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/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