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
  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