fs/nfs/cache_lib.c

   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(&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 }