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#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
  23static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =
  24                                "/sbin/nfs_cache_getent";
  25static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT;
  26
  27module_param_string(cache_getent, nfs_cache_getent_prog,
  28                sizeof(nfs_cache_getent_prog), 0600);
  29MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");
  30module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);
  31MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "
  32                "the cache upcall is assumed to have failed");
  33
  34int 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';
  60out:
  61        return ret > 0 ? 0 : ret;
  62}
  63
  64/*
  65 * Deferred request handling
  66 */
  67void 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
  73static 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_all(&dreq->completion);
  80        nfs_cache_defer_req_put(dreq);
  81}
  82
  83static 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
  94struct 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
 107int 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
 115int 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        BUG_ON(dir == NULL);
 122        ret = sunrpc_cache_register_pipefs(dir, cd->name, 0600, cd);
 123        dput(dir);
 124        return ret;
 125}
 126
 127int nfs_cache_register_net(struct net *net, struct cache_detail *cd)
 128{
 129        struct super_block *pipefs_sb;
 130        int ret = 0;
 131
 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        }
 137        return ret;
 138}
 139
 140void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
 141{
 142        if (cd->u.pipefs.dir)
 143                sunrpc_cache_unregister_pipefs(cd);
 144}
 145
 146void nfs_cache_unregister_net(struct net *net, struct cache_detail *cd)
 147{
 148        struct super_block *pipefs_sb;
 149
 150        pipefs_sb = rpc_get_sb_net(net);
 151        if (pipefs_sb) {
 152                nfs_cache_unregister_sb(pipefs_sb, cd);
 153                rpc_put_sb_net(net);
 154        }
 155}
 156
 157void nfs_cache_init(struct cache_detail *cd)
 158{
 159        sunrpc_init_cache_detail(cd);
 160}
 161
 162void nfs_cache_destroy(struct cache_detail *cd)
 163{
 164        sunrpc_destroy_cache_detail(cd);
 165}
 166
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