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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 
 23 static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =
 24                                 "/sbin/nfs_cache_getent";
 25 static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT;
 26 
 27 module_param_string(cache_getent, nfs_cache_getent_prog,
 28                 sizeof(nfs_cache_getent_prog), 0600);
 29 MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");
 30 module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);
 31 MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "
 32                 "the cache upcall is assumed to have failed");
 33 
 34 int 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';
 60 out:
 61         return ret > 0 ? 0 : ret;
 62 }
 63 
 64 /*
 65  * Deferred request handling
 66  */
 67 void 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 
 73 static 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 
 83 static 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 
 94 struct 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 
107 int 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 
115 int 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         ret = sunrpc_cache_register_pipefs(dir, cd->name, 0600, cd);
122         dput(dir);
123         return ret;
124 }
125 
126 int nfs_cache_register_net(struct net *net, struct cache_detail *cd)
127 {
128         struct super_block *pipefs_sb;
129         int ret = 0;
130 
131         sunrpc_init_cache_detail(cd);
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                 if (ret)
137                         sunrpc_destroy_cache_detail(cd);
138         }
139         return ret;
140 }
141 
142 void nfs_cache_unregister_sb(struct super_block *sb, struct cache_detail *cd)
143 {
144         if (cd->u.pipefs.dir)
145                 sunrpc_cache_unregister_pipefs(cd);
146 }
147 
148 void 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 

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