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 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 */ 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 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 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 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 } 107 108 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 } 115 116 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 } 126 127 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 } 142 143 void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd) 144 { 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