getent_prog), 0600); 29 MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program"); 30 module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600); 31 MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which " 32 "the cache upcall is assumed to have failed"); 33 34 int 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'; 60 out: 61 return ret > 0 ? 0 : ret; 62 } 63 64 /* 65 * Deferred request handling 66 */ 67 void 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 73 static 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 83 static 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 94 struct 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 } 106 107 int 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 } 114 115 int 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 } 125 126 int 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 } 141 142 void 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 } 147 148 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