linux/fs/nfs/cache_lib.c
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   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
  22static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =
  23                                "/sbin/nfs_cache_getent";
  24static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT;
  25
  26module_param_string(cache_getent, nfs_cache_getent_prog,
  27                sizeof(nfs_cache_getent_prog), 0600);
  28MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");
  29module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);
  30MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "
  31                "the cache upcall is assumed to have failed");
  32
  33int 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';
  59out:
  60        return ret > 0 ? 0 : ret;
  61}
  62
  63/*
  64 * Deferred request handling
  65 */
  66void 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
  72static 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
  82static 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
  93struct 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
 106int 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
 114int nfs_cache_register(struct cache_detail *cd)
 115{
 116        struct vfsmount *mnt;
 117        struct path path;
 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, &path);
 124        if (ret)
 125                goto err;
 126        ret = sunrpc_cache_register_pipefs(path.dentry, cd->name, 0600, cd);
 127        path_put(&path);
 128        if (!ret)
 129                return ret;
 130err:
 131        rpc_put_mount();
 132        return ret;
 133}
 134
 135void nfs_cache_unregister(struct cache_detail *cd)
 136{
 137        sunrpc_cache_unregister_pipefs(cd);
 138        rpc_put_mount();
 139}
 140
 141