fs/nfs/cache_lib.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * linux/fs/nfs/cache_lib.c
0004  *
0005  * Helper routines for the NFS client caches
0006  *
0007  * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
0008  */
0009 #include <linux/kmod.h>
0010 #include <linux/module.h>
0011 #include <linux/moduleparam.h>
0012 #include <linux/mount.h>
0013 #include <linux/namei.h>
0014 #include <linux/slab.h>
0015 #include <linux/sunrpc/cache.h>
0016 #include <linux/sunrpc/rpc_pipe_fs.h>
0017 #include <net/net_namespace.h>
0018
0019 #include "cache_lib.h"
0020
0021 #define NFS_CACHE_UPCALL_PATHLEN 256
0022 #define NFS_CACHE_UPCALL_TIMEOUT 15
0023
0024 static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =
0025                 "/sbin/nfs_cache_getent";
0026 static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT;
0027
0028 module_param_string(cache_getent, nfs_cache_getent_prog,
0029         sizeof(nfs_cache_getent_prog), 0600);
0030 MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");
0031 module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);
0032 MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "
0033         "the cache upcall is assumed to have failed");
0034
0035 int nfs_cache_upcall(struct cache_detail *cd, char *entry_name)
0036 {
0037     static char *envp[] = { "HOME=/",
0038         "TERM=linux",
0039         "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
0040         NULL
0041     };
0042     char *argv[] = {
0043         nfs_cache_getent_prog,
0044         cd->name,
0045         entry_name,
0046         NULL
0047     };
0048     int ret = -EACCES;
0049
0050     if (nfs_cache_getent_prog[0] == '\0')
0051         goto out;
0052     ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
0053     /*
0054      * Disable the upcall mechanism if we're getting an ENOENT or
0055      * EACCES error. The admin can re-enable it on the fly by using
0056      * sysfs to set the 'cache_getent' parameter once the problem
0057      * has been fixed.
0058      */
0059     if (ret == -ENOENT || ret == -EACCES)
0060         nfs_cache_getent_prog[0] = '\0';
0061 out:
0062     return ret > 0 ? 0 : ret;
0063 }
0064
0065 /*
0066  * Deferred request handling
0067  */
0068 void nfs_cache_defer_req_put(struct nfs_cache_defer_req *dreq)
0069 {
0070     if (refcount_dec_and_test(&dreq->count))
0071         kfree(dreq);
0072 }
0073
0074 static void nfs_dns_cache_revisit(struct cache_deferred_req *d, int toomany)
0075 {
0076     struct nfs_cache_defer_req *dreq;
0077
0078     dreq = container_of(d, struct nfs_cache_defer_req, deferred_req);
0079
0080     complete(&dreq->completion);
0081     nfs_cache_defer_req_put(dreq);
0082 }
0083
0084 static struct cache_deferred_req *nfs_dns_cache_defer(struct cache_req *req)
0085 {
0086     struct nfs_cache_defer_req *dreq;
0087
0088     dreq = container_of(req, struct nfs_cache_defer_req, req);
0089     dreq->deferred_req.revisit = nfs_dns_cache_revisit;
0090     refcount_inc(&dreq->count);
0091
0092     return &dreq->deferred_req;
0093 }
0094
0095 struct nfs_cache_defer_req *nfs_cache_defer_req_alloc(void)
0096 {
0097     struct nfs_cache_defer_req *dreq;
0098
0099     dreq = kzalloc(sizeof(*dreq), GFP_KERNEL);
0100     if (dreq) {
0101         init_completion(&dreq->completion);
0102         refcount_set(&dreq->count, 1);
0103         dreq->req.defer = nfs_dns_cache_defer;
0104     }
0105     return dreq;
0106 }
0107
0108 int nfs_cache_wait_for_upcall(struct nfs_cache_defer_req *dreq)
0109 {
0110     if (wait_for_completion_timeout(&dreq->completion,
0111             nfs_cache_getent_timeout * HZ) == 0)
0112         return -ETIMEDOUT;
0113     return 0;
0114 }
0115
0116 int nfs_cache_register_sb(struct super_block *sb, struct cache_detail *cd)
0117 {
0118     int ret;
0119     struct dentry *dir;
0120
0121     dir = rpc_d_lookup_sb(sb, "cache");
0122     ret = sunrpc_cache_register_pipefs(dir, cd->name, 0600, cd);
0123     dput(dir);
0124     return ret;
0125 }
0126
0127 int nfs_cache_register_net(struct net *net, struct cache_detail *cd)
0128 {
0129     struct super_block *pipefs_sb;
0130     int ret = 0;
0131
0132     sunrpc_init_cache_detail(cd);
0133     pipefs_sb = rpc_get_sb_net(net);
0134     if (pipefs_sb) {
0135         ret = nfs_cache_register_sb(pipefs_sb, cd);
0136         rpc_put_sb_net(net);
0137         if (ret)
0138             sunrpc_destroy_cache_detail(cd);
0139     }
0140     return ret;
0141 }
0142
0143 void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
0144 {
0145     sunrpc_cache_unregister_pipefs(cd);
0146 }
0147
0148 void nfs_cache_unregister_net(struct net *net, struct cache_detail *cd)
0149 {
0150     struct super_block *pipefs_sb;
0151
0152     pipefs_sb = rpc_get_sb_net(net);
0153     if (pipefs_sb) {
0154         nfs_cache_unregister_sb(pipefs_sb, cd);
0155         rpc_put_sb_net(net);
0156     }
0157     sunrpc_destroy_cache_detail(cd);
0158 }