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/sunrpc/cache.h> 14 #include <linux/sunrpc/rpc_pipe_fs.h> 15 16 #include "cache_lib.h" 17 18 #define NFS_CACHE_UPCALL_PATHLEN 256 19 #define NFS_CACHE_UPCALL_TIMEOUT 15 20 21 static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] = 22 "/sbin/nfs_cache_getent"; 23 static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT; 24 25 module_param_string(cache_getent, nfs_cache_getent_prog, 26 sizeof(nfs_cache_getent_prog), 0600); 27 MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program"); 28 module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600); 29 MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which " 30 "the cache upcall is assumed to have failed"); 31 32 int nfs_cache_upcall(struct cache_detail *cd, char *entry_name) 33 { 34 static char *envp[] = { "HOME=/", 35 "TERM=linux", 36 "PATH=/sbin:/usr/sbin:/bin:/usr/bin", 37 NULL 38 }; 39 char *argv[] = { 40 nfs_cache_getent_prog, 41 cd->name, 42 entry_name, 43 NULL 44 }; 45 int ret = -EACCES; 46 47 if (nfs_cache_getent_prog[0] == '\0') 48 goto out; 49 ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC); 50 /* 51 * Disable the upcall mechanism if we're getting an ENOENT or 52 * EACCES error. The admin can re-enable it on the fly by using 53 * sysfs to set the 'cache_getent' parameter once the problem 54 * has been fixed. 55 */ 56 if (ret == -ENOENT || ret == -EACCES) 57 nfs_cache_getent_prog[0] = '\0'; 58 out: 59 return ret > 0 ? 0 : ret; 60 } 61 62 /* 63 * Deferred request handling 64 */ 65 void nfs_cache_defer_req_put(struct nfs_cache_defer_req *dreq) 66 { 67 if (atomic_dec_and_test(&dreq->count)) 68 kfree(dreq); 69 } 70 71 static void nfs_dns_cache_revisit(struct cache_deferred_req *d, int toomany) 72 { 73 struct nfs_cache_defer_req *dreq; 74 75 dreq = container_of(d, struct nfs_cache_defer_req, deferred_req); 76 77 complete_all(&dreq->completion); 78 nfs_cache_defer_req_put(dreq); 79 } 80 81 static struct cache_deferred_req *nfs_dns_cache_defer(struct cache_req *req) 82 { 83 struct nfs_cache_defer_req *dreq; 84 85 dreq = container_of(req, struct nfs_cache_defer_req, req); 86 dreq->deferred_req.revisit = nfs_dns_cache_revisit; 87 atomic_inc(&dreq->count); 88 89 return &dreq->deferred_req; 90 } 91 92 struct nfs_cache_defer_req *nfs_cache_defer_req_alloc(void) 93 { 94 struct nfs_cache_defer_req *dreq; 95 96 dreq = kzalloc(sizeof(*dreq), GFP_KERNEL); 97 if (dreq) { 98 init_completion(&dreq->completion); 99 atomic_set(&dreq->count, 1); 100 dreq->req.defer = nfs_dns_cache_defer; 101 } 102 return dreq; 103 } 104 105 int nfs_cache_wait_for_upcall(struct nfs_cache_defer_req *dreq) 106 { 107 if (wait_for_completion_timeout(&dreq->completion, 108 nfs_cache_getent_timeout * HZ) == 0) 109 return -ETIMEDOUT; 110 return 0; 111 } 112 113 int nfs_cache_register(struct cache_detail *cd) 114 { 115 struct nameidata nd; 116 struct vfsmount *mnt; 117 int ret; 118 119 mnt = rpc_get_mount(); 120 if (IS_ERR(mnt)) 121 return PTR_ERR(mnt); 122 ret = vfs_path_lookup(mnt->mnt_root, mnt, "/cache", 0, &nd); 123 if (ret) 124 goto err; 125 ret = sunrpc_cache_register_pipefs(nd.path.dentry, 126 cd->name, 0600, cd); 127 path_put(&nd.path); 128 if (!ret) 129 return ret; 130 err: 131 rpc_put_mount(); 132 return ret; 133 } 134 135 void nfs_cache_unregister(struct cache_detail *cd) 136 { 137 sunrpc_cache_unregister_pipefs(cd); 138 rpc_put_mount(); 139 } 140 141