LXR linux/fs/nfs/cache

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * linux/fs/nfs/cache_lib.c
   4 *
   5 * Helper routines for the NFS client caches
   6 *
   7 * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
   8 */
   9#include <linux/kmod.h>
  10#include <linux/module.h>
  11#include <linux/moduleparam.h>
  12#include <linux/mount.h>
  13#include <linux/namei.h>
  14#include <linux/slab.h>
  15#include <linux/sunrpc/cache.h>
  16#include <linux/sunrpc/rpc_pipe_fs.h>
  17#include <net/net_namespace.h>
  18
  19#include "cache_lib.h"
  20
  21#define NFS_CACHE_UPCALL_PATHLEN 256
  22#define NFS_CACHE_UPCALL_TIMEOUT 15
  23
  24static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =
  25                                "/sbin/nfs_cache_getent";
  26static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT;
  27
  28module_param_string(cache_getent, nfs_cache_getent_prog,
  29                sizeof(nfs_cache_getent_prog), 0600);
  30MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");
  31module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);
  32MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "
  33                "the cache upcall is assumed to have failed");
  34
  35int nfs_cache_upcall(struct cache_detail *cd, char *entry_name)
  36{
  37        static char *envp[] = { "HOME=/",
  38                "TERM=linux",
  39                "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
  40                NULL
  41        };
  42        char *argv[] = {
  43                nfs_cache_getent_prog,
  44                cd->name,
  45                entry_name,
  46                NULL
  47        };
  48        int ret = -EACCES;
  49
  50        if (nfs_cache_getent_prog[0] == '\0')
  51                goto out;
  52        ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
  53        /*
  54         * Disable the upcall mechanism if we're getting an ENOENT or
  55         * EACCES error. The admin can re-enable it on the fly by using
  56         * sysfs to set the 'cache_getent' parameter once the problem
  57         * has been fixed.
  58         */
  59        if (ret == -ENOENT || ret == -EACCES)
  60                nfs_cache_getent_prog[0] = '\0';
  61out:
  62        return ret > 0 ? 0 : ret;
  63}
  64
  65/*
  66 * Deferred request handling
  67 */
  68void nfs_cache_defer_req_put(struct nfs_cache_defer_req *dreq)
  69{
  70        if (refcount_dec_and_test(&dreq->count))
  71                kfree(dreq);
  72}
  73
  74static void nfs_dns_cache_revisit(struct cache_deferred_req *d, int toomany)
  75{
  76        struct nfs_cache_defer_req *dreq;
  77
  78        dreq = container_of(d, struct nfs_cache_defer_req, deferred_req);
  79
  80        complete(&dreq->completion);
  81        nfs_cache_defer_req_put(dreq);
  82}
  83
  84static struct cache_deferred_req *nfs_dns_cache_defer(struct cache_req *req)
  85{
  86        struct nfs_cache_defer_req *dreq;
  87
  88        dreq = container_of(req, struct nfs_cache_defer_req, req);
  89        dreq->deferred_req.revisit = nfs_dns_cache_revisit;
  90        refcount_inc(&dreq->count);
  91
  92        return &dreq->deferred_req;
  93}
  94
  95struct nfs_cache_defer_req *nfs_cache_defer_req_alloc(void)
  96{
  97        struct nfs_cache_defer_req *dreq;
  98
  99        dreq = kzalloc(sizeof(*dreq), GFP_KERNEL);
 100        if (dreq) {
 101                init_completion(&dreq->completion);
 102                refcount_set(&dreq->count, 1);
 103                dreq->req.defer = nfs_dns_cache_defer;
 104        }
 105        return dreq;
 106}
 107
 108int nfs_cache_wait_for_upcall(struct nfs_cache_defer_req *dreq)
 109{
 110        if (wait_for_completion_timeout(&dreq->completion,
 111                        nfs_cache_getent_timeout * HZ) == 0)
 112                return -ETIMEDOUT;
 113        return 0;
 114}
 115
 116int nfs_cache_register_sb(struct super_block *sb, struct cache_detail *cd)
 117{
 118        int ret;
 119        struct dentry *dir;
 120
 121        dir = rpc_d_lookup_sb(sb, "cache");
 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        sunrpc_init_cache_detail(cd);
 133        pipefs_sb = rpc_get_sb_net(net);
 134        if (pipefs_sb) {
 135                ret = nfs_cache_register_sb(pipefs_sb, cd);
 136                rpc_put_sb_net(net);
 137                if (ret)
 138                        sunrpc_destroy_cache_detail(cd);
 139        }
 140        return ret;
 141}
 142
 143void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
 144{
 145        sunrpc_cache_unregister_pipefs(cd);
 146}
 147
 148void 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}
 159