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 22 static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] = 23 "/sbin/nfs_cache_getent"; 24 static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT; 25 26 module_param_string(cache_getent, nfs_cache_getent_prog, 27 sizeof(nfs_cache_getent_prog), 0600); 28 MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program"); 29 module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600); 30 MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which " 31 "the cache upcall is assumed to have failed"); 32 33 int 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'; 59 out: 60 return ret > 0 ? 0 : ret; 61 } 62 63 /* 64 * Deferred request handling 65 */ 66 void 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 72 static 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 82 static 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 93 struct 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 } 105 106 int 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 } 113 114 int 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; 131 err: 132 rpc_put_mount(); 133 return ret; 134 } 135 136 void nfs_cache_unregister(struct cache_detail *cd) 137 { 138 sunrpc_cache_unregister_pipefs(cd); 139 rpc_put_mount(); 140 } 141 142